Is ¹⁸F-FDG-PET/CT a Valid Non-Invasive Predictor for Regression Grade after Neoadjuvant Treatment in Patients with NSCLC Stage III?

Natalie Desiree Klass, Richard P. Baum, Michael Schmuecking, Norbert Presselt, Klaus-Michael Mueller, Thomas G. Wendt, Reiner Bonnet

Department of Nuclear Medicine, Zentralklinik Bad Berka, Bad Berka, Germany.
Department of Pneumology, Zentralklinik Bad Berka, Bad Berka, Germany.
Department of Radiation Oncology, University of Jena, Jena, Germany.
Department of Radiation-Oncology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
Department of Thoracic Surgery, Zentralklinik Bad Berka, Bad Berka, Germany.
Institute of Pathology, University of Münster, Münster, Germany.

DOI: 10.4236/jct.2014.56061                

Abstract

Introduction: CT alone cannot provide sufficient information referring to response after neoadjuvant therapy in a timely manner. To evaluate the role of ¹⁸F-FDG-PET after neoadjuvant chemoradiation as a valid, non-invasive predictor for early therapy response and its effect on survival as compared to histopathologic tumor response, data of 32 of 210 randomized patients with NSCLC stage IIIA/IIIB, who were treated in a prospective randomized controlled multicenter trial (LUCAS- MD), were re-evaluated. Material and Methods: For 32 patients with NSCLC stage IIIA (44%) IIIB (56%) neoadjuvant treatment consisted of two to three cycles of chemotherapy (225 mg/m² paclitaxel and carboplatin AUC 6 d1q22) and concomitant chemoradiation (50 mg/m² paclitaxel and carboplatin AUC 2 d1, d8, d15; 1.5 Gy b.i.d. up to 45 Gy). Documentation of involved lymph node stations as detected by ¹⁸F-FDG-PET/CT and lymph node sampling during surgery according to the IASLC lymph node mapping (2009). Evaluation of histological regression grade (RG) according to Junker et al. (2001) and correlation with ¹⁸F-FDG-PET/CT for primary tumor and each lymph node station. Calculation of disease free survival using Kaplan-Meier estimates and log rank tests. Results: Actuarial tumor specific survival for the 32 patients with concomitant chemoradiation plus chemotherapy: complete vs. incomplete metabolic remission prior to surgery after 60 months: 40% vs. 24% (p = 0.018). RG III/IIb (no/less than 10% of vital tumor cells) vs. RG IIa/I (more than 10% vital tumor cells) after 60 months: 46% vs. 15% (p = 0.006). 18/32 (56%) patients had RG III/IIb, 8/32 (25%) patients had regression grade III. 1/8 pts. with RG III were in the ¹⁸F-FDG- PET/CT false positive, 10 pts. with RG IIb (i.e. all pts. with RG IIb) were in the ¹⁸F-FDG-PET/CT false negative. One patient with RG IIa was in the ¹⁸F-FDG-PET/CT false negative. Hence, the cut-off level in detecting vital tumor cells by ¹⁸F-FDG-PET/CT after neoadjuvant chemoradiation for NSCLC is about 10%. Conclusion: Histological regression grading correlates well with metabolic remission as detected by ¹⁸F-FDG-PET. Thus, ¹⁸F-FDG-PET precedes CT in measuring the tumor response and may predict long-term therapeutic outcome in patients with stage III NSCLC. Invasive staging procedures may be avoided and patients who will not profit from resection due to insufficient downstaging after neoadjuvant treatment will be easily detected by using ¹⁸F-FDG-PET as standard imaging in workup and evaluation of treatment response.

Keywords

NSCLC, ¹⁸18F-FDG-PET, Neoadjuvant Treatment, Non-Invasive Predictor

Keywords:

1. Introduction

Lung cancer is still one of the most frequent and lethal solid tumors in most countries. 80% of all lung cancers are represented by non-small-cell lung cancer. About one third of those patients present with locally advanced disease at diagnosis (stage IIIA and B). In this heterogeneous group the average 5-year-survival rate has been in the range of 15% - 27% at best [1] -[5] . A very important factor for survival is a good local and regional, especially mediastinal control [1] [2] [4] [5] . At diagnosis, 50% of all cases show lymph node metastases. In over 70% of the first hilar lymph nodes followed by mediastinal and then supraclavicular lymph nodes are involved. This fact also depends on the histology of the tumor: 33% of squamous cell tumors, 54% of adenocarcinomas and 57% of non-differentiated tumors present lymph node metastases at diagnosis. At the same time even very small tumors tend to metastasize quite early so that lung cancer is a systemic disease.

The initial tumor extension is decisive for further therapy stratification. Although lots of molecular and immunological factors such as RAS mutation, p53 and EML4-ALK were found, none of them play a role in therapy management according to multimodality treatment vs. definitive chemoradiation in NSCLC [6] - [8] .

In these cases positron emission tomography (PET) offers the possibility to display cellular tumor metabolism by using ¹⁸F-FDG (2-[¹⁸F]-fluoro-2-deoxy-D-glucose) with high sensitivity and specificity. In contrast to computed tomography (CT) the stage of disease can be determined in a more exact way which leads to an optimized therapy management for the patients [9] - [14] .

1.1. Goals of Therapy

50% - 80% of all patients with stage IIIA or IIIB disease die because of systemic relapse, only 20% - 37% of all patients because of local relapse. These data show that surgery, radiotherapy, antibody therapy and chemotherapy lead to a sufficient local control in locally advanced lung cancer. However, to improve overall survival, not only loco-regional control but also systemic tumor control has to be optimized. The sequence of systemic and loco-regional therapy is still topic of ongoing discussions, but there is a trend that concurrent chemoradiation might be superior to sequential treatment [10] [15] - [18] .

In cases of resectable NSCLC stage III the aim of induction therapy is to reduce initial tumor volume and thereby to improve resectability. This procedure is also called downstaging. An optimal downstaging allows a R0 resection in primary tumor and initially positive lymph nodes. Second aim is systemic tumor control, achieved by systemic therapy. Some data, based on a small number of patients, hypothesize that complete remission in mediastinal lymph node metastases is predictive for systemic tumor control [4] [19] .

1.2. Improvement of Diagnostic Imaging Is Inevitable

At this point problems concerning diagnostic imaging become clear: data prove that the correct evaluation of initial tumor extent and tumor response to chemotherapy in cases of NSCLC by using CT alone is imprecise [14] [20] [21] . Furthermore, there is no correlation detectable between histological tumor regression and therapy response, but histological response after induction therapy is a very important predictor for systemic tumor control [22] - [29] . To evaluate the morphologic regression grading the classification according to Junker et al. is usually used [25] - [27] .

In our study we examined the following questions:

· Is there a correlation between morphological regression and metabolic remission?

· Is there an improved overall survival (OS) stratified by regression grading and molecular remission as detected by ¹⁸F-FDG-PET?

· Can ¹⁸F-FDG-PET be used as a valid non-invasive predictor according to local and systemic control?

2. Material and Methods

Patients with histologically confirmed stage III NSCLC (American Joint Committee on Cancer [AJCC] sixth edition) out of a randomized multicenter phase III trial (LUCAS-MD) were included in this retrospective analysis. Details of baseline characteristics, treatment, and follow-up findings were entered prospectively into a database, managed by Alcedis GmbH (Giessen, Germany). All patients provided written informed consent to participate in this study, and the Institutional Review Board as well as the local ethics committee approved the study. Data confidentiality was preserved according to the Revised Helsinki Declaration of Bioethics in 2008.

2.1. Inclusion Criteria

So far, we retrospectively re-evaluated data of 32 of 210 randomized patients with NSCLC stage IIIA/IIIB who were treated in a prospective randomized controlled multicenter trial (LUCAS-MD) between 2000 and 2005. Follow-up time was 60 months.

Patients with a performance status ECOG 0-1, age between 18 - 70, functional resectability, and adequate hematologic, renal and hepatic function were included.

After diagnostic workup by CT and/or MRI, randomization to one of the two arms was done (Figure 1). To evaluate the significance of PET in therapy of NSCLC, ¹⁸F-FDG-PET was done for every patient after randomization prior to treatment.

2.2. Neoadjuvant Treatment

All patients received the same neoadjuvant treatment. The only difference was the point in time of concurrent chemoradiation therapy (early vs. late concurrent chemoradiation therapy). Neoadjuvant treatment consisted of 2 - 3 cycles of paclitaxel (225 mg/m² d1q22) and Carboplatin (AUC = 6, d1q22) followed by concurrent chemoradiation (radiotherapy according to ICRU 62: total dose 45 Gy, single dose 1.5 Gy b.i.d., concomitant 50 mg/m² paclitaxel and carboplatin AUC = 2 d1, d8, d15). For radiation treatment planning the target volume delineation was based on ¹⁸F-FDG-PET. If available ^99mTc-MAA SPECT/CT was used to optimize radiation treatment plans, referring to individual lung function [30] .

2.3. CT and ¹⁸F-FDG-PET

Within 5 days all patients received CT and ¹⁸F-FDG-PET in tidal breathing position. The positioning was the same as during radiotherapy. Fusion of PET and CT was done by a fusion software, installed on a HERMES computer (Nuclear diagnostics, Sweden). It was mandatory to fuse the images to ensure the detailed localization of PET positive lymph nodes according to IASLC recommendations. Alternatively ¹⁸F-FDG-PET/CT was done: these patients were examined on a dual-modality PET/CT tomograph (biograph duo, Siemens Medical Solutions). The CT component of the biograph BGO duo corresponds to a Somatom Emotion Duo (Siemens Medical Solutions), a 2-row spiral CT system with a maximum continuous scan time of 100 s and a maximum rotation speed of 75 rpm. The PET components of the combined PET/CT tomograph are based on a full-ring lutetium orthosilicate (LSO) PET system. PET scan emission images were recorded for 4 min per bed position; for non- uniform attenuation correction, CT images were used (acquisition parameters: 140 kV, 90 mA, 0.8 s, tube rotation, 5 mm thickness). PET images were acquired from the skull base to the middle part of the thigh. The CT transmission images were used for attenuation correction of the PET emission data. After scatter and attenuation correction, PET emission data were reconstructed using an attenuation-weighted ordered subsets expectation maximization approach with 2 iterations and 8 subsets on 128 × 128 matrices and with a 5-mm Gaussian post-reconstruction filtering.

Just before surgery a second ¹⁸F-FDG-PET was also mandatory (Figure 1). During surgery lymph node sampling according to IASLC recommendations was done, to correlate histology with the results found in CT and ¹⁸F-FDG-PET [31] [32] .

2.4. Histology

The surgical specimens were morphologically analyzed regarding to therapy-induced changes of the tumor tissue. Initially, the formalin-fixed resection samples were inspected macroscopically. From the primary lesion, regions with likely vital tumor tissue or former, now regressively altered, tumor tissue, as well as all resected mediastinal lymph nodes were embedded in paraffin. Hematoxylin-eosin and van Gieson stains were available for analysis of the specimens. In order to determine the degree of tumor regression, the type and extent of the vital tumor tissue, and the degree of tumor necrosis were taken into account. These findings were classified according to the following regression grading according to Junkers et al. (Table 1) [25] -[27] .

2.5. Statistics

The primary objective of this study was to assess overall survival (OS) stratified by regression grading and molecular remission as detected by PET. All time-to-event end points were calculated from the start of induction chemotherapy. Survival rates were calculated using the Kaplan-Meier product limit methodology. The influence of response to induction chemotherapy on OS was compared using a two-sided log-rank test (Mantel 1966, Breslow 1975, Kaplan Meier 1958). A p value of <0.05 was considered statistically significant. Statistical analysis was performed using SPSS version 10.0 (SPSS Inc., Chicago, IL, USA). Descriptive statistics included

Figure 1. Trial design: mandatory ¹⁸F-FDG-PET after randomization and in 15th week after end of neo- adjuvant therapy, correlation of ¹⁸F-FDG-PET results with regression grading in surgical specimens (lymph node sampling according to IASLC recommendations).

Table 1. Grading of tumor regression according to Junker et al.

absolute and relative frequencies for categorical variables, and the median and range for quantitative variables. Additionally, due to the small number of patients, the statistical power was estimated by Gail and Gart [33] [34] .

3. Results

18/32 (56%) patients had a regression grading (RG) III or IIb. 8/32 (25%) patients had RG III. 1 of those 8 patients with RG III was false positive in ¹⁸F-FDG-PET/CT due to inflammation which was histologically confirmed. All patients (10) with RG IIb (<10% residual tumor cells) were false negative in ¹⁸F-FDG-PET/CT. One patient with RG IIa (15% of vital tumor cells) was false negative in ¹⁸F-FDG-PET/CT: Hence, the cut-off level in detecting vital tumor cells by ¹⁸F-FDG-PET/CT after neoadjuvant chemoradiation for NSCLC is about 10%.

Actuarial tumor specific survival, stratified to RG IIb and III vs. RG I and IIa was significantly increased after 60 months: 46% vs. 15 %, respectively (p = 0.006) (Figure 2). Patients who showed a complete metabolic remission lived significantly longer than those with no remission. Survival time after 60 months was 40% vs. 24%, respectively (p = 0.018) (Figure 3). Tumor specific survival according to RG in lymph nodes only was far better for patients with RG IIb or III (41% after 60 months) vs. those with RG I or IIa (0% after 18 months): p =< 0.001 (Figure 4). In lack of larger numbers of patients the statistical power is 70%.

Figure 5 shows an example of a patient with no metabolic response after neoadjuvant treatment (no change, NC according to WHO criteria). Initial imaging detected a cT4 cN2-3 cM0 tumor, according to ¹⁸F-FDG- PET/CT. After neoadjuvant treatment a RG I was found in surgical specimen, ypT2a ypN3, with concordant results for lymph node metabolism and over-estimation of the T-status in the post-therapeutic ¹⁸F-FDG-PET/CT: cT4 cN3 cM0.

Figure 6 shows an example of a patient with complete metabolic response. Pre-therapeutic ¹⁸F-FDG-PET/CT detected a NSCLC cT3-4 cN3 cM0. After neoadjuvant chemoradiation complete metabolic remission was seen in ¹⁸F-FDG-PET. CT still showed primary tumor with a diameter of 2.3 cm. Exemplarily this case demonstrates that ¹⁸F-FDG-PET may be superior to CT according to therapy response. Histology proved complete regression, RG III: ypT0 ypN0.

Examples for histological regression grading can be seen in Figure 7.

4. Discussion

Moon et al. showed very nicely in 52 patients with stage IV NSCLC that metabolic response evaluated by ¹⁸F- FDG-PET/CT has a potential in identifying a subgroup of patients who may benefit from immediate maintenance therapy after first-line chemotherapy. The parameter used in this study for risk-stratification was a decrease in total lesion glycolysis (TLG) with a cut-off value of <50% [35] . Also, Kim et al. emphasized the role of ¹⁸F-FDG-PET/CT for prognostic stratification in 19 patients with advanced NSCLC (stage III and IV) using DeltaSUV (max) to retrospectively identify non-responders to chemotherapy [36] . The strong correlation between histological regression grading and overall survival was shown by the German Lung Cancer Cooperative Group (GLCCG), proving that patients showing regression grading IIb or III had significantly better progression free survival and overall survival [37] .

The aim of our study was to correlate ¹⁸F-FDG-PET/CT with histological regression as described by Junker et al. [25] . Univariate analysis showed significantly improved survival for patients with complete metabolic response in ¹⁸F-FDG-PET or regression grade IIb/III in specimen.

The evaluation of response to treatment in CT is insecure and not contemporary, as shown in several studies.

Figure 2. Tumor specific survival according to regression grading of primary tumor and lymph nodes.

Figure 3. Tumor specific survival according to metabolic response.

Figure 4. Tumor specific survival according to metabolic response.

Figure 5. Example for no metabolic response after neoadjuvant treatment.

Figure 6. Example for metabolic response. Pre-therapeutic ¹⁸F-FDG-PET/CT, cT3-4 cN3 cM0, SUV_max 23.5 in primary tumor and SUV_max 10.2 in lymph node metastasis 4L. After neoadjuvant treatment complete metabolic remission, physiologically normal SUV_max 1.5 - 2.0 in mediastinum. In CT primary tumor showed still a diameter of 2.3 cm. Histology: ypT0 ypN0.

Thus, CT alone as a morphologic imaging is an improper non-invasive predictor to loco-regional, but also sys- temic tumor control [22] - [24] [29] .

Nevertheless, ¹⁸F-FDG-PET/CThas its limitations. There are false positive and false negative findings which should be discussed critically.

False positive findings in ¹⁸F-FDG-PET according to primary tumor are mostly due to inflammation or side effects by radiotherapy which could be proved by histology, as shown not only by Poettgen et al. but also in our data [38] [39] . Patients with false positive findings in mediastinum represent a special problem, if ¹⁸F-FDG-PET should play an important role as non-invasive predictor to loco-regional and systemic tumor control and basis for future therapy decisions. The PET based strategy, not to operate patients remaining positive in ¹⁸F-FDG-PET after neoadjuvant treatment, because of lacking mediastinal remission and high risk of dying due to systemic tumor progression means that those patients with false positive findings in PET may be deprived of a curative option.

Otherwise it is going to be discussed whether patients with complete metabolic response in primary tumor and

Figure 7. (a) 4 months after neoadjuvant chemoradiation of an adenocarcinoma. Regression grading IIa: multiple pleomorphic tumor areas and inflammation induced desmoplastic reaction; (b) Regression grading IIb in adenocarcinoma after neoadjuvant chemoradiation with less than 10% of vital tumor cells; (c) Regression grading III with complete tumor necrosis after neoadjuvant chemoradiation.

in initially positive lymph nodes will benefit from additional resection according to overall survival. In this con- text the false negative findings in PET may represent a problem. In our patient population especially patients with regression grade IIb are concerned. In our study we summed up regression grade IIb and III for correlation with complete metabolic remission. Hence, false negative means a detection of <10% of vital tumor cells in his- tology while in ¹⁸F-FDG-PET a complete metabolic remission was found. In all of our patients showing a RG IIb in primary tumor (vital tumor cells <10%), ¹⁸F-FDG-PET was negative. This is correlative to data by Fischer et al. who showed a detection limit of PET in the magnitude of 10⁵ to 10⁶ malignant cells [40] [41] . Hence, false negative results may occur if there is a low vital tumor cell density leading to very low PET signals in the voxels [42] . According to data by Fischer et al. false negative results are also possible due to small or well-differentiat- ed malignancies, such as bronchioalveolar carcinoma or carcinoid [40] [41] . For a subgroup analysis the current number of patients is far too low. A correlation of patients with identical histology and grading is needed for that. Even if ¹⁸F-FDG-PET shows complete metabolic remission, <10% of tumor cells found in specimen does not mean complete response. Those cells might have an accelerated repopulation, leading to a loco-regional recurrence in quite a short time if not treated. Thus, discordant findings in ¹⁸F-FDG-PET and histology can be explained.

There is a growing body of evidence that in future newer techniques like deep inspiration breath hold acquisition or high resolution PET/CT with time-of-flight (TOF) technology may lead to higher sensitivity in detection of smaller lesions or lesions with low density of tumor cells [43] - [45] .

Similar results according to correlation of ¹⁸F-FDG-PET with histology were found in patients with induction chemotherapy alone. Betticher et al. achieved by using docetaxel-cisplatin as neoadjuvant chemotherapy a pathologic complete remission rate in 15% of their patients, comparable with data by Martini et al. who used neoadjuvant mitomycin, vindesine, vinblastine and cisplatin leading as well to a complete remission rate of 15% [46] [47] . In contrast, our complete remission rate was 28%. This shows a gap of >10% and might indicate a positive impact for an intensified neoadjuvant protocol consisting of 2-3 cycles of chemotherapy and concurrent chemoradiation as standard neoadjuvant treatment. Assuming a number of 540 patients the intensified treatment regimen consisting of concomitant chemoradiation plus chemotherapy will be statistically superior to the other neoadjuvant treatment regimens.

Our preliminary data underline that a second ¹⁸F-FDG-PET/CT may also play an important role as a non-inva- sive, post-therapeutic intervention after chemoradiation, for an optimized therapeutic management as published by Hellwig et al. [48] .

The final evaluation of regression grading in over 210 patients of the LUCAS-MD trial and in 232 patients included in the SAKK 16/00 trial (all together 442 patients) will show if an intensified neoadjuvant protocol is justified. However, a prospective randomized trial is needed to evaluate the hypothesis that an intensified approach is superior to chemotherapy alone or sequential neoadjuvant chemoradiation.

5. Conclusion

Histological regression grading after neoadjuvant treatment correlates well with metabolic remission as detected by ¹⁸F-FDG-PET, especially according to lymph nodes. Thus, ¹⁸F-FDG-PET precedes CT in measuring the tumor response and may predict long-term therapeutic outcome in patients with stage III NSCLC. By correlating a high number of patient’s histology with ¹⁸F-FDG-PET, it will be possible to define a realistic cut-off level for detecting vital tumor cells, especially for the newer PET/CT systems. Our preliminary data suggest that the cut- off-level of vital tumor cells is about 10%. This detection threshold of ¹⁸F-FDG-PET may have an important influence on molecular radiotherapy planning and target volume definition.

We could also prove that patients with metabolic complete remission (CR) or morphological regression grading IIb/III showed an improved overall survival. ¹⁸F-FDG-PET can be used as a quality control after neoadjuvant treatment, and may change the initial treatment schedule. Invasive staging procedures could be avoided, and patients, who will not profit from resection due to insufficient downstaging, could be easily detected.

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Aerts, H.J., Bosmans, G., Van Baardwijk, A., et al. (2008) Stability of 18F-Deoxyglucose Uptake Locations within Tumor during Radiotherapy for NSCLC: A Prospective Study. International Journal of Radiation Oncology * Biology *Physics, 71, 1402-1407. http://dx.doi.org/10.1016/j.ijrobp.2007.11.049
[2]	Aerts, H.J., Van Baardwijk, A., Petit, F., et al. (2009) Identification of Residual Metabolic-Active Areas within Individual NSCLC Tumors Using a Pre-Radiotherapy 18Fluorodesoxyglucose-PET-CT Scan. Radiotherapy and Oncology, 91, 386-392. http://dx.doi.org/10.1016/j.radonc.2009.03.006
[3]	Baum, R.P., Schmuecking, M., Plichta, K., et al. (2000) Staging of Non-Small-Cell Lung Cancer (NSCLC)—Is PET Really Clinically Important or Just a Research Tool? Journal of Nuclear Medicine, 41, 293.
[4]	Gandara, D.R., Leigh, B., Vallieres, E. and Albain, K.S. (1999) Preoperative Chemotherapy in Stage III Non-Small Cell Lung Cancer: Long-Term Outcome. Lung Cancer, 26, 3-6. http://dx.doi.org/10.1016/S0169-5002(99)00056-2
[5]	Giraud, P., Antoine, M., Larrouy, A., et al. (2000) Evaluation of Microscopic Tumor Extension in Non-Small Cell Lung Cancer (NSCLC) for Three-Dimensional Con-Formal Radiotherapy (3DCRT) Planning. International Journal of Radiation Oncology * Biology * Physics, 48, 1015-1024. http://dx.doi.org/10.1016/S0360-3016(00)00750-1
[6]	Albain, K.S., Swann, R.S., Rusch, V.W., et al. (2009) Radiotherapy plus Chemotherapy with or without Surgical Resection for Stage III Non-Small-Cell Lung Cancer: A Phase III Randomized Controlled Trial. Lancet, 374, 379-386. http://dx.doi.org/10.1016/S0140-6736(09)60737-6
[7]	Müller, K.-M. and Wiethege, T. (2004) Pathologie, Klassifikation und Stadieneinteilung b?sartiger Lungentumoren. Radiologe, 44, 415-426. http://dx.doi.org/10.1007/s00117-004-1052-6
[8]	Rosell, R., Carcereny, E., Gervais, R., et al. and the Spanish Lung Cancer Group in Collaboration with GroupeFran?ais de Pneumo-Cancérologie and Associazione Italiana Oncologia Toracica (2012) Erlotinib versus Standard Chemotherapy as First-Line Treatment for European Patients with Advanced EGFR Mutation-Positive Non-Small-Cell Lung Cancer (EURTAC): A Multicentre, Open-Label, Randomized Phase 3 Trial. The Lancet Oncology, 13, 239-246. http://dx.doi.org/10.1016/S1470-2045(11)70393-X?
[9]	Antoch, G., Stattaus, J., Nemat, A.T., et al. (2003) Non-Small Cell Lung Cancer: Dual-Modality PET/CT in Pre-Operative Staging. Radiology, 229, 526-533. http://dx.doi.org/10.1148/radiol.2292021598
[10]	Auperin, A., Le Pechoux, C., Rolland, E., et al. (2010) Meta-Analysis of Concomitant versus Sequential Radiochemotherapy in Locally Advanced Non-Small-Cell Lung Cancer. Journal of Clinical Oncology, 28, 2181-2190
[11]	Gupta, N.C., Tamim, W.J., Graeber, G.G., et al. (2001) Mediastinal Lymph Node Sampling Following Positron Emission Tomography with Fluorodeoxyglucose Imaging in Lung Cancer Staging. Chest, 120, 521-527. http://dx.doi.org/10.1378/chest.120.2.521
[12]	Vansteenkiste, J.F., Stroobants, S.G., De Leyn, P.R., et al. (1998) Lymph Node Staging in Non-Small-Cell Lung Cancer with FDG-PET Scan: A Prospective Study on 690 Lymph Node Stations from 68 Patients. Journal of Clinical Oncology, 16, 2142-2149.
[13]	Vansteenkiste, J.F., Stroobants, S.G., De Leyn, P.R., et al. (1998) Potential Use of FDG-PET Scan after Induction Chemotherapy in Surgically Staged IIIa-N2 Non-Small-Cell Lung Cancer: A Prospective Pilot Study. The Leuven Lung Cancer Group. Annals of Oncology, 9, 1193-1198. http://dx.doi.org/10.1023/A:1008240127706
[14]	Knollmann, F.D., Kumthekar, R., Fetzer, D., et al. (2014) Assessing Response to Treatment in Non-Small-Cell Lung Cancer: Role of Tumor Volume Evaluated by Computed Tomography. Clinical Lung Cancer, 15, 103-109. http://dx.doi.org/10.1016/j.cllc.2013.11.001
[15]	Liang, H.Y., Zhou, H., Li, X.L., et al. (2010) Chemo-Radiotherapy for Advanced Non-Small Cell Lung Cancer: Concurrent or Sequential? It’s No Longer the Question: A Systematic Review. International Journal of Cancer, 127, 718-728. http://dx.doi.org/10.1002/ijc.25087
[16]	Rosell, R., Gomez-Codina, J., Camps, C., Maestre, J., Padille, J., Canto, A., Mate, J.L., Li, S.R., Roig, J., Olazabal, A., Canela, M., Ariza, A., Skacel, Z., Morera-Prat, J. and Abad, A. (1994) A Randomized Trial Comparing Preoperative Chemotherapy Plus Surgery with Surgery Alone in Patients with Non-Small-Cell Lung Cancer. New England Journal of Medicine, 330, 153-158. http://dx.doi.org/10.1056/NEJM199401203300301
[17]	Roth, J.A., Fossella, F., Komaki, R., Ryan, M.B., Putnam Jr., J.B., Lee, J.S., Dhingra, H., De Caro, L., Chasen, M., McGavran, M., Atkinson, E.N. and Hong, W.K. (1994) A Randomized Trial Comparing Perioperative Chemotherapy and Surgery with Surgery Alone in Resectable Stage IIIA Non-Small-Cell Lung Cancer. Journal of the National Cancer Institute, 86, 673-680. http://dx.doi.org/10.1093/jnci/86.9.673
[18]	Roth, J.A., Atkinson, E.N., Fossella, F., Komaki, R., Ryan, M.B., Putnam, J.B., Lee, J.S., Dhingra, H., De Caro, L., Chasen, M. and Hong, W.K. (1998) Long-Term Follow-Up of Patients Enrolled in a Randomized Trial Comparing Perioperative Chemotherapy and Surgery with Surgery Alone in Resectable Stage IIIA Non-Small-Cell Lung Cancer. Lung Cancer, 21, 1-6. http://dx.doi.org/10.1016/S0169-5002(98)00046-4
[19]	Eberhardt, W., Fietkau, R., Griesinger, F., Passlick, B. and Stuschke, M. (2006) Operation und adjuvante Therapie des nicht kleinzelligen Lungenkarzinoms (NSCLC) (Stadium I bis operables IIIA). Onkologie, 29, 7-10. http://dx.doi.org/10.1159/000094948
[20]	Schmuecking, M., Plichta, K., Lopatta, E.C., Przetak, C., Leonhardi, J., Gottschild, D., Wendt, T.G. and Baum, R.P. (2000) Image Fusion of F-18 FDG PET and CT. Is There a Role in 3D-Radiation Treatment Planning of Non-Small Cell Lung Cancer? International Journal of Radiation Oncology * Biology * Physics, 48, 130. http://dx.doi.org/10.1016/S0360-3016(00)80056-5
[21]	Schmuecking, M., Baum, R.P., Griesinger, F., Presselt, N., Bonnet, R., Przetak, C., Niesen, A., Leonhardi, J., Lopatta, E.C., Herse, B. and Wendt, T.G. (2003) Molecular Whole-Body Cancer Staging Using Positron Emission Tomography: Consequences for Therapeutic Management and Metabolic Radiation Treatment Planning. Recent Results in Cancer Research, 162, 195-202. http://dx.doi.org/10.1007/978-3-642-59349-9_19
[22]	Hemmerlein, B., Paul, J., et al. (2000) Correlation of Morphometric Tumor Response after Induction Chemotherapy with Docetaxel (D) or Paclitaxel (P) and Carboplatin (P) in Stage III NSCLC. Lung Cancer, 29, 94. http://dx.doi.org/10.1016/S0169-5002(00)80309-8
[23]	Herse, B., Dalichau, H., Wormann, B., Hemmerlein, B., Schmidberger, H., Hess, C.F., Hannemann, P., Criée, C.P., Hiddemann, W. and Griesinger, F. (1998) Induction Combination Chemotherapy with Docetaxel and Carboplatin in Advanced Non-Small-Cell Lung Cancer. Thoracic and Cardiovascular Surgeon, 46, 298-302. http://dx.doi.org/10.1055/s-2007-1010242
[24]	Junker, K., Thomas, M., Schulmann, K., Klinke, F., Bosse, U. and Müller, K.M. (1997) Tumor Regression in NonSmall-Cell Lung Cancer Following Neoadjuvant Therapy. Histological Assessment. Journal of Cancer Research and Clinical Oncology, 123, 469-477. http://dx.doi.org/10.1007/BF01192200
[25]	Junker, K., Thomas, M., Schulmann, K., Klinke, V., Bosse, U. and Müller, K.M. (1997) Regression Grading of Neoadjuvant Non-Small-Cell Lung Carcinoma Treatment. Der Pathologe, 18, 131-140. http://dx.doi.org/10.1007/s002920050201
[26]	Junker, K., Langner, K., Klinke, F., Bosse, U. and Thomas, M. (2001) Grading of Tumor Regression in Non-Small Cell Lung Cancer: Morphology and Prognosis. Chest, 120, 1584-1591. http://dx.doi.org/10.1378/chest.120.5.1584
[27]	Junker, K., Müller, K.M., Abker, S., Bosse, U., Klinke, F. and Thomas, M. (2004) Zellul?re Ver?nderungen NichtKleinzelliger Lungenkarzinome Nach Neoadjuvanter Therapie. Der Pathologe, 25, 193-201. http://dx.doi.org/10.1007/s00292-003-0643-8
[28]	Rusch, V.W., Giroux, D.J., Kraut, M.J., Crowley, J., Hazuka, M., Johnson, D., Goldberg, M., Detterbeck, F., Shepherd, F., Burkes, R., Winton, T., Deschamps, C., Livingston, R. and Gandara, D. (2001) Induction Chemoradiation and Surgical Resection for Non-Small Cell Lung Carcinomas of the Superior Sulcus: Initial Results of Southwest Oncology Group Trial 9416 (Intergroup Trial 0160). Journal of Thoracic and Cardiovascular Surgery, 121, 472-483. http://dx.doi.org/10.1067/mtc.2001.112465
[29]	Thomas, M., Rübe, C., Semik, M., von Eiff, M., Freitag, L., Macha, H.N., Wagner, W., Klinke, F., Scheld, H.H., Willich, N., Berdel, W.E. and Junker, K. (1999) Impact of Preoperative Bimodality Induction Including Twice-Daily Radiation on Tumor Regression and Survival in Stage III Non-Small-Cell Lung Cancer. Journal of Clinical Oncology, 17, 1185-1193.
[30]	Klass, N.D., Boy, C., Klaeser, B., Bigler, R., Hentschel, M., Cihoric, N., Tille, J., Krause, T., Aebersold, D.M. and Schmuecking, M. (2012) Is There a Role of 99MTC-MAA SPECT/CT for Radiation Treatment Planning in Thoracic Tumors Using VMAT? Strahlentherapie und Onkologie, 188, 727-728.
[31]	Rusch, V.W., Asamura, H., Watanabe, H., Giroux, D.J., Rami-Porta, R., Goldstraw, P. and Members of IASLC Staging Committee (2009) The IASLC Lung Cancer Staging Project: A Proposal for a New International Lymph Node Map in the Forthcoming Seventh Edition of the TNM Classification for Lung Cancer. Journal of Thoracic Oncology, 4, 568-577.
[32]	Naruke, T., Suemasu, K. and Ishikawa, S. (1978) Lymph Node Mapping and Curability at Various Levels of Metastases in Resected Lung Cancer. Journal of Thoracic and Cardiovascular Surgery, 76, 832-839.
[33]	Kaplan, E.L. and Meier, P. (1958) Nonparametric Estimation from Incomplete Observations. Journal of the American Statistical Association, 53, 447-457.
[34]	Gail, M. and Gart, J.J. (1973) The Determination of Sample Size for Use with the Exact Conditional Test in 2 × 2 Comparative Trials. Biometrics, 29, 441-448. http://dx.doi.org/10.2307/2529167
[35]	Moon, S.H., Cho, S.H., Park, L.C., Ji, J.H., Sun, J.M., Ahn, J.S., Park, K., Choi, J.Y. and Ahn, M.J. (2013) Metabolic Response Evaluated by 18F-FDG PET/CT as a Potential Screening Tool in Identifying a Subgroup of Patients with Advanced Non-Small Cell Lung Cancer for Immediate Maintenance Therapy after First-Line Chemotherapy. European Journal of Nuclear Medicine and Molecular Imaging, 40, 1005-1013. http://dx.doi.org/10.1007/s00259-013-2400-4
[36]	Kim, Y.S., Lee, M.K., Kim, S.J., Kim, I.J., Kim, Y.K., Jo, W.S. and Park, S.K. (2010) Prognostic Stratification Using F-18 FDG PET/CT in Patients with Advanced Stage (Stage III and IV) Non-Small Cell Lung Cancer. Neoplasma, 57, 241-246. http://dx.doi.org/10.4149/neo_2010_03_241
[37]	Thomas, M., Rübe, C., Hoffknecht, P., et al. (2008) Effect of Preoperative Chemoradiation in Addition to Preoperative Chemotherapy: A Randomised Trial in Stage III Non-Small-Cell Lung Cancer. Lancet Oncology, 9, 636-648. http://dx.doi.org/10.1016/S1470-2045(08)70156-6
[38]	Poettgen, C., Theegarten, D., Eberhardt, W., Levegruen, S., Gauler, T., Krbek, T., Stamatis, G., Teschler, H., Kuehl, H., Bockisch, A. and Stuschke, M. (2007) Correlation of PET/CT Findings and Histopathology after Neoadjuvant Therapy in Non-Small Cell Lung Cancer. Oncology, 73, 316-323. http://dx.doi.org/10.1159/000134474
[39]	Ryu, J.S., Choi, N.C., Fischman, A.J., Lynch, T.J. and Mathisen, D.J. (2002) FDG-PET in Staging and Restaging Non-Small Cell Lung Cancer after Neoadjuvant Chemoradiotherapy: Correlation with Histopathology. Lung Cancer, 35, 179-187. http://dx.doi.org/10.1016/S0169-5002(01)00332-4
[40]	Fischer, B., Olsen, M., Ley, C., Klausen, T.L., Mortensen, J., H?jgaard, L. and Kristjansen, P.E. (2006) How Few Cancer Cells Can Be Detected by Positron Emission Tomography? A Frequent Question Addressed by an in Vitro Study. European Journal of Nuclear Medicine and Molecular Imaging, 33, 697-702.
[41]	Fischer, B. and Mortensen, J. (2006) The Future in Diagnosis and Staging of Lung Cancer: Positron Emission Tomography. Respiration, 73, 267-276. http://dx.doi.org/10.1159/000092080
[42]	Hicks, R.J., Mac Manus, M.P., Matthews, J.P., Hogg, A., Binns, D., Rischin, D., Ball, D.L. and Peters, L.J. (2004) Early FDG-PET Imaging after Radical Radiotherapy for Non-Small Cell Lung Cancer: Inflammatory Changes in Normal Tissues Correlate with Tumor Response and Do Not Confound Therapeutic Response Evaluation. International Journal of Radiation Oncology * Biology * Physics, 60, 412-418. http://dx.doi.org/10.1016/j.ijrobp.2004.03.036
[43]	Nagamachi, S., Wakamatsu, H., Kiyohara, S., Fujita, S., Futami, S., Arita, H., Tamura, S. and Kawai, K. (2010) The Reproducibility of Deep-Inspiration Breath-Hold 18F-FDG PET/CT Technique in Diagnosing Various Cancers Affected by Respiratory Motion. Annals of Nuclear Medicine, 24, 171-178. http://dx.doi.org/10.1007/s12149-010-0352-3
[44]	Schmuecking, M., Klaeser, B., Frueh, M., Toepfer, M., Malthaner, M., Born, E., Bromme, J., Vock, J., Plasswilm, L., Krause, T. and Aebersold, D.M. (2011) What Is the Additional Role of the Breath Hold Acquisition Using F-18 FDG PET/CT in Staging Non-Small Cell Lung Cancer (NSCLC) Prior to Stereotactic Body Radiotherapy (SBRT)? Strahlentherapie und Onkologie, 187, 71.
[45]	Yamashita, S., Yokoyama, K., Onoguchi, M., Yamamoto, H., Hiko, S., Horita, A. and Nakajima, K. (2014) Feasibility of Deep-Inspiration Breath-Hold PET/CT with Short-Time Acquisition: Detectability for Pulmonary Lesions Compared with Respiratory-Gated PET/CT. Annals of Nuclear Medicine, 28, 1-10. http://dx.doi.org/10.1007/s12149-013-0774-9
[46]	Betticher, D.C., Shu-Fang, H.S., Toetsch, M., et al. (2003) Mediastinal Lymph Node Clearance after Docetaxel-Cisplatinneoadjuvant Chemotherapy Is Prognostic of Survival in Patients with Stage IIIA pN2 Non-Small-Cell Lung Cancer: A Multicenter Phase II Trial. Journal of Clinical Oncology, 21, 1752-1759. http://dx.doi.org/10.1200/JCO.2003.11.040
[47]	Martini, N., Kris, M.G., Flehinger, B.J., Gralla, R.J., Bains, M.S., Burt, M.E., Heelan, R., McCormack, P.M., Pisters, K.M.W., Rigas, J.R., Rusch, V.W. and Ginsberg, R.J. (1993) Preoperative Chemotherapy for Stage IIIa (N2) Lung Cancer: The Sloan-Kettering Experience with 136 Patients. Annals of Thoracic Surgery, 55, 1365-1374. http://dx.doi.org/10.1016/0003-4975(93)91072-U
[48]	Hellwig, D., Graeter, T.P., Ukena, D., Georg, T., Kirsch, C.M. and Schafers, H.J. (2004) Value of F-18-Fluorodeoxyglucose Positron Emission Tomography after Induction Therapy of Locally Advanced Bronchogenic Carcinoma. Journal of Thoracic and Cardiovascular Surgery, 128, 892-899. http://dx.doi.org/10.1016/j.jtcvs.2004.07.031