Bone Metastases : Experience of Rheumatology Unit of National Hospital University Hubert Koutoukou Maga of Cotonou

Aim: To determine the epidemiological, diagnosis and treatment of secondary bone cancer at the National Hospital University Hubert Koutoukou Maga of Cotonou. Patients and Method: It was a retrospective descriptive cross-sectional study carried out from January 1999 to December 2013 on the records of patients treated in the rheumatology department. The selected files had radiological images of tumor appearance objectified by two radiologists. The diagnosis of secondary bone cancer was confirmed after a bone biopsy or the discovery of a primitive tumor site. Patients with hematologic malignancy and incomplete or insufficiently explored records were excluded. Results: Among 10,292 patients followed in the service, 51 (0.5%) had documented bone metastasis. The sex ratio was 1.83. The mean age of patients was 54 ± 9 [26 85] years, with 53% of those over 60 years old. Secondary cancers were on the spine (74.5%), pelvis (35.3%) and the long bones (39.2%). The primary cancer most frequently found was that of the prostate and breast (45.1% and 27.6%, respectively) followed by genital and digestive cancers (9.8% and 7.8%, respectively). Treatment was dominated by hormone therapy (83%) bisphosphonates (70.5%) and chemotherapy (57%). Conclusion: The profile of bone cancer in Benin hospital is very diverse and dominated by the types and osteolytic ostéocondensant. Primary cancers were dominated by the prostate and breast. Bisphosphonates took an important place in the treatment of the disease.


Introduction
Bone is the third site of metastasis of cancer after the liver and lungs.This underpins that the bone is a good "soil" for the "seed" tumor.The inaugural metastases are common and represent 22.6% to 30% of bone metastases [1]- [3].The primary focus of these metastases is often the prostate, breast, kidney, lung and thyroid.Cancers of the five foci represent between 80% and 96% of cancers responsible bone metastases [2]- [5].
The recognition of a secondary bone tumor based on the comparison of epidemiological, clinical, radiological and pathological.Imaging of bone tumors remains dominated by X-ray.
Their treatment requires a multidisciplinary approach.Radiation therapy is one of the key resources available to treat bone metastases near all medical or surgical arsenals [4].According to Conroy, the median survival of bone cancer is five months after diagnosis with 5% at five-year survival and 1% at ten-year survival [3].Many African studies have discussed the issue as reflected the recently published [6]- [11].In Benin, no study has been done on bone metastases.The objective of this study was to clarify the epidemiological, diagnostic and therapeutic aspects of bone metastases in the Rheumatology Department of the National Hospital University Hubert Koutoukou Maga of Cotonou.

Patients and Method
It was a descriptive and retrospective cross-sectional study, carried out over 15 years from 1999 to December 2013 on the records of patients treated in the rheumatology department.Patients met the following criteria: • Have consulted or been hospitalized in the rheumatology department during the study period; • Have presented an inflammatory bone pain or pathological fracture of long or flat bones or bone swelling related to a secondary bone cancer.The diagnosis of secondary bone cancer was confirmed after a bone biopsy or the discovery of a primitive cancer.
Patients with hematologic malignancy or with incomplete or insufficiently explored records were excluded from the study.
Variables evaluated were: socio-demographic (age, sex), therapeutic itinerary, cliniac features (pain, fever, lameness), radiological, etiological and therapeutic parameters.The statistical analysis of results was performed using Epi info 7.0 software and STATA/IC 11.0.
This investigation was approved by the local Ethics Committee.

Socio-Demographic Data
Among 10,292 patients seen in the unit of Rheumatology (about 750 patients per year), 51 (0.5%) had bone metastases.There were 33 men and 18 women (sex ratio = 1.83).The mean age of patients was 54 ± 9 [26 -85] years and 53% of those were over 60 years.

Therapeutic Itinerary
Before their arrival in the unit, 30 patients (59%) had preferred a traditional healer, 17 patients (33%) were referred by a city health officer and 4(8%) patients consulted directly by friends.

Clinical Features
The reasons for consultation cases of bone secondary cancers are shown in Figure 1.The pain was seen as a frequently symptom with 44 cases, or 86%.

Paraclinical Features
X-ray was the main radiological examination performed in patients.Bone metastases frequently sat at the spine (lumbar and thoracic), long bones and pelvis.Table 1 shows the breakdown by site of bone metastases.Figure 2 shows the distribution by site and the nature of the primary cancer that gave bone metastasis.The bone lesions were essentially condensing and lysis.Table 2 shows the radiographic features of bone lesions.The prostate   cancer gave mostly bone condensing metastases while breast cancer gave exclusively bone lysis metastases.
Figure 3 shows the distribution of the type of injury according to the nature of the primary tumor that gave bone metastasis.
Metastases were inaugural in 16 cases leading to the realization of a surgical biopsy in 5 cases and percutaneous in 4 cases.Tumor markers were assayed in all patients and was contributory in 35 cases (Prostatic Specific Antigen in 23 cases, CA 15.3 in 5 cases, CA 125 in 4 cases, Alfa Foeto Protein in 2 cases and carcinoembryonic antigen in 1 case).Primary cancers are reported in Table 3.
Eleven (11) patients died during hospitalization and survival at 6 months was estimated at 71.4%.

Discussion
Although Tubiana-Hulin has reported that bone metastases accounted for over 90% of malignant disease of the bone [5], they are relatively rare in our series (51 patients had bone metastases over 15 years) and other African series like the recently published works (77 cases in 19 years in Togo and 81 cases in 7 years in Congo) [6] [7].
The frequency of bone metastases is certainly underestimated in the world.Indeed, some post-mortem series seeking to determine the prevalence of bone metastases at death revealed it can reach up to 73% [5].Male predominance has been reported by the same authors in their series.This dominance is classic as described by many authors [8]- [12].It seems to be explained by the frequency of prostate cancer which diagnosis is easy in our professional context [13] [14].The mean age of patients was 54 ± 9 [26 -85] years.These data were found in African work such as Kouakou in Cote d'Ivoire in 1994 [15], Ntsiba in Congo in 2013 [7] and Oniankitan in Lome in 2014 [6].Bone metastases appear later in the Western series represented by Houze et al. and Vandecandelaere et al. who reported 77 and 63 years old for mean age of their patients respectively [14] [16].
In X-rays, radiological lesions were usually multiple with an equal proportion of osteoblastic and osteolytic lesions.These lesions mainly sit on pelvis, spine and femur.This distribution of the lesions was found by Oniankitan [6].The achievement of the long bones was present in 18.2% of their patients.The same observations were made in the series of Ntsiba with a majority reached at the lumbar spine (33.3%), femur (19.0%) and pelvis (14.3%) [7].These African data are similar to those published by other Maghrebian and Western authors [12] [16].This appears as geographic distribution in the case of prostate cancer.Prostate is located in the pelvis and its cancer metastasis in pelvis, thoracolumbar spine and the femur.On the other side, the geographical distribution is less obvious in breast cancer cases.However, the extraordinary mass and exchange surface that forms the spine appears to be one explanation for the preponderance of spinal disease [16].
The distribution of the primay cancer is the same as African [6]- [12] and Western series [5] [16].It was unknown in 1.9% of cases in our series unlike the Ntsiba where it was 6.2% [7].

Conclusion
The occurrence of bone metastases was relatively frequent in carcinomas of the prostate, breast and stomach.In our country, a good physical examination of the patient combined with radiological images allows referral to the primary tumor.

Figure 1 .
Figure 1.Distribution of the patients according to the symptoms.

Figure 2 .
Figure 2. Distribution of the patients according to the primary cancer.

Figure 3 .
Figure 3. Type of radiological lesion of bone according to the primary cancer.

Table 1 .
Distribution of bone metastases.

Table 2 .
Radiological features of bone metastases.

Table 3 .
Distribution of patients according to the primary cancer.