Primary osteosarcoma of the ribs: A report from the Cooperative Osteosarcoma Study Group

Purpose Primary rib osteosarcoma has not been investigated extensively, and clinical characteristics and optimal therapeutic strategies have not been defined. The authors used the database of the Cooperative Osteosarcoma Study Group (COSS) to analyze this tumor‐site in depth. Methods The COSS database was searched for treatment‐naive, high‐grade osteosarcomas of the rib. Affected patients were analyzed for demographic and tumor‐related factors, treatments, and outcomes. Results A total of 44 patients (23 males, 21 females; median age, 23 years [range, 6–59]) were identified. Primary metastases were detected in six of 44 (14%) patients. Surgery was performed in 40 of 44 (91%) patients and rendered 35 of 44 (80%) patients macroscopically disease‐free. Chemotherapy was known to have been administered in 43 of 44 (98%) patients and radiotherapy in seven of 42 (17%) (no data for two patients). A good response to chemotherapy was only noted in five (33%) of those 15 evaluable patients who had received any preoperative chemotherapy. After a median follow‐up of 2.49 (0.22–40.35) years for all patients and 6.61 (0.25–40.35) years for 26 survivors (21 of these in first complete remission), 5‐year actuarial overall and event‐free survival were 53.0% (8.5%) and 42.2% (8.1%), respectively. Incomplete tumor surgery was the most notable negative prognostic factor. Osteoblastic histology and a poor response to chemotherapy may have contributed. Conclusion This large series provides evidence that patients with costal primaries are older than the average osteosarcoma patient, but appear to share the similar tumor biology and—if treated according to standard protocols—prognostic factors with tumors of other sites. Early, preoperative diagnosis and permanent, definitive local control remain major challenges and should contribute to improved outcomes. The same treatment strategies used for extremity primaries should be used for osteosarcomas arising in a rib. The risk of local failure is substantial, but overall results are otherwise acceptable.