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Simple Summary Pelvic osteosarcoma has a poor prognosis compared to osteosarcomas in other locations, and the reasons for this remains unknown. Surgical resection of pelvic osteosarcoma is technically demanding and often results in dysfunction and complications. In this study, we investigated the reasons underlying the poor prognosis of pelvic osteosarcoma by comparing it to femoral osteosarcoma using data from the Bone Tumor Registry in Japan. We used propensity score analysis to determine whether surgical resection of pelvic osteosarcoma improved its prognosis. We demonstrated that pelvic osteosarcoma had a poor prognosis because it occurred more often in the elderly, often had a larger tumor size, and had metastasis at presentation more often in comparison to femoral osteosarcoma. These three factors were also associated with the non-surgical treatment of pelvic osteosarcoma, which also led to a poor outcome. The overall survival rate was only comparable in pelvic osteosarcoma and femoral osteosarcoma in cases treated with surgical resection. Propensity score analysis revealed that surgical treatment improved the prognosis of pelvic osteosarcoma. As such, we propose that surgical resection should be considered based on tumor stage and patient age in order to improve the prognosis of pelvic osteosarcoma. Abstract Pelvic osteosarcoma has a poor prognosis compared to osteosarcomas in other locations, and the reasons for this remain unknown. Surgical resection of pelvic osteosarcoma is technically demanding and often results in dysfunction and complications. In this study, we investigated the reasons underlying the poor prognosis of pelvic osteosarcoma by comparing it to femoral osteosarcoma using data from the Bone Tumor Registry in Japan. We used propensity score analysis to determine whether surgical resection of pelvic osteosarcoma improved its prognosis. We demonstrated that pelvic osteosarcoma had a poor prognosis because it occurred more often in the elderly, often had larger tumor size, and had metastasis at presentation more often in comparison to femoral osteosarcoma. These three factors were also associated with the non-surgical treatment of pelvic osteosarcoma, which also led to a poor outcome. The overall survival rate was only comparable in pelvic osteosarcoma and femoral osteosarcoma in cases treated with surgical resection. Propensity score analysis revealed that surgical treatment improved the prognosis of pelvic osteosarcoma. As such, we propose that surgical resection should be considered based on tumor stage and patient age in order to improve the prognosis of pelvic osteosarcoma.

Surgeries of pelvic bone tumors are very challenging due to the complexity of anatomical structures and the irregular bone shape. CT and MRI are used in clinic for tumor evaluation, each with its own advantages and shortcomings. Combining the data of both CT and MRI images would take advantage of the merits of both images and provide better model for preoperative evaluation. We utilized an artificial intelligence (AI)-assisted CT/MRI image fusion technique and built a personalized 3-D model for preoperative tumor margin assessment. A young female patient with pelvic osteosarcoma was evaluated with our novel image fusion 3-D model in comparison with the 3-D model based solely on CT images. The fusion image model showed more detailed anatomical information and discovered multiple emboli within veins which were previously neglected. The discovery of emboli implied abysmal prognosis and discouraged any attempts for complex reconstruction after tumor resection. Based on the experience with this pelvic osteosarcoma, we believe that our image fusion model can be very informative with bone tumors. Though further validation with a large number of clinical cases is required, we propose that our model has the potential to benefit the clinic in the preoperative evaluation of bone tumors.

Aims and backgroundInformation is scarce on systemic treatment of pelvic osteosarcoma because most chemotherapy protocols for osteosarcoma include patients with extremity tumors and aged up to 30–40 years.MethodsData on patients ResultsForty patients between 11 and 36 years were included. The most frequent histological subtype was osteoblastic followed by chondroblastic (37.5%). Complete surgical remission was achieved in 65% of patients. Eighteen patients had MAP/standard-dose ifosfamide, 22 MAP/high-dose ifosfamide. Primary chemotherapy was given to 25 patients and 6 (24%) of them had a good histological response. Median follow-up was 32 months (range, 4–134). Five-year overall survival was 27.5%: 33% in localized and 0 in metastatic patients (P = 0.02); 45% in patients with complete surgical remission and 0 for patients without complete surgical remission (P = 0.001). Local recurrence rate was 46%. In patients with complete surgical remission, 5-year overall survival was 32% with MAP/standard-dose ifosfamide and 59% with MAP/high-dose ifosfamide regimen (P = 0.3).ConclusionsLocal control is the major issue in the treatment of pelvic osteosarcoma. Poor pathological response and high incidence of chondroblastic variant indicate different characteristics between pelvic and extremity osteosarcoma. Chemotherapy with MAP and high-dose ifosfamide might be beneficial in patients with pelvic osteosarcoma and warrants further investigation.