1692PTreatment outcomes for adult patients with localized osteosarcoma treated with chemotherapy without methotrexate

Abstract Background In pediatric patients (pts) with localized osteosarcoma, cure rates higher than 60% have been reported. A chemotherapy (CT) regimen frequently suggested as standard in this scenario is the three-drug regimen MAP (methotrexate [MTX], doxorubicin, and cisplatin). However, the addition of MTX remains controversial, especially in adult pts in whom high-grade toxicities are frequent. We aimed to evaluate the outcomes of adult pts with localized osteosarcoma after treatment with CT without MTX. Methods A single-center cohort of adult pts with high-grade osteosarcoma treated with CT without MTX was retrospectively evaluated. Pts were treated between 2007 and 2018. Overall survival (OS) was calculated from the date of diagnosis to death. Recurrence-free survival (RFS) was time from diagnosis to recurrence or death. Kaplan-Meier method was used for survival analysis. Prognostic factors were evaluated with Cox regression. Results A total of 97 consecutive adult pts with osteosarcoma were studied. Median age was 27 years (range 16 – 69). Primary tumor site was extremity in 79.4% of pts (N = 77), and axial in 20.6% (N = 20). Most pts (N = 61; 63%) presented localized resectable disease, while 36 (37%) had unresectable or metastatic disease. Among pts with localized resectable disease, 56 (91%) pts received neoadjuvant/ adjuvant CT without MTX: 48 (86%) received cisplatin and doxorubicin; 8 (14%) received other combinations of cisplatin, doxorubicin, ifosfamide, and/or etoposide. With a median follow-up of 34 months, 3-year and 5-year RFS rates were 42.4% (IC 95% 28 – 55%) and 37.1% (IC 95% 23 – 50%). 3-year and 5-year OS rates were 81.6% (95% CI, 67% – 90%) and 67.3% (95% CI, 48% – 80%). Median RFS and OS were 31.8 months and not reached, respectively. The only factor associated with OS was the number of neoadjuvant/ adjuvant CT cycles (≥ 6 vs