TREATMENT OUTCOMES AND PROGNOSTIC FACTORS FOR ADULT PATIENTS WITH OSTEOSARCOMA AFTER PROGRESSION ON FIRST-LINE CHEMOTHERAPY: A 10-YEAR ANALYSIS

Background Studying osteosarcoma in adult patients (pts) is challenging due to its rarity. For pts with unresectable or metastatic disease, treatment strategies remain limited, especially after progression on first-line chemotherapy (CT). We studied a cohort of adult pts with osteosarcoma with the aim of evaluating the outcomes and prognostic factors after progression on first-line CT. Methods A cohort of adult pts with osteosarcoma who progressed on first-line CT was retrospectively evaluated. Pts were treated between 2008 and 2018 in an academic cancer center. Overall survival (OS) was calculated from time of progression on first-line CT to death. Kaplan-Meier method was used for survival analysis. Prognostic factors were evaluated with Cox regression. Results A total of 70 consecutive adult pts with osteosarcoma were studied. Median age was 27 years (range 16 69). Primary tumor site was lower limb, upper limb and axial in 68.5%, 11.4%, and 20% of pts, respectively. Most pts (N = 49) presented localized disease at diagnosis (EI, 8.5%; EII, 48.5%; EIII 12.8%), but 51% of them (N = 25) recurred. Metastatic disease (EIV) at presentation occurred in 21 pts (30%). Thirty-six pts with advanced disease (at presentation or after recurrence) progressed after first-line CT. Among these pts, 77.8% (28/36) received second-line CT and 33.3% (12/36), third-line CT. Most common CT regimens were ifosfamide plus etoposide (N = 19) as second-line and gemcitabine plus docetaxel (N = 4) or oral ciclofosfamide (N = 4) as third-line. After progression on first-line chemotherapy, median OS was 16.4 months (95% CI, 9.3 NR). One-year and 3-year OS rates were 63.1% (95% CI, 43 77%) and 32.4% (95% CI, 13 53%), respectively. Factors associated with inferior OS were ECOG performancestatus (PS) 3-4 (HR 71.7, 95% CI 6.75 761.7, P < 0.001), EIV at diagnosis (HR 11.7, 95% CI 3.2 42.3, P < 0.001), and telangiectatic histologic subtype (HR 17.8, 95% CI, 1.5 211.4, P = 0.022). Gender, age, and primary tumor site were not associated with survival. Conclusion After progression on first-line CT, adult pts with osteosarcoma present poor survival outcomes. ECOG PS 3-4, metastatic disease at diagnosis and telangiectatic histologic subtype were identified as prognostic factors.