4094 - Treatment outcomes for adult patients with localized osteosarcoma treated with chemotherapy without methotrexate

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 < 6 cycles: HR 0.25, 95% CI 0.07 – 0.83, P = 0.025).

Conclusions

Adult pts with localized osteosarcoma treated with CT without MTX had unfavorable survival outcomes in comparison with the literature for pediatric pts. A number of neoadjuvant/ adjuvant CT cycles of 6 or more was associated with superior OS. Improving therapeutic approaches for adult pts is of utmost importance to achieve better results.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.