The fate of new fosfamides in phase III studies in advanced soft tissue sarcoma

Abstract

For decades, doxorubicin alone or in combination with ifosfamide has been used in advanced soft tissue sarcoma (STS). In 2014, a comparison of doxorubicin alone versus the combination with ifosfamide (in the randomised phase III EORTC 62012) showed no difference in overall survival (OS), but a difference in response and progression-free survival (PFS) were observed in favour of the combination but at the expense of increased toxicity. Newer fosfamides, with slightly different modes of action, and potentially less toxicity, namely evofosfamide and palifosfamide have recently been tested in randomised phase III clinical trials in STS. The TH CR-406/SARC021 (June 2017) and the PICASSO III (September 2016) studies compared doxorubicin, as the standard arm, to doxorubicin in combination with evofosfamide and palifosfamide, respectively. In both studies, the combination arm produced increased response rates but at the expense of higher toxicity. However, there was no difference in OS or PFS in favour of the combination. Importantly, the median OS of patients receiving standard of care, doxorubicin, in both studies appeared improved from 12.8 months (95.5% CI 10.5-14·III) in the EORTC 62012 to 16.9 months (95% CI 14.8 to 22.9) in PICASSO III and 19.0 months (95% CI 16.2-22.4) in TH CR-406/SARC021. The results of these three randomised phase III studies highlight several critical issues related to the design and conduct of such trials in STS. We discuss these issues aiming to contribute to the ongoing debate about the optimal approach to perform clinical research in STS.

Keywords: Advanced soft tissue sarcoma; Evofosfamide; Fosfamides; Ifosfamide; Palifosfamide; Phase III; Trial design.