Advances in soft-tissue sarcoma - There are no mistakes, only lessons to learn!

In this decade the treatment of advanced sarcoma has seen many highs and lows in terms of successful trials and failed trials. This is possible due to great collaborations, newer therapies and histology focused trials.

In ASCO 2019 many sarcoma trials were presented and we chose 3 challenging clinical trials that widen our perspective on soft tissue sarcoma. We have critically analyzed the data and have discussed the implications of these trials on current practice. First trial was ANNOUNCE trial which was done to confirm the efficacy of olaratumab after its dramatic success in advanced soft tissue sarcoma in a phase 2 trial. Another trial STRASS trial, which was unique because of being first successfully conducted randomized trial addressing preoperative radiotherapy in retroperitoneal soft tissue sarcoma. Third trial was phase 2 trial SARC 028 trial exploring the role of immunotherapy in pleomorphic undifferentiated sarcoma and liposarcoma subgroup.

ANNOUNCE trial failed to show OS benefit in olaratumab/doxorubicin arm as compared to doxorubicin/placebo arm. Based upon this FDA has revoked the approval of olaratumab leading to nihilism and disappointment amongst oncologists. In STRASS trial failed to meet the primary end point though there was a benefit in the liposarcoma subgroup in terms of abdominal recurrence free survival. There are several reasons that this trial might have failed. First, RPSs are not homogeneous population. RPSs might behave very differently as per the histopathology ranging from well differentiated LPS to leiomyosarcoma. Since the event rate in well-differentiated liposarcoma might happen late, the median follow-up of 43 months might not be sufficient. In SARC trial ORR in pleomorphic undifferentiated sarcoma (PUS) cohort was 9/40 (22.5%), while response rates in liposarcoma cohort were 4/39 (10.2%). There was poor correlation between the response and the tumor cells' PD-L1 positivity. Simultaneously, we must not take for granted the role of pembrolizumab in PUS as the previous study (PEMBROSARC) had also showed dismal outcomes with immunotherapy.

In this paper we discuss the intricacies of these trials and how they affect the rapidly changing landscape in advanced soft tissue sarcoma.