In search of effective therapies: the current landscape of phase II trials in patients with advanced soft tissue sarcoma

Purpose Soft tissue sarcomas (STS) are diagnosed in 4-6 cases per 100 000 people a year and are associated with an unfavorable prognosis. Around one-third of patients will develop metastatic disease that requires palliative systemic therapy. Current therapeutic options have limited activity, and new treatments are tested, mainly in phase II trials. There is high variability and no standardization of phase II designs. We aimed to analyze the current landscape of phase II studies in STS and evaluate how its statistical design can affect the results. Methods Full-text phase II studies published in STS patients between 2005 and 2020 were identified and analyzed. Results We have identified 102 trials, of which 77.4% were single-arm trials, 16.7% were randomized comparative trials (RCT), and 5.9% were randomized noncomparative trials. Including multiple cohorts, 22 randomized and 128 single-arm cohorts were analyzed. Nearly 80% of trials reported full statistical bases of the design. Over 20 different primary endpoints were used, with PFS as the most common in RCT trials (81.8%) and ORR (36.7%) and 3-months progression-free survival (PFS) rate (21.9%) in single-arm trials. Overall, 27.3% of RCT and 37.5% of single-arm trials were positive. Among single-arm trials, studies using 3- or 6-month rates were more often positive than those based on ORR. Conclusions There is high heterogeneity in sarcoma trial designs, mainly in primary-endpoint and hypotheses used for size calculation. There is an unmet need for standardization that will incorporate factors associated with the rarity of the disease, outcomes detected in previous trials and real-life studies, and specific characteristics of new therapeutic agents.