Differences in the responses to pazopanib and the prognoses of soft tissue sarcomas by their histological eligibility for the PALETTE study

In Japan, pazopanib has been made available to soft tissue sarcoma patients, also to patients histologically diagnosed as ineligible for the international Phase 3 study (PALETTE). However, clinical evidence for the use of pazopanib in PALETTE-ineligible patients is currently insufficient. We retrospectively reviewed medical records of soft tissue sarcoma patients treated with pazopanib at our institute. By pathological review, the patients' eligibility for the PALETTE study was evaluated and the differences in their responses to pazopanib and incidences of adverse events were investigated. From November 2012 to August 2014, a total of 47 patients received pazopanib, 38 (81%) of whom were histologically eligible for the PALETTE study, and 9 of whom (19%) were not. The median follow-up time was 7.5 months (range 1.4-20.3 months). An objective response was observed in both groups, but the patients' survival tended to be longer in the PALETTE-eligible patients; median progression-free survival was 4.5 months vs. 2.9 months (P = 0.15) and overall survival was 10.7 months vs. 7.8 months (P = 0.55), though these differences were not statistically significant. There were no significant differences in the incidence of adverse events by PALETTE eligibility, but dose skipping or dose reduction was more likely to be observed in PALETTE-ineligible patients. Pazopanib is tolerable to soft tissue sarcoma patients ineligible for the PALETTE study and some of them respond to pazopanib, but the prognoses of patients ineligible for the PALETTE study might be worse than those of PALETTE-eligible patients. The indication of pazopanib for soft tissue sarcoma patients with PALETTE-ineligible histologies should be decided carefully.