Patients with metastatic or non-metastatic NRSTS were eligible to enroll if they had initially unresectable extremity or trunk tumors with the expectation that they would be resectable after therapy. Patients had to be 2 years or older— there was no upper age limit—and had to be able to swallow a tablet whole. The dose-finding phase of the study determined the pediatric dose to be 350 mg/m2 and the adult dose to be 600 mg/m2, both taken orally and once daily. Patients in the chemotherapy cohort were then randomized to receive chemotherapy—ifosfamide and doxorubicin—with or without pazopanib. At 4 weeks, patients in both arms received preoperative radiotherapy (45 Gy in 25 fractions), and at week 13, surgery of the primary site if they did not have progressive disease. After surgery, patients received continuation therapy with or without pazopanib according to their randomization arm. Upon completion and recovery from the continuation therapy, patients could receive surgery/radiotherapy of their metastatic sites.
Results
As of the June 30, 2018, cutoff, 81 patients were enrolled on the chemotherapy arms: 42 in the pazopanib plus chemoradiation arm and 39 in the chemoradiation-only arm. Sixty-one percent of all patients were 18 years or older, and the median age was 20.3 years. Most patients (73%) did not have metastatic disease, and the major histologies represented were synovial sarcoma (49%) and undifferentiated pleomorphic sarcoma (25%).
At week 13, patients in the pazopanib arm showed significant improvement, with 14 (58%) of those evaluated having pathologic necrosis of at least 90%, compared with 4 (22%) in the chemoradiation-only arm (P=.02). The study was closed to further accrual.
Eighteen patients were not evaluable for pathologic response and 21 were pending pathologic evaluation at week 13. Radiographic response rates were not statistically significant on either arm. No complete responses (CR) were achieved in the pazopanib arm, but 14 patients (52%) achieved a partial response (PR) and 12 (44%) had stable disease (SD). In the chemoradiation-only arm, 2 patients (8%) achieved a CR, 12 (50%) a PR, and 8 (33%) SD. Fifteen patients in each arm were not evaluated for radiographic response.
The pazopanib arm experienced more febrile neutropenia and myelotoxicity during induction and continuation phases than the chemoradiation-only arm. In general, investigators indicated pazopanib combined with chemoradiation was well tolerated and no unexpected toxicities arose during the trial.
In the post-presentation discussion, Dr. Raphael E. Pollock, MD, PhD, of The Ohio State University, called it a tremendous challenge to interdigitate primary local therapies in systemic approaches, particularly in the neoadjuvant context. He pointed out that in an earlier study, a 95% to 100% necrosis level was needed to achieve a significant positive impact on outcomes and perhaps a subsequent prospective trial could determine the best level. He questioned whether the availability of only 60% of patient responses could affect the conclusions and whether the high number of toxicities (73.8% grade 3/4 with pazopanib) might be too high to consider the treatment for most patients, given the intensity of the regimen.
SOURCE: Weiss AR, et al. J Clin Oncol 37, 2019 (suppl; abstr 11002)
The study was sponsored by the National Cancer Institute.
Drs. Weiss and Pollock had no relationships with commercial interests to disclose. A few investigators disclosed advisory, consulting, or research roles with pharmaceutical companies, including one who received institutional research funding from Novartis (pazopanib).
Gemcitabine Plus Pazopanib a Potential Alternative in STS
In a phase 2 study of gemcitabine with pazopanib (G+P) or gemcitabine with docetaxel (G+D), investigators concluded the combination with pazopanib can be considered an alternative to that with docetaxel in select patients with advanced soft tissue sarcoma (STS). They reported similar progression-free survival (PFS) and rate of toxicity for the two regimens. Neeta Somaiah, MD, of the University of Texas MD Anderson Cancer Center in Houston, presented the findings of the investigator-initiated effort (NCT01593748) at ASCO.