medwireNews: The BONSAI trial has demonstrated encouraging efficacy and manageable toxicity of cabozantinib in treatment-naïve patients with metastatic collecting duct renal cell carcinoma (RCC).
The study met its primary endpoint of objective response rate (ORR), “reaching a noticeable ORR of 35%,” say Giuseppe Procopio (Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy) and co-investigators in JAMA Oncology.
They therefore propose that “cabozantinib may be considered as a therapeutic option” for this uncommon type of non-clear cell RCC “with poor prognosis and no standard treatment.”
In the single-center, phase 2 trial, 23 patients with previously untreated metastatic collecting duct carcinoma received oral cabozantinib at a daily dose of 60 mg until disease progression or unacceptable toxicity.
Of the 22 evaluable patients, one achieved a complete response and seven had a partial response, giving an ORR of 35%. An additional three patients had stable disease and the remaining 11 had progressive disease.
The median progression-free survival (PFS) was 4 months and median overall survival (OS) was 7 months; 43% of patients were alive and 23% were continuing treatment at the 12-month mark.
All participants experienced at least one grade 1–2 adverse event (AE), with the most common being fatigue (60%), followed by anorexia (39%), hand–foot syndrome (30%), hypothyroidism (30%), mucositis (30%), diarrhea (22%), and hypertension (13%).
There were six AEs of grade 3 – two cases each of arterial hypertension and fatigue, and one each of pulmonary thromboembolism and bleeding – but there were no grade 4 or 5 AEs.
A total of 17% of patients required a dose interruption due to AEs and an identical proportion needed a dose reduction to 40 mg/day, but no participant discontinued treatment permanently as a result of toxicity.
Discussing the results, Procopio and colleagues say that “[p]laced in the context of the little prospective evidence available, the results of the BONSAI trial are promising.”
They highlight the need for caution with cross-trial comparisons, but note that single-agent cabozantinib “appeared to be more active than platinum-gemcitabine chemotherapy” in this setting “and resulted in similar antitumor activity compared with the combination of platinum-based chemotherapy plus sorafenib.”
Furthermore, the toxicity profile of cabozantinib appeared to be more favorable than platinum–gemcitabine without or with sorafenib, say the researchers.
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