A pilot study of the neoadjuvant use of vemurafenib plus cobimetinib in patients with BRAF-mutant melanoma with palpable lymph node metastases: Survival results.

Abstract

9579 Background: Melanoma patients with palpable nodal metastases have a very poor prognosis with the majority recurring within the first 2-3 years post-resection with survival ranging from 20-50% at 5 years. We aimed to ascertain if patients with a BRAF V600 mutation that receive vemurafenib and cobimetinib before surgery (neoadjuvantly) have a higher probability of resectability, pathologic complete response (pCR), and a lower risk of local recurrence and a longer disease free survival (DFS), distant metastatic free survival (DMFS) and overall survival (OS). Methods: This was a single arm, prospective, multi centre phase II study in patients with histologically confirmed, BRAF V600 mutated Stage IIIB and IIIC melanoma (AJCC 7th Edition) with palpable nodal disease. Patients received vemurafenib 960mg PO BID and cobimetinib 60mg PO OD for 4 months prior to resection followed by 8 months of adjuvant therapy post-surgery. CTscans were performed at baseline and before resection and every 6 months for the first 3 years and yearly in year 4 and 5. Biopsies for correlative studies and diagnosis were performed at baseline prior to starting therapy. The primary outcomes were the proportion of patients achieving resectability, radiologic response as per RECIST and the proportion of patients achieving a pCR. Presented here are the LRFS, DMFS, DFS and OS. Results: Twenty-four patients were enrolled and received neoadjuvant vemurafenib and cobimetinib and 21 underwent resection. Following resection and pathological evaluation 12 (57%; 95% CI 34.02-78.18)) patients achieved a pCR, 8 (38%; 95% CI 18.11-61.56) had a partial pathologic response and 1 had no pathologic response. Of the 24 patients, 2 patients (8%) developed local recurrence, 6 patients (25%) developed distant metastasis, and 8 patients (33%) had either local or distant recurrences. 7 patients (29%) died due to metastatic disease. At 60 months, LRFS was 89.5% (76.7-100%), DMFS was 75.0% (59.5-94.5%), DFS was 85.7% (72.0-100%), and OS was 63.9% (95% CI 43.5-93.8). Among total 20 evaluable patients, 17 patients had CR/PR and 3 had PD/SD as best response. There was no significant difference between patients with CR/PR or SD/PD (log-rank p-value = 0.0548) with 48 month survival of 82.4% for CR/PR population compared to 33.3% with SD or PD. Conclusions: In this small phase II study, neoadjuvant vemurafenib and cobimetinib led to a higher LRFS, DMFS, DFS and OS of all resected patients with bulky nodal disease compared to historical survival rates. Clinical trial information: NCT02036086 .