Predicting early relapse in patients with BRAFV600E melanoma with a highly sensitive blood BRAF assay.
8516 Background: Many patients (pts) with metastatic melanoma (MM) who progress on BRAF inhibitors (BRAFi) develop rapidly progressive disease (PD) which is difficult to manage. Identification of an early marker of PD may allow for therapeutic intervention prior to clinical deterioration. We have developed a highly sensitive and inexpensive assay in our laboratory which can detect as little as 1 BRAFV600E mutant melanoma cell in 400,000 peripheral blood lymphocytes (PBL). We aimed to determine the utility of our assay as a tool to follow pts with BRAF mutant MM who are being treated with a BRAFi. Methods: Every pt had a BRAFV600E mutation detected from a tumor sample in a CLIA-approved laboratory prior to commencing BRAFi therapy. 20 pts with stage IV BRAFV600E MM underwent serial venopunctures before and every 4 weeks during treatment with a BRAFi. BRAFV600E level was quantified using our proprietary assay (Panka et al Melanoma Research 2010). Serial BRAFV600E levels were generated for every pt and normalized to the pre-treatment value. BRAFV600E level was then correlated with response to therapy and PD. Results: BRAFV600E was detected in the PBL of each pt. To date, 10 pts have had BRAFV600E levels quantified at 3 or more time points (data for all 20 pts will be available at time of presentation). Relative BRAFV600E levels reduced by half following the first and second cycles of treatment in 7 pts, which correlated with disease regression in each pt. Following the third cycle of treatment, the relative BRAFV600E levels varied greatly with a subset of pts having continued suppression while others having a rise in their BRAFV600E levels. In each pt with PD, the BRAF assay showed an increase > 4 wks in advance of clinically or radiographically defined PD. Conclusions: Our assay is able to quantify changes in BRAFV600E levels in the blood of pts with BRAF mutant MM receiving BRAFi therapy. In these pts, the BRAFV600E levels are reduced in the setting of initial disease regression and increase well in advance of clinical or radiographic PD. While further development is necessary, such a test could be used to identify pts who may be selected to receive alternative therapy prior to clinical or radiographic PD.