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Abstract 564:BRAFV600mutation in circulating tumor DNA can predict outcomes in early-stage melanoma

Background: Up to 70% of patients with resected high-risk melanoma develop disease recurrence within 5 years. Adjuvant immunotherapy or targeted therapy can reduce the recurrence rate below approximately 60%. It is, however, at the cost of possible toxicity including long-term side effects. We hypothesize that detection of plasma-derived circulating tumor DNA (ctDNA) from patients with resected melanoma can identify patients at high-risk of disease recurrence. Methods: We developed an ultrasensitive and specific droplet digital PCR (ddPCR) - based method (Bio-Rad) to detect BRAFV600E-mutated ctDNA in pre-amplified cell-free DNA with sensitivity up to 2 mutant copies in the wild-type background. Plasma samples from patients with surgically resectable melanoma were collected before and after surgery and during follow-up visits for BRAFV600E ctDNA detection. Results obtained from ddPCR analysis were correlated with clinical outcomes. Results: Total of 53 patients with resectable melanoma (29 males [54.7%]; 15 stage III [28.3%], 22 stage II [41.5%], 10 stage I [18.9%], 3 CIS [5.7%]; 25 with mutant tissue BRAF [47.2%]) and a median age of 60 years were included in the study. BRAFV600E-mutated ctDNA was detected in 25 patients (48%) before surgery and in 17 patients (32%) after surgery. Conversion of ctDNA BRAF status (from mutant to wild-type) in preoperative and postoperative samples occurred in 11 patients (21%). Patients with detectable ctDNA in samples collected after surgery had more disease recurrences (47.1% [n=8] vs. 20.6% [n=7]; P Conclusions: Our results demonstrate that ultrasensitive droplet digital PCR method can detect ctDNA in patients with resectable melanoma and that patients with detectable ctDNA in blood samples collected after surgery have inferior clinical outcomes. Citation Format: Mohamed Alaa Gouda, Jiri Polivka, Helen Huang, Inka Treskova, Kristyna Pivovarcikova, Funda Meric-Bernstam, Martin Pesta, Filip Janku. BRAFV600 mutation in circulating tumor DNA can predict outcomes in early-stage melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 564.