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3521 Background: CHIP is the clonal expansion of hematopoietic stem cells following acquisition of somatic mutations. It is a common incidental finding in cell-free DNA (cfDNA). We investigated the incidence of CHIP in cfDNA from patients with solid tumors and explored its association with outcomes and adverse events (AEs). Methods: We reviewed cfDNA results from a local prospective solid tumor cohort (PREDICT-L) and two randomized trials: CCTG CO.26 (durvalumab + tremelimumab D+T or best supportive care BSC in metastatic colorectal cancer mCRC) and CCTG PA.7 (gemcitabine and nab-paclitaxel GN +/- D+T in metastatic pancreatic adenocarcinoma mPDAC). CHIP+ was defined as any mutation in DNMT3A, TET2, ASXL1or ATM with a variant allele frequency (VAF) 2% or higher. Variants were considered germline if the VAF was >40%, or were annotated as germline by respective assays. The first line of treatment after cfDNA was reviewed for grade 3 or higher and dose-limiting AEs. Results: The prevalence of CHIP was 10%-21% and was more common in older patients (p=0.003). There was no association between CHIP and sex (p=0.80) or ECOG status (p=0.31). The VAF of CHIP variants was similar across all panels, and DNMT3A was the gene most frequently mutated in all cohorts. Patients with CHIP in PA.7 treated with immunotherapy (IO) had improved progression-free survival (PFS) versus patients without CHIP (p=0.036, p-interaction=0.061 multivariable). However, patients with CHIP treated with chemotherapy (Chemo) showed a trend towards worse overall survival (OS) in the PREDICT-L cohort (p=0.057). There was no significant difference in the rates of AEs between the CHIP+ versus CHIP- groups for those treated with Chemo or IO. Conclusions: CHIP is common in patients with solid tumors. Although not appearing to impact rates of AEs, CHIP may impact outcomes from Chemo or IO. Table: see text
Krishnan et al. (Sat,) studied this question.