Circulating Tumour DNA Guided Adjuvant Chemotherapy Decision Making in Stage II Colon Cancer—A Clinical Vignette Study

SIMPLE SUMMARY: Circulating tumour DNA is a biomarker of significant research interest with a number of randomised controlled trials comparing a ctDNA-informed approach to adjuvant decision making in stage II colon cancer compared to standard of care. However, it is unknown if medical oncologist would recommend ctDNA testing in real-world clinical practice and how results may influence treatment recommendations. We presented medical oncologists with a series of stage II colon cancer clinical vignettes, demonstrating that surveyed participants are willing to organise ctDNA testing in most clinical scenarios. Importantly, oncologists were more likely to recommend adjuvant chemotherapy and escalate treatment following a positive result (i.e., detectable ctDNA). Following a negative result, oncologists were inclined to de-escalate or avoid chemotherapy. The results demonstrate that ctDNA testing can influence treatment decision making and can also be utilised in future economic evaluations to help secure access to testing. ABSTRACT: Circulating tumour DNA (ctDNA) is a promising biomarker that may better identify stage II colon cancer (CC) patients who will benefit from adjuvant chemotherapy (AC) compared to standard clinicopathological parameters. The DYNAMIC study demonstrated that ctDNA-informed treatment decreased AC utilisation without compromising recurrence free survival, but medical oncologists’ willingness to utilise ctDNA results to inform AC decision is unknown. Medical oncologists from Australia, Canada and New Zealand were presented with clinical vignettes for stage II CC comprised of two variables with three levels each (age: ≤50, 52–69, ≥70 years; and clinicopathological risk of recurrence: low, intermediate, high) and were queried about ctDNA testing and treatment recommendations based on results. Sixty-four colorectal oncologists completed at least one vignette (all vignettes, n = 59). The majority of oncologist were Australian (70%; Canada: n = 13; New Zealand: n = 6) and had over 10 years of clinical experience (n = 41; 64%). The proportion of oncologists requesting ctDNA testing exceeded 80% for all vignettes, except for age ≥ 70 and low-risk disease (63%). Following a positive ctDNA result, the proportion of oncologists recommending AC (p < 0.01) and recommending oxaliplatin-based doublet (p < 0.01) increased in all vignettes. Following a negative result, the proportion recommending AC decreased in all intermediate and high-risk vignettes (p < 0.01).