Association of positive ctDNA-based minimal residual disease assays during surveillance and undiagnosed concomitant radiographic recurrences in colorectal cancer (CRC): Results from the MD Anderson INTERCEPT program.

Abstract

3522 Background: Observational cohorts have shown that detection of circulating tumor DNA (ctDNA)-defined minimal residual disease (MRD) following curative intent therapy has very high specificity and positive predictive value for future radiographic recurrence with a lead time of over 9 months. However, such data have not incorporated rigorous clinical evaluation for concomitant recurrence, nor have they established the clinical utility of MRD monitoring after completion of curative intent therapy. Methods: Pts with stages II-IV CRC (6/1/19 - 12/31/22, data cutoff) treated with curative intent at MD Anderson Cancer Center were evaluated with a tumor-informed MRD assay (Signatera, Natera), as part of the institutional INTERCEPT program that aims to integrate MRD-based testing into CRC clinical care. Surveillance visits including scans and tumor markers were performed per established guidelines. ctDNA was recommended post-operatively and q3m with each surveillance visit. Pts and providers were informed of the results and subsequent clinical courses including additional radiologic testing for ctDNA+ MRD tests were tracked. Results: 1259 pts were included in the INTERCEPT program (median 57y, [21-93]; 55% male; stage% I-III/IV 69/31; colon/rectum% 61/39), with 1049 pts tested after curative intent surgery. Of these, 159/1049 pts (15%) had ctDNA+; distribution of pts, % (+ve/total) from time of such surgery in m was: 0 - 3 (54.6/43.8); 3-6 (21.3/30); 6-12 (24/33.2). Of the pts with ctDNA+ after surgery, 49 pts (32%) were ctDNA+ prior to or during adjuvant therapy and 86 (57%) during surveillance. Of the 86 pts who were ctDNA+ during surveillance, imaging revealed concomitant new metastases in 46 (53%); i.e. only 40 (47%) were true MRD+. A total of 191 imaging studies were done (range 1-4) within 90d of the initial ctDNA+ including 99 as routine surveillance concurrent with ctDNA testing and 92 as additional follow up based on results. Of 40 pts with true MRD, majority (27 pts, 67.5%) were enrolled onto ongoing MRD trials ( https://crcmrd.com/ ). Conclusions: Our experience provides support for the feasibility of incorporation of MRD testing as part of routine surveillance. ctDNA+ results trigger a high rate of reflex imaging and, as a result, 53% of ctDNA+ patients have concomitant new radiographic findings. While clinical trials are feasible in true MRD+ pts, eligibility criteria for these trials need to be carefully specified about adequate radiographic evaluation.