ctDNA appears useful in monitoring patients with anal cancer undergoing CRT

With a high detectability rate and a low technical failure rate, measuring circulating tumour (ct)DNA was a useful response assessment in patients with anal cancer who were treated with chemoradiation (CRT). Further studies need to clarify whether patients can be stratified according to risk, and whether treatment de-escalation can be aligned with ctDNA measurements.

“The response evaluation in patients with anal cancer who underwent CRT is often delayed by 3–6 months,“ stated Dr Janet Alvarez (Memorial Sloan Kettering Cancer Center, NY, USA) [1]. “Therefore, there is a strong need for an early response biomarker and ctDNA has demonstrated to be a promising candidate for this matter.” The retrospective study that was performed by Dr Alvarez and colleagues included 31 patients with non-metastatic anal squamous cell carcinoma who were treated with definitive-intent CRT.

In 23 of the 27 assessable patients, ctDNA was detected at baseline, corresponding to a detectability rate of 85%. In addition, 2 out of 4 patients in whom ctDNA was not detectable at baseline had excisional biopsies prior to baseline ctDNA measurement. According to Dr Alvarez, the technical failure rate was 3%. Furthermore, ctDNA was cleared within 21 days of treatment in 57% of the patients. In further detail, 73% of the patients with stage I or II disease cleared mid-treatment in a median of 30 days and 50% of the patients with stage III disease cleared mid-treatment in a median of 31 days. Next, in 96% of the patients, ctDNA was cleared by the end of treatment. Finally, ctDNA clearance appeared to precede a clinical complete response, which was observed in this group of patients in a median of 136 days.

In summary, ctDNA showed to be a useful biomarker to track responses in patients with anal cancer undergoing CRT, with ctDNA clearance preceding clinical complete response by approximately 100 days. Longer follow-up data and larger trials are needed  to assess the clinical utility.

1. Alvarez J, et al. Circulating tumor DNA (ctDNA) for response assessment in patients with anal cancer treated with definitive chemoradiation. Abstract 1, ASCO GI 2023, 19–21 January, San Francisco, CA, USA.

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Posted on 17 March, 2023