Value of transanal multipoint full-layer puncture biopsy for determining the response of rectal cancer to neoadjuvant...

Assessing tumour response following neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer is essential for selecting patients for the watch-and-wait procedure. The accuracy of clinical complete response (cCR) for predicting pathological complete response (pCR) is inadequate. The aim of this study was to assess the ability of transanal multipoint full-layer puncture biopsy (TMFP) to predict pCR following nCRT for rectal cancer.

This nonrandomized prospective multicentre trial enrolled 113 patients from four centres between April 2020 and June 2023. Of these, 63 were assigned to the in vitro TMFP group and 50 to the in vivo TMFP group. The primary outcome measured was the predictive accuracy of TMFP for pCR.

All patients underwent total mesorectal excision. TMFP showed significantly higher accuracy for predicting pCR than cCR (87.6% vs. 68.1%, p = 0.016). The positive predictive value was higher for in vivo than for in vitro TMFP (90.0% vs. 64.5%, p = 0.018), and the predictive accuracy did not differ significantly between the two groups (94.0% vs. 82.5%, p = 0.066). In cCR patients, although with no significant difference between in vivo and in vitro TMFP regarding positive predictive value (95.0% vs. 86.7%, p = 0.794) and accuracy (96.0% vs. 92.9%, p = 1.000), the predictive accuracy of in vivo TMFP was as high as 96%.

TMFP is safe and feasible for assessing the response of rectal cancer to nCRT. TMFP showed high sensitivity and accuracy for predicting pCR and could be a useful supplement to the current cCR standard.