ENDOSCOPIC RESPONSE TO CHEMORADIOTHERAPY IN LOW RECTAL CANCER: ARE THE WAIT-AND-SEE CRITERIA TOO STRICT?

Aims:

In the wait-and-see (W&S) strategy, locally advanced low rectal adenocarcinoma patients who achieve clinical complete response (cCR) after chemoradiotherapy (CRT) undergo regular surveillance, with surgery being reserved for tumor “regrowth”. Endoscopic complete response is characterized by light/white mucosa, scar, telangiectasia or edema. Erosion and ulceration are considered an absence of response.

To evaluate the accuracy of endoscopy in a W&S program.

Methods:

Single-center prospective observational study. All patients with low rectal adenocarcinoma, stage I to III, discussed in a multidisciplinary colorectal cancer clinic since the implementation of the W&S strategy (11/2014 – 11/2016) were evaluated. We analyzed the endoscopic features, MRI and clinical observation results, clinical decisions, pathology results, when available and patient outcome.

Results:

From the 56 patients found, 41 were reevaluated after CRT (mean of 6,7 weeks). 17% (7/41) displayed cCR and entered W&S surveillance program. In this subgroup (maximum follow-up = 25 months) there was only one (14%) “regrowth”. From the remaining 34 patients, 20% had pathological CR (pCR).

In the subgroup of patients with cCR, 2 had erosions at reevaluation and a second endoscopy was done, in which a scar was present. The only regrowth was found in one of these patients.

In the subgroup of patients without cCR, 15 had an endoscopic reevaluation (Ulcer: 11; Obvious tumor: 4) and 5 of them displayed pCR in the surgical specimen. Four of these had a second reevaluation due to uncertainties – 3: maintained an ulcer and one switched from an ulcer to erosion. Three of them had pCR's.

Endoscopy predicted complete response (either sustained CR at the end of follow-up or pCR) with AUC 72,7% (Sensitivity 54,5%. Specificity 90,9%), p = 0,071.

Conclusions:

Our series showed that using these criteria endoscopy predicts CR with high specificity. Despite low sensitivity, the extension of the criteria would impair the specificity to values unacceptable in a cancer-curing strategy.