The importance of measuring baseline tumour volume (or alternatively tumour length along with its rectal circumferential extent) in the watch-and-wait strategy in rectal cancer: a review.

Background: The impact of the tumour volume or size on achieving clinical complete response (cCR) after radio(chemo)therapy is poorly understood.

Materials And Methods: A literature search was performed to gather data on the predictive value of baseline tumour volume or size in achieving cCR.

Results: In total, nine reports were identified. In two of three studies evaluating the baseline tumour volumetry, the tumour volume was the most powerful predictor for cCR. In four of six studies evaluating baseline tumour size without volumetry, tumour dimension was significantly associated with cCR, in one study reached borderline significance and in one report was insignificant. In three of four studies where a multivariable analysis was performed, the cT category did not show an independent predictive value for cCR. Because the tumour shape is often (semi)annular, its circumferential rectal extent along with the tumour length probably impact the tumour volume most, and thus, could be considered an acceptable alternative for time-consuming volumetry.

Conclusions: Our review suggests that baseline tumour volume (or alternatively, tumour length along with its circumferential rectal extent) is the most relevant clinical predictor of cCR. Therefore, we postulate assessing and reporting these parameters in studies on the watch-and-wait strategy.