Tumour volume predicts pathologic complete response in rectal cancer patients

In locally advanced rectal cancer patients on neoadjuvant chemoradiation, a tumour volume threshold of 37.3 cm³ is associated with pathologic complete response (pCR), suggests a recent study.

“Tumours above this volume threshold corresponded to a greater than 78-percent probability of not achieving pCR,” the investigators said. “This information will be helpful at diagnosis for clinicians who are considering potential candidates for nonoperative management (NOM).”

This retrospective analysis included 412 locally advanced rectal cancer patients. Pretreatment magnetic resonance imaging was used to determine tumour volumes.

The investigators then analysed clinical parameters, including tumour volume, stage, and location via univariate and multivariate analyses against pCR. They also generated a receiver operator characteristic curve to identify a tumour volume cutoff with the highest clinically relevant Youden index for predicting pCR.

Of the patients, 75 (18 percent) achieved pCR. A tumour volume threshold of 37.3 cm³ was found to be predictive of pCR. Regression analysis revealed that a tumour volume >37.3 cm³ was associated with >78-percent likelihood of not achieving pCR.

A tumour volume <37.3 cm³ (odds ratio [OR], 3.7; p<0.0001) significantly correlated with a high pCR rate on multivariate analysis, while tumour length >4.85 cm was predictive of pCR on univariate (OR, 3.03; p<0.01) but not on multivariate analysis (OR, 1.45; p=0.261).

“Other clinical parameters did not impact pCR rates,” the investigators said.