Additional MR imaging performed during chemoradiation therapy could be an early predictor of a rectal cancer patient’s pathological response to treatment, according to research out of San Raffaele Hospital in Milan.

MRI has long been a diagnostic tool of choice for locally advanced rectal cancer (LARC) staging, lead author Anna Palmisano and colleagues wrote in Clinical Radiology, because its ability to generate accurate, high-resolution soft-tissue images results in a detailed picture of both the cancer and its physical surroundings. Scans are also often repeated after neoadjuvant chemoradiation therapy (CRT), the authors said, to assess a patient’s response to the treatment and aid in surgical planning.

But—although pre- to post-CRT MRI data have shown success and promise—taking this approach can be lengthy and has a limited capability of distinguishing partial from complete responses to the therapy. In addition, the study stated, the minor percentage of patients who don’t benefit from neoadjuvant CRT are exposed to unnecessary toxicity throughout the process while more successful treatment is delayed.

“In order to increase the chance of recovery and improve oncological outcome, it is important to determine beforehand what kind of response to CRT patients will achieve, in order to assign patients to the appropriate treatment strategy,” Palmisano et al. wrote. “Assuming that tumor shrinkage is expected to occur mostly in the earlier phases of CRT in responding patients, the aim of the present study was to investigate the usefulness of an additional MRI study performed during CRT for the early prediction of histopathological tumor regression grade.”

The researchers identified 48 study participants with LARC, all of whom underwent neoadjuvant CRT at the Milan facility. MRI scans at 1.5 T,  including high-resolution T2-weighted sequences that were acquired parallel and perpendicular to the main axis of the tumor, were taken before, during and six to eight weeks after the conclusion of CRT.

The majority of patients—52 percent—were considered partial responders to the treatment, the authors reported, while 27 percent and 22 percent were complete responders and non-responders, respectively. Tumor shrinkage seemed to mainly take place shortly after CRT, and a combined assessment of cancer volume and tumor reduction rate determined that the scans performed during CRT were most indicative of how a patient would respond to the therapy.

“Adding an intermediate MRI could offer useful information about the early trend of response and predict histopathological tumor regression grading with high accuracy,” Palmisano and co-authors wrote. “It could be useful in tailoring treatment, with eventual adaptation of the CRT scheme in order to increase the chance of recovery. Obtaining crucial information for the management of patients based on the addition of a single MRI during treatment could indeed be highly beneficial, especially considering the low cost of the examination and the short acquisition time.”