Vecchio FM et al. (2005) The relationship of pathologic tumor regression grade (TRG) and outcomes after preoperative therapy in rectal cancer. Int J Radiat Oncol Biol Phys 62: 752–760

Preoperative chemoradiation aims to minimize recurrence of cancer and enable more patients to proceed with tissue-sparing surgery. For patients with rectal cancer who achieve a partial response to preoperative chemoradiation, predicting long-term outcome can be difficult. Vecchio's group studied the ability of the TUMOR REGRESSION GRADE (TRG) system to predict outcome at 5 years for these patients.

This retrospective, single-center, Italian study included 144 patients, most of whom had clinical stage T3 or T4 and/or node-positive rectal cancer. Patients underwent surgery 4–8 weeks after completion of radiotherapy and were followed up for at least 3 years. Proctoscopic biopsy specimens were obtained and examined both before treatment and 4–5 weeks after preoperative therapy ended. The degree of cytologic and stromal changes in the specimens led to assignment of TRG. Clinical response was evaluated by comparing pretreatment and post-treatment RECTAL REFERENCE INDEX SCORES.

This study suggests that, of all pretreatment and post-treatment factors, older age at diagnosis, low TRG and low pathologic nodal stage are statistically significant predictors of long-term survival. TRG was a more reliable indicator than other scoring methods such as digital rectal examination and tumor downstaging according to WHO criteria, with less interobserver variability. The authors acknowledged that the study's retrospective nature might have influenced the results, which should be validated in larger, prospective studies. Assessment of TRG might assist in identifying lower-risk patients for whom conservative surgery would be possible after preoperative radiotherapy.