When classifying response to chemoradiation among patients with locally advanced rectal cancer, the American Joint Committee on Cancer (AJCC) Cancer Staging Manual (7th edition) system “is most accurate and should be adopted as the standard,” Attaphorn Trakarnsanga, MD, and colleagues at Memorial Sloan Kettering Cancer Center concluded after comparing several published classification schemes. The comparisons of the predictive accuracies of these schemes were published in the Journal of the National Cancer Institute.
Currently, there are several different systems for tumor regression grade, a measure of histopathologic response of rectal cancer to neoadjuvant chemoradiation that is associated with outcomes. “A single measure of rectal cancer response would assist in comparing results across institutions and in designing future rectal cancer studies,” the researchers wrote.
“Review of a prospective database identified 563 patients with locally advanced rectal cancer (T3/4 and/or N1) treated between 1998 and 2007 with long-course chemoradiation and total mesorectal excision. Tumor regression grade was determined by measuring the proportion of tumor mass replaced by fibrosis,” the investigators explained. Patients were classified into tumor regression grade schemes: AJCC (4-tier), system, the Mandard (five-, three-tier), Dowrak/Rödel (five-, three-tier), Memorial Sloan Kettering Cancer Center (MSKCC, 3-tier). The schemes were compared by analyzing association with tumor recurrence and survival using concordance index.
Although all tumor regression grade systems were predictive of tumor recurrence, the AJCC system more accurately predicted recurrence than the three-tier Mandard (P = .002) or Dowrak/Rödel (P = .006) and had a higher concordance index than the three-tier MSKCC scheme, although this did not reach statistical significance (P = .068), the researchers reported. Higher concordance numbers denote better prediction, and the AJCC system had the highest number, 0.694. Concordance indices for the other systems were 0.683 for the MSKCC, 0.665 for the Mandard, and 0.653 for the Dowrak/ Rödel.
“Tumor regression grade may provide a valuable tool for clinical decision making for patients with rectal cancer who undergo neoadjuvant chemoradiation and surgery. The data from Trakarnsanga et al provide guidance as to which of the tumor regression grade systems is most predictive for recurrence following preoperative chemoradiation and surgery for rectal cancer,” noted an accompanying editorial by Bruce D. Minsky, MD, of the University of Texas MD Anderson Cancer Center, Houston, and Claus Rodel, MD, University Cancer Center University Hospital, Frankfurt Germany. Despite several caveats, including tumor regression grade systems not accounting for possible involvement of pelvic lymph nodes and dependence on the expertise and dedication of the pathologist, “the four-tier AJCC tumor regression grade system appears to be a good choice,” Drs. Minsky and Rodel wrote. However, this classification system needs to be prospectively tested on multiple datasets to validate its reproducibility in the broader setting.” ■