Axel Grothey, MD, Professor of Oncology at the Mayo Clinic, Rochester, Minnesota, said that classifying colorectal cancer by intrinsic subtypes is “the right route forward,” especially if subtypes can be reliably linked to therapeutic response and survival. “We will not be treating all colorectal cancers alike. We know that, but we have lacked the tools to distinguish among them.”

Paula R. Pohlmann, MD, PhD, Assistant Professor of Medicine at Vanderbilt-Ingram Cancer Center, Nashville, looks forward to validation of these findings in a more contemporary patient population. “This is based on a series of patients treated with [fluorouracil (5-FU)], which was the standard of care at the time. We need to see the study repeated in patients treated with oxaliplatin,” Dr. Pohlmann said.

She also questioned whether assumptions about chemotherapy benefit can be made from a study this size. “Based on P values, the investigators said that subtypes A and C did not derive benefit from chemotherapy, but I believe the sample may be too small,” she said. “Subtype A did appear to get some benefit from 5-FU according to the separation of the survival curve, so I would not want to withhold chemotherapy from them.”

“I would suggest validating this in an oxaliplatin-based treatment subset and increasing the sample size to have more confidence that patients will not respond to chemotherapy,” Dr. Pohlmann said. ■