Debu Tripathy, MD, Professor of Medicine, Co-Leader of the Women’s Cancer Program, and the Priscilla and Art Ulene Chair in Women’s Cancer at the University of Southern California Norris Cancer Center, Los Angeles, commented on the APT study for The ASCO Post.

“In treating early-stage HER2-positive breast cancer, we know that chemotherapy plus trastuzumab [Herceptin] lowers the risk of recurrence. But when the risk itself is very low for small node-negative tumors, the question is, at what point is it not worth it, because there are side effects,” he said.

Dr. Tripathy noted that most trastuzumab trials included few tumors less than 1 or 2 cm, “so we don’t know much about the benefit of treatment in those situations.” Even studies attempting to estimate benefit are not felt to be very accurate, he said.

Absence of Doxorubicin

Since this is a small population of patients who have a favorable outcome, and since accruing HER2-positive patients to a placebo arm would be impossible, a properly powered randomized trial was out of the question. Instead, Dr. Winer and his team designed a single-arm study to define outcomes in a uniformly treated patient cohort, without a comparator but with an appreciation of the expected rate of events in such a population. The weekly paclitaxel was standard treatment, but the omission of doxorubicin was not.

“Did the absence of doxorubicin affect outcomes? We don’t know, but the number of events is low enough that it really doesn’t matter. The outcomes surpassed their expectations,” Dr. Tripathy pointed out, concluding that the research points to “a treatment option—a ‘niche regimen’—for these smaller tumors.” ■

Disclosure: Dr. Tripathy’s institution (University of Southern California) receives payment under contract for clinical research studies from Genentech/Roche.