Efficacy of radiation therapy in 'good-risk' DCIS patients

"This is an interesting study for two reasons," explained Hartford. "First, it gives us an important group of baseline data about DCIS recurrence for patients who forego radiotherapy that shows a five-year risk of recurrence at 3.5% and nearly 7% at seven years. We will need to watch the following years closely. Secondly, if a patient did choose to have radiation therapy, that risk fell to 0.4% at five years and 0.9% at seven years."

At the time this study (RTOG 9804) opened in 1998, radiation therapy was known to cut the risk of recurrence for patients with DCIS (not selected for 'good-risk') in about half, from more than 20% at five years to 10%. However, it was not clear how much benefit, if any, radiation therapy yielded for patients with good-risk DCIS. The study was designed to answer that question. The unexpectedly low rate of recurrence found in RTOG 9804 for patients who chose radiation therapy was a statistically significant finding despite an overall low number of patients accrued to the trial.

The trial was randomized from 1998-2006 in 636 selected women found to have low- or intermediate- grade DCIS with good-risk features. Tamoxifin use was optional, and the primary end point was ipsilateral local failure.

"For patients, the findings are useful as they consider whether to choose radiation therapy or not," said Hartford. "If a woman presents with good-risk DCIS, maybe it's not unreasonable for her to forego radiation therapy to avoid side effects and potential complications. However, these data are still young, and it is possible the risks of recurrence will continue to rise after seven years. The other reading is that radiation therapy substantially reduces the risk of recurrence for patients with good-risk DCIS, down to below 1% at seven years. This is a dramatic improvement."

Hartford cautions that the number of recurrences in the treated arm of the study is small and the confidence intervals are large. It is possible that the observed rate of less than 1% recurrence may be off due to random chance and that the true actual risk may be somewhat higher.

Dartmouth's Norris Cotton Cancer Center contributed a total of 19 patients to the trial, and participates regularly in national cooperative group trials from its oncology hub at Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire. Dr. Hartford is a radiation oncologist at Norris Cotton Cancer Center where he leads radiation oncology, treats patients, and is a physician scientist.