PARIS--Detection rates of ductal carcinoma in situ (DCIS) have soared
thanks to mammography but, to date, only one randomized trial has attempted
to quell the resulting therapeutic turmoil. Now, eight-year follow-up results
from that NSABP trial indicate that the advantages of breast irradiation
following local excision continue to be maintained over the long term.
"All patients benefit from radiation," Bernard Fisher, MD, scientific
director of the NSABP, said at the Seventh International Congress on Anti-Cancer
Treatment (ICACT). "The most optimal prevention of second ipsilateral
breast tumors is free specimen margins and post-lumpectomy radiation."
Dr. Fisher pointed out that second tumors in the ipsilateral breast
developed in 27% of women with DCIS who had been treated with lumpectomy
alone and that nearly half of these tumors were invasive. In contrast,
only 12% of women treated with postsurgical breast irradiation developed
second tumors, roughly a third of which were invasive.
"The important question is whether you get an invasive cancer from
DCIS, and these data show how well radiation works in controlling the development
of ipsilateral invasive breast tumors," he said. The eight-year rates
of local-regional disease, distant disease, and deaths were equally small
in both NSABP treatment arms, however.
In an effort to pinpoint those subgroups of patients that would most
benefit from radiation, the NSABP investigators examined the value of pathologic
characteristics in predicting the development of a second ipsilateral breast
tumor. Multivariate analysis revealed that comedo necrosis and margin involvement
were the only independent prognostic factors, Dr. Fisher said.
Nevertheless, he emphasized, radiation was effective irrespective of
nuclear grade, histologic type, tumor size, the presence or absence of
comedo necrosis, and margin involvement.
Best and Worst Scenarios
"Even in the worst scenario, with involved margins and marked comedo
necrosis, radiation reduces the risk of ipsilateral breast tumors to a
very low level," he said. "And if you take the best scenario,
with free margins and absent-to-slight comedo necrosis, radiation still
has some effect in improving the situation."
Thus, Dr. Fisher maintains that "despite its heterogeneity, DCIS
warrants management by local excision and radiation regardless of the presence
or absence of favorable tumor characteristics."
He warned against the use of prognostic models in clinical decision
making, reminding the audience that models to predict which DCIS patients
can safely forego radiation, such as the Van Nuys index, have never been
validated with prospective clinical trials.
In a newly completed NSABP trial, Dr. Fisher said, women with more extensive
DCIS have been treated with lumpectomy and breast irradiation, stratified
by age, and then randomized to tamoxifen (Nolvadex) or placebo.