Retrospective studies of women with DCIS have compared breast conserving surgery (lumpectomy) to mastectomy and found that survival rates are similar. However, women who have lumpectomy alone, without further treatment, are at higher risk of developing invasive breast cancer in the same breast. Whether women who develop invasive breast tumors after DCIS are also at higher risk of dying of breast cancer has not been clear.
To explore this question as well as the long-term effects of treatments aimed at avoiding invasive recurrence after lumpectomy, Irene Wapnir, M.D., of Stanford University School of Medicine, and James Dignam, PhD of University of Chicago looked at the long-term outcomes of patients with localized DCIS who took part in two large randomized trials, both carried out by the National Surgical Adjuvant Breast and Bowel Project (NSABP). The B-17 trial compared lumpectomy alone to lumpectomy plus radiation therapy in women with DCIS. The B-24 trial compared lumpectomy plus radiation in combination with either tamoxifen or placebo.
Wapnir and colleagues analyzed data on outcomes in both trials after 15 years, including overall and breast cancer-specific survival and survival after development of invasive breast cancer in the same, or ipsilateral, breast.
They found that the development of invasive ipsilateral breast cancer was associated with death rates that were statistically significantly higher than those in women who did not develop an invasive ipsilateral breast cancer. Recurrence of DCIS was not associated with higher mortality. Radiation treatment after lumpectomy reduced the risk of ipsilateral invasive breast cancer compared to lumpectomy alone, and treatment with radiation and tamoxifen reduced the risk compared to radiation only. The reductions in risk were statistically significant.
Among all patients in the trials, the 15-year cumulative incidence of death from breast cancer was 4.7% or less for all treatment groups. Some of these events could be attributed to new invasive contralateral breast cancers.
The authors conclude that, regardless of treatment, women with DCIS have an excellent overall prognosis "despite persistent risks of breast cancer in the same or contralateral breast." They note that three other NSABP trials now in progress will provide more information on other treatment options following lumpectomy.