A new study has reported that radiation treatment after lumpectomy reduces the risk of invasive breast cancer in the same breast compared to lumpectomy alone among women with ductal carcinoma in situ (DCIS). Treatment with radiation and tamoxifen reduces the risk of recurrence compared to radiation only. Ipsilateral breast tumor recurrence (i.e., recurrence in the same breast that was treated) is the most common failure event after lumpectomy for DCIS.

The study included participants in two National Surgical Adjuvant Breast and Bowel Project (NSABP) randomized trials for DCIS. In the NSABP B-17 trial (enrollment period: October 1, 1985, to December 31, 1990), women with localized DCIS were randomly assigned to receive either lumpectomy only (403 participants) or lumpectomy followed by radiotherapy (410 participants). In the NSABP B-24 double-blinded, placebo-controlled trial (enrollment period: May 9, 1991, to April 13, 1994), patients were randomly assigned to receive either lumpectomy followed by radiotherapy plus a placebo (900 participants) or lumpectomy followed by radiotherapy plus tamoxifen (899 participants). Data was collected regarding invasive ipsilateral breast tumor recurrence, DCIS ipsilateral breast tumor recurrence, contralateral breast cancer (cancer in the opposite or untreated breast), overall and breast cancer-specific survival, and survival after invasive ipsilateral breast tumor recurrence. Study participants were followed for a median of 207 months for the B-17 trial and 163 months for the B-24 trial.

A total of 490 recurrences in the breast originally treated for DCIS were diagnosed in study participants during the study period, of which 263 (53.7%) were invasive breast cancer and the remainder were DCIS. Lumpectomy followed by radiation treatment was found to reduce invasive ipsilateral breast recurrence by 52% compared to lumpectomy alone. Lumpectomy followed by radiotherapy plus tamoxifen reduced invasive ipsilateral breast recurrence by 32% compared to lumpectomy followed by radiotherapy plus placebo. The estimated 15-year cumulative incidence of invasive ipsilateral breast recurrence was found to be 19.4% for lumpectomy only, 8.9% for lumpectomy followed by radiotherapy, 10.0% for lumpectomy followed by radiotherapy plus placebo, and 8.5% for lumpectomy followed by radiotherapy plus tamoxifen. The estimated 15-year cumulative incidence of all contralateral (in the opposite breast from the original DCIS) breast cancers was 10.3% for lumpectomy only, 10.2% for lumpectomy followed by radiotherapy, 10.8% for lumpectomy followed by radiotherapy plus placebo, and 7.3% for lumpectomy followed by radiotherapy plus tamoxifen. Invasive ipsilateral breast recurrence was associated with increased risk of death, while recurrence of DCIS was not. Twenty-two of the 39 deaths that occurred after invasive ipsilateral breast recurrence were from breast cancer. Among all patients (whether or not they experienced invasive ipsilateral breast recurrence), the 15-year cumulative incidence of breast cancer-specific death was 3.1% for lumpectomy only, 4.7% for lumpectomy followed by radiotherapy, 2.7% for lumpectomy followed by radiotherapy plus placebo, and 2.3% for lumpectomy followed by radiotherapy plus tamoxifen. The authors conclude that although invasive ipsilateral breast recurrence increases the risk for breast cancer-specific death, radiation treatment and tamoxifen can reduce invasive ipsilateral breast recurrence, and long-term prognosis remains excellent after lumpectomy for DCIS.

Please see our article on ductal breast cancer and DCIS for more information on DCIS prevention, risk and recurrence.