Breast-Conserving Therapy in Patients with Multiple Lesions

The safety of breast-conserving therapy (BCT) in patients with multiple ipsilateral breast cancer (MIBC) had not been assessed in a prospective clinical trial. Now, in a prospective, phase 2, single-arm trial, investigators evaluated 5-year cumulative incidence of local recurrence (LR) in patients with MIBC undergoing BCT. Women aged ≥40 years with 2 or 3 foci of biopsy-proven cN0-1 breast cancer were enrolled between 2012 and 2016; in 2015, a requirement for preoperative breast MRI was lifted. Treatment entailed lumpectomy, with a requirement for negative margins, followed by whole breast radiation with a boost to each lumpectomy bed. A 5-year LR rate <8% was defined as “clinically acceptable” based on prior reported experience.

Of 270 women enrolled, 204 underwent BCT; the remaining patients were ineligible, converted to mastectomy, did not have negative margins, or withdrew consent. During a median follow-up of 66.4 months, LR occurred in 6 patients, for an estimated 5-year cumulative LR incidence of 3.1%. Age, number of breast cancer sites, estrogen receptor and HER2 status, and pathologic T and N categories were not associated with LR risk. In an exploratory analysis, the 5-year LR rate was 1.7% in the 189 patients who underwent preoperative MRI compared with 22.6% in the 15 patients who did not undergo preoperative MRI.