Biopsy findings after breast conservation therapy for early-stage invasive breast cancer.

PURPOSE: To determine the patterns and factors predictive of positive ipsilateral breast biopsy after conservation therapy for early-stage breast cancer. METHODS AND MATERIALS: We performed a retrospective review of Stage I-II breast cancer patients initially treated with lumpectomy and radiotherapy between 1977 and 1996, who later underwent post-treatment ipsilateral breast biopsies.
RESULTS: A total of 223 biopsies were performed in 193 treated breasts: 171 single and 22 multiple biopsies. Of the 223 biopsies, 56% were positive and 44% were negative for recurrence. The positive biopsy rate (PBR) was 59% for the first and 32% for subsequent biopsies. The median time to the first post-treatment biopsy was 49 months. Of the patients with negative initial biopsy findings, 11% later developed local recurrence. The PBR was 40% among patients with physical examination findings only, 65% with mammographic abnormalities only, and 79% with both findings (p = 0.001). Analysis of the procedure type revealed a PBR of 86% for core and 58% for excisional biopsies compared with 28% for aspiration cytology alone (p = 0.025). The PBR varied inversely with age at the original diagnosis: 49% if >or=51 years, 57% if 36-50 years, and 83% if <or=35 years (p = 0.05). The PBR correlated directly with the interval after radiotherapy: 49% if <or=60 months, 59% if 60.1-120 months, 77% if 120.1-180 months, and 100% if >180 months after completing postlumpectomy radiotherapy (p = 0.01). The PBR was not linked with recurrence location, initial pathologic T or N stage, estrogen receptor/progesterone receptor status, or final pathologic margins (all p >or= 0.15).
CONCLUSION: After definitive radiotherapy for early-stage breast cancer, a greater PBR was associated with the presence of both mammographic and clinical abnormalities, excisional or core biopsies, younger age at the initial diagnosis, and longer intervals after radiotherapy completion.