A new study has reported that certain women with close or positive surgical margins after lumpectomy or other breast conserving surgery are at increased risk of recurrence in the same breast despite radiation treatment. The study was designed to investigate the influence of surgical margin status on local recurrence (i.e., in the treated breast) and survival following breast-conserving therapy (lumpectomy or partial mastectomy). The authors also intended to identify characteristics of patients with close or positive margins who have high risk of local recurrence.

The study included 2,264 women with operable nonmetastatic invasive breast cancer, treated with breast-conserving surgery and whole breast radiation with or without boost radiotherapy. Boost radiotherapy was used in 92% of participants who had close or positive margins. Five-year local recurrence, breast cancer-specific survival and overall survival were compared between women with negative (1,980 participants), close (222), and positive (62) margins. The women were followed for a median of 5.2 years.

The estimated five-year local recurrence rate in participants with negative surgical margins was 1.3%; the rates were 4.0% for close and 5.2% for positive margins. However, five-year breast cancer-specific survival and overall survival were similar for all three surgical margin subgroups. In the women with close or positive margins, local recurrence rates were found be 10.2% for those diagnosed before age 45, 11.8% among those with grade III tumors, 11.3% for those with lymphovascular invasion (invasion of cancer cells into the blood vessels or lymphatic channels), and 26.3% among those with at least four positive lymph nodes. Corresponding local recurrence rates among women with negative margins were 2.3%, 2.4%, 1.0%, and 2.4%, respectively. Among the entire study group, close or positive margins, Grade III histology, four or more positive nodes, and lack of systemic treatment were significantly associated with higher risk of local recurrence. The difference in five-year local recurrence remained significant when the women with close or positive margin cases were matched to controls (4.25% vs. 0.7%). The authors conclude that women with close or positive margins have five-year local recurrence rates greater than 10% despite whole breast plus boost radiotherapy if they also have one or more of the following risk factors: diagnosed under age 45, grade III tumor, lymphovascular invasion, or at least four positive lymph nodes. These patients should be considered for additional surgery.