Breast conserving surgery for invasive breast cancer: Risk factors for ipsilateral breast tumor recurrences

To identify risk factors associated with an increased risk for ipsilateral breast tumor recurrence following breast-conserving surgery, a cohort of 759 women with T-1-T-2 tumors were studied. The majority of the patients (88%) had received postoperative radiation therapy to the breast. Median follow-up time was 10 (range: 6-17) years. There was a 1-1.5 % yearly increase in ipsilateral breast tumor recurrences. For women < 50 ya the cumulative recurrence rate at 10 years was 18% and for women greater than or equal to 50 ys, 9%. Node positive women had a cumulative breast recurrence rate of 25% versus 10% for node negative women. Ten years postoperatively, irradiated patients had a cumulative recurrence rate of 11% versus 26% when no irradiation was given. The beneficial effect of radiotherapy was substantial during the first four postoperative years. The relative risk for an ipsilateral breast tumor recurrence during this period was 4.5 times higher than for non irradiated patients. However, the protective effect of radiotherapy decreased with time. After ten years the relative risk of ipsilateral breast tumor recurrence was the same among irradiated and non-irradiated patients although the number of events during this period was low. Univariate analysis showed that seven factors were significantly associated with an increased risk of ipsilateral breast tumor recurrence, namely age < 50 ys, increasing tumor size, uncertain microscopic margins, axillary lymph node metastases, no postoperative tamoxifen treatment, premenopausal status, and no postoperative radiotherapy. Three factors remained independently significant after multivariate analysis: age < 50 ys, no postoperative radiation therapy, and positive lymph nodes. In conclusion, radiotherapy reduced the breast recurrence rate, but the effect decreased with time. Node-negative women greater than or equal to 50 were a low risk-group for ipsilateral breast tumor recurrence, with a cumulative risk at 10 years of 9% without radiation therapy and 5 % with breast irradiation.