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

To identify risk factors associated with an increasedrisk for ipsilateral breast tumor recurrence following breast-conservingsurgery, a cohort of 759 women with T1–T2tumors were studied. The majority of the patients(88%) had received postoperative radiation therapy to thebreast. Median follow-up time was 10 (range: 6–17)years. There was a 1–1.5% yearly increase inipsilateral breast tumor recurrences. For women < 50ys the cumulative recurrence rate at 10 yearswas 18% and for women ≥ 50 ys,9%. Node positive women had a cumulative breastrecurrence rate of 25% versus 10% for nodenegative women. Ten years postoperatively, irradiated patients hada cumulative recurrence rate of 11% versus 26%when no irradiation was given. The beneficial effectof radiotherapy was substantial during the first fourpostoperative years. The relative risk for an ipsilateralbreast tumor recurrence during this period was 4.5times higher than for non irradiated patients. However,the protective effect of radiotherapy decreased with time.After ten years the relative risk of ipsilateralbreast tumor recurrence was the same among irradiatedand non-irradiated patients although the number of eventsduring this period was low.Univariate analysis showed that seven factors were significantlyassociated with an increased risk of ipsilateral breasttumor recurrence, namely age < 50 ys, increasingtumor size, uncertain microscopic margins, axillary lymph nodemetastases, no postoperative tamoxifen treatment, premenopausal status, andno postoperative radiotherapy. Three factors remained independently significantafter 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≥ 50 were a low risk-group for ipsilateralbreast tumor recurrence, with a cumulative risk at10 years of 9% without radiation therapy and5% with breast irradiation.