Breast Cancer

Abstract

This synthesis of the literature on radiotherapy for breast cancer is based on 97 scientific articles, including 5 meta-analyses, 38 randomized studies, and 27 retrospective studies. These studies involve 387 634 patients.

Radiotherapy is the most effective method for preventing locoregional recurrence following primary surgery for invasive breast cancer, and radiotherapy is currently more effective than adjuvant chemotherapy after either mastectomy or breast-conserving surgery (1, 2).

Radiotherapy in patients at high risk for locoregional recurrence, eg, patients with spread to the axillary lymph nodes, leads to a significant increase in relapse-free survival (eg, 1, 3). Meta-analyses have shown that radiotherapy in these subgroups of patients can reduce the risk for distant metastasis and reduce the risk for cancer death (4, 5). These analyses have not statistically confirmed an improvement in total survival, probably because reduced mortality from breast cancer has been offset by increased mortality from cardiovascular disease. However, the results have successively improved, and survival gains are significantly greater in recent studies using modern treatment methods (5). It is probable that survival gains from radiotherapy do not exceed those that can be achieved by other adjuvant treatment of breast cancer such as chemotherapy or hormones, ie, a reduction in mortality by 20% to 30%, leading to an increased total survival after, eg, 10 years of 5% to 10% (4, 6).

The heart is the most important organ at risk during radiotherapy for breast cancer. Minimizing radiation doses to the heart muscle and the coronary arteries is necessary for avoiding later effects of ischemic cardiovascular disease. These side effects were particularly prominent in early treatment studies that used older radiotherapy methods (7-9).

Radiotherapy in conjunction with breastconserving surgery for invasive breast cancer significantly reduces the recurrence frequency in the breast (1013). Clinical studies are under way that aim at further defining the role of radiotherapy as an element in a breastconserving treatment strategy, eg, determining the value of boost, and identifying prognostic/predictive factors for breast recurrence. Improved knowledge about such factors should eventually permit identification of patient groups at such low risk for breast recurrence that routine radiotherapy is unnecessary, or at such high riskeven with radiotherapythat alternatives to breast conserving surgery should be considered.