Following breast reconstruction, radiation therapy can be delivered to the chest wall and regional nodes either in the adjuvant setting or if local disease recurs. Radiation therapy following reconstruction with a breast prosthesis may affect cosmesis, and the incidence of capsular fibrosis, pain, or the need for implant removal may be increased.
Adjuvant Radiation Therapy
Radiation therapy is regularly employed after breast-conservation surgery. Radiation therapy also can be indicated for postmastectomy patients. The main goal of adjuvant radiation therapy is to eradicate residual disease thus reducing local recurrence.
Post-breast conservation surgery
For women who are treated with breast-conserving surgery, the most common site of local recurrence is the conserved breast itself. The risk of recurrence in the conserved breast is substantial (>20%) even in confirmed axillary lymph node-negative women. Thus, whole breast radiation therapy after breast-conserving surgery is recommended.
Although all trials assessing the role of radiation therapy in breast-conserving therapy have shown highly statistically significant reductions in local recurrence rate, no single trial has demonstrated a statistically significant reduction in mortality. However, in the 2005 Early Breast Cancer Trialists' Collaborative Group's (EBCTCG) update, when all relevant trials were combined, 15-year breast cancer mortality was reduced from 35.9% to 30.5% in women receiving radiation therapy (absolute difference of 5.4%; 95% CI, 2.1%-8.7%; breast cancer death rate ratio 0.83; 95% CI, 0.75-0.91; P = .002). There was a similar effect on all-cause mortality.
Although adjuvant whole-breast radiation is standard treatment, no trials have addressed the role of regional lymph node radiation therapy in this setting. The National Cancer Institute of Canada's study (CAN-NCIC-MA20 [NCT00005957]) has closed, but until results are reported, decisions regarding the use of such therapy must rely on extrapolations from the postmastectomy setting and on knowledge of the local-regional recurrence rates following conservation therapy with axillary lymph node dissection for a given lesion.
Postoperative chest wall and regional lymph node adjuvant radiation therapy has traditionally been given to selected patients considered at high risk for local-regional failure following mastectomy. Radiation therapy can decrease local-regional recurrence in this group, even among those patients who receive adjuvant chemotherapy. Patients at highest risk for local recurrence include those with four or more positive axillary nodes, grossly evident extracapsular nodal extension, large primary tumors, and very close or positive deep margins of resection of the primary tumor.[63,64,65]
Patients with one to three involved nodes without any of the previously noted risk factors are at low risk of local recurrence, and the value of routine use of adjuvant radiation therapy in this setting has been unclear. The 2005 EBCTCG update indicates, however, that radiation therapy is beneficial, regardless of the number of lymph nodes involved.[Level of evidence: 1iiA] For women with node-positive disease postmastectomy and axillary clearance, radiation therapy reduced the 5-year local recurrence risk from 23% to 6% (absolute gain = 17%; 95% confidence interval [CI], 15.2%-18.8%). This translated into a significant (P = .002) reduction in breast cancer mortality, 54.7% versus 60.1% with an absolute gain of 5.4% (95% CI, 2.9%-7.9%). In subgroup analyses, the 5-year local recurrence rate was reduced by 12% (95% CI, 8.0%-16%) for women with one to three involved lymph nodes and by 14% (95% CI, 10%-18%) for women with four or more involved lymph nodes. In contrast, for women with node-negative disease, the absolute reduction in 5-year local recurrence was only 4% (P = .002; 95% CI, 1.8%-6.2%), and there was not a statistically significant reduction in 15-year breast cancer mortality in these patients (absolute gain = 1.0%; P > .1 95%; CI, -0.8%-2.8%). Further, an analysis of NSABP trials showed that even in patients with large (>5 cm) primary tumors, when axillary nodes were negative, the risk of isolated locoregional recurrence was low enough (7.1%) that routine locoregional radiation therapy was not warranted.