Internal mammary node irradiation neither decreases distant metastases norimproves survival in stage I and II breast cancer

Purpose: To compare outcome for ipsilateral breast tumor recurrence (IBTR), or regional node recurrence, initial and subsequent distant metastases, an d overall and cause-specific survival in women treated with conservative su rgery and radiation based on whether or not radiation was targeted to the i nternal mammary nodes (IMN). Methods and Materials: From 1979-1994, 1383 women with Stage I-II breast ca ncer underwent wide excision, axillary node dissection with greater than or equal to 10 nodes removed, and radiation. Median follow-up was 6 gears; me dian age was 55 years. A total of 114 women had radiation targeted to the I MN with deep tangents and 1269 did not. Women who received IMN treatment we re more often axillary node-positive (40% vs. 25%, p = 0.002), had central or inner quadrant tumors (61% vs. 40%, p = 0.001), and had T2 tumors (47% v s. 31%, p = 0.001). All axillary node-positive women received adjuvant chem otherapy and/or tamoxifen. For axillary node-negative women, 13% of the IMN treatment group received adjuvant systemic therapy compared to 37% of the no treatment group (p = 0.001). Radiation was directed to the breast only i n 97% of the axillary node-negative women who had IMN treatment and 99% of the no IR IN treatment group. For axillary node-positive women, 98% of the IMN-treated group had radiation to the breast and supraclavicular nodes a a posterior axillary field compared to 77% of the no IMN treatment group (p = 0.001). There mere no significant differences between the two groups for median age, menopausal status, histology, final surgical margin, estrogen a nd progesterone receptor status, or the number of positive nodes. Results: There were no significant differences in the 5- and 10-year cumula tive incidence of an IBTR, regional node recurrence, initial or total dista nt metastases for the two groups. Similarly 5- and 10-year actuarial overal l and cause-specific survival were not significantly different. However, su bset analysis revealed a statistically significant increase in initial (29% vs. 15% at 10 yr, p = 0.002) and total (30% vs. 17% at 10 yr, p = 0.01) di stant metastases and a significant decrease in cause-specific survival (76% vs. 89% at 10 yr, p = 0.02) for postmenopausal women who received IMN trea tment. These findings could not be attributed to differences in the use of systemic therapy or the number of positive nodes. Axillary node-positive pa tients did not experience a significant decrease in initial (36% vs. 22% at 10 yr, p = 0.21) or total distant metastases (37% vs. 28% at 10 yr, p = 0. 62) or a significant improvement in cause-specific survival (72% vs. 76% at 10 yr, p = 0.76) with IMN treatment regardless of whether the tumor was la teral or medial/central in location. IMN treatment was not associated with an increase in non-breast cancer deaths during this period of observation. Conclusions: This retrospective series was unable to identify a significant benefit for IMN irradiation in terms of distant metastases or cause-specif ic survival for the entire patient population, and in particular, for patie nts with positive axillary nodes and medially located lesions. The results of the proposed or ongoing prospective randomized trials will further addre ss this controversial issue. (C) 2000 Elsevier Science Inc.