Randomized clinical trial comparing level II and level III axillary node dissection in addition to mastectomy for breast cancer

Background: In addition to mastectomy, level II and level III axillary node dissection procedures are performed widely in Japan. A randomized clinical trial was performed to determine which procedure was more effective. Methods: One group of women had resection of the pectoralis minor muscle and dissection of level I, II and III axillary lymph nodes (level III dissection). In a second group, the pectoralis minor muscle was left intact and level III axillary lymph node dissection was not performed (level H dissection). A total of 1209 women with stage H breast cancer were enrolled in the study and randomly assigned to one of the two groups. Results: The 10-year cumulative survival rate was 86.6 per cent after level II and 85.7 per cent after level III axillary dissection (hazard ratio (HR) 1.02; P = 0.931, log rank test). The 10-year disease-free survival rate was 73.3 and 77.8 per cent respectively (HR 0.94, P = 0.666). Overall survival and disease-free survival rates in the two groups were similar after both procedures. The duration of surgery was significantly shorter (P < 0.001) and blood loss was significantly less (P = 0.001) after level II dissection. In a survey of patients' symptoms on follow-up, no significant differences were found between the two procedures. Conclusion: The addition of pectoralis minor muscle resection and level III axillary lymph node dissection to mastectomy for stage II breast cancer did not improve overall or disease-free survival rates.