Her2/neu-positive disease does not increase risk of locoregional recurrence for patients treated with neoadjuvant doxorubicin-based chemotherapy, mastectomy, and radiotherapy

Purpose Preclinical data suggest that overexpression of Her2/neu confers cellular radioresistance. We retrospectively studied whether Her2/neu-positive disease was associated with locoregional recurrence (LRR) after postmastectomy radiotherapy (RT) for breast cancer. Methods and materials Data from 337 patients treated in four institutional prospective clinical trials neoadjuvant doxorubicin-based chemotherapy, mastectomy, and RT were reviewed. The trials were conducted between 1989 and 2000. Of the 337 patients, 108 (32%) had tumors that were tested for Her2/neu, with positivity defined by 3+ immunohistochemistry staining or gene amplification detected by fluorescence in situ hybridization. RT was delivered to the chest wall and draining lymphatics (median dose, 50 Gy) followed by a chest wall boost (median dose, 10 Gy). Results Thirty-two patients had Her2/neu-positive disease and 76 patients had Her2/neu-negative disease. The Her2/neu-positive tumors were associated with a greater rate of estrogen receptor-negative disease (p = 0.03), the presence of supraclavicular disease at diagnosis (p = 0.027), and a greater number of positive lymph nodes after chemotherapy (p = 0.026). Despite these adverse features, the actuarial overall LRR rate was roughly equivalent for the patients with Her2/neu-positive tumors vs. those with Her2/neu-negative tumors (5-year rate 17.5% vs. 13.9%, respectively; 10-year rate 17.5% vs. 18.9%, respectively; p = 0.757). On Cox regression analysis of LRR adjusted for N stage and estrogen receptor status, the hazard ratio for Her2/neu positivity was 0.89 (95% confidence interval, 0.31-2.59; p = 0.83). Conclusion Her2/neu overexpression does not appear to predispose to LRR after neoadjuvant doxorubicin-based chemotherapy, mastectomy, and RT.