Women under 40 with estrogen receptor-positive breast cancer may not get as much benefit from chemotherapy as those patients over 40 with estrogen receptor-negative disease, according to study results published in the Oct. 11 issue of Breast Cancer Research.
"These results confirm that chemotherapy alone cannot be considered optimal adjuvant systemic treatment in breast cancer patients 40 years old or younger with hormone receptor-positive tumors," wrote Cornelis van de Velde, MD, of Leiden University Medical Center.
The researchers collected data from four European Organization for Research and Treatment of Cancer trials, which consisted of 934 early-stage breast cancer patients 40 or younger at the time of diagnosis, of whom 480 had tumor samples available for immunohistochemistry analysis.
Among the 279 women who received adjuvant chemotherapy, 85 percent were lymph node-positive, and nearly all, 94 percent, of the 201 who did not receive chemotherapy were node-negative.
Estrogen receptor status was positive for 288 women, and progesterone status was positive for 223. Less than 5 percent of the women received adjuvant hormonal therapy, because it was not yet recommended at the time of the trials.
After a median of 7.3 years of follow-up, 22 percent of the participants died and 32 percent had developed a distant recurrence, or died.
Overall, estrogen receptor-positive tumors were associated with 37 percent better overall survival, but not distant metastasis-free survival compared with estrogen receptor-negative cancer. Similarly, progesterone receptor positivity was associated with better overall survival, but not distant metastasis-free survival.
Even after controlling for nodal status, tumor size, and chemotherapy in multivariate analysis, both hormone receptors were significant factors in overall survival.
The researchers did not make a direct comparison between chemotherapy and the lack thereof by hormone receptor status because "the confounding effect of auxiliary lymph node status would have introduced a significant selection bias," according to the study.