[Long-term survival analysis of different breast cancer molecular subtypes: Shanghai Breast Cancer Survival Study]

To analyze the survival of breast cancer molecular subtypes and to examine the effect of therapy on the long-term prognosis of different subtypes.

This study included 3 586 breast cancer patients with estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2) information in Shanghai Breast Cancer Survival Study, a population-based prospective cohort study established in 2002. Molecular subtypes, based on immunohistochemistry were categorized as follows: Luminal A, Luminal B, HER2, and triple-negative subtype. Characteristics and clinical data were collected through questionnaires and medical records at baseline survey and sequential follow-up surveys. Survival rates of different molecular subtypes were analyzed and compared with Log-rank tests. Multiple Cox regression models were used to evaluate the effect of therapy on long-term prognosis of different molecular subtypes.

Among the 3 586 cases, Luminal A, Luminal B, HER2 and triple-negative breast cancer subtypes accounted for 54.5%, 16.6%, 13.9%, and 14.9%, respectively. With a median follow-up of 10.3 years (ranging 0.6 to 12.8 years), the 10-year overall survival (OS) rates for the four subtypes were 82.7% (95% CI: 80.9% to 84.4%), 77.7% (95% CI: 74.1% to 80.8%), 76.3% (95% CI: 72.3% to 79.8%), and 74.8% (95% CI: 70.9% to 78.3%), respectively. The 10-year disease to free survival (DFS) rates were 79.0% (95% CI: 76.7% to 81.0%), 76.0% (95% CI: 71.9% to 79.5%), 73.6% (95% CI: 68.9% to 77.7%), and 74.5% (95% CI: 69.4% to 78.9%), respectively. Significant difference in survival among four subtypes was observed (Log-rank test, P<0.01). Multivariate Cox regression indicated that hormonal therapy can significantly reduce the long-term risk of total mortality and recurrence breast cancer specific mortality among Luminal A subtype patients. Adjuvant chemotherapy could improve the long-term prognosis of triple-negative breast cancer. No benefit from radiotherapy was observed for four subtypes of breast cancer in terms of long-term prognosis.

Molecular subtypes based on ER/PR/HER2 could provide important information to predict breast cancer prognosis. The hormonal status was an important basis for individualized therapy and precision medicine.