Smoking And Risk Of Breast Cancer According To Hormone Receptor Status In A Racially/Ethnically Diverse Population

Inger GRAM, UiT The Arctic University of Norway, Norway
PARK S. 2 , KOLONEL L. 2 , MASKARINEC G. 2 , WILKENS L. 2 , HAIMAN C. 3 , LE MARCHAND L. 2

1 Department of Community Medicine, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway
2 Epidemiology Program, University of Hawai’i Cancer Center, Honolulu, Hawai’i, United States
3 Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, Unite

Purpose: To examine the risk of breast cancer from smoking for women diagnosed with Estrogen Receptor (ER) +, ER-, Progesterone Receptor (PR) + and PR- tumors.
Methods: From 1993 to 2010, we followed 83,300 women who were enrolled in the Multiethnic Cohort Study at 45–75 years of age. We identified cancer cases via linkage to the Surveillance, Epidemiology, and End Results Program cancer registries that covered the states of Hawaii and California through December 2010. We used Cox proportional hazards models to estimate hazard ratios (HR)s and 95% confidence intervals (CI) while adjusting for a priori selected confounders. .
Results: During a mean follow-up of 14.6 years, 4,484 women developed invasive breast cancer, of whom 560 (12.5 %) had unknown status for hormone receptor.  Altogether, 3,183 (71.0%) women were diagnosed with ER+, 730 with ER-, 2,541 (56.7%) with PR+ and 1,151 with PR- breast cancer. Women who had smoked for more than 5 years before their first childbirth had an overall HR for  ER+ breast cancer that was 31% higher (95% CI 1.11- 1.54) compared with parous never smokers. The corresponding HR for ER- breast cancer was 0.99 (95% CI 0.68 - 1.44). Among women who had a PR+ tumor status, the risk was 26% higher (HR = 1.26, 95% CI 1.05 - 1.52) and for PR- breast cancer 25% higher (HR = 1.25, 95% CI 0.95 - 1.64). The P interaction by tumor status was 0.22 for ER+/ER- tumors and 0.63 for PR+/PR- tumors.
Conclusions: For parous women who had smoked more than 5 years before their first childbirth, we found a smoking-related increase in breast cancer risk for both ER+ and PR+ tumors. These risks did not differ significantly by hormone receptor positive and negative tumors.
Funding source:  Grant  U01 CA164973 from the US National Cancer Institute.