Abstract C87: Risk of second primary cancer (SPC) after breast cancer: A pooled analysis of Hispanic and non-Hispanic white women from New Mexico

Breast cancer is the most common form of cancer diagnosed among women. With the advances in early detection and breast cancer treatment, the population of long-term survivors is growing. Breast cancer survivors have increased risk of developing a second primary cancer (SPC) relative to a first primary cancer. Several population-based studies have examined the associations of specific risk factors, such as radiation treatment, with risk of SPC; however, few have investigated ethnic/racial differences in risk, or have examined the associations with modifiable risk factors such as smoking or obesity. We evaluated the risk of SPC among Hispanic (H) and non-Hispanic white (NHW) women from a pooled sample of 1,699 (1011 NHW, 688 H) incident breast cancer cases from the New Mexico Women9s Health Study (1992-1994) and the 4-Corner9s Breast Cancer Study (1999-2004). Data on lifestyle/behavioral risk factors, cancer diagnoses/characteristics, and primary breast cancer treatment were available. Adjusted Cox regression models were calculated to estimate hazard ratios (HR) and 95% confidence intervals (CI) for associations of SPC with ethnicity, age at first primary breast cancer diagnosis, cigarette smoking history, and obesity (body mass index (BMI)≥30 kg/m 2 ). Multivariable models were adjusted for age, study site/center, ethnicity, and breast cancer treatment. There were a total of 223 cases with SPC. There was no difference between NHW and H women for occurrence of SPC (13.5% vs. 12.7%; chi. sq. p=0.63) or the average number of years from first primary to SPC (H= 9.8 years vs. NHW= 9.5 years, p=0.102). The most common SPC observed was secondary primary breast cancer (n=117), followed by lung (n=15) and colon cancer (n=15). Obesity was not significantly associated with risk of SPC. However, women 50 years or older were at an increased risk for SPC compared to women under age 50 (HR, 1.67, 95% CI 1.23-2.28, p=0.001). With the evaluation of smoking history, former smokers had longer durations of smoking compared to current smokers; however, current smokers, compared to former, smoked on average more cigarettes/day. Compared to never smokers, women who smoked more than 20 pack-years (HR, 1.61; 95% CI 1.16-2.24, p=0.02), an average of 20 or more cigarettes/day (HR, 1.52; 95% CI 1.10-2.10, p=0.09), or for more than 30 years (HR, 1.69; 95% CI 1.19-2.40, p=0.03) had increased risk for SPC. Women who were ever smokers vs. never smokers also had an increased risk for SPC (HR, 1.35; 95% CI 1.04-1.76, p=0.03). The association among current smokers was not statistically significant (HR, 1.27; 95% CI 0.94-1.71), but there was a significant positive association found for former smokers (HR, 1.52; 95% CI 1.06-2.18, p=0.05). Our results suggest that women diagnosed with primary breast cancer are more likely to develop SPC if they are over the age of 50 years at diagnosis or have a history of cigarette smoking. These results were statistically significant after adjustment for breast cancer treatment. These findings further suggest that smoking cessation programs or interventions should be clinically advised for breast cancer survivors, as this population of women is at an increased risk for developing SPC. Citation Format: Avonne E. Connor, Richard N. Baumgartner, Stephanie D. Boone, Christina M. Pinkston, Kathy B. Baumgartner. Risk of second primary cancer (SPC) after breast cancer: A pooled analysis of Hispanic and non-Hispanic white women from New Mexico. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C87. doi:10.1158/1538-7755.DISP13-C87