Reproductive cancer risk factors among Alaska Native women: the Alaska Education and Research Towards Health (EARTH) Study

Invasive breast cancer among Alaska Native women in Alaska

Female breast cancer is the most common cancer diagnosed among Alaska Native (AN) women. We examined characteristics of and trends for female breast cancer among AN women. We assessed descriptive statistics, incidence trends (1969-2014), and cause-specific survival for female breast cancers recorded in the Alaska Native Tumor Registry. Results indicated that the majority of breast cancers among AN were diagnosed among women aged over 50 years, at local stage, and with Hormone receptor (HR)+/Human Epidermal Growth Factor (HER) 2- subtype. Five-year average incidence (95% CI) in the most recent time-period (2009-2014) was 145.0/100,000 (130.4, 159.5)); this was not statistically different from the previous time-period. Survival from breast cancer was high and varied by stage and cancer subtype. Hazard of death was greater among those diagnosed with regional/distant/unknown disease, relative to local disease (HR (95%CI): 4.65 (1.66, 12.98)), and higher among those with HER2-/HR- cancers, relative to those with HER2-/HR+ cancers (HR (95%CI): 6.59 (2.23, 19.49)). This study provides a comprehensive description of breast cancer among AN women, providing new and updated information on clinical and demographic factors, cancer incidence trends, regional variations and breast cancer survival. Abbreviations: AIAN: American Indian/Alaska Native; AN: Alaska Native; ANMC: Alaska Native Medical Center; ANTR: Alaska Native Tumor Registry; CI: Confidence Interval; HR: Hazard Ratio; ICD-O-3: International Classification of Diseases for Oncology - Third Edition; NHW - Non-Hispanic Whites; SEER: Surveillance, Epidemiology and End Results.

Cancer incidence and associations with known risk and protective factors: the Alaska EARTH study

PURPOSE

Cancer is the leading cause of mortality among Alaska Native (AN) people. The Alaska Education and Research Towards Health (EARTH) cohort was established to examine risk and protective factors for chronic diseases, including cancer, among AN people. Here, we describe the cancer experience of the Alaska EARTH cohort in relation to statewide- and region-specific tumor registry data, and assess associations with key cancer risk factors.

METHODS

AN participants were recruited into the Alaska EARTH cohort during 2004-2006. Data collected included patient demographic, anthropometric, medical and family history, and lifestyle information. This study linked the Alaska EARTH data with cancer diagnoses recorded by the Alaska Native Tumor Registry (ANTR) through 12/31/15. We compared EARTH incidence to ANTR statewide incidence. We examined independent associations of smoking status, diet, BMI, and physical activity with incident all-site cancers using multivariable-adjusted Cox proportional hazards models.

RESULTS

Between study enrollment and 2015, 171 of 3,712 (4.7%) Alaska EARTH study participants were diagnosed with cancer. The leading cancers among Alaska EARTH participants were female breast, lung, and colorectal cancer, which reflected those observed among AN people statewide. Incidence (95% CI) of cancer (all sites) among Alaska EARTH participants was 629.7 (510.9-748.6) per 100,000 person-years; this was comparable to statewide rates [680.5 (660.0-701.5) per 100,000 population]. We observed lower risk of all-sites cancer incidence among never smokers.

CONCLUSIONS

Cancer incidence in the Alaska EARTH cohort was similar to incidence observed statewide. Risk and protective factors for leading cancers among AN people mirror those observed among other populations.