Treatment-related side effects among Hispanic and non-Hispanic white long-term breast cancer survivors by tamoxifen use and duration.

PURPOSE: To determine the associations between ethnicity, age at diagnosis, obesity, multimorbidity, and odds of experiencing breast cancer (BC) treatment-related side effects among long-term Hispanic and non-Hispanic white (NHW) survivors from New Mexico and explore differences by tamoxifen use.

METHODS: Lifestyle and clinical information including self-reported tamoxifen use and presence of treatment- related side effects were collected at follow-up interviews (12-15 years) for 194 BC survivors. Multivariable logistic regression models were used to examine associations between predictors and odds of experiencing side effects overall and by tamoxifen use.

RESULTS: Women ranged in age at diagnosis (30-74, M = 49.3, SD = 9.37), most were NHW (65.4%) and had in-situ or localized BC (63.4%). Less than half reportedly used tamoxifen (44.3%), of which 59.3% reported using > 5 years. Overall, survivors who were overweight/obese at follow-up were 5.42 times more likely to experience treatment-related pain (95% CI 1.40-21.0) compared to normal weight survivors. Survivors with multimorbidity, compared to survivors without, were more likely to report treatment-related sexual health issues (aOR 6.90, 95% CI 1.43-33.2) and poorer mental health (aOR 4.51, 95% CI 1.06-19.1). The statistical interactions between ethnicity and overweight/obese with tamoxifen use were significant (p-interaction < 0.05) for treatment-related sexual health issues.

CONCLUSION: Our results demonstrate that survivors with overweightness/obesity or multimorbidity may be more likely to experience BC treatment-related side effects. Tamoxifen use modifies associations between ethnicity, being overweight/obese, and sexual health issues following treatment. The likelihood of experiencing treatment-related side effects were more favorable for those on tamoxifen or those who had used tamoxifen for longer durations. These findings highlight the importance of fostering side effect awareness and applying appropriate interventions to assist with disease management throughout BC survivorship care.