Background: Chemotherapy (CT) is one of the most common factors associated with fatigue among breast cancer (BC) patients. However, there is a paucity of research on the impact of different types of CT on fatigue, specifically, whether women who receive anthracycline-based (Anth) CT experience greater fatigue than those who receive non-anthracycline-based (noAnth) CT. Methods: Analyses are from the longitudinal Understanding and Predicting fatigue, cardiovascular decline, and events after BrEast cAncer sTudy (UPBEAT: WF 97415)), conducted through the NCI Community Oncology Research Program (NCORP). We compared fatigue 3-months after initiating cancer treatment, controlling for fatigue measured just prior to beginning CT (baseline), in 3 groups of women: BC patients receiving Anth CT (N = 103 at baseline), BC patients receiving NoAnth CT (N = 155), and women without cancer (N = 145). Fatigue was measured by the Functional Assessment of Chronic Illness Therapy Fatigue scale where lower scores indicate greater fatigue. Scores < 30 indicate severe fatigue. We used ANOVA and ANCOVA models (PROC GLM; SAS v. 9.4) to generate unadjusted and adjusted mean fatigue scores in the 3 groups at the relevant time point. Given that selection to CT type was not random, we further adjusted for patient characteristics that influence treatment type (stage and comorbidities) in a model with the two CT groups only. Results: Mean age of participants (75.7% White and 18.1% Black) was 53.9 years. Among BC patients, the Anth group had higher tumor stage compared to the NoAnth group. Both cancer treatment groups reported significantly greater (unadjusted) fatigue pre-chemotherapy and at 3 months than healthy controls, but did not differ from each other. Adjusting for age and baseline fatigue, 3-month fatigue scores were significantly worse for the two CT groups (32.3 for Anth group, 34.3 for the NoAnth group) compared to the controls (44.6) (p < .0001). In a model of cancer patients only, the difference between Anth and NoAnth groups remained non-significant (p = 0.10), after adjusting additionally for number of comorbidities and cancer stage. The unadjusted percentage of women with severe fatigue at 3 months was significantly greater for the BC patients (39% in the Anth group; 38% in the NoAnth group) compared to the healthy controls (1%), but again the two chemotherapy groups were not significantly different from each other. Adjustment for covariates listed above did not change this finding. Conclusions: Analyses support previous studies showing significant fatigue among BC patients treated with CT compared to women without cancer. Our data suggest that fatigue significantly impacts patients receiving CT irrespective of the regimen selected.

¹lower score = greater fatigue. Funding provide by: 2UG1CA189824, R01CA199167, and 2UG1CA189828.