Exercise prescription and adherence for breast cancer: One size does not FITT All

Purpose: To prospectively assess adherence to oncologist-referred, exercise programming consistent with current recommendations for cancer survivors among women with early breast cancer across the trajectory of adjuvant treatment. Methods: Sixty-eight women participated in supervised, hour-long, moderate-intensity, aerobic, and resistance exercise thrice per week during adjuvant chemotherapy ± radiation, with a step-down in frequency for 20 additional weeks. Adherence to exercise frequency (i.e., attendance), intensity, and time/duration, and barriers to adherence were tracked and compared during chemotherapy versus radiation, and during treatment (chemotherapy plus radiation, if received) versus after treatment. Results: Attendance decreased with cumulative chemotherapy dose (cycles 1–2 vs cycles 3–8, cycle 3 vs cycles 7–8, all P ≤ 0.05) and was lower during chemotherapy than radiation (64% ± 25% vs 71% ± 32%, P = 0.02) and after treatment than during treatment (P < 0.01). Adherence to exercise intensity trended toward being higher during chemotherapy than radiation (69% ± 23% vs 51% ± 38%, P = 0.06) and was higher during than after treatment (P = 0.01). Adherence to duration did not differ with treatment. Overall adherence to the resistance prescription was poor, but was higher during chemotherapy than radiation (57% ± 23% vs 34% ± 39%, P < 0.01) and was not different during than after treatment. The most common barriers to attendance during treatment were cancer-related (e.g., symptoms, appointments), and after treatment were life-related (e.g., vacation, work). Conclusions: Adherence to supervised exercise delivered in a real-world clinical setting varies among breast cancer patients and across the treatment trajectory. Behavioral strategies and individualization in exercise prescriptions to improve adherence are especially important for later chemotherapy cycles, after treatment, and for resistance exercise.