Chemotherapy for primary breast cancer causes significant declines in cardiorespiratory fitness (CRF)
predisposing patients to increased symptom burden and increased risk of morbidity and mortality from cancer
and non-cancer conditions. Randomized trials demonstrate aerobic training (AT) is feasible during chemotherapy
for primary breast cancer and attenuates treatment-induced impairments in CRF. However, our recent findings
indicate that even with AT during and after chemotherapy, CRF remains substantially below normative values,
and less than 25% of patients have a clinically meaningful CRF response. Increasing the dose of AT substantially
increases CRF response; however, higher AT doses are associated with lower AT adherence. Thus, use of a
conventional dose-response design wherein patients are assigned to fixed doses is likely imprudent considering
lower fixed AT doses will result in underdosing in some patients, and poor adherence in others. A more patient-
centered approach used in drug trials is flexible dosing, where the dose is escalated for each patient as tolerated.
There have been no trials directly assessing the efficacy of flexible AT dosing on CRF in any cancer setting. To
address this fundamental knowledge gap in exercise-oncology research, the objective of this study is to
compare the effects of flexible versus standard fixed AT dosing and response-adapted AT on CRF response. In
this randomized trial, a total of 140 inactive (<90 mins of moderate-intensity exercise/wk) patients with primary
breast cancer scheduled to initiate chemotherapy will be randomly allocated (1:1) to Flexible dosing: Individual
AT doses escalated; or Standard fixed dosing: 90 mins/week for ~32 weeks (during and after chemotherapy).
Patients who do not respond (<3.50 ml/kg/min CRF improvement) at 32 weeks will complete 20 weeks of
extended flexible dosing AT. We will address 3 specific aims: AIM 1: Compare the effects of flexible versus
standard dosing on CRF response rate. AIM 2: Ascertain the effects on adherence, safety, and patient-reported
outcomes. AIM 3: Evaluate the effects of extended AT in CRF non-responders. IMPACT: This study challenges
the current dogma that all patients respond equally to a fixed AT dose and will be the first to evaluate flexible AT
dosing in any cancer population. Receiving cancer treatment is not a qualifying condition for structured AT and,
as such, AT is not currently considered a standard aspect of cancer management. We anticipate the proposed
trial will directly address an unmet clinical need by identifying the AT regimen that maximizes CRF response rate
and, if successful, findings from this investigation will help guide the AT regimen for translation to clinical care.
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