Do exercise oncology guidelines have to be met to obtain improvements in breast cancer outcomes?

Introduction: The importance of exercise as part of cancer care is clear, with benefits potentially extending to survival. However, treatment, personal and behavioural barriers may influence the amount of exercise undertaken during any given week. Aim: To explore whether compliance to weekly exercise targets predicts improvements in outcomes in women with breast cancer who participated in the SAFE trial (ACTRN12616000954426). Methods: Sixty physically inactive breast cancer survivors (stage II-IV, mean age 50.1±9.0) were randomised to 20 or 5 supervised sessions with an exercise physiologist during a 12-week individually-tailored exercise intervention. The weekly exercise target was consistent with international guidelines of 600MET-minutes including 2 resistance exercise sessions. Exercise completed (mode, frequency, minutes, intensity) was recorded weekly and used to calculate MET-mins. Exercise compliance defined as (1) average weekly volume ≥weekly target or (2) weekly target met in ≥80% of weeks. Multivariable regression analyses (adjusted for age, disease, BMI, group) were used to evaluate if exercise compliance predicted change pre- and post-intervention in physical health (PROMIS global), aerobic fitness (6-minute walk test) and strength (YMCA bench press). Results: Sixty-three per cent and 27% of the sample were compliant when defined by average weekly volume and ≥80% of weeks, respectively. Having an average weekly exercise volume that was ≥ weekly target predicted a clinically meaningful improvement in physical health (Δ±SE: 7.2±1.0 P < 0.01), aerobic fitness (59.8±11.4 m, P < 0.05) and strength (11.4±2.2, P = 0.25). Meeting weekly targets ≥80% of intervention weeks did not predict change in outcomes (P ≥ 0.05). Conclusion: These findings suggest that fluctuating levels of weekly exercise completed does not jeopardise the potential benefit of exercise if on average patients meet recommended levels. This is particularly reassuring for patients who have short term declines in exercise as a ...