Evaluating individual level change in physical function response following an exercise program for cancer survivors

Cancer survivors physical function response to exercise programs at the group level is well-established. However, to advance toward a more personalized approach in exercise oncology, a greater understanding of individual response is needed. This study utilized data from a well-established cancer-exercise program to evaluate the heterogeneity of physical function response and explore characteristics of participants who did vs. did not achieve a minimal clinically important difference (MCID).

Physical function measures (grip strength, 6-min walk test (6MWT), and sit-to-stand) were completed pre/post the 3-month program. Change scores for each participant and the proportion achieving the MCID for each physical function measure were calculated. The independent t-tests, Fisher's exact test, and decision tree analyses were used to explore differences in age, body mass index (BMI), treatment status, exercise session attendance, and baseline value between participants who achieved the MCID vs. those who did not.

Participants (N = 250) were 55 ± 14 years old, majority female (69.2%), white (84.1%), and diagnosed with breast cancer (36.8%). Change in grip strength ranged from - 42.1 to + 47.0 lb, and 14.8% achieved the MCID. Change in 6MWT ranged from - 151 to + 252 m, and 59% achieved the MCID. Change in sit-to-stand ranged from - 13 to + 20 reps, and 63% achieved the MCID. Baseline grip strength, age, BMI, and exercise session attendance were related to achieving MCID.

Findings illustrate wide variability in the magnitude of cancer survivors' physical function response following an exercise program, and that a variety of factors predict response. Further investigation into the biological, behavioral, physiological, and genetic factors will inform tailoring of exercise interventions and programs to maximize the proportion of cancer survivors who can derive clinically meaningful benefits.