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Physical exercise during chemotherapy is not only safe, but helps to prevent declines in cardiorespiratory fitness and to facilitate a faster return to normal daily activities, compared with waiting until after chemotherapy is completed, the prospective showed.

Among 266 patients with mostly breast, testicular, or colon cancer who were randomized to a 24-week exercise intervention either during or after chemotherapy, peak oxygen uptake declined significantly from baseline to post-chemotherapy in both groups, but this decline was less pronounced in those who exercised during chemotherapy (adjusted between-group difference 3.1 mL/kg/min, 95% CI 2.2-4.0, P<0.001), reported Annemiek Walenkamp, MD, PhD, of University Medical Center Groningen in the Netherlands, and colleagues in .

The adjusted between-group differences in peak oxygen uptake for each of the three tumor types immediately post-chemotherapy were:

• Testicular cancer: 4.4 mL/kg/min (95% CI 2.7-6.1, P<0.001)
• Breast cancer: 2.2 mL/kg/min (95% CI 1.1-3.3, P<0.001)
• Colon cancer: 3.5 mL/kg/min (95% CI 1.2-5.7, P=0.004)

However, there were no differences between groups either immediately or 1 year after completion of the exercise intervention.

"These findings suggest that the optimal timing of physical exercise is during chemotherapy," Walenkamp and team wrote. "However, initiating a physical exercise program after chemotherapy is a viable alternative when exercising during chemotherapy is not possible."

Similar benefits in muscle strength, health-related quality of life, and fatigue were also seen in both groups, again with better results in the group who exercised during chemotherapy.

Fatigue in particular "is considered one of the most distressing adverse effects of cancer therapy and occurs in up to 80% of patients treated with chemotherapy," the authors noted, and "can negatively affect reintegration, social relationships, and participation in daily activities."

"In this trial, we found a clinically significant difference in general and physical fatigue between the groups in favor of the group that exercised during treatment, measured directly after chemotherapy, which might accelerate the return to everyday life," they added.

Specifically, Walenkamp and team found that immediately after completion of chemotherapy, patients who exercised during treatment experienced less general fatigue and physical fatigue, as determined by the Multidimensional Fatigue Inventory, and scored higher on the reduced activity subscale than patients who exercised after, with adjusted between-group differences of -2.1 (95% CI -3.3 to -0.8, P=0.001) for general fatigue, -2.9 (95% CI -4.3 to -1.5, P<0.001) for physical fatigue, and -1.5 (95% CI -2.9 to -0.1, P=0.03) for reduced activity.

In a , Neil M. Iyengar, MD, of Memorial Sloan Kettering Cancer Center in New York City, called this a "clinically impactful finding given the lack of effective treatments for this highly prevalent and distressing adverse effect."

The ACT trial randomized 266 patients with breast (n=139), testicular (n=95), and colon cancer (n=30), as well as two patients with lymphoma, from three centers in the Netherlands 1:1 to the exercise intervention during chemotherapy (mean age 45.8, 57% women) or after chemotherapy (mean age 48.3, 58% women).

The intervention consisted of 12 weeks of supervised exercise followed by 12 weeks of home-based unsupervised exercise. The first group initiated the 12-week supervised exercise intervention during chemotherapy and continued with the 12-week unsupervised home-based exercise after completing chemotherapy. Patients in the second group initiated the supervised exercise intervention approximately 3 weeks after the administration of the final dose of chemotherapy.

Exercise was moderate to vigorous in intensity and included work on a stationary bike, resistance training, and badminton.

Of note, the median adherence rate to the intervention among patients who exercised during chemotherapy was 75.0%, and 83.3% for those who exercised after.

In his commentary, Iyengar noted that adherence and tolerability are "critical factors that can limit the feasibility, duration, and efficacy of exercise interventions." He pointed out that in the ACT trial, the dropout rate was 29%, while about one-third of patients did not log adherence during home-based exercise.

"Cardiorespiratory fitness recovery in participants that started supervised exercise after completing chemotherapy caught up to participants that started exercise during chemotherapy but transitioned to home-based exercise after chemotherapy," he wrote. "These findings suggest the superiority of supervised exercise over home-based exercise, while highlighting the challenges of maintaining adherence."

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