In 2008, more than 12 million people worldwide were diagnosed with cancer (http://globocan.iarc.fr/). Because of improvements in early diagnosis and the introduction of more aggressive treatments over the past 20 years, cancer survivors are now living longer.1 However, treatment often leads to a range of undesirable and debilitating adverse effects.

In the linked meta-analysis (doi:10.1136/bmj.e70), Fong and colleagues assess the effects of physical activity after treatment for cancer on 48 separate health related outcomes.2 The potential for exercise interventions to benefit survivors of cancer is a burgeoning area of research, and systematic reviews and meta-analyses have reported that exercise can reduce fatigue and improve functional outcomes and health related quality of life.3 4 5 These reports have also called for larger trials that have a greater focus on study quality and adverse events and longer follow-up.

Fong and colleagues’ meta-analysis reviewed 34 randomised trials (of which 22 were dedicated breast cancer studies) that assessed the effects of aerobic exercise, and in some studies also …