Effects of Cancer and Cancer Treatments on Physiological and Functional Capacity
Mechanisms, not just labels
Impairments come from the tumor itself (mass effect, obstruction, bleeding, pain, cachexia) and from treatment. Cardiotoxicity: anthracyclines cause dose-dependent injury that may appear early or years later; trastuzumab typically causes reversible dysfunction during therapy; chest radiation accelerates coronary and valvular disease over decades. Pulmonary: bleomycin, busulfan, and radiation pneumonitis. Neurologic: taxane, platinum, and vinca neuropathy; cisplatin ototoxicity. Endocrine and metabolic: androgen deprivation and aromatase inhibitors reduce bone density and lean mass; corticosteroids cause myopathy and hyperglycemia; immunotherapy can trigger thyroiditis, colitis, and myositis. Hematologic: anemia, thrombocytopenia, neutropenia. Surgical and radiation effects: lymphedema, shoulder dysfunction, fibrosis, adhesions, stoma.
Deconditioning, cancer-related fatigue, sarcopenia, and reduced activity compound one another. Fatigue is the most common and most treatable symptom; it is not a reason to withhold exercise, but new, unexplained, or disproportionate fatigue warrants screening for anemia, hypothyroidism, depression, sleep disturbance, and cardiac dysfunction.
Traps
Assuming toxicities are only acute; attributing all dyspnea to deconditioning when anemia or pneumonitis is possible; dismissing neuropathy as minor when it raises fall and burn risk.
Worked example
A man on androgen deprivation therapy reports six months of fatigue and 4 kg weight loss. Resistance and aerobic training are indicated, plus bone-loading activity and bone density review - do not restrict exercise because of the therapy.
Rule of thumb
Name the treatment, name its toxicity, then ask how that toxicity changes the prescription (falls, cardiac monitoring, infection, bone).