Table 2.
Proposed mechanisms of impaired cardiorespiratory fitness in patients with cancer
| Organ component of oxygen system | Oxygen transport component | Tumour and/or cancer therapy-associated impairment | At-risk cancer patient population | ||||
|---|---|---|---|---|---|---|---|
| Tumour presence | Surgery | Chemotherapy | Radiation | Hormone suppression | |||
| Pulmonary | Reduced diffusion capacity Increased alveolar hypoventilation Pulmonary vascular damage, remodelling, and fibrosis |
Primary or secondary lung cancer (↑↑↑) | Thoracic surgery (↑↑↑) | Platinum-based chemotherapy (↑) Other classes (unknown) |
Thoracic radiation (↑↑) | Unknown | Primary or secondary thoracic malignancies Presenting with concomitant respiratory disease Any population receiving thoracic or total-body irradiation |
| Cardiac | Left ventricular systolic dysfunction Reduced left ventricular relaxation Reliance on late rather than early filling Reduced ventricular compliance Reduced stroke volume Reduced cardiac output Reduced chronotropic reserve Reduced myocardial perfusion |
NA | NA | Anthracycline-based chemotherapy (↑↑↑) Other classes (↑↑) |
Thoracic radiation (↑↑) | ADT (↑) Endocrine therapy (unknown) |
Any population receiving chemotherapy particularly anthracycline-containing regimens Presenting with concomitant cardiovascular disease or cardiovascular risk factors Any population receiving thoracic or total-body irradiation Elderly patients (>65 years) |
| Blood | Reduced haemoglobin concentration | Haematological malignancy (↑↑↑) Extensive bone metastases (↑↑) |
Extensive surgery (↑↑↑) | All classes (↑↑↑) | Femur exposure (↑) | Unknown | The majority of cancer patients receiving any type of anticancer therapy |
| Vascular function | Impaired vasodilatory response to hyperaemia (that is, endothelial dysfunction) Increased arterial stiffness Increased reactive oxygen species or decreased anti-inflammatory expression |
NA | NA | Anthracycline-based chemotherapy (↑) Other classes (unknown) |
Thoracic radiation (↑) | Unknown | Any population receiving chemotherapy particularly anthracycline-containing regimens Presenting with concomitant cardiovascular disease or cardiovascular risk factors Any population receiving thoracic or total-body irradiation |
| Skeletal muscle oxidative capacity | Muscle atrophy Reduced capillarisation Reduced enzymes for oxidative phosphorylation Reduced mitochondrial density Reduced myoglobin concentration Fiber type transition to more glycolytic phenotype |
Advanced disease (↑↑↑) | NA | Anthracycline-based chemotherapy (↑) Other classes (unknown) |
Muscle- implicated radiation (unknown) | Unknown | Any population receiving chemotherapy, particularly anthracycline-containing regimens Patients experiencing cachexia Prolonged bed-rest (for example, post BMT) Presenting with concomitant cardiovascular disease or respiratory disease |
Abbreviations: ↑, weak evidence; ↑↑, moderate evidence; ↑↑↑, strong evidence; ADT, androgen deprivation therapy; BMT, bone marrow transplantation; NA, not applicable.