Which factor is most important when adjusting chemotherapy dosing for elderly patients?

• A. Chronologic age
• B. Cancer type
• C. Individual physiologic function and organ reserve
• D. Patient height

Answer: (C)

When adjusting chemotherapy dosing in older adults, the most important factor is the patient’s physiologic function and organ reserve. Chronologic age alone does not reliably predict tolerance because aging affects individuals differently; some elderly patients retain good organ function and marrow reserve, while others have significant comorbidities and reduced function.

Drug exposure and toxicity depend on how the body processes and clears medications. Renal function determines clearance for many agents, so reduced kidney function increases drug exposure and toxicity risk. Hepatic function affects metabolism, altering how drugs are activated or inactivated. Bone marrow reserve and overall performance status influence susceptibility to myelosuppression, infections, fatigue, and other adverse effects. Therefore, dosing adjustments should be guided by labs and functional measures such as eGFR/creatinine clearance, liver function tests, performance status, and comorbidity burden.

Cancer type helps determine which regimen is appropriate, but it does not substitute for evaluating physiologic reserve when deciding on dose. Height or body size may influence some dosing calculations, but the central consideration remains the patient’s physiologic capacity to tolerate treatment.

In short, tailor chemotherapy to the individual’s functional status to balance effectiveness with safety.