Trastuzumab Deruxtecan in Elderly Patients — and Those With Other Illnesses

Age alone is not an exclusion for this drug. Clinical trials included patients across a range of ages, and NCCN guidance does not set an age cutoff. What matters more is how your body is functioning overall — your heart, lungs, kidneys and liver — rather than your age in years. Older patients are more likely to have some impairment in one of these areas, which is why the pre-treatment assessment is more detailed. Your oncologist will discuss what the findings mean for your specific plan.

Pre-existing lung disease is the most important safety concern with trastuzumab deruxtecan. The drug can cause interstitial lung disease, and that risk is higher when the lungs are already damaged. Patients with active ILD were excluded from the main clinical trials, so data in this group is limited. Before starting, your team will likely arrange a CT scan of your chest and review your breathing. If active lung inflammation is present, treatment is generally not started until that has been assessed and addressed.

Mild to moderate kidney impairment generally does not require a dose change, according to the prescribing information. Severe kidney impairment has been less studied, and your team will assess this carefully before deciding. Your kidney function will be monitored through regular blood tests during treatment. Tell your team about any kidney condition you already have, including whether you are on dialysis, so they can plan your monitoring accordingly.

Mild liver impairment is generally manageable with standard monitoring. More significant liver impairment is not well studied with this drug, and the prescribing guidance reflects that caution. Your liver function will be checked regularly through blood tests during treatment. If you have hepatitis B, hepatitis C, or cirrhosis, tell your team before you start — these conditions may affect whether additional precautions or specialist involvement are needed.

Pre-existing heart disease does not automatically rule out this drug, but it means monitoring is more frequent. Your team will test your heart function before you start, usually with an echocardiogram or a similar scan. This is repeated at regular intervals during treatment. If your heart function falls significantly from your starting level, treatment may be paused while the situation is assessed. Your oncologist and, where needed, a cardiologist will advise on this together.

Previous chest radiation can leave lasting changes to the lung tissue, even when your breathing feels normal day to day. This background damage can raise your risk of developing ILD on this drug. Your team will review your radiation history and is likely to arrange baseline chest imaging before starting. Many patients who have had chest radiation receive this drug successfully, but with more frequent monitoring during treatment.

Some medicines interact with trastuzumab deruxtecan and may need to be reviewed before you start. The chemotherapy payload in the drug is broken down by a liver enzyme, and medicines that strongly affect this enzyme can change how much of the drug is active in your body. Your team will review your full medicine list before prescribing. Include herbal supplements and over-the-counter medicines, not just prescribed ones. Do not start or stop any regular medicine without telling your oncology team first.

Not necessarily. Dose adjustments with this drug are usually made in response to side effects that appear during treatment — such as nausea, low blood counts, or any sign of lung inflammation — rather than being set lower from the start because of a pre-existing condition. The exception is significant liver impairment, where the prescribing guidance advises caution because the drug has not been well studied in that group. Your team will tell you the planned dose and explain the reasons for any change from the standard.