Topoisomerase Inhibitor — Chemotherapy: What to Expect

Hair loss varies by drug. Anthracyclines such as doxorubicin tend to cause significant hair loss. Irinotecan causes less dramatic thinning in most people. Topotecan falls in between. Your oncologist can tell you what to expect with the specific drug you are having, because variation within this class is wide. Hair almost always regrows after treatment ends, though the timing varies from person to person.

It can be, if it becomes severe and is not reported promptly. The early type — starting within 24 hours — is usually short-lived and managed on the treatment day. The late type — starting more than 24 hours after treatment — can escalate quickly to dehydration and become a medical emergency if not treated. ASCO and NCCN guidance treats late diarrhoea on irinotecan as needing same-day contact with your team, not a wait-and-see approach. Most people manage well when it is reported early and treated correctly.

Your team will assess your heart function before starting — usually with an echocardiogram — and at intervals during treatment. Anthracyclines can reduce the heart's pumping efficiency with cumulative doses, and this effect is not always reversible. Total lifetime dose is tracked, which is why your oncologist needs to know about any anthracyclines you have had before, even years earlier. Most people complete treatment without significant heart effects, but the monitoring is not optional — it is what makes the treatment safe.

Treatment-related acute myeloid leukaemia (t-AML) is a rare second cancer that can develop months to years after chemotherapy with topoisomerase II inhibitors. It is a recognised long-term risk in NCCN and ASCO follow-up guidance. It is uncommon — this is why surveillance blood tests continue after treatment ends, so that any early change is caught. Being informed of the risk is not a reason to avoid a treatment that is indicated for you; it is the reason your follow-up is structured the way it is.

For the late diarrhoea pattern seen with irinotecan, many oncology teams do provide specific guidance on using loperamide at home — but only after explaining exactly when and how to use it. Do not start taking it without being told to. For the early cholinergic pattern, loperamide is the wrong medicine and will not help. The first step is always to tell your team which pattern you have and when it started — that information decides what they will recommend.

For most people, the acute side effects — nausea, diarrhoea, low blood counts — resolve after treatment ends. The effects to monitor for afterwards are the rarer long-term ones: heart function if you had anthracyclines, and blood count changes that might signal secondary leukaemia. This is why follow-up appointments and blood tests continue rather than stopping when treatment does. Tell your follow-up team about any unexplained fatigue, easy bruising, or repeated infections, even months after finishing chemotherapy.