Why Does Chemotherapy — Cause Side Effects?

Most standard chemotherapy drugs do not significantly affect the heart or kidneys, because those organs divide slowly and are largely bypassed. A small number of specific drugs carry a known risk to heart or kidney function; when those are part of your regimen, your team will tell you in advance and monitor accordingly. If you are unsure which drugs you are receiving and what their specific risks are, that is a reasonable question to ask at your next appointment.

Fatigue comes from several causes, not only the effect on dividing cells. When bone marrow output falls, red cell counts can drop, and fewer red cells means less oxygen reaching your tissues — which causes tiredness. The body also uses energy to repair damaged tissue between doses. Fatigue is one of the most common and often the most difficult side effect to manage; your team can suggest approaches specific to your situation.

Hair loss depends on which drugs you are given, not on chemotherapy in general. Some regimens cause significant hair loss, others cause thinning, and some cause none at all. Your oncologist or chemotherapy nurse will tell you what to expect before your first cycle. If hair loss is expected and scalp cooling is available at your centre, your team can discuss whether it is suitable for your regimen.

Chemotherapy reduces the bone marrow's output of white blood cells — the cells that fight infection. When white cell counts are low, your body cannot respond to bacteria or viruses the way it normally would. A temperature that would be mild in other circumstances can signal a serious infection when white cells are suppressed. Your team will tell you what temperature to call about and what to do. Do not wait until morning for a fever that develops overnight.

Many people eat normally for most of their treatment, though nausea and taste changes are common. Small, frequent meals are usually better tolerated than large ones. Your team has access to a dietitian who can advise for your specific regimen and your difficulties. Do not start supplements or make major dietary changes without telling your oncologist first — some foods and supplements can affect how chemotherapy drugs work in the body.

This varies with the drugs used, the number of cycles, and your general health going in. Most acute side effects — nausea, mouth sores, low blood counts — improve within weeks of the final cycle. Fatigue can take longer, sometimes several months. Hair typically begins returning within weeks to a few months. Some nerve-related symptoms take longer still. Ask your oncologist what recovery looks like for your specific regimen, and report anything not improving on the expected schedule.