Hepatitis B and Cancer Treatment: — Understanding Reactivation Risk

Yes. Having hepatitis B does not mean chemotherapy is off the table. What it means is that your team needs to know before treatment starts so they can check your liver status, assess your reactivation risk, and start antiviral prophylaxis if it is recommended. The precautions are well established. Most patients with hepatitis B go through cancer treatment safely when their hepatitis is managed alongside their cancer care.

Hepatitis B virus can remain inactive in your liver cells for many years after the original infection. Treatments that suppress the immune system allow the virus to begin multiplying again. That rise in viral activity can inflame the liver, causing a flare. This can happen even in people who had previously cleared the virus and whose blood tests had shown no sign of active infection for years.

Yes, and this is one of the most important things to understand. A past hepatitis B infection that appears to have resolved can still leave dormant virus in the liver. Certain cancer treatments — particularly rituximab, other anti-CD20 antibodies, and high-dose corticosteroids — can reactivate the virus even when your blood tests have been clear for years. ASCO recommends screening all patients regardless of whether their infection is considered resolved.

It depends on your hepatitis B status and the specific treatment you are having. ASCO and ESMO guidance recommends antiviral prophylaxis for patients at higher risk — generally those with active hepatitis B, or those with past infection who are receiving treatments that significantly suppress the immune system. Your oncologist and, ideally, a liver specialist will decide together. If prophylaxis is recommended, it should start before your cancer treatment begins, not partway through.

Early reactivation often has no symptoms, which is why blood monitoring matters more than watching for warning signs alone. When symptoms do appear, they can include unusual fatigue, yellowing of the skin or eyes, dark-coloured urine, pain in the upper right abdomen, and nausea. Tell your oncology team the same day if you notice any of these during treatment. Do not wait for your next scheduled appointment.

Hepatitis C behaves differently to hepatitis B. Treatments that stress the liver can worsen active hepatitis C, and some immunotherapy drugs have been associated with changes in hepatitis C activity. Reactivation in the same well-defined sense as hepatitis B is less commonly described in clinical guidelines, but the risk of liver toxicity is real. If you have hepatitis C, tell your oncologist before treatment starts and ask whether a liver specialist should be involved in your care.

Significant liver inflammation or impaired liver function can affect how some cancer medicines are processed and cleared from the body, which may require a dose adjustment or a temporary pause in treatment. This is one of the reasons liver function tests are monitored regularly during cancer treatment — so that any changes can be acted on early. Your team will explain what the results mean for your specific regimen.

The duration depends on which cancer treatment you are having and how long it suppresses your immune system. For some regimens antivirals continue for the duration of treatment. For others — particularly those involving rituximab or anti-CD20 antibodies — ASCO and ESMO guidance recommends continuing for a period after treatment ends, because reactivation can still occur during the recovery phase when the immune system has not yet returned to normal. Do not stop without checking with your team first.