What should you know about a PET scan after chemo?

PET imaging uses a radiotracer to highlight metabolic activity, while CT shows anatomy. Cancer cells may be active on a scan, but healing tissue, inflammation or infection can also take up tracer. Chemotherapy can change both a tumour and surrounding tissue, so a scan is scheduled according to the treatment plan and the cancer being assessed.

A lower level of activity may support a treatment response, while remaining activity may need correlation with symptoms, examination, blood tests or another scan. The result is not a stand-alone verdict and does not replace the oncology team’s review.

Follow the centre’s instructions about fasting, fluids, exercise and medicines. Tell staff about diabetes, recent infection, steroid use, allergies and any treatment side effects. Arrive early enough for the tracer injection and quiet uptake period; keeping still during imaging helps produce clearer pictures.

Bring details of recent chemotherapy, other treatments and earlier scans if the centre has not already received them. Ask when your clinician will explain the report and what the next decision might be if the scan is reassuring, unclear or shows ongoing activity.

Tell the scan team immediately about sudden breathing difficulty, facial swelling, widespread rash or feeling faint after the tracer. Seek urgent help for severe breathing trouble or collapse. After chemotherapy, contact your oncology team urgently for fever, shaking chills, confusion, severe shortness of breath or inability to keep fluids down, following the emergency instructions they gave you.

Why is the scan being done at this point in my treatment? Which changes would suggest response, healing or persistent disease? Could recent infection or treatment affect the result? What preparation applies to my medicines or diabetes? When will we discuss the report and decide on the next step?