PET scans and brain metastases

The brain naturally uses glucose, so normal brain activity can make small metastatic deposits difficult to separate on an FDG PET scan. PET may still help identify the primary cancer or active disease in the chest, abdomen, bones, or other tissues. MRI with contrast is commonly considered when symptoms or other findings raise concern about spread to the brain.

Brain metastases are secondary tumours that have travelled from another cancer. The original cancer may be in the lung, breast, skin, or another site. A scan result is interpreted with the neurological examination, symptoms, earlier images, and the known cancer history.

Tell the oncology team about headaches, seizures, weakness, balance changes, speech difficulty, vision changes, or altered behaviour. Bring prior brain imaging and a current medicine list. Ask whether MRI, tissue confirmation, or review by radiation, surgical, and medical oncology teams is appropriate.

Treatment options can include [Stereotactic Radiosurgery](/treatments/radiation-oncology/stereotactic-radiosurgery/), [Whole Brain Radiotherapy](/treatments/radiation-oncology/whole-brain-radiotherapy/), or [Brain Tumour Surgery](/treatments/surgical-oncology/brain-tumour-surgery/) depending on the number, size, location, and symptoms of lesions.

Seek urgent medical help for a first seizure, a seizure lasting longer than usual, sudden one-sided weakness, difficulty speaking, loss of consciousness, severe new headache with vomiting, or rapidly worsening confusion. Do not wait for a planned PET appointment when neurological symptoms are sudden or severe.

Is PET being used to assess the whole body rather than the brain alone? Do I need a contrast MRI? What symptoms should trigger urgent help? If a lesion is found, who will coordinate treatment and tissue diagnosis?