Seizures and Breast Cancer: How Common, Why They Happen, and How They’re Managed

Seizures are not a common symptom of breast cancer in the breast, but they can occur when breast cancer spreads to the brain or affects the brain indirectly. ^[1] Seizures happen because abnormal electrical activity in the brain is triggered by tumors, swelling, or treatment-related changes, and they can often be controlled with medicines and targeted cancer therapies. ^{[2] [3]}

How common are seizures in breast cancer?

• Breast cancer in the breast rarely causes seizures; seizures typically signal involvement of the central nervous system. ^[1]
• Brain metastases can cause seizures, headaches, nausea, vision or speech problems depending on the tumor’s location. ^{[2] [4]}
• Seizures are relatively common in people with brain tumors, including metastatic tumors, and may persist even after treatment, although many can be managed. ^{[5] [6]}

What causes seizures in this context?

• Brain metastases: A tumor in the brain can disrupt electrical signaling, leading to partial or generalized seizures. ^{[2] [4]}
• Pressure and swelling (edema): Metastases increase pressure and swelling in the brain, which can provoke seizures and other symptoms like headaches or vomiting. ^{[4] [3]}
• Treatment-related effects:
  • Prior brain radiotherapy can, rarely, lead to later complications that include seizures (for example, stroke‑like migraine attacks after radiation). [PM16]
  • Drug interactions between cancer medicines and anti‑seizure drugs can change blood levels and seizure control; phenytoin levels may rise with capecitabine, requiring monitoring and dose adjustments, whereas valproate may be less affected. [PM15] ^[7]
• Paraneoplastic/autoimmune syndromes: Some cancers can trigger immune‑related brain inflammation that may cause seizures, and anti‑seizure medicines are part of care when this occurs. ^[8]

What do seizures look like?

A seizure is a sudden, uncontrolled change in the brain’s electrical activity; partial seizures may affect one brain area and cause symptoms such as muscle jerks, stiffening, unusual smells or tastes, tingling, or speech trouble. ^[9] These symptoms vary based on which brain region is involved, and may be accompanied by confusion or temporary weakness afterward. ^[9]

When to seek urgent care

• New or worsening seizures, severe headaches, persistent nausea/vomiting, sudden vision or speech changes, or new weakness warrant prompt medical evaluation because they may signal brain metastases or swelling. ^{[1] [4]}
• Follow‑up schedules after breast cancer treatment include checking for signs of recurrence, and reporting new neurological symptoms can speed diagnosis and care. ^[1]

How are seizures evaluated?

• Neurologic exam and brain MRI to look for metastases and swelling. Imaging helps locate and characterize brain lesions. ^[10]
• EEG (electroencephalogram) may be used to monitor brain waves and help assess seizure activity and its origin. ^[6]
• Medication review to identify potential drug interactions between anti‑cancer therapies and anti‑seizure medicines. ^[7] Adjustments may be needed to maintain safety and seizure control. [PM15]

Management: treating the cause and controlling seizures

• Anti‑seizure medicines (anticonvulsants): Often prescribed to control seizures; your team selects drugs considering other cancer treatments and potential interactions. ^[3] Monitoring blood levels and clinical response helps tailor dosing. ^{[6] [7]}
• Steroids (corticosteroids): Used to reduce brain swelling from metastases, which can relieve pressure‑related symptoms and help decrease seizure triggers. ^[3]
• Cancer‑directed therapy:
  • Surgery for accessible brain lesions to reduce tumor burden and relieve symptoms. ^[10]
  • Radiation (including stereotactic radiosurgery) to target brain metastases, often improving seizures and neurological deficits when lesions are controlled. ^[10]
  • Systemic therapy guided by the cancer’s subtype to control disease and reduce further brain involvement. ^[10]
• Supportive and ongoing care: Seizures are common with brain tumors even after treatment; regular follow‑up with neurology and oncology, EEG monitoring if needed, and symptom tracking are important for long‑term management. ^{[5] [6]}

---

Quick reference: causes and care

Topic	Key points
Typicality in breast cancer	Not typical unless brain is involved; report any new neurological symptoms. [1]
Main causes	Brain metastases, brain swelling, treatment effects, rare paraneoplastic syndromes. [2] [4] [3] [PM16] [8]
Symptoms of seizures	Jerking/stiffening, unusual smells/tastes, tingling, speech issues, variable by brain area. [9]
Urgent signs	New seizures, severe morning headaches, persistent vomiting, vision/speech changes. [4]
Evaluation	MRI brain, EEG, medication interaction review. [10] [6] [7]
Core management	Anti‑seizure meds, steroids for edema, surgery/radiation/systemic therapy for metastases. [3] [10]

---

Practical tips for safer care

• Tell your clinicians about all medicines and supplements, including anti‑seizure drugs, because certain anticancer agents can alter seizure medication levels or vice versa. ^[7] Phenytoin levels may rise with capecitabine and need monitoring, while valproate may be less affected. [PM15]
• Do not start or stop seizure medicines abruptly; work with your team to adjust doses based on symptoms and lab checks. ^[6]
• Keep a seizure log (date, duration, type of symptoms, triggers) and share it at appointments to fine‑tune treatment plans. ^[6]
• Ask about steroids and edema management if you have headaches or focal symptoms, since reducing swelling can lower seizure risk. ^[3]

---

Bottom line

• Seizures are not a typical sign of breast cancer in the breast itself, but they can occur when cancer spreads to the brain or due to treatment‑related changes. ^[1] They result from disrupted electrical activity in the brain and are often manageable with a combination of anti‑seizure medicines, steroids, and cancer‑targeted therapies. ^{[2] [3] [10]} Regular communication with your care team and prompt evaluation of new neurological symptoms can improve outcomes and quality of life. ^{[1] [5] [6]}