Brain Metastases

Brain metastasis consists of secondary tumors formed by dissemination of primary cancer from another body region to the brain via bloodstream. It accounts for 40-50% of all brain tumors in adults and is 10 times more common than primary brain tumors. Most common cancers that metastasize to the brain: Lung cancer (40-50%), breast cancer (15-20%), melanoma (10-15%), renal cell carcinoma (5-10%), colorectal cancer (5%). Eighty percent of metastases are located in the cerebral hemispheres, 15% in the cerebellum, and 5% in the brainstem. Multiple metastases are observed in 60-80% of cases.

Prognosis depends on multiple factors: Primary cancer type (breast cancer and melanoma have better prognosis, lung cancer worse), number of metastases (single metastasis better), performance status (Karnofsky score >70 better), extracranial disease control (controlled disease better), age (younger than 65 years better). Prognostic scores: GPA (Graded Prognostic Assessment), RPA (Recursive Partitioning Analysis). General median survival: Single metastasis with controlled primary cancer 6-12 months, multiple metastases with widespread disease 2-4 months. However, with modern treatments (SRS, targeted therapy, immunotherapy), control can be achieved for years in some patients. Tumors responsive to targeted therapy such as EGFR-mutant lung cancer or HER2-positive breast cancer have much better prognosis.

Both have advantages and decision is made on a patient-by-patient basis. Stereotactic radiosurgery (Gamma Knife, CyberKnife, LINAC-SRS) is preferred for: Small to medium-sized lesions (less than 3 cm), deeply located lesions, multiple metastases (1-10 lesions), patients with high surgical risk. Single session, non-invasive, local control rate 80-90%. Surgical resection is preferred for: Large lesions (greater than 3 cm), symptomatic lesions (mass effect, hydrocephalus), easily accessible location, solitary metastasis, unknown primary (tissue diagnosis needed). Surgery provides immediate symptom relief. Cavity radiotherapy after surgery reduces local recurrence risk. Combined treatment is optimal for many patients: Surgical resection plus cavity SRS.

WBRT use has decreased due to neurocognitive side effects and advancement of modern SRS technology. WBRT is still indicated for: Extensive metastases (more than 10 lesions), leptomeningeal dissemination, small cell lung cancer, progression after SRS, patients not suitable for SRS. Usually delivered as 30 Gy in 10 fractions. WBRT improves brain control (reduces new metastasis development) but has limited contribution to overall survival. Side effects: Acute (fatigue, nausea, hair loss - transient), late-onset (memory loss, learning difficulties, neurocognitive slowdown - may be permanent). Side effect reduction: Hippocampal-sparing WBRT (protects memory center), memantine (NMDA antagonist, neuroprotective agent).

Yes, targeted therapies with good brain penetration are highly effective. Lung cancer: For EGFR-mutant, osimertinib (3rd generation, excellent brain penetration, response rate 70-80%), for ALK-positive, alectinib, brigatinib, lorlatinib (high brain penetration), for ROS1-positive, entrectinib. Breast cancer: For HER2-positive, trastuzumab-deruxtecan (T-DXd, brain response rate 60-70%), tucatinib plus trastuzumab plus capecitabine. Melanoma: For BRAF-mutant, dabrafenib plus trametinib (brain response rate 50-60%). Renal cell carcinoma: Cabozantinib, lenvatinib. These drugs cross the blood-brain barrier and can be used with systemic therapy or as monotherapy in brain metastases.

Yes, immunotherapy is also effective in brain metastases. Most effective cancer types: Melanoma: Pembrolizumab or nivolumab (monotherapy), ipilimumab plus nivolumab (combination, brain response rate 50-60%, higher toxicity), complete response achieved in some patients. Lung cancer (NSCLC): Pembrolizumab (PD-L1 high), atezolizumab plus chemotherapy, brain response rate 30-40%. MSI-high or TMB-high tumors: Pembrolizumab effective regardless of cancer type. Renal cell carcinoma: Nivolumab plus ipilimumab. Synergistic effect: When immunotherapy is combined with SRS, abscopal effect (response in distant metastases) can be observed. Side effects: Immune-related adverse events (pneumonitis, colitis, hepatitis, hypophysitis) require monitoring.

Brain MRI screening indications: Lung cancer: Small cell lung cancer (mandatory at diagnosis, 10-20% have brain metastases), non-small cell lung cancer (adenocarcinoma, stage 2-4) recommended at diagnosis and follow-up. Breast cancer: HER2-positive or triple-negative type (high brain metastasis risk), stage 4 disease, development of neurological symptoms. Melanoma: Stage 3-4 disease, regular MRI during follow-up. Renal cell carcinoma: Metastatic disease. Early detection of asymptomatic brain metastases allows appropriate treatment at optimal timing (SRS or targeted therapy), resulting in better prognosis. Waiting until symptoms develop leads to delayed diagnosis.

Leptomeningeal metastasis is the dissemination of cancer cells to the membranes surrounding the brain and spinal cord (meninges). More common in breast cancer, lung cancer, and melanoma. Symptoms: Headache, nausea-vomiting, neck stiffness, cranial nerve palsies (double vision, hearing loss, facial palsy), radicular pain, leg weakness, urinary retention. Diagnosis: Contrast-enhanced brain and spinal MRI (leptomeningeal contrast enhancement), CSF cytology (tumor cells), elevated CSF protein-low glucose. Prognosis: Poor, median survival 2-4 months. Treatment: Whole brain and spinal radiotherapy, intrathecal chemotherapy (methotrexate, cytarabine - direct drug to CSF), systemic chemotherapy (high-dose methotrexate), targeted therapy (high brain penetration), supportive care. Novel treatments: Intrathecal trastuzumab (HER2-positive), immunotherapy.

In 5-10% of cases, brain metastasis is detected before the primary cancer. Diagnostic approach: Surgical resection of brain metastasis (both therapeutic and provides tissue diagnosis), pathological examination (immunohistochemistry to determine primary source: TTF-1 lung, CK7/CK20 GIS, GATA3 breast, S100-HMB45 melanoma). Primary cancer search: Chest CT (lung), abdomen-pelvis CT (kidney, colon), breast ultrasound-mammography (women), upper-lower GI endoscopy, skin examination (melanoma), whole-body PET-CT, prostate evaluation in men, ovarian evaluation in women. Molecular tests: NGS (next-generation sequencing) for genomic profiling, which both helps predict primary source and shows targeted therapy options. If primary is not found: Treated as cancer of unknown primary (CUP), broad-spectrum chemotherapy or targeted therapy based on molecular profile.

Quality of life is very important during and after treatment of brain metastasis. Symptom control: Steroids (dexamethasone) for edema reduction, headache management, antiepileptic drugs (in seizure patients), nausea-vomiting control. Neurological rehabilitation: Physical therapy (weakness, balance problems), occupational therapy (activities of daily living), speech therapy (if aphasia present). Cognitive support: Neurocognitive rehabilitation (memory exercises), especially important for patients receiving WBRT. Psychological support: Depression-anxiety treatment (cancer diagnosis, brain metastasis diagnosis are traumatic), patient-family counseling, support groups. Social support: Family and friend support, participation in social activities, continuing hobbies. Nutrition: Balanced diet, appetite stimulants (if needed), steroid side effect management (blood sugar, weight control). Palliative care: Pain control in advanced disease, end-of-life care planning. Multidisciplinary team: Cooperation of oncologist, neurosurgeon, radiation oncologist, palliative care, psychology, rehabilitation.