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Partial hippocampal sparing whole brain radiotherapy in a patient with bilateral malignant melanoma metastases to the hippocampus: a case report

: Whole brain radiotherapy (WBRT) has been used for some decades in the treatment of metastatic cancer to the brain. It modestly improves overall survival of brain metastasis patients and in some randomised studies has been shown to prevent neurological deterioration and distant in-brain failure rates. WBRT can however, be associated with adverse quality-of-life and neurocognitive defects. Since the hippocampus has a major role in short term memory and cognitive function, hippocampal-avoidance WBRT (HA-WBRT) has become a more prevalent WBRT technique in recent years. It does not seem to be associated with increased hippocampal failures in magnetic resonance imaging-screened patients. We present the case of a 64-year-old male with metastatic malignant melanoma to the brain, who had multiple brain metastases including bilateral hippocampal metastases. We treated him with partial HA-WBRT, namely, by including in the high dose volume the hippocampal-associated metastases along with the rest of the brain, avoiding high dose to the remainder of the normal hippocampi, in an attempt to maximise his neurocognitive function. For the right hippocampal avoidance structure, the D100% was 10 Gy, maximum 18.4 Gy, while for the left hippocampal avoidance structure, the D100% was 8.45 Gy, maximum 18.1 Gy. The planning target volume (PTV) received 28.9 Gy, with <2% receiving >31 Gy. We prioritised minimising hot spots in the PTV because of the patient’s previous stereotactic radiosurgery (SRS) treatment (adjacent to the brainstem).