QSPC-10 Development of Isolated Brain Metastases Underneath the Blocked Portion of Prophylactic Cranial Irradiation Field in a Patient With Small Cell Lung Cancer, Leading to Significant Morbidity and Death

INTRODUCTION The paradigm shift towards forgoing prophylactic cranial irradiation (PCI) in small cell lung carcinoma (SCC) management in favor of a surveillance approach raises concerns regarding metastases-induced patient morbidity. We present here a case exemplifying the morbidity associated with the development of brain metastases in a portion of the radiation field blocked due to concerns of increased toxicity due to re-irradiation. CASE PRESENTATION A 69-year-old male presented with a history of T1N0M0 laryngeal cancer treated with small field definitive radiation, followed by adjuvant post-prostatectomy radiation therapy to 68 Gy delivered in 34 fractions with androgen deprivation, and finally a history of pT1N2bM0 oropharyngeal cancer, treated with a comprehensive large-field radiation with concurrent chemotherapy. The oropharyngeal radiation field included a portion of the midbrain and cerebellum. Five years later, the patient developed limited stage SCC, for which he received definitive chemoradiation, followed by PCI. The previously irradiated mid-brain and cerebellum regions were blocked from the whole brain PCI fields due to 
concerns for toxicity. Two years post-PCI, the patient developed multiple symptomatic brain metastases, with a dominant lesion located in the mid-brain, responsible for his double-vision, as well as several lesions in the cerebellum causing complete ambulatory dysfunction. Stereotactic radiosurgery (SRS) was administered but the patient succumbed to his illness two weeks later from neurologic death. DISCUSSION This case underscores the benefit of PCI in preventing significant neurologic morbidity in patients with SCC. Forgoing PCI and adopting a surveillance approach may increase the risk of introducing increased metastases-induced morbidity in SCC patients.