NCOG-15. A PROSPECTIVE STUDY OF HIPPOCAMPAL-SPARING PROPHYLACTIC CRANIAL IRRADIATION (PCI) IN LIMITED STAGE SMALL CELL LUNG CANCER (SCLC)

Abstract

PURPOSE: The purpose of this prospective study is to evaluate cognitive function, quality of life, and intra-cranial failure patterns following hippocampal (HC)-sparing PCI for limited stage SCLC. METHODS: Adult patients with limited stage SCLC, with CR to concurrent chemo-radiotherapy and no brain metastases eligible. Patients received PCI 25 Gy/10 fractions with mean HC dose <8 Gy and ≥90% of brain receiving 90% of prescribed dose. Cognitive testing performed at baseline, 6, 12 months following RT. Brain MRIs performed at baseline, 6, 12, 18, 24 months. Primary endpoint was memory according to Hopkins Verbal Learning Test-Revised Delayed Recall (HVLT-R) at 6 months following PCI. The 25 Gy arm of RTOG 0212 using standard PCI was used as a reference. Development of intracranial metastases recorded. RESULTS: 20 patients with median age 61 years (range 39-76) enrolled. Two-year OS 88% (95% CI, 68-100%). No significant decline in performance between baseline and 6 or 12 months for any cognitive tests. Decline in performance on HVLT-R between baseline and 6 months was 0.38 compared to decline of 1 with standard PCI on RTOG 0212 (p=0.15, power 18% for 1-sided 0.05-level test with SD 3.6). MRI revealed asymptomatic brain metastases in 2 patients at 6 months and in 2 patients at 1 year (cumulative rate 20%) with no concurrent extracranial progression. Two patients (10%) developed a metastasis in underdosed region. Neither involved HC dentate gyrus, but 1 involved the HC avoidance region (HC + 5 mm). Both patients concurrently developed ≥1 additional metastasis in fully treated brain regions. There was 1 neurologic death. CONCLUSIONS: This prospective study suggests a potential benefit of HC-sparing in limiting neuro-psychological sequelae of brain radiation, but with risk of failures in spared region. These data strongly support enrollment on NRG-CC003 which is accruing patients with both limited and extensive stage disease.