Phase II clinical trial of hippocampal-sparing prophylactic cranial irradiation in patients with small cell lung cancer

Abstract

Objective To evaluate the dose distribution and clinical efficacy of hippocampal-sparing prophylactic cranial irradiation (HS-PCI) in patients with small cell lung cancer by using helical tomotherapy. Methods Clinical data of 49 patients with small cell lung cancer receiving HS-PCI using helical tomotherapy in Cancer Hospital between 2014 and 2017 were retrospectively analyzed. All patients received brain MRI to exclude the possibility of brain metastasis within 1 month after standard surgery or radio-and chemo-therapy. The prescription dose was 95% PTV, 25 Gy in 10 fractions. The adverse reactions and cognitive functions of patients were observed before, 6 months and 1 year after treatment, and the dose distribution in the hippocampal gyrus, survival rate and brain metastasis rate were analyzed. Results The median follow-up time was 16 months. The average dose in the hippocampal gyrus was 7.23 Gy and 8.46 Gy in the reduction region, which was reduced by 71.88% and 66.16% compared with the prescription dose. The maximum dose in the hippocampal gyrus was 10.66 Gy and 15.43 Gy in the reduction region. Among 49 patients, 8 died, the 1-year survival rate was 85.1% and the 2-year survival rate was 70.3%.Nine patients (18.3%) had brain metastases, and one of them with extensive multiple brain metastases (n=13) presented with metastasis adjacent to the hippocampal gyrus. The main adverse reactions included mild headache, dizziness and brain edema, whereas no ≥ grade 2 adverse reactions occurred. At 6 months after treatment, the HVLT-R score was significantly decreased, and declined by 6.78% at 12 months after treatment. The HVLT-R scores did not significantly differ in patients without brain metastasis before and 12 months after treatment (P>0.05). Conclusion Application of HS-PCI using helical tomotherapy meets the dose requirement, effectively protects the cognitive function and yields slight adverse reactions. Key words: Cancer, small cell lung, limited stage; Prophylactic cranial irradiation; Cognitive function