Analyses of distribution and dosimetry of brain metastases in small cell lung cancer with relation to the neural stem ce
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RESEARCH
Open Access
Analyses of distribution and dosimetry of brain metastases in small cell lung cancer with relation to the neural stem cell regions: feasibility of sparing the hippocampus in prophylactic cranial irradiation Lei Zhao1, Yan Shen2, Jin-Dong Guo1, Heng-Le Gu1, Wen Yu1, Jia-Ming Wang1, Chang-Xing LV1, Jun Liu1, Xu-Wei Cai1 and Xiao-Long Fu1*
Abstract Background: This work aims to assess the feasibility of selectively sparing the hippocampus during prophylactic cranial irradiation (PCI) for small cell lung cancer (SCLC). Methods: SCLC patients with brain metastases (BMs) diagnosed with MRI were enrolled. Lesions localized to the neural stem cell (NSC) compartments [subventricular zone (SVZ) or hippocampus] were analyzed. Patients were categorized by the total number of intracranial metastases, the therapy processes and the symptoms. Hippocampi and enhanced lesions within 15 mm from the hippocampus were contoured. IMRT treatment plans were generated for hippocampal avoidance (HA)-PCI (25Gy in 10 fractions). Results: From Jan 2011 to Oct 2014, 1511 metastases were identified in 238 patients. The overall ratio of metastatic lesions located in NSC regions was 2.0% in the 1511 total metastases and 9.7% in the 238 overall patients. Among the NSC region metastases, 15 (1.0%) lesions involved the HA region of 14 (5.9%) patients and another 15 (1.0%) involved the SVZ of 15 (6.3%) patients. The involvement of HA region or SVZ was significantly different between patients with oligometastatic and non-oligometastatic BMs (P < 0.05). Based on the dosimetric analysis, 26 (10.9%) patients with 41 (2.7%) metastases within 15 mm from the hippocampus had inadequate dosage in case that HA-PCI was applied. Conclusions: Our retrospective review of 1511 metastases in 238 patients (among whom 89.5% were male) suggests that the metastatic involvement of the NSC regions (especially hippocampus) is unusual and limited primarily to patients with non-oligometastatic disease in SCLC. Also, dosimetric analysis shows that about 10% of patients may have adequate dosage due to HA-PCI treatment. But we believe that this is still an acceptable clinical treatment strategy for SCLC. Keywords: Hippocampal avoidance, Prophylactic cranial irradiation, Brain metastases, Small cell lung cancer
* Correspondence: [email protected] A portion of this work was presented at the 57th Annual Meeting of American Society for Radiation Oncology (ASTRO), San Antonio, October 18-21th, 2015. 1 Department of Radiation Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No.241 West Huaihai Road, Shanghai 200030, China Full list of author information is available at the end of the article © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a li
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