Abstract
BackgroundThis work aims to assess the feasibility of selectively sparing the hippocampus during prophylactic cranial irradiation (PCI) for small cell lung cancer (SCLC).MethodsSCLC 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).ResultsFrom 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.ConclusionsOur 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.
Highlights
This work aims to assess the feasibility of selectively sparing the hippocampus during prophylactic cranial irradiation (PCI) for small cell lung cancer (SCLC)
From Jan 2011 to Oct 2014, 238 SCLC patients with brain metastases (BMs) were enrolled for the research
The overall ratio of metastatic lesions located in neural stem cells (NSCs) regions was 2.0% in the 1511 total metastases (30/1511)
Summary
This work aims to assess the feasibility of selectively sparing the hippocampus during prophylactic cranial irradiation (PCI) for small cell lung cancer (SCLC). Prophylactic cranial irradiation (PCI) is a standard treatment for patients with limited-stage small cell lung cancer (SCLC) who have a good response to initial therapy [1]. In patients with extensive-stage SCLC that has responded to systemic therapy, PCI decreases brain metastases (BMs) [2]. Brown [3] et al reported that among patients with 1 to 3 brain metastases, the use of stereotactic radiosurgery (SRS) alone, compared with SRS combined with whole brain radiation therapy (WBRT), resulted in less cognitive deterioration at 3 months. Neurocognitive disorders after WBRT/PCI have a multifactorial etiology, it is currently believed that they are mostly caused by a loss of neural stem cells (NSCs) [5]. Avoidance of hippocampus in WBRT/PCI appears to be of essence
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