Clinical Features of Brain Metastases in Small Cell Lung Cancer: an Implication for Hippocampal Sparing Whole Brain Radiation Therapy

Abstract

PURPOSE: To assess the clinical features and distribution of brain metastases (BMs) of small cell lung cancer (SCLC) in the hippocampal and perihippocampal region, with the purpose of exploring the viability of hippocampal-sparing whole-brain radiation therapy (HS-WBRT) on reducing neurocognitive deficits. METHODS: This was a retrospective analysis of the clinical characteristics and patterns of BMs in patients with SCLC. Associations between the clinical characteristics and hippocampal metastases (HMs)/perihippocampal metastases (PHMs) were evaluated in univariate and multivariate regression analyses. RESULTS: A total of 1594 brain metastatic lesions were identified in 180 patients. Thirty-two (17.8%) patients were diagnosed with BMs at the time of primary SCLC diagnosis. The median interval between diagnosis of primary SCLC and BMs was 9.3 months. There were 9 (5.0%) and 22 (12.2%) patients with HMs and PHMs (patients with BMs located in or within 5 mm around the hippocampus), respectively. In the univariate and multivariate analysis, the number of BMs was the risk factor for HMs and PHMs. Patients with BMs ≥ 5 had significantly higher risk of HMs (odds ratio [OR] 7.892, 95% confidence interval [CI] 1.469-42.404, P = .016), and patients with BMs ≥ 7 had significantly higher risk of PHMs (OR 5.162, 95% CI 2.017-13.213, P = .001). Patients with extracranial metastases are also associated with HMs. CONCLUSIONS: Our results indicate that patients with nonoligometastatic disease are significantly associated with HMs and PHMs. The incidence of PHMs may be acceptably low enough to perform HS-WBRT for SCLC. Our findings provide valuable clinical data to assess the benefit of HS-WBRT in SCLC patients with BMs.

Radiological distribution of brain metastases and its implication for the hippocampus avoidance in whole brain radiotherapy approach

“…In Gondi's study, patients with primary small cell lung cancer and melanoma had higher incidence of melanoma patients. Similar to our results were reported by Guo's and coll 14 . Wan's study 17 found that the rate of metastases was 3.4 and 4.3% in hippocampus and subventricular zone.Wu's study 18 With available risk factors, we found that the risk of HI increases significantly and continuously with number of BMs.…”

Perihippocampal metastasis following hippocampus-avoiding prophylactic cranial irradiation for small cell lung cancer: a case report

“…A known risk factor for HA region metastasis is a large number of BMs. 14 , 18 The current case was therefore unusual as this patient had a single BM in the HA region. Although this solitary BM was removed by surgical resection, stereotactic radiosurgery may be a good alternative.…”

“…Two retrospective studies examined the incidence of hippocampal metastasis exclusively in SCLC patients. 14 , 15 Guo et al 14 assessed a total of 1,594 BMs (at presentation or follow-up) in 180 SCLC patients. HA region metastasis was detected in 22 (12.2%) patients: 13 perihippocampal (≤ 5 mm of hippocampus) and nine hippocampal metastases.…”

Prophylactic cranial irradiation in SCLC

“…The outcome of this study suggests the benefit of hippocampal sparing in limiting the neuropsychological sequelae of brain radiation, but with a risk of failures in the spared region. Two studies analysed the incidence of hippocampal metastasis (38,39). Guo et al (38), based on retrospective analysis of the clinical characteristics and patterns of brain metastases detected at the time of diagnosis or during the followup in patients with SCLC, concluded that the incidence of perihippocampal metastases (12%) may be acceptably low enough to justify hippocampal-sparing techniques for SCLC.…”