The retrospective evaluation of prophylactic cranial irradiation in patients treated for limited stage small-cell lung cancer — a single centre study

Introduction. The standard treatment for patients with LD SCLC (limited stage small-cell lung cancer) is combined modality therapy that includes chemotherapy (ChT) with platinum-based regimens and thoracic radiotherapy (RT), followed by prophylactic cranial irradiation (PCI) in patients with a response in the thorax. Objectives. The evaluation of PCI in patients with LD SCLC and the analysis of the effects of certain therapeutic factors on the frequency and occurrence of brain metastases. Materials and methods. Between 2002 and 2015, a total of 271 patients with LD SCLC received chemo-radiotherapy (concurrently in 122 pts — 45% and sequential in 149 pts — 55%). PCI was administered in 167 pts (61.6%) with total dose of 30 Gy given to the whole brain; 86 pts (51.1%) received PCI after completed chemo-radiotherapy and in 81 pts (48.9%) PCI was administered immediately after the end of thoracic irradiation. The following statistical methods were used: Kaplan-Meier method (evaluation of survival rates: overall survival — OS, and brain metastases-free survival — BMFS), log-rank test (for comparison of survival rates), Cox’ proportional hazard model (for multivariate analysis), Pearson chi2 test for independence (for categorized variables comparison) and variance analysis (for continuous variables comparison). All the calculations were performed using Statistica v. 13.3 software (TIBCO Software Inc.) and the significance level for all the statistical methods was p < 0.05. Results. Complete response in thorax was observed in 172 pts (63.5%) and remaining 99 pts (36.5%) developed partial response. During follow-up, 120 pts (44.3%) developed distant metastases from which brain metastases were most frequent (61 cases — 60.8%). The cumulative 5-year incidence of brain metastases amounted to 18.9% (when PCI was administered) and 45.9% (when PCI was omitted) and these differences were significant (p < 0.0001). PCI was an independent prognostic factor for BMFS and for OS. Omitted PCI is related with HR amounted: 6.25 for BMFS and 1.81 for OS. Conclusions. PCI significantly reduces the incidence of brain metastases and delays the development of brain metastases in patients treated for LD SCLC. PCI is a significant independent prognostic factor for brain metastases-free survival and overall survival. The development of brain metastases is the most common type of failure in patients with LD SCLC and 90% of such relapses occurred during the 24 months following the completion of chemo-radiotherapy.