High Risk Factors Of Brain Metastasis Developed After Intervention Of Prophylactic Cranial Irradiation In Patients With Small Cell Lung Cancer

Objective: Our research aimed at investigating the high risk factors of brain metastasis developed after the intervention of prophylactic cranial irradiation(PCI)in the patients with small cell lung cancer(SCLC).Materials and methods: Totally 99 eligible patients with accurate pathology of SCLC were all treated with 4-6 cycle EP or EC chemotherapy and thoracic radiotherapy.More than one month after thoracic radiotherapy,prophylactic cranial irradiation was given to all of the patients.Of the 99 patients enrolled,32 patients developed brain metastasis after the intervention of PCI and 67 cases did not develop brain metastasis.The median occurrence time of brain metastasis was24.05 months.The median follow-up was 23.0 months.Of the 99 patients enrolled,9 patients were lost to follow-up(3 of the brain metastasis group,6 of the control group).The follow-up rate was 90.9%,and the median follow-up time was 23 months.According to the occurrence of brain metastasis,the patients were divided into two groups: brain metastasis group(experimental group)and control group.The TNM staging,gender,age,PCI dose and some other factors were analyzed between the two groups.The paired t test,chi-square test and rank-sum test were used forunivariate analysis.Logistic regression was performed for multivariate analysis.Results: The results of univariate analysis suggested that:(1)For T stage,the incidence of brain metastasis was 10.7% in the patients with stage 1-2,32.0% in stage 3,61.9% in stage 4,respectively(P = 0.001).For N stage,the incidence of brain metastasis was 6.45% in the patients with stage 0-1,44.1% in stage 2–3,respectively(P < 0.001).(2)Patients who developed distant metastasis other than brain during the disease course and those with poor local control of lung lesions were of high risk of developing brain metastasis after PCI(P < 0.05).(3)The incidence of brain metastasis after PCI was 41.2% in male patients,12.9% in female patients,respectively(P = 0.005).(4)In the experimental group,the median dose of PCI was 25.3 ± 1.23 Gy,in the control group,that was26.5 ± 3.01 Gy(P = 0.023).The results of multivariate analysis suggested that:(1)For T stage,the higher the stage was,the greater the risk of brain metastasis was,OR = 3.648,95% CI 1.491 ~ 8.928;for N stage,the risk of brain metastasis with N stage 2-3 was 10.6 times of that in stage 0-1,95% CI was 2.502 ~ 44.535.(2)Compared with those who did not develop distant metastasis,the risk of brain metastasis in the patients with other distant metastasis during the disease course was greater,OR = 4.873,95% CI 1.218 ~ 19.492.For local control of lung lesions,the risk of brain metastasis of patients with poor local control was greater,OR = 3.983,95% CI 1.092 ~ 14.526.(3)For gender factors,the risk of brain metastasis after PCI in males was 4.545 times of that in females(95% CI1.233-16.667).(4)For PCI dose factor,the greater the dose of PCI was,the smaller the risk of brain metastasis was,OR=0.855,95% CI0.739~0.988.Conclusion: The T and N stage of primary lung lesions,other organmetastasis during the disease course,poor control of lung lesions are the independent influencing factors of brain metastasis after the intervention of PCI in SCLC patients,and male patients are of high incidence of brain metastasis.Dose slightly higher than the conventional PCI dose may reduce the incidence of brain metastasis,and thus improve prognosis.