Tumor Volume Changing Tendency Of Brain Metastases Of Non-Small Cell Lung Cancer After Intensity Modulated Radiation Therapy And Its Influencing Factors

Objective:The aim of this study was to evaluate the tumor volume changing tendency of brain metastases of non-small cell lung cancer(NSCLC) after intensity modulated radiation therapy(IMRT) and find its influencing factors.Methods:The authors conducted a retrospective review data of patients who had undergone IMRT for brain metastases from NSCLC during June 2012 to June 2015. All patients data of pre- and post-radiation MRIs were evaluated. We used Ray station treatment planning system to contour the tumor with 5 mm or more in the short axis to accurately define tumor volume. The 1-, 3-,6-,and 12-month tumor volume after IMRT were measured. The percentage of tumor volume reduction at each follow-up was determined and compared to the baseline tumor volume. Tumor volume responses were evaluated by Thompson standard. The tumor volume change between adjacent group were examined with Wilcoxon test. Potential influencing factors of tumor regression were examined in univariable and multivariable analyses. The age, gender, pathological type, the graded prognostic assessment(GPA), chemotherapy, targeted therapy,the pattern of radiation therapy,primal tumor volume, brain metastases biological effective dose were calculated and their predictive values were tested in univariable analysis.Statistical significance was defined as a p value < 0.05.Results:45 cases were analyzed. The 1-, 3-, 6-, and 12-month average volume regression were 56%, 71%,79%, 84%. Tumor volume regression in the first month after radiotherapy was the most remarkable, a relatively slowly between 1- and 3-months, and tumor volume regressed barely between 3- and 12- months. The univariable analyses showed that primal tumor volume was the significant factor for tumor volume regression(P=0.026). The multivariable analyses showed that primal tumor volume was less than 3 cm3, Tumor volume regressed better(P=0.018).Conclusions: Brain metastases of NSCLC showed good response for IMRT. Our results indicated brain metastases continuously regress in the first 3 months, and are relatively stable thereafter. The primal tumor volume is less than 3 cm3, tumor volume regressed better.