Apparent diffusion coefficient and genetic mutations as effective indexes for radiotherapy time of brain metastases from lung cancer retrospective analysis.

Abstract

e20641 Background: The potential value of apparent diffusion coefficient (ADC) before chemoradiotherapy and genetic mutation as monitors for radiotherapy time of lung adenocarcinoma patients with brain metastases were retrospective analysed. Methods: Fifty-seven patients of lung adenocarcinoma with brain metastases were enrolled into the clinical trial. Conventional magnetic resonance imaging (MRI) examination and diffusion weighted imaging (DWI) were performed one week before therapy and after two cycles of chemotherapy or after one month targeted therapy. Symptoms such as headache, nausea, vomiting would be alleviated with mannitol and dexamethasone. Chemotherapy,once every 3 weeks, using in these patients with wild gene included pemetrexed, DDP, bevacizumab (pemetrexed 500mg per square meter ; DDP 75mg per square meter and bevacizumab 15mg per kilogram). 27 Patients with genetic mutations includ ed 1 patient with ALK genetic mutations, 2 patients with T790 genetic mutations, the presence of EGFR mutations was determined by the presence of deletions with exons 19 in 9 patients and 20 in 10 patients and L858R point mutations in exon 21 in 5 patients. Patients with genetic mutations were given targeted drug therapy. After these above treatment, if brain metastasis symptoms persist, brain radiotherapy was performed ahead of schedule. Patients with no obvious symptoms or relieved symptoms after targeted therapy or chemotherapy, two-month review was performed with enhanced MRI, radiotherapy was not added until the lesion no longer continues to shrink. Results: In the cohort of patients with wild gene , when ADC values less than 1.01 in 15 patients, the maximum diameter of tumors were significantly decreased after two treatment cycles, While 14 patients with ADC values greater than 1.01, the maximum diameter of the tumors are no difference after two treatment cycles. After targeted therapy for one month, In patients with ALK and T790 genetic mutations, the maximum diameter of tumors were significantly decreased, while no difference in 18 patients and decreased in 6 patients with presence of EGFR. Conclusions: ADC values and genetic mutation may as effective indexes of radiotherapy time for lung adenocarcinoma patients with brain metastases.