Abstract 5260: Mitochondrial DNA phylogenetic analysis for local recurrences and second primary tumors from patients with oral cavity squamous cell carcinoma

Abstract

Abstract Local recurrences (LRs) and second primary tumors (SPTs) are commonly observed in patients with oral squamous cell carcinoma (OSCC). A lower survival rate has been demonstrated in patients with LRs with respect to patients with SPTs. Therefore, the criteria for differentiating LRs and SPTs are indispensable for determining appropriate treatment. Currently, criteria based on histology, the distance and relapse time between new lesions and index primary tumor are generally used in clinical classification. In the genomic era, molecular classification based on the clonal relationship between the first and the second lesions may be more reliable than traditional clinical classification. The aim of the present study tried to establish a feasible molecular classification based on mitochondrial DNA (mtDNA) phylogenetic analysis. The study population consisted of 44 OSCC patients with multiple lesions for a total of 47 (19 LRs and 28 SPTs) paired lesions. The mtDNA analysis was performed by direct sequencing. The phylogenetic and molecular evolutionary analyses were conducted by using MEGA software version 6 and three common phylogenetic evolutionary methods (Maximun Likelihood (ML), Neighbor-Joining (NJ) and Unweighted Pair Group Method with Arithmetic Mean (UPGMA) method) were applied. Preliminary analysis indicated that the prevalence of clonality for LRs and SPTs was 26.3% and 3.6%, respectively. A discrepancy between the clinical classification and mtDNA analysis was found in 15 paired tumors (31.9%) in which 14 paired lesions were classified as LRs based on clinical criteria, while mtDNA analysis suggested that they were nonclonal-related SPTs. Survival analysis indicated that there was no difference between patients with LRs and patients with SPTs based on clinical classification. On the other hand, patients with clonal second lesions had poorer overall survival than patients with nonclonal second lesions based on mtDNA analysis. In conclusion, our preliminary findings suggested that molecular clonality analysis could improve the accuracy in differentiating LRs from SPTs. Citation Format: Chih-Hsiung Lai. Mitochondrial DNA phylogenetic analysis for local recurrences and second primary tumors from patients with oral cavity squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5260. doi:10.1158/1538-7445.AM2015-5260