Development of lung adenocarcinomas with exclusive dependence on oncogene fusions

This report delivers a comprehensive genetic alteration profile of lung adenocarcinomas (LADC) driven by ALK, RET, and ROS1 oncogene fusions. These tumors are difficult to study because of their rarity. Each drives only a low percentage of LADCs. Whole-exome sequencing and copy-number variation analyses were performed on a Japanese LADC cohort (n = 200) enriched in patients with fusions (n = 31, 15.5%), followed by deep resequencing for validation. The driver fusion cases showed a distinct profile with smaller numbers of nonsynonymous mutations in cancer-related genes or truncating mutations in SWI/SNF chromatin remodeling complex genes than in other LADCs (P < 0.0001). This lower mutation rate was independent of age, gender, smoking status, pathologic stage, and tumor differentiation (P < 0.0001) and was validated in nine fusion-positive cases from a U.S. LADCs cohort (n = 230). In conclusion, our findings indicate that LADCs with ALK, RET, and ROS1 fusions develop exclusively via their dependence on these oncogene fusions. The presence of such few alterations beyond the fusions supports the use of monotherapy with tyrosine kinase inhibitors targeting the fusion products in fusion-positive LADCs.