 Irinitecan was more strongly beneficial for patients with hypermethylated "WRN" promoters (39.4 months survival) than for those with unmethylated "WRN" promoters (20.7 months survival).Thus, a topoisomerase inhibitor appeared to be synthetically lethal with deficient expression of "WRN".Further evaluations have also indicated synthetic lethality of deficient expression of "WRN" and topoisomerase inhibitors.