Recently, the mTOR kinase has been identified as an essential kinase in SCLC [36], and the therapeutic priority of mTOR pathway inhibitors has been suspected based on the high frequency of genetic alterations affecting the PI3K/Akt/mTOR pathway in SCLC [30], which are hypothesized to result in mTOR hyperactivation in cancer cells. This evidence concerns the gene PIK3CA and cancer.