MGMT and small cell lung carcinoma: The rationale for its application in SCLC is strong, as temozolomide has a good penetration through the blood–brain barrier, which can be useful for brain metastasis, and SCLC has aberrantly methylated O6-methylguanine-DNA methyltransferase MGMT, the enzyme involved in the repair mechanism of the DNA damage induced by temozolomide [93].