['The MDR1 gene encodes P-glycoprotein (PGP), which plays an important role in mediating multidrug resistance to chemotherapeutic agents. Polymorphisms in the MDR1 gene may have an impact on the expression and function of PGP, thereby influencing the response to chemotherapy.', 'We investigated the potential association of MDR1 polymorphisms (2677G>T at exon 21 and 3435C>T at exon 26) and their haplotypes with chemotherapy response in 54 small cell lung cancer (SCLC) patients who received a combination chemotherapy of etoposide-cisplatin.', 'The 3435 CC genotype was associated with a significantly better chemotherapy response compared with the combined 3435 CT and TT genotype (P = 0.025). The 2677 GG genotype was also associated with a better chemotherapy response compared with the combined 2677 GT and TT genotype, although it was not statistically significant. Consistent with the results of genotyping analyses, patients harboring the 2677G-3435C haplotype had a statistically significant better response to chemotherapy compared with those with the other haplotypes combined (P = 0.015).'] Do mDR1 polymorphisms predict the response to etoposide-cisplatin combination chemotherapy in small cell lung cancer?