GSTP1 and neoplasm: In subgroup analyses, the GSTP1 polymorphism was associated with increased tumour response when the sample size was large (GA vs. AA OR = 1.38, 95% CI 1.02–1.88, P = 0.038; and dominant model OR = 1.45, 95% CI 1.02–2.06, P = 0.829), but this association was not found when the sample size was small, or with any ethnicity subgroup.