The ABCC11 variant c.1637C>T was strongly associated with severe leukopenia in patients carrying risk variants in DPYD, encoding the key fluoropyrimidine-metabolizing enzyme dihydropyrimidine dehydrogenase (odds ratio (OR): 71.0; 95% confidence interval (CI): 2.5-2004.8; P<sub>c.1637C>T*DPYD</sub>=0.013).
Univariate and multivariate analysis identified rs17822471 (G>A, T546M) as risk factor of severe leukopenia (p = 0.021, odds ratio [95%CI]: 3.31 [1.26-8.66]) but not of other toxicity types.