The ABCG2 Q141K variant (the CA/AA genotype) was not only associated with improved PFS but was also found to be associated with increased toxicity i.e. higher risk of grade 3 or 4 thrombocytopenia (low platelet count) compared to the wild-type genotype (CC) (70.7% vs 44.7% respectively, HR 3.79 (95% CI 1.42-10.1) adjusted P = 0.008) (Table 3). Here, ABCG2 is linked to Thrombocytopenia.