ABCC1 and Ewing sarcoma: Among these, loss of ABCC1 exon 9 was predictive for relapse in six ES patients, suggesting that alternative splicing may represent an additional mechanism of ABCC1 expression control [53]; however, it must be underlined that the same study did not reveal any correlation between ABCC1 expression level and chemotherapy-induced tumor necrosis, time to first relapse, or overall survival [53].