ERCC4 and neoplasm: Even if we tried to cope with the inter-xenograft (inter-patient) and intra-tumoral heterogeneity, as we used a TMA that includes two different distant pieces of the same tumor, and we verified the intra-tumor heterogeneity (i.e., both the distribution of ERCC1/XPF foci and DNA pol β in the two TMA samples were homogenous), the selected biomarkers were not strong enough to discriminate sensitive/resistant tumors.