NR4A1 and neoplasm: Beside patient characteristics, selection criteria for APBI also reflect technical limits of the method itself (e.g. applicator size for IORT with 50 kV/balloon catheter, or number of possible catheters in multi-catheter brachytherapy) or the biological and oncological rationales of tumor treatment (e.g. subclinical tumor invasion around the tumor bed or better prognosis of hormone receptor positive tumors).