MKI67 and neoplasm: Ki-67 <15% (p = 0.005) was associated with longer PFS, whereas PRRT received as first-line therapy, tumor type, visual response on scintigraphy (≥50%), biochemical response, number of cycles, administered activity, and previous therapies (surgery, radiotherapy, chemotherapy, 131I-MIBG) were all factors unrelated to PFS.