MKI67 and neoplasm: Based on the second-line strategy (i.e., PRRT or targeted therapies), eligible subjects will be allocated to two substudies and subsequently randomized 1:1 to maintenance or withdrawal of SSAs (octreotide LAR 30 mg or lanreotide ATG 120 mg) according to the tumor site and Ki67 (<10%, G1 or low G2, or ≥10%, high G2).