Treatment tactics of new NET G3 subgroup in first line of therapy

Abstract

Considering the fact that the group of neuroendocrine carcinomas (NECs) grade 3 is heterogenous, in the year of 2017 a new subgroup of welldifferentiated neuroendocrine tumors grade 3 (NETs G3) was described. NETs G3 are tumors with more favorable prognosis and less sensitive to platinum-based chemotherapy regimens than NECs, they also have peculiar morphogenetical qualities: lower ki‑67 index (mean 35.0 %), higher somatostatin receptors expression, absence of DAXX/ATRX/MEN 1 genes mutation, p53 expression in the absence of TP53 mutation. Nowadays treatment standard for NETs G3 subgroup is still remain unclear due to lack of prospective clinical trials. At the same time taking in note historical retrospective data, NETs G3 should be treated in line with NETs G1/G2 and only patients with higher ki‑67 index can be treated as NECs with platinum-based chemotherapy. In our non-randomised phase II prospective trial, we accessed the efficacy of different chemotherapy regimens in combination with somatostatin analogues in new NETs G3 subgroup. 153 patients with IHC-confirmed neuroendocrine neoplasm diagnose were included: NETs G3 n = 53 mean ki‑67 36.4 % [21.0–60.0 %], NETs G2 n = 50 mean ki‑67 15.7 % [2.1–20.0 %], NECs n = 50 mean ki‑67 69.0 % [38.0–96.0 %]). Patients from NETs G3 subgroup received 4 chemotherapy regimens: Aranose (n = 19), Aranose (arabinopiranosilmethyl nitrosocarbamide, ALK, – cytostatic drug with a chemical structure similar to Streptozotocin and Nitrosomethylurea, approved in Russian Federation for melanoma and welldifferentiated neuroendocrine tumors treatment), XELOX (n = 8), TemCAP (n = 11), EP/EC (n = 10). mPFS in Aranose-subgroup was 19.3 ± 5.9 months (95 % CI: 7.7–30.8), in XELOX – 10.8 ± 3.6 months (3.7–17.8), in TemCAP – 14.8 ± 4.2 months (6.6–23.1) and in platinum-based regimens – 4.4 ± 1.9 months (0.6–8.2) (p = 0.01). DCR in Aranose subgroup was 73.6 % and ORR – 36.8 %, PDR – 21.1 %, in XELOX subgroup ORR was 62.5 %, SDR was 50.0 % and PDR – 25.0 %, in TemCAP subgroup DCR was 63.6 %, ORR – 9.1 %, PDR – 18.2 % and in platinum-based regimens SDR was 40.0 %, PDR – 50.0 % (p = 0.05).