1. A method of using a kit for determining treatment responsiveness in a subject with a gastroenteropancreatic neuroendocrine neoplasm (GEP-NEN), the method comprising: (a) contacting a biological test sample from the subject with primers specific for at least three GEP-NEN biomarkers selected from the group consisting of: AKAP8L, ATP6V1H, BNIP3L, C21orf7, COMMD9, ENPP4, FAM131A, FLJ10357, GLT8D1, HDAC9, HSF2, LEO1, MORF4L2, NOL3, NUDT3, OAZ2, PANK2, PHF21A, PKD1, PLD3, PQBP1, RNF41, RSF1, RTN2, SMARCD3, SPATA7, SST1, SST3, SST4, SST5, TECPR2, TRMT112, VPS13C, WDFY3, ZFHX3, ZXDC, ZZZ3, APLP2, CD59, ARAF1, BRAF1, KRAS, and RAF1, wherein the length of the primers is at least 15 base pair (bp) and wherein the sequence of the primers comprises SEQ ID NOs: 106-179, 41-48, 65, 66, 83 or 84; (b) performing a reverse-transcriptase polymerase chain reaction (RT-PCR) on the biological test sample from (a); (c) measuring the amount of GEP-NEN biomarker complementary DNA molecule (cDNA) generated for each of the at least three GEP-NEN biomarkers so reverse transcribed; (d) detecting whether the level of the at least three GEP-NEN biomarkers is elevated in a biological test sample from the subject as compared to a normal or a reference biomarker level; (e) computing the differential in the level of the detected GEP-NEN biomarker cDNA to the level of the normal or the reference biomarker cDNA; (f) diagnosing the subject with a GEP-NEN nonresponsive to treatment when the level of the least three GEP-NEN biomarkers is elevated in the biological test sample as compared to the normal or the reference biomarker level; and (g) recommending that GEP-NEN treatment of the subject is modified based on the elevated level so detected, wherein the treatment comprises at least one selected from the group consisting of surgical intervention, chemical therapy, hormonal therapy and somatostatin analog therapy.