Table 3.

NET factors evaluated in PRRT studies

FACTORS ASSOCIATED WITH A RESPONSE TO PRRT
Parameters	Criteria	Type of Response	Type of study	Patient number	Primary Site	Refs
Clinical	Reduced performance status	ORR	R	310	GEP-NETs	2,75
	Extensive liver disease	TTP	R	310	GEP-NETs	2
	Bone metastases	TTP	R	310	GEP-NETs	2
	Functionality	TTP PFS	R R	310 61	GEP-NETs SI-NETs	2 76
Pathological	Ki-67	PFS	R	68	P-NETs	55
	Primary tumor site	ORR	R	310	GEP-NETs	2
Radiation Absorbed Dose	Dose correlation with response
	P-NETs: demonstrated	ORR	P	24	P-NETs	17
	SI-NETs: no correlation (activity correlated)	ORR	P	25	SI-NETs	49
	Early per-cycle reduction in tumor dose	ORR	R	27	GEP-NETs	77
PET/SPECT	Image-based heterogeneity
	SSR heterogeneity (asphericity) at pre-PRRT SPECT c/w poor response	ORR	R	20	GEP-NETs	78
	Textural features (entropy) at pre-PRRT SSR PET	PFS	R	141	NETs	54
	Intensity of uptake at SRI
	Baseline OctreoScan uptake	ORR	R	310	GEP-NETs	2
	Baseline SUV max and SUV max/av at PET	ORR	R	55	GEP-NETs	79
	Early per-cycle reduction of SUV T/S , SUV max at PET	TTP	R	31	NETs	80
	Intensity of uptake at FDG PET
	FDG positive lesions	PFS	R	60	P-NETs	81
	Discordant FDG and SRI lesions	ORR	R	50	GEP-NETs	82
CT	TGR at baseline (e.g. >0.33%/month)	ORR	R	39	GEP-NETs	83
MR	DCE-MRI-derived pretreatment signal enhancement ratio at 40% to 60% radial distance	ORR	A	-	Human SI-NET cell line GOT1	21
Mono/bi-analyte Biomarkers	CgA>600 ng/ml	PFS PFS	R R	22 61	BP-NETs SI-NETs	75 76
	Inflammation-based index (serum C-reactive protein and albumin)	PFS PFS	R P (failed correlation)	55 43	NETs, PPGL NETs	84 85
Genomic multianalyte biomarkers	PPQ	PFS	P	158	GEP, BP-NETs	62

(R), Retrospective study; (P), prospective study; (A), animal study; c/w, correlated with; SRI, somatostatin receptor imaging, either OctreoScan or ⁶⁸Ga-SSA-PET/CT; TTP, time-to-progression.; TGR, tumor growth ratio; DCE, dynamic contrast-enhanced; PPQ, PRRT Predictive Quotient.