Circulating vitamin D level before initiating chemotherapy impacts on the time-to-outcome in metastatic colorectal cancer patients: systematic review and meta-analysis

Table 1 Study characteristics and quality

First author, year	Study design	Vitamin D assessment	Vitamin D adjusted per season	N. of patients	TTO	Comparison modalities	Other biomarkers evaluated	MINORS score	NOS score	RoB2 assessment
Ng, 2011	P	RIA	Yes	515	OS, PFS	Interquartile comparison, lowest ≤ 13.1 ng/mL vs highest ≥ 27.2 ng/mL)	No	7	7	NA
Obermannova, 2015	P	EBA	Yes	84	OS, PFS	Normal vs Low (cutoff: 40 nmol/L)	CEA	7	5	NA
Golubić, 2017	P	EBA	No	72	OS, PFS	No supplementation vs Supplementation (2000 UI/die) For two years Measurement in nmol/L*	No	NA	NA	Some concerns
Ng, 2019	P	RIA	No	139	OS, PFS	High dose supplementation (8000 IU/die for the cycle 1, then 4000 IU/die) vs Standard dose (400 UI/die) Chronic administration Measurement in ng/mL**	No	NA	NA	Low risk
Yuan, 2019	P	RIA	Yes	1041	OS, PFS	Interquintile comparison, lowest ≤ 10.8 ng/mL vs highest ≥ 24.1 ng/mL	No	7	6	NA

The table provides a summary of methodology and quality-related details from pertinent studies that explore the association between Vitamin D and clinical outcomes in metastatic colorectal cancer patients. The included studies are presented with the first author's name and publication year, followed by information on study design, methods of Vitamin D assessment, adjustment for Vitamin D levels per season, the number of patients involved, treatment outcomes, comparison modalities, other evaluated biomarkers, and assessment scores for MINORS, NOS, and RoB2
%FAT percentage body fat, BMI Body Mass Index, CEA Carcino-embryonic antigen, EBA electrochemiluminescence binding assay, LA locally advanced, LC/MS liquid chromatography-tandem mass spectrometry, MINORS Methodological Index for Non-Randomized Studies, NA not applicable, NOS Newcastle–Ottawa Scale, OS overall survival, P prospective, PFS progression free survival, RIA Radioimmunoassay, RoB2 Risk-of-Bias v.2, TTO time-to-outcome
^*No monitoring of VD levels was performed
^**The VD levels after the first cycle of chemotherapy in high-dose VD group were constantly double compared to standard-dose group

ISSN: 1479-5876