Page 103 - Vitamin D and Cancer

90 E. Giovannucci

25(OH)D was low at pre-transplant (17.6 ng/mL) and further reduced after the
transplant (post-transplant patients are advised to avoid sun exposure). Thirty-two
cancers were diagnosed over 5 years of follow-up. 25(OH)D levels were lower in
patients who developed cancer after transplantation (13.7 ± 6 vs 18.3 ± 17.8 ng/mL,
P = 0.022). The risk of total cancer increased by 12% for each 1 ng/mL (2.5 nmol/L)
decrement in 25(OH)D (RR = 1.12; 95% CI = 1.04–1.23; P = 0.021).

4.10.2 Predicted 25(OH)D

In the Health Professionals Follow-up Study cohort, predicted 25(OH)D levels
were examined in relation to risk of total cancer in men. The methods for this analy-
sis were discussed above (Sect. 4.3.2). From 1986 through January 31, 2000, 4,286
incident cancers (excluding organ-confined prostate cancer and non-melanoma skin
cancer) and 2,025 cancer deaths from cancer were identified. An increment of
25 nmol/L in predicted 25(OH)D level was associated with a 17% reduction in total
cancer incidence (multivariate RR = 0.83, 95%CI = 0.74–0.92) and a 29% reduction
in total cancer mortality (multivariate RR = 0.71, 95% CI = 0.60–0.83). The reduc-
tion was largely confined to cancers of the digestive tract system, including esopha-
gus, stomach, pancreas, colon, and rectum; as a group, there was a 45% reduction
in mortality associated with a 25 nmol/L increment in 25(OH)D (multivariate
RR = 0.55, 95% CI = 0.41–0.74).

4.10.3 Randomized Trials (RCT)

Two RCTs of vitamin D supplementation and total cancer risk were identified. The
first was an RCT of 2,037 men and 649 women aged 65–85 years living in the
general community in the UK. The subjects took either 100,000 IU oral vitamin D
(cholecalciferol) supplementation or placebo every 4 months over 5 years [86].
After treatment, the 25(OH)D level was 74.3 nmol/L in the vitamin D group and
53.4 nmol/L in the placebo group. There were 188 incident cancer cases in the
vitamin D group and 173 in the placebo group, and no overall reduction was
observed for cancer risk (RR = 1.09, 95%CI = 86–1.36), although a slight, nonsig-
nificant reduction in risk of cancer mortality was suggested (RR = 0.86;
95%CI = 0.61–1.20).
The other RCT was a 4-year, community-based, double-blind, placebo-con-
trolled RCT of vitamin D and calcium of 1,179 US women aged >55 years living
in Nebraska; the primary outcome was fracture incidence and the principal second-
ary outcome was cancer incidence [87]. The subjects were randomly assigned to
receive daily 1,400–1,500 mg supplemental calcium/d alone (Ca-only), supplemental
calcium plus 1,100 IU vitamin D (Ca + D), or placebo. The achieved 25(OH)D level
after treatment was 96 nmol/L in the vitamin D group and 71 in the non-vitamin D