Calcium plus vitamin D supplementation and the risk of colorectal cancer
Jean Wactawski-Wende, Jane Morley Kotchen, Garnet L Anderson, Annlouise R Assaf, Robert L Brunner, Mary Jo O'Sullivan, Karen L Margolis, Judith K Ockene, Lawrence Phillips, Linda Pottern, Ross L Prentice, John Robbins, Thomas E Rohan, Gloria E Sarto, Santosh Sharma, Marcia L Stefanick, Linda Van Horn, Robert B Wallace, Evelyn Whitlock, Tamsen Bassford, Shirley A A Beresford, Henry R Black, Denise E Bonds, Robert G Brzyski, Bette Caan, Rowan T Chlebowski, Barbara Cochrane, Cedric Garland, Margery Gass, Jennifer Hays, Gerardo Heiss, Susan L Hendrix, Barbara V Howard, Judith Hsia, F Allan Hubbell, Rebecca D Jackson, Karen C Johnson, Howard Judd, Charles L Kooperberg, Lewis H Kuller, Andrea Z LaCroix, Dorothy S Lane, Robert D Langer, Norman L Lasser, Cora E Lewis, Marian C Limacher, JoAnn E Manson, Women's Health Initiative Investigators, Jean Wactawski-Wende, Jane Morley Kotchen, Garnet L Anderson, Annlouise R Assaf, Robert L Brunner, Mary Jo O'Sullivan, Karen L Margolis, Judith K Ockene, Lawrence Phillips, Linda Pottern, Ross L Prentice, John Robbins, Thomas E Rohan, Gloria E Sarto, Santosh Sharma, Marcia L Stefanick, Linda Van Horn, Robert B Wallace, Evelyn Whitlock, Tamsen Bassford, Shirley A A Beresford, Henry R Black, Denise E Bonds, Robert G Brzyski, Bette Caan, Rowan T Chlebowski, Barbara Cochrane, Cedric Garland, Margery Gass, Jennifer Hays, Gerardo Heiss, Susan L Hendrix, Barbara V Howard, Judith Hsia, F Allan Hubbell, Rebecca D Jackson, Karen C Johnson, Howard Judd, Charles L Kooperberg, Lewis H Kuller, Andrea Z LaCroix, Dorothy S Lane, Robert D Langer, Norman L Lasser, Cora E Lewis, Marian C Limacher, JoAnn E Manson, Women's Health Initiative Investigators
Abstract
Background: Higher intake of calcium and vitamin D has been associated with a reduced risk of colorectal cancer in epidemiologic studies and polyp recurrence in polyp-prevention trials. However, randomized-trial evidence that calcium with vitamin D supplementation is beneficial in the primary prevention of colorectal cancer is lacking.
Methods: We conducted a randomized, double-blind, placebo-controlled trial involving 36,282 postmenopausal women from 40 Women's Health Initiative centers: 18,176 women received 500 mg of elemental calcium as calcium carbonate with 200 IU of vitamin D3 [corrected] twice daily (1000 mg of elemental calcium and 400 IU of vitamin D3) and 18,106 received a matching placebo for an average of 7.0 years. The incidence of pathologically confirmed colorectal cancer was the designated secondary outcome. Baseline levels of serum 25-hydroxyvitamin D were assessed in a nested case-control study.
Results: The incidence of invasive colorectal cancer did not differ significantly between women assigned to calcium plus vitamin D supplementation and those assigned to placebo (168 and 154 cases; hazard ratio, 1.08; 95 percent confidence interval, 0.86 to 1.34; P=0.51), and the tumor characteristics were similar in the two groups. The frequency of colorectal-cancer screening and abdominal symptoms was similar in the two groups. There were no significant treatment interactions with baseline characteristics.
Conclusions: Daily supplementation of calcium with vitamin D for seven years had no effect on the incidence of colorectal cancer among postmenopausal women. The long latency associated with the development of colorectal cancer, along with the seven-year duration of the trial, may have contributed to this null finding. Ongoing follow-up will assess the longer-term effect of this intervention. (ClinicalTrials.gov number, NCT00000611.).
Copyright 2006 Massachusetts Medical Society.
Source: PubMed