Postdiagnosis Calcium and Milk Intake May Be Associated With Improved Overall Survival in Colorectal Cancer Patients
Higher intakes of calcium, vitamin D, and dairy product are associated with lower risk of colorectal cancer, but the effect of such intake on survival in colorectal cancer is unclear. In a study reported in the Journal of Clinical Oncology, Yang et al found that higher postdiagnosis intake of calcium and milk were associated with improved overall survival.
Study Details
The study involved 2,284 participants in the prospective Cancer Prevention Study II Nutrition Cohort who were diagnosed with invasive nonmetastatic colorectal cancer between baseline in 1992/1993 and 2009 with follow-up for mortality through 2010. Prediagnosis risk factor information was collected using a baseline questionnaire and postdiagnosis information was collected using questionnaires in 1999 and 2003, with postdiagnosis information being available for 1,111 patients.
Participants had an average age of 64 years at baseline and 73 years at diagnosis, 56% were men, and most were white. There were no differences across quartiles of prediagnostic total calcium intake for distribution in year of diagnosis, sex, tumor stage, grade, tumor subsite, treatment, or history of hypertension, myocardial infarction, diabetes, or stroke. Participants with high calcium intake at baseline were slightly older, better educated, more physically active, leaner, more likely to use nonsteroidal anti-inflammatory drugs and postmenopausal hormones, more likely to have a healthier overall diet, and less likely to smoke.
No Beneficial Effect of Prediagnosis Intake
Among the 2,284 patients included in the prediagnosis analyses, 949 died during a mean follow-up of 7.5 years, including 408 from colorectal cancer. No significant associations with prediagnosis diet variables, including calcium, vitamin D, and dairy products, were observed for all-cause mortality or colorectal cancer–specific mortality.
Analysis restricted to the 1,111 patients included in the postdiagnosis analysis showed that prediagnosis use of supplemental calcium ≥ 250 mg/d was significantly associated with higher risk of all-cause mortality (relative risk [RR] = 1.65, 95% confidence interval [CI] = 1.16–2.35), primarily reflecting increased risk of cardiovascular mortality (RR = 1.83, 95% CI = 0.82–4.09).
Postdiagnosis Intake
Among the 1,111 patients included in the postdiagnosis analyses, 429 died during mean follow-up of 7.6 years, including 143 from colorectal cancer. Mean time between diagnosis and completion of the postdiagnosis questionnaire was 2.6 years. On multivariate analysis adjusting for age at diagnosis, sex, tumor stage, and postdiagnosis total energy intake and folate intake, higher postdiagnosis intakes (highest vs lowest quartile) of total calcium (RR = 0.72, P = .02 for trend) and milk (RR = 0.72, P = .02 for trend) were associated with lower all-cause mortality, with a borderline significant effect observed for higher total dairy intake (RR = 0.75, P = .05 for trend).
Results were similar for total calcium and milk after adjustment for prediagnosis intake. For the highest vs lowest quartile, postdiagnosis total calcium intake was associated with reduced risk of colorectal cancer–specific mortality (RR = 0.59, P = .01 for trend).
A sensitivity analysis excluding deaths within the first 2 years of follow-up after completion of the postdiagnosis questionnaire was performed to account for differences in diet that might be due to serious illness preceding death. On this analysis, higher intake was associated with reduced risk of all-cause mortality for total calcium (RR = 0.69, P = .03 for trend) and milk (RR = 0.68, P = .02) and reduced risk of colorectal cancer–specific morality for total calcium (RR = 0.53, P = .02 for trend).
There was no evidence that the inverse associations of postdiagnosis total calcium and milk intakes with all-cause mortality were modified by age at diagnosis, sex, tumor stage, tumor subsite, postdiagnosis body mass index, physical activity, total energy intake, or total folate intake.
The investigators concluded, “[H]igher intakes of total calcium and milk after, but not before, colorectal cancer diagnosis may be associated with lower overall mortality. Our findings, if replicated in future observational studies and randomized trials, will provide important guidance for cancer survivors who are actively seeking diet and lifestyle changes to improve their prognosis.”
Peter T. Campbell, PhD, of the American Cancer Society, Atlanta, is the corresponding author for the Journal of Clinical Oncology article.
The study was supported by the American Cancer Society. The study authors reported no potential conflicts of interest.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
