Are exposure-disease relationships assessed in cohorts of health professionals generalizable?: a comparative analysis based on WCRF/AICR systematic literature reviews

Multivitamin use after diagnosis and prostate cancer survival among men with nonmetastatic prostate cancer

BACKGROUND

Multivitamin use is common among cancer patients. Whether post-diagnostic multivitamin supplementation is beneficial for prostate cancer survival is largely unknown, and some evidence even suggests potential harm.

METHODS

We prospectively assessed post-diagnostic multivitamin use in relation to prostate cancer survival among 4756 men with nonmetastatic prostate cancer at diagnosis in the Health Professionals Follow-up Study (1986-2016). Cox regression models were used to evaluate the association between post-diagnostic multivitamin use and frequency and risk of lethal prostate cancer (distant metastases or prostate cancer-specific death) and all-cause mortality.

RESULTS

We observed 438 lethal prostate cancer and 2609 deaths during a median follow-up of 11 years. Compared to non-users, post-diagnostic multivitamin use was not associated with risk of lethal prostate cancer (HR [95% CI], 0.98 [0.74-1.30]) or all-cause mortality (1.00 [0.88-1.12]), after adjustment for potential confounders. Similarly, null associations were observed across various categories of use frequency. Compared to non-users, men who used multivitamins regularly (6-9 tablets/week) after cancer diagnosis had similar risk of lethal prostate cancer (0.96 [0.72-1.28]) and all-cause mortality (0.99 [0.88-1.12]).

CONCLUSIONS

We found no evidence that post-diagnostic multivitamin use among men with nonmetastatic prostate cancer was associated with better or worse survival in a well-nourished population.

Vitamin C intake and colorectal cancer survival according to KRAS and BRAF mutation: a prospective study in two US cohorts

BACKGROUND

The associations of vitamin C intake with colorectal cancer (CRC) survival according to tumour KRAS or BRAF mutation status remain unclear.

METHODS

We used the inverse probability weighted multivariable Cox proportional hazards regression model to calculate the hazard ratio (HR) of mortality, and spline analysis to evaluate the dose-response relationship in the Nurses' Health Study and Health Professionals Follow-up Study. We also assessed SLC2A1 mRNA expression according to KRAS or BRAF mutation in the TCGA database.

RESULTS

During an average of 12.0 years of follow-up, we documented 2,096 CRC cases, of which 703 cases had KRAS and BRAF mutation data. The association between total vitamin C intake and CRC-specific mortality suggestively differed according to KRAS or BRAF mutation status (Pinteraction = 0.04), with the multivariable HR (95% CI) per 400 mg/day increase in vitamin C intake for CRC-specific mortality of 1.07 (0.87-1.32, Ptrend = 0.52) in cases with both wild type and 0.74 (0.55-1.00, Ptrend < 0.05) in cases with either KRAS or BRAF mutant type. TCGA analysis showed a higher mRNA SLC2A1 expression in KRAS or BRAF-mutated tumours than in wild-type tumours (P = 0.02).

CONCLUSION

Our findings support the laboratory evidence for a potential benefit of vitamin C for CRC patients with KRAS or BRAF mutated tumours.

A Comparative Study of Healthy Dietary Patterns for Incident and Fatal Digestive System Cancer

INTRODUCTION

We examined multiple dietary patterns in relation to total digestive system cancer (DSC) incidence and death.

METHODS

A total of 213,038 health professionals from the Health Professionals Follow-up Study (1986-2016), the Nurses' Health Study (1986-2018), and the Nurses' Health Study II (1991-2017) with no cancer diagnosis at baseline were analyzed. DSC incidence and death were estimated using time-varying Cox proportional hazards regression models.

RESULTS

During up to 32 years of follow-up, 5,724 DSC cases accrued. Adherence to 8 healthy diet patterns was associated with a 7%-13% lower risk of DSC, particularly for digestive tract cancers. An inverse association with gastrointestinal tract cancer was also shown for all pattern scores except Alternate Mediterranean Diet and the healthful Plant-based Diet Index, with hazard ratios between 0.84 and 0.89. Inverse associations were shown for the reversed empirical dietary index for hyperinsulinemia (hazard ratio for 90th vs 10th percentile 0.64, 95% confidence interval [CI] 0.47-0.87) and the empirical dietary index associated with lower inflammation (rEDIP) (0.53, 95% CI 0.39-0.72) for stomach cancer, and for the rEDIP (0.58, 95% CI 0.37-0.92) for small intestine cancer. Among accessory cancers, the Alternate Healthy Eating Index-2010, alternate Mediterranean diet, and diabetes risk reduction diet were associated with a 43%-51% lower risk of liver cancer. The reversed empirical dietary index for hyperinsulinemia, rEDIP, and the Alternate Healthy Eating Index-2010 were inversely associated with the risk of fatal DSC.

DISCUSSION

Adherence to healthy diets was associated with a lower risk of incident and fatal DSC, although the magnitude of the association varied slightly among the patterns.

Different operationalizations of the 2018 WCRF/AICR cancer prevention recommendations and risk of cancer

BACKGROUND

The standardized scoring system assessing adherence to the 2018 World Cancer Research Fund (WCRF)/American Institute for Cancer Research (AICR) cancer prevention recommendations assigns equal weight for each recommendation, thereby giving higher weight to dietary factors collectively (5 points) than adiposity (1 point) and physical activity (1 point). An alternative score assigning equal weights to the adiposity, physical activity, alcohol, and other dietary (composite) recommendations may better predict cancer associations.

METHODS

We examined associations between standardized and alternative scores with cancer risk in two US prospective cohorts. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression.

RESULTS

During 28 years of follow-up, 16,342 incident cancer cases in women and 8729 cases in men occurred. Individuals in the highest versus lowest quintile of the standardized score had a reduced overall cancer risk (women: HR = 0.89, 95% CI: 0.85, 0.94; men: HR = 0.87, 95% CI: 0.81, 0.94). Results were slightly stronger for the alternative score (women: HR = 0.83, 95% CI: 0.79, 0.87; men: HR = 0.81, 95% CI: 0.75, 0.86). Similar patterns were observed for obesity-related, alcohol-related, smoking-related, and digestive system cancers.

CONCLUSIONS

Greater adherence to the WCRF/AICR cancer prevention recommendations was associated with lower cancer risk. A score assigning equal weights to the adiposity, physical activity, alcohol, and all remaining diet components yielded stronger associations than the standardized score.

Influence of analytic methods, data sources, and repeated measurements on the population attributable fraction of lifestyle risk factors

Population attributable risk (PAR%) reflects the preventable fraction of disease. However, PAR% estimates of cancer have shown large variation across populations, methods, data sources, and timing of measurements. Three statistical methods to estimate PAR% were identified from a systematic literature review: the Levin's formula, the comparative incidence rate method, and the comparative risk assessment method. We compared the variations in PAR% of postmenopausal breast cancer in the Nurses' Health Study to evaluate the influence by method choice, source of prevalence data, use of single vs repeated exposure measurements, and potential joint effects of obesity, alcohol, physical activity, fruit and vegetable intake. Across models of the three methods, the estimated PAR% using repeated measurements were higher than that using baseline measurement; overall PAR% for the baseline, simple update, and cumulative average models were 13.8%, 21.1%, 18.6% by Levin's formula; 13.7%, 28.0%, 31.2% by comparative risk assessment; and 17.4%, 25.2%, 29.3% by comparative incidence rate method. The estimated PAR% of the combination of multiple risk factors was higher than the product of the individual PAR%: 18.9% when assuming independence and 31.2% when considering the risk factors jointly. The three methods provided similar PAR% based on the same data source, timing of measurements, and target populations. However, sizable increases in the PAR% were observed for repeated measures over a single measure and for calculations based on achieving all recommendations jointly rather than individually.

Dietary Inflammatory and Insulinemic Potentials, Plasma Metabolome and Risk of Colorectal Cancer

The inflammatory and insulinemic potentials of diets have been associated with colorectal cancer risk. However, it is unknown whether the plasma metabolite profiles related to inflammatory diets, or to insulinemic diets, underlie this association. The aim of this study was to evaluate the association between metabolomic profile scores related to the food-based empirical dietary inflammatory patterns (EDIP), the empirical dietary index for hyperinsulinemia (EDIH), and plasma inflammation (CRP, IL-6, TNFα-R2, adiponectin) and insulin (C-peptide) biomarkers, and colorectal cancer risk. Elastic net regression was used to derive three metabolomic profile scores for each dietary pattern among 6840 participants from the Nurses' Health Study and Health Professionals Follow-up Study, and associations with CRC risk were examined using multivariable-adjusted logistic regression, in a case-control study of 524 matched pairs nested in both cohorts. Among 186 known metabolites, 27 were significantly associated with both the EDIP and inflammatory biomarkers, and 21 were significantly associated with both the EDIH and C-peptide. In men, odds ratios (ORs) of colorectal cancer, per 1 standard deviation (SD) increment in metabolomic score, were 1.91 (1.31-2.78) for the common EDIP and inflammatory-biomarker metabolome, 1.12 (0.78-1.60) for EDIP-only metabolome, and 1.65 (1.16-2.36) for the inflammatory-biomarkers-only metabolome. However, no association was found for EDIH-only, C-peptide-only, and the common metabolomic signatures in men. Moreover, the metabolomic signatures were not associated with colorectal cancer risk among women. Metabolomic profiles reflecting pro-inflammatory diets and inflammation biomarkers were associated with colorectal cancer risk in men, while no association was found in women. Larger studies are needed to confirm our findings.

Plant-based dietary patterns and the risk of digestive system cancers in 3 large prospective cohort studies

Little is known about the relation between plant-based dietary patterns and digestive system cancers. This study investigated the prospective association between 3 pre-defined indices of plant-based dietary pattern and risk of digestive system cancers, as a whole or individually. We utilized data from 3 prospective cohorts, the Nurses' Health Study (1984-2018, 74,496 women aged 65 ± 10.9 years), Nurses' Health Study II (1991-2017, 91,705 women aged 49.3 ± 8.3 years), and Health Professionals Follow up Study (1986-2016, 45,472 men aged 65.4 ± 11.0 years). We used Cox proportional hazards regression models to estimate multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) of digestive system cancers across 3 plant-based diet index scores: overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI). During a follow-up of 4,914,985 person-years, we identified 6,518 cases of digestive system cancers. In the pooled analysis of 3 cohorts, the HRs (95% CIs) per 10-point increase in hPDI score were 0.93 (0.89, 0.97) for total digestive system cancer, 0.94 (0.89, 0.99) for gastrointestinal tract cancer, 0.89 (0.81, 0.98) for accessory organ cancer, and 0.68 (0.52, 0.91) for liver cancer. In contrast, the HRs (95% CIs) per 10-point increase in uPDI score was 1.06 (1.01, 1.11) for gastrointestinal tract cancer and 1.07 (1.01, 1.13) for colorectal cancer. A healthy plant-based dietary pattern was associated with reduced risks of total digestive system cancers as well as individual cancers in the gastrointestinal tract and the accessory organs. Emphasizing the healthiness and quality of plant-based diets may be important for the prevention of developing cancers in the digestive system.

Dietary patterns and risk of colorectal cancer: a comparative analysis

BACKGROUND

Although several dietary patterns have been associated with incident colorectal cancer (CRC), it is unclear which diet is optimal.

METHODS

Participants included 48 409 men and 169 772 women from three USA-based prospective cohort studies. We compared the associations of 18 dietary patterns with CRC risk, including two reference scores. The reference scores were derived based on the dietary recommendations for cancer prevention and CRC-specific dietary risk factors mentioned in the 2018 World Cancer Research Fund/American Institute of Cancer Research (WCRF/AICR) Third Expert Report. Multivariable Cox proportional hazards models were fitted to estimate hazard ratios (HRs) and 95% CIs.

RESULTS

Most dietary patterns showed moderate correlations with the WCRF dietary score (absolute values of Spearman correlation coefficients: 0.45-0.63), except the Plant-based diet index, low-carbohydrate diets, the Empirical dietary index for hyperinsulinemia (EDIH) and Empirical dietary inflammation pattern (EDIP). HR for the 10th-90th percentile difference in the score was 0.86 (95% CI: 0.78-0.94) for the Dietary Approaches to Stop Hypertension score (DASH), 1.15 (1.06-1.26) for Western dietary pattern, 1.20 (1.10-1.31) for EDIH and 1.23 (1.13-1.34) for EDIP. These associations between patterns and CRC risk persisted after adjusting for the two reference scores.

CONCLUSIONS

Although further research is needed to improve the WCRF/AICR dietary recommendations, our comprehensive assessment of dietary patterns revealed that the DASH, Western dietary pattern, EDIH and EDIP may be the most relevant diets for preventing CRC.