Sara Gandini

Metformin and Cancer Risk in Diabetic Patients: A Systematic Review and Meta-analysis

Metformin, an insulin-lowering agent, has been associated with decreased cancer risk in epidemiologic studies in diabetic patients. We performed a comprehensive literature search and meta-analysis of epidemiologic studies to assess the effect of metformin on cancer incidence and mortality in diabetic patients, using Pubmed, ISI Web of Science, Embase, and the Cochrane library until May 2009, with no language or time restrictions. Independent reports with sufficient information to allow risk estimation of cancer risk/mortality and a measure of uncertainty were reviewed and cross-checked independently by three investigators. Eleven studies were selected for relevance in terms of intervention, population studied, independence, and reporting of cancer incidence or mortality data, reporting 4,042 cancer events and 529 cancer deaths. A 31% reduction in overall summary relative risk (0.69; 95% confidence interval, 0.61-0.79) was found in subjects taking metformin compared with other antidiabetic drugs. The inverse association was significant for pancreatic and hepatocellular cancer, and nonsignificant for colon, breast, and prostate cancer. A trend to a dose-response relationship was noted. Metformin is associated with a decreased risk of cancer incidence compared with other treatments among diabetic patients. Given the retrospective nature of most studies and the possibility that the control treatments increase risk, phase II trials are needed before large cancer prevention trials are launched. Cancer Prev Res; 3(11); 1451–61. ©2010 AACR.

Tobacco smoking and cancer: A meta-analysis

We conducted a systematic meta‐analysis of observational studies on cigarette smoking and cancer from 1961 to 2003. The aim was to quantify the risk for 13 cancer sites, recognized to be related to tobacco smoking by the International Agency for Research on Cancer (IARC), and to analyze the risk variation for each site in a systematic manner. We extracted data from 254 reports published between 1961 and 2003 (177 case‐control studies, 75 cohorts and 2 nested case‐control studies) included in the 2004 IARC Monograph on Tobacco Smoke and Involuntary Smoking. The analyses were carried out on 216 studies with reported estimates for ‘current’ and/or ‘former’ smokers. We performed sensitivity analysis, and looked for publication and other types of bias. Lung (RR = 8.96; 95% CI: 6.73–12.11), laryngeal (RR = 6.98; 95% CI: 3.14–15.52) and pharyngeal (RR = 6.76; 95% CI: 2.86–15.98) cancers presented the highest relative risks (RRs) for current smokers, followed by upper digestive tract (RR = 3.57; 95% CI: 2.63–4.84) and oral (RR = 3.43; 95% CI: 2.37–4.94) cancers. As expected, pooled RRs for respiratory cancers were greater than the pooled estimates for other sites. The analysis of heterogeneity showed that study type, gender and adjustment for confounding factors significantly influence the RRs estimates and the reliability of the studies.

Vitamin D and musculoskeletal health, cardiovascular disease, autoimmunity and cancer: Recommendations for clinical practice

BACKGROUND There is increasing evidence that, in addition to the well-known effects on musculoskeletal health, vitamin D status may be related to a number of non-skeletal diseases. An international expert panel formulated recommendations on vitamin D for clinical practice, taking into consideration the best evidence available based on published literature today. In addition, where data were limited to smaller clinical trials or epidemiologic studies, the panel made expert-opinion based recommendations. METHODS Twenty-five experts from various disciplines (classical clinical applications, cardiology, autoimmunity, and cancer) established draft recommendations during a 2-day meeting. Thereafter, representatives of all disciplines refined the recommendations and related texts, subsequently reviewed by all panelists. For all recommendations, panelists expressed the extent of agreement using a 5-point scale. RESULTS AND CONCLUSION Recommendations were restricted to clinical practice and concern adult patients with or at risk for fractures, falls, cardiovascular or autoimmune diseases, and cancer. The panel reached substantial agreement about the need for vitamin D supplementation in specific groups of patients in these clinical areas and the need for assessing their 25-hydroxyvitamin D (25(OH)D) serum levels for optimal clinical care. A target range of at least 30 to 40 ng/mL was recommended. As response to treatment varies by environmental factors and starting levels of 25(OH)D, testing may be warranted after at least 3 months of supplementation. An assay measuring both 25(OH)D(2) and 25(OH)D(3) is recommended. Dark-skinned or veiled individuals not exposed much to the sun, elderly and institutionalized individuals may be supplemented (800 IU/day) without baseline testing.

Cutaneous melanoma attributable to sunbed use : systematic review and meta-analysis

Objective To estimate the burden of melanoma resulting from sunbed use in western Europe. Design Systematic review and meta-analysis. Data sources PubMed, ISI Web of Science (Science Citation Index Expanded), Embase, Pascal, Cochrane Library, LILACS, and MedCarib, along with published surveys reporting prevalence of sunbed use at national level in Europe. Study selection Observational studies reporting a measure of risk for skin cancer (cutaneous melanoma, squamous cell carcinoma, basal cell carcinoma) associated with ever use of sunbeds. Results Based on 27 studies ever use of sunbeds was associated with a summary relative risk of 1.20 (95% confidence interval 1.08 to 1.34). Publication bias was not evident. Restricting the analysis to cohorts and population based studies, the summary relative risk was 1.25 (1.09 to 1.43). Calculations for dose-response showed a 1.8% (95% confidence interval 0% to 3.8%) increase in risk of melanoma for each additional session of sunbed use per year. Based on 13 informative studies, first use of sunbeds before age 35 years was associated with a summary relative risk of 1.87 (1.41 to 2.48), with no indication of heterogeneity between studies. By using prevalence data from surveys and data from GLOBOCAN 2008, in 2008 in the 15 original member countries of the European Community plus three countries that were members of the European Free Trade Association, an estimated 3438 cases of melanoma could be attributable to sunbed use, most (n=2341) occurring among women. Conclusions Sunbed use is associated with a significant increase in risk of melanoma. This risk increases with number of sunbed sessions and with initial usage at a young age (<35 years). The cancerous damage associated with sunbed use is substantial and could be avoided by strict regulations.

Meta-analysis of observational studies of serum 25-hydroxyvitamin D levels and colorectal, breast and prostate cancer and colorectal adenoma.

Epidemiological studies have suggested a reduced risk of several cancers associated with high vitamin D status. We performed a systematic review with meta‐analyses of observational studies of serum 25‐hydroxyvitamin D level and colorectal, breast and prostate cancer and colonic adenoma. The literature of December 2009 was searched without language restriction. The meta‐regression analysis was done to compute dose‐response effects. Because in case‐control studies, serum 25‐hydroxyvitamin D level is measured after the diagnosis of cancer, separate analyses for case‐control and prospective studies were done. We identified 35 independent studies. The seven studies on colorectal adenomas were heterogeneous in terms of endpoint and control for major confounding factors, and we did not perform a meta‐analysis of these data. The summary relative risk (SRR) and (95% confidence interval) for a 10 ng/ml increase in serum 25‐hydroxyvitamin D was 0.85 (0.79; 0.91) for colorectal cancer (2,630 cases in 9 studies); 0.89 (0.81;0.98) for breast cancer (6,175 cases in 10 studies); and 0.99 (0.95;1.03) for prostate cancer (3,956 cases in 11 studies). For breast cancer, case‐control studies (3,030 cases) had major limitations and obtained SRR of 0.83 (0.79; 0.87) whereas SRR of prospective studies (3,145 cases) was 0.97 (0.92; 1.03). For colorectal and breast cancer, differences between cases and controls in the season of blood draw or in overweight/obesity or physical inactivity could not explain the results. In conclusion, a consistent inverse relationship between serum 25‐hydroxyvitamin D levels and colorectal cancer was found. No association was found for breast and prostate cancer.

MC1R variants, melanoma and red hair color phenotype: a meta-analysis.

Melanocortin‐1‐receptor (MC1R) is one of the major genes that determine skin pigmentation. MC1R variants were suggested to be associated with red hair, fair skin, and an increased risk of melanoma. We performed a meta‐analysis on the association between the 9 most studied MC1R variants (p.V60L, p.D84E, p.V92M, p.R142H, p.R151C, p.I155T, p.R160W, p.R163Q and p.D294H) and melanoma and/or red hair, fair skin phenotype. Eleven studies on MC1R and melanoma, and 9 on MC1R and phenotype were included in the analysis. The 7 variants p.D84E, p.R142H, p.R151C, p.I155T, p.R160W, p. R163Q and p.D294H were significantly associated with melanoma development, with ORs (95%CI) ranging from 1.42 (1.09–1.85) for p.R163Q to 2.45 (1.32–4.55) for p.I155T. The MC1R variants p.R160W and p.D294H were associated both with red hair and fair skin, while p.D84E, p.R142H, and p.R151C were strongly associated with red hair only‐ ORs (95%CI) ranged from 2.99 (1.51–5.91) for p.D84E to 8.10 (5.82–11.28) for p.R151C. No association with melanoma or phenotype was found for p.V60L and p.V92M variants. In conclusion this meta‐analysis provided evidence that some MC1R variants are associated both with melanoma and phenotype, while other are only associated with melanoma development. These results suggest that MC1R variants could play a role in melanoma development both via pigmentary and non‐pigmentary pathways.

Review and meta-analysis on vitamin D receptor polymorphisms and cancer risk

It was suggested that vitamin D levels influence cancer development. The vitamin D receptor (VDR) is a crucial mediator for the cellular effects of vitamin D. Results from previous studies on the association of VDR polymorphisms with different cancer types are somewhat contradictory, and the role of VDR in the etiology of cancer is still equivocal. We therefore performed a meta-analysis on the association between the two most studied VDR polymorphisms (FokI and BsmI) and any cancer site. Up to January 2009, we identified 67 independent studies. We used random-effects models to provide summary odds ratio (SOR) for VDR polymorphisms and cancer. We tested homogeneity of effects across studies and publication bias and explored between-study heterogeneity. When comparing FokI ff with FF carriers, we found a significant increase in skin cancer [SOR; 95% confidence intervals (CIs): 1.30; 1.04-1.61] and breast cancer (SOR; 95%CI: 1.14; 1.03-1.27) risk. For the same genotype comparison, we found a significantly higher risk of cancer when we pooled estimates from cancer sites possibly associated with vitamin D levels (prostate, breast, skin, ovary, non-Hodgkin lymphoma and colorectal). A significant reduction in prostate cancer risk was observed for carriers of BsmI Bb compared with bb genotype (SOR; 95%CI: 0.83; 0.69-0.99). In Caucasian populations, both Bb and BB carriers had a significant reduced risk of cancer at any site. In conclusion, this meta-analysis showed that VDR FokI and BsmI polymorphisms might modulate the risk of cancer of breast, skin and prostate and possibly affect cancer risk at any site in Caucasians.

Vitamin D Status and Mortality Risk in CKD: A Meta-analysis of Prospective Studies

BACKGROUND Vitamin D deficiency, assessed as low 25-hydroxyvitamin D (25[OH]D) level, is highly prevalent in patients with chronic kidney disease (CKD) and is associated with various adverse health outcomes. Whether low 25(OH)D levels in patients with CKD are an independent risk factor for mortality remains to be studied in detail, and this was the objective of our work. STUDY DESIGN A systematic review and meta-analysis of prospective observational studies. SETTING & POPULATION Patients with CKD. CKD was diagnosed mainly as decreased estimated glomerular filtration rate. SELECTION CRITERIA FOR STUDIES We performed a systematic literature search in MEDLINE, ISI, and EMBASE to identify prospective studies reporting on 25(OH)D levels and mortality. PREDICTOR 25(OH)D serum concentrations. OUTCOME All-cause mortality. RESULTS 10 studies with an overall sample of 6,853 patients with CKD were included. Relative risk of mortality per 10-ng/mL (25-nmol/L) increase in 25(OH)D level was 0.86 (95% CI, 0.82-0.91), with no indication of publication bias or significant heterogeneity (I(2) =15%; P = 0.3). Summary estimates for CKD cohorts with and without dialysis treatment showed homogeneous results (P = 0.9). LIMITATIONS Results may be limited by heterogeneity, unconsidered confounders, and the observational design of the studies. Furthermore, publication bias by unpublished null findings on the association of 25(OH)D level and mortality cannot be ruled out and ascertainment of CKD was based largely on estimated glomerular filtration rate. CONCLUSIONS Higher 25(OH)D levels are associated with significantly improved survival in patients with CKD. Whether treatment of low 25(OH)D level using natural vitamin D supplementation improves survival in patients with CKD remains to be elucidated in randomized controlled trials.

Metformin and Cancer Risk and Mortality: A Systematic Review and Meta-Analysis taking into account Biases and Confounders

Previous meta-analyses have shown that the antidiabetic agent metformin is associated with reduced cancer incidence and mortality. However, this effect has not been consistently demonstrated in animal models and recent epidemiologic studies. We performed a meta-analysis with a focus on confounders and biases, including body mass index (BMI), study type, and time-related biases. We identified 71 articles published between January 1, 1966, and May 31, 2013, through Pubmed, ISI Web of Science (Science Citation Index Expanded), Embase, and the Cochrane library that were related to metformin and cancer incidence or mortality. Study characteristics and outcomes were abstracted for each study that met inclusion criteria. We included estimates from 47 independent studies and 65,540 cancer cases in patients with diabetes. Overall cancer incidence was reduced by 31% [summary relative risk (SRR), 0.69; 95% confidence interval (CI), 0.52–0.90], although between-study heterogeneity was considerable (I2 = 88%). Cancer mortality was reduced by 34% (SRR, 0.66; 95% CI, 0.54–0.81; I2 = 21%). BMI-adjusted studies and studies without time-related biases also showed significant reduction in cancer incidence (SRR, 0.82; 95% CI, 0.70–0.96 with I2 = 76% and SRR, 0.90; 95% CI, 0.89–0.91 with I2 = 56%, respectively), albeit with lesser magnitude (18% and 10% reduction, respectively). However, studies of cancer mortality and individual organ sites did not consistently show significant reductions across all types of analyses. Although these associations may not be causal, our results show that metformin may reduce cancer incidence and mortality in patients with diabetes However, the reduction seems to be of modest magnitude and not affecting all populations equally. Clinical trials are needed to determine if these observations apply to nondiabetic populations and to specific organ sites. Cancer Prev Res; 7(9); 867–85. ©2014 AACR.

Oral contraceptive use and breast or ovarian cancer risk in BRCA1/2 carriers: A meta-analysis

BACKGROUND Women with BRCA1 or BRCA2 mutations are at increased risk of breast and ovarian cancer. Oral contraceptives (OC) use has been associated with a reduction in ovarian cancer risk and with a moderately increased breast cancer risk, which tends to level off in the few years after stopping. The association between oral contraceptive and BRCA1 or BRCA2 gene mutations carriers is unclear. METHODS We performed a comprehensive literature search updated to March 2010 of studies on the associations between OC users and breast or ovarian cancer for ascertained BRCA1/2 carriers. We obtained summary risk estimated for ever OC users, for duration of use and time since stopping. RESULTS A total of 2855 breast cancer cases and 1503 ovarian cancer cases, carrying an ascertained BRCA1/2 mutation, were included in our meta-analyses, based on overall 18 studies. Use of OC was associated with a significant reduced risk of ovarian cancer for BRCA1/2 carriers (summary relative risk (SRR)=0.50; 95% confidence interval (CI), 0.33-0.75). We also observed a significant 36% risk reduction for each additional 10 years of OC use (SRR: 0.64; 95% CI, 0.53-0.78; P trend<0.01). We found no evidence of a significant association between OC and breast cancer risk in carriers (SRR: 1.13; 95% CI, 0.88-1.45) and with duration of use. OC formulations used before 1975 were associated with a significant increased risk of breast cancer (SRR: 1.47; 95% 1.06, 2.04), but no evidence of a significant association was found with use of more recent formulations (SRR: 1.17; 95% 0.74, 1.86). CONCLUSIONS OC users carrying an ascertained BRCA1/2 mutation have a reduced risk of ovarian cancer, proportional to the duration of use. There is no evidence that recent OC formulations increase breast cancer risk in carriers.