Body mass index and colon cancer risk in Chinese people: menopause as an effect modifier

Overweight and obesity significantly increase colorectal cancer risk: a meta-analysis of 66 studies revealing a 25-57% elevation in risk

The incidence of colorectal cancer (CRC) has been steadily rising, and obesity has been identified as a significant risk factor. Numerous studies suggest a strong correlation between excess body weight and increased risk of CRC, but comprehensive quantification through pooled analysis remains limited. This study aims to systematically review and meta-analyze the existing literature to evaluate the association between obesity and CRC risk, considering variations across sex and study designs. A systematic literature search was conducted in PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science to identify randomized controlled trials and human clinical trials from 1992 to 2024. Statistical analysis was performed using the https://metaanalysisonline.com web application using a random effects model to estimate the pooled hazard rates (HR). Forest plots, funnel plots, and Z-score plots were utilized to visualize results. We identified 52 clinical trials and 14 case-control studies, encompassing a total of 83,251,050 and 236,877 subjects, respectively. The pooled analysis indicated that obesity significantly increased the prevalence of CRC (HR = 1.36, 95% CI = 1.24-1.48, p < 0.01). This effect was consistent across sexes, with HRs of 1.57 (95% CI = 1.38-1.78, p = 0.01) for males and 1.25 (95% CI = 1.14-1.38, p < 0.01) for females. Case-control studies specifically showed an effect, but with marginal significance only (HR = 1.27, 95% CI = 0.98-1.65, p = 0.07). The Z-score plot indicated the need for additional analysis in the case-control group. A significant heterogeneity was observed across studies in all four settings. This meta-analysis provides robust evidence that obesity is a significant risk factor for colorectal cancer, with an overall hazard rate indicating a 36% increased risk. The effect is pronounced across both sexes, with males showing a slightly higher risk compared to females. Although case-control studies showed a weaker association, the overall trend supports the link between obesity and CRC. These results underscore the importance of public health interventions aimed at reducing obesity to potentially lower the risk of colorectal cancer.

Chemoprophylaxis Effect of EGCG on the Recurrence of Colorectal Cancer: A Systematic Review and Meta-Analysis

BACKGROUND AND AIMS

The recurrence rate of Colorectal Cancer (CRC) after cure is always high. The purpose of this study was to investigate whether green tea extract (-)-Epigallocatechin gallate (EGCG) has an effective preventive effect on the recurrence of CRC.

METHODS

We conducted a systematic literature review and meta-analysis of the effects of taking EGCG or placebo on disease recurrence in patients after colon polyp removal.

RESULTS

Five Randomized Controlled Trials (RCTs) were included in this review. A double-blind drug trial involving 1389 participants involved EGCG and placebo. The results showed no significant publication bias or heterogeneity in the five studies (I2 = 38%; p = 0.17). Patients taking EGCG had a lower recurrence rate of CRC than those in the placebo group. The results were statistically significant (Z=2.83, p < 0.05).

CONCLUSION

This study demonstrated that long-term EGCG can prevent CRC recurrence to a certain extent.

A Cone Beam CT Study of Upper Airway Morphology in Perimenopausal and Postmenopausal Women

Purpose

Menopause is accompanied by a decline in estrogen and progesterone. Several studies have demonstrated that upper airway patency decreases in women after menopause, while morphology changes are still a lack of evidence. This study aimed to explore upper airway morphology changes in perimenopausal and postmenopausal women.

Methods

This retrospective cross-sectional study included 367 consecutive Chinese female patients over 25 years old who had routinely taken large-field cone beam computed tomography in the imaging library of Peking University School and Hospital of Stomatology from October 2016 to September 2020. A total of 283 males were screened as sex controls according to the same age group. Upper airway morphology, hyoid position and facial pattern were measured. The association between perimenopausal and postmenopausal years and upper airway morphology in both sexes was analyzed.

Results

Perimenopausal women (aged 45-54 years) showed a significant decrease in the volume (3172.91mm³, 95% CI = 653.86-5691.96) and minimum cross-sectional area (37.08 mm², 95% CI = 5.36-68.80), and a significant increase in the length (-1.96mm, 95% CI = -3.62 to -0.29) of upper airway compared to adjacent reproductive years (aged 35-44), while this difference was neither seen in other adjacent two reproductive age groups of females nor in the same age groups of males. In postmenopausal women (55 years and older), hyoid position was significantly lower (-2.74mm, 95% CI = -4.42 to -1.07) than either age group, while no similar changes were seen in men.

Conclusion

Women had smaller airway volume, reduced upper airway cross-sectional area and longer airway length in perimenopausal years, and a significantly lower hyoid position in postmenopausal years. These changes may be related to menopause itself and independent of the changes associated with aging.

Association of Body Mass Index With Risk of Early-Onset Colorectal Cancer: Systematic Review and Meta-Analysis

INTRODUCTION

Incidence of colorectal cancer (CRC) in young adults has been increasing in recent decades in many countries for still widely unclear reasons. Suspected candidates include increasing prevalence of overweight and obesity, but specific evidence on their role for early-onset CRC (EOCRC) is sparse. We conducted a systematic review and meta-analysis to summarize available evidence on the association of body mass index (BMI) with EOCRC.

METHODS

We systematically searched PubMed, EMBASE, and Web of Science up to February 2021 for studies that evaluated the association of BMI (before diagnosis but not near diagnosis) with CRC risk and reported specific results for EOCRC. Results from studies with similar BMI groupings were summarized in meta-analyses using random-effects models.

RESULTS

Twelve studies were eligible and included. Results of 6 studies were pooled in meta-analyses, which yielded a higher risk of EOCRC for overweight and obesity (BMI ≥25 kg/m2) compared with normal weight (odds ratio [OR] 1.42, 95% confidence interval [CI] 1.19-1.68). An increasing risk with increasing BMI was observed, with much higher risk for obesity (OR 1.88, 95% CI 1.40-2.54) than for overweight (OR 1.32, 95% CI 1.19-1.47).

DISCUSSION

Obesity is a strong risk factor for EOCRC, and its increasing prevalence in younger generations is likely to substantially contribute to the increase in EOCRC. Efforts to limit the obesity epidemic in adolescents and younger adults may be crucial for reducing CRC incidence in future generations of adults.

The association between predicted inflammatory status and colorectal adenoma

We developed a diet and lifestyle score based on high sensitivity C-reactive protein (hsCRP), and investigated its association with odds of adenoma. We performed stepwise linear regression to develop the predicted hsCRP score among 23,330 participants in the Health Examinee Study and examined its association with colorectal adenoma among 1,711 participants in a cross-sectional study of colorectal adenoma. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) of colorectal adenoma using logistic regression models. Variances in hsCRP explained by body mass index were 61.1% in men and 64.5% in women in the prediction model. The increasing predicted hsCRP score was positively associated with colorectal adenoma (OR_{quartile 4 VS quartile 1} 1.71, 95% CI: 1.12–2.62; P_trend = 0.011 in men; OR_{quartile 4 VS quartile 1} 2.86, 95% CI: 1.26–6.49; P_trend = 0.019 in women). In subgroups, the associations differed by age and menopausal status among women, with stronger associations among women aged less than 50 years (OR_{≥median VS <median} 3.74, 95% CI: 1.77–7.90, p for interaction 0.014) or premenopausal women (OR_{≥median vs <median} 4.21, 95% CI: 2.12–8.36, p for interaction <0.001). The associations were more pronounced in the advanced or distal colon/rectum in men and in the advanced or proximal colon in women. The associations were attenuated after further adjustment for body mass index. In conclusion, we found that the predicted hsCRP score was positively associated with colorectal adenoma, suggesting that diet and lifestyle lowering inflammation may be a strategy to prevent colorectal neoplasia.

Impact of Estrogen on the Relationship Between Obesity and Renal Cell Carcinoma Risk in Women

The relationship between obesity and renal cell carcinoma (RCC) has been widely investigated. However, the effect of estrogen on this relationship in female RCC patients has not been evaluated. We conducted a case-control study to investigate the role of estrogen as a potential modifier of the association between obesity and RCC risk in Chinese women.

A total of 497 consecutive female patients with pathologically confirmed RCC, including 364 clear cell RCC (ccRCC), were enrolled. Age-matched controls were selected from cancer-free females seeking physical examination in our institution. Estrogen receptor-β (ER-β) and insulin-like growth factor (IGF)-1 receptor (IGF-1R) expression levels were detected in RCC tissues. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated by logistic regression models.

We observed a positive association between overweight and RCC risk in pre-menopausal but not post-menopausal women. Similar association was also observed between overweight and ccRCC risk. Overweight pre-menopausal women had an increased risk of RCC (OR: 1.67, 95%CI: 1.01–2.76), as well as an increased risk of ccRCC (OR: 1.73, 95%CI: 1.02–2.99), after adjusting for potential confounders. IGF-1R expression levels were higher in pre-menopausal compared with post-menopausal cases (P = 0.015).

These results suggest that estrogen plays an important role in RCC etiology and may modify the association between obesity and RCC risk in women. We hypothesize that estrogen may up-regulate IGF-1R and potentiate the deleterious effects of obesity-related elevations of insulin and IGFs.

Body mass index and the risk of cancer incidence in patients with type 2 diabetes in Japan: Results from the National Center Diabetes Database

AIMS/INTRODUCTION

Both type 2 diabetes and obesity increase the risk of some types of cancers, and underlying mechanisms are thought to be, at least in part, common. In the present study, we carried out a retrospective cohort study of the relationship between body mass index (BMI) categories and cancer development in Japanese type 2 diabetic patients.

MATERIALS AND METHODS

A total of 113 incident cancers including 35 cancers whose incidence was reported to be increased by obesity (27 colorectal cancers, two breast cancers in postmenopausal women, one endometrial cancer, four renal cancers and one gallbladder cancer) were identified in 2,334 type 2 diabetic patients (1,616 men and 718 women) over an average observation period of 5.1 years.

RESULTS

In men, there was no significant association between the BMI categories at the start of the observation period and the development of any cancer. In contrast, the incidence of all of the cancers in the women was significantly higher in the group with a BMI of less than 22.0 kg/m2 (hazard ratio 3.07, 95% CI 1.01-9.36). In either sex, there was no significant relationship between the BMI categories and the development of cancers whose risk is known to be increased by obesity.

CONCLUSIONS

The findings of the present study were limited by the relatively small number of patients in the cohort, which posed a danger of not finding significance. However, the results suggested that obesity did not become an additional risk factor for cancer in Japanese type 2 diabetic patients.

Visceral fat accumulation is associated with colorectal cancer in postmenopausal women

Background

Obesity is a known risk factor for colorectal cancer (CRC), and emerging data suggest that this association is mediated by visceral fat rather than total body fat. However, there is a lack of studies evaluating the association between visceral fat area and the prevalence of CRC.

Methods

To investigate the relationship between visceral adiposity and prevalence of CRC, data of 497 women diagnosed with CRC and 318 apparently healthy women were analysed and data of well-balanced 191 pairs of women with CRC and healthy women matched based on propensity scores were additionally analysed. Diagnosis of CRC was confirmed by colonoscopy and histology. Metabolic parameters were assessed, along with body composition, using computed tomography.

Results

The median visceral fat area was significantly higher in the CRC group compared with the control group before and after matching. The prevalence of CRC increased significantly with increasing visceral fat tertiles after matching (p for trend <0.01). A multivariate analysis showed that mean visceral fat area of individuals in the 67^th percentile or greater group was associated with an increased prevalence of CRC (adjusted odds ratio: 1.80; 95% confidence interval: 1.12–2.91 before matching and adjusted odds ratio: 2.96; 95% confidence interval: 1.38–6.33) compared with that of individuals in the 33^th percentile or lower group.

Conclusion

Thus, we conclude that visceral fat area is positively associated with the prevalence of CRC. Although we could not determine the causality, visceral adiposity may be associated with the risk of CRC. Further prospective studies are required to determine the benefits of controlling visceral obesity for reducing CRC risk.

Obesity and colorectal adenomatous polyps: a cross-sectional study in Korean adults

OBJECTIVE

This study aimed to examine the association between obesity and the risk of colorectal adenomatous polyps.

DESIGN AND METHODS

The design of this study is a cross-sectional study. A total of 1,574 participants (818 males and 756 females), who had undergone colonoscopy for health examinations at the National Cancer Center hospital in South Korea from February to September 2009, were included in the analysis.

RESULTS

The prevalence of colorectal adenomatous polyps was 39.5% in males and 22.6% in females. In multiple logistic regression analysis, obesity (odds ratio [OR] = 1.69, 95% CI = 1.16-2.48) and abdominal obesity (OR = 1.59, 95% CI = 1.13-2.23) were significantly associated with an increased risk of colorectal adenomatous polyps in males, but not in females. In the subgroup analyses by age, obesity (OR = 2.27, 95% CI = 1.32-3.89), and abdominal obesity (OR = 1.76, 95% CI = 1.12-2.76) significantly increased a risk of colorectal adenomatous polyps in males aged <50 years, but not in males aged ≥50 years. However, interaction terms were not significant between obesity and gender (P = 0.397) and between obesity and age (P = 0.531) in the overall analyses.

CONCLUSION

Our findings should be explored in further research.

Meta-analyses of colorectal cancer risk factors

PURPOSE

Demographic, behavioral, and environmental factors have been associated with increased risk of colorectal cancer (CRC). We reviewed the published evidence and explored associations between risk factors and CRC incidence.

METHODS

We identified 12 established non-screening CRC risk factors and performed a comprehensive review and meta-analyses to quantify each factor's impact on CRC risk. We used random-effects models of the logarithms of risks across studies: inverse-variance weighted averages for dichotomous factors and generalized least squares for dose-response for multi-level factors.

RESULTS

Significant risk factors include inflammatory bowel disease (RR = 2.93, 95 % CI 1.79-4.81); CRC history in first-degree relative (RR = 1.80, 95 % CI 1.61-2.02); body mass index (BMI) to overall population (RR = 1.10 per 8 kg/m(2) increase, 95 % CI 1.08-1.12); physical activity (RR = 0.88, 95 % CI 0.86-0.91 for 2 standard deviations increased physical activity score); cigarette smoking (RR = 1.06, 95 % CI 1.03-1.08 for 5 pack-years); and consumption of red meat (RR = 1.13, 95 % CI 1.09-1.16 for 5 servings/week), fruit (RR = 0.85, 95 % CI 0.75-0.96 for 3 servings/day), and vegetables (RR = 0.86, 95 % CI 0.78-0.94 for 5 servings/day).

CONCLUSIONS

We developed a comprehensive risk modeling strategy that incorporates multiple effects to predict an individual's risk of developing CRC. Inflammatory bowel disease and history of CRC in first-degree relatives are associated with much higher risk of CRC. Increased BMI, red meat intake, cigarette smoking, low physical activity, low vegetable consumption, and low fruit consumption were associated with moderately increased risk of CRC.

Estrogen in obesity-associated colon cancer: friend or foe? Protecting postmenopausal women but promoting late-stage colon cancer

Obesity is associated with the increased incidence of colon cancer. Many cancer risk factors have been identified including increased blood levels of insulin, leptin, interleukin-6, interleukin-17, tumor necrosis factor-alpha, and decreased blood levels of adiponectin. However, the role of blood levels of estrogen in obesity-associated colon cancer is controversial. Evidence showed that obesity affected men more strongly than women in the carcinogenesis of colon cancer, indicating protective effect of estrogen which is increased in obesity. However, an epidemiological study has also shown that endogenous estradiol level is an independent risk factor for colon cancer, positively associated with colon cancer after normalizing insulin, IGF-1. The controversial opinions may be caused by different effects of ER-alpha and ER-beta. ER-alpha can increase colon cancer cell proliferation and increase cancer incidence. ER-beta has the opposite effect to ER-alpha, and it causes apoptosis of colon cancer cells. The normal colonocytes mainly express ER-beta. Therefore, increased estrogen in obesity may have protective effect via ER-beta in obesity-associated colon cancer. However, with the development of colon cancer, ER-alpha is increased and ER-beta is decreased. In the late stage of colon cancer, estrogen may promote cancer development via ER-alpha. The different effects and expression of ER-alpha and ER-beta may explain the different results observed in several epidemiological studies as well as several animal experiments. Therefore, manipulation of estrogen-caused signal pathways to inhibit ER-alpha and stimulate ER-beta may have preventive and therapeutic effect for obesity-associated colon cancer.

Estimation of cancer incidence and mortality attributable to overweight, obesity, and physical inactivity in China

The objective was to provide an evidence-based, systematic assessment of the burden of cancer due to overweight/obesity and physical inactivity in China. This study evaluated the proportion of cancers of colon, rectum, pancreas, breast (postmenopausal), endometrium, and kidney attributable to overweight [30 kg/m(2) > body mass index (BMI) ≥ 25 kg/m(2))/obesity (BMI ≥ 30 kg/m(2)) and physical inactivity in China in 2005. Data of prevalence of overweight/obesity and lack of physical activity were derived from cross-sectional surveys among representative samples of Chinese population, and data of relative risks on cancers were derived from meta-analyses or large-scale studies from China and East Asian populations. The attributable fractions were calculated by combining both data of prevalence and relative risks. In China in 2005, 0.32% of cancer deaths and 0.65% of cancer cases were attributable to overweight and obesity combined. Lack of physical activity was responsible for 0.27% of cancer deaths and 0.39% of cancer cases. Future projections indicate that the contribution of overweight and obesity to the overall cancer burden will increase in the next decades. The largest increased attributable fractions will be for endometrial cancer. The increase in attributable fractions would be greater in men and in rural populations. Although the current burden of cancer associated with overweight/obesity and physical inactivity is still relatively small in China, it is expected to increase in the future.

Body mass index and death rate of colorectal cancer among a national cohort of U.S. adults

Substantial evidence suggests that increasing adiposity is associated with an increased death rate of colorectal cancer, but no studies were conducted among national representative populations in the United States. The current study examined the death rate across BMI levels in 7,016 adults who participated in the National Health and Nutrition Examination Survey in 1971-1975. BMI categories were defined as normal (18.5-24.9 kg/m(2)), overweight (25-29.9), and obese (≥30). A total of 519 cancer deaths were identified during a 17-yr follow-up with 118,998 person-years. No significantly increased death rates of total cancers, lung, breast, and prostate cancer were observed among participants with an increased BMI. However, colorectal cancer death rates were 0.39, 0.68, and 0.96/1,000 person-years, respectively, for normal weight, overweight, and obese (P value for log-rank trend test < 0.001), and the corresponding adjusted hazard ratios [95% confidence intervals (CI)] were 1.00 (reference), 1.25 (95% CI = 0.72-2.19), and 2.04 (1.08-3.83), respectively. No gender difference of the association was identified. The authors conclude that a significantly increased death rate of colorectal cancer was associated with excess body weight. The current study is an addition to the expanding body of literature indicating an increased risk of colorectal cancer development among the obese.

Body size and incident colorectal cancer: a prospective study of older women

Obesity is a controversial risk factor for colorectal cancer (CRC) in older women. We evaluated associations between multiple body size parameters and incident CRC in the prospective, population-based Iowa Women's Health Study (IWHS). IWHS participants, ages 55 to 69 years, provided data regarding height; weight; weight at ages 50, 40, 30, 18 years; hip circumference; and waist circumference at baseline (1986). Derived variables included body mass index (BMI), waist-to-hip ratio (WHR), and "overweight years" (OWY; conceptually similar to cigarette pack-years). Incident CRC cases (n = 1,464) were ascertained from the State Health Registry of Iowa, through 2005. Multivariable Cox regression models were fit to estimate body size-associated CRC risks. Among 36,941 women (619,961 person-years), baseline height, weight, BMI, hip circumference, waist circumference, and WHR were all positively associated with incident CRC (P(trend) ≤ 0.003 for each). Baseline BMI yielded the highest CRC risk estimates (obese III versus normal, RR = 1.56; 95% CI = 1.10-2.22; P(trend) < 0.001) and was more closely associated with distal than proximal tumors (P(trend) < 0.001 versus 0.06). Conversely, height was more closely associated with proximal than distal tumors (P(trend) < 0.001 versus 0.04). Other body size parameters were less predictive of incident CRC. These data strongly support a positive association between increased body size and CRC risk among older women. Further investigation of when increased body size has the greatest effect on CRC risk (i.e., early adulthood versus later adulthood) might also be informative, particularly with respect to defining subsite-specific pathways of colorectal carcinogenesis.

The nutrition-based comprehensive intervention study on childhood obesity in China (NISCOC): a randomised cluster controlled trial

BACKGROUND

Childhood obesity and its related metabolic and psychological abnormalities are becoming serious health problems in China. Effective, feasible and practical interventions should be developed in order to prevent the childhood obesity and its related early onset of clinical cardiovascular diseases. The objective of this paper is to describe the design of a multi-centred random controlled school-based clinical intervention for childhood obesity in China. The secondary objective is to compare the cost-effectiveness of the comprehensive intervention strategy with two other interventions, one only focuses on nutrition education, the other only focuses on physical activity.

METHODS/DESIGN

The study is designed as a multi-centred randomised controlled trial, which included 6 centres located in Beijing, Shanghai, Chongqing, Shandong province, Heilongjiang province and Guangdong province. Both nutrition education (special developed carton style nutrition education handbook) and physical activity intervention (Happy 10 program) will be applied in all intervention schools of 5 cities except Beijing. In Beijing, nutrition education intervention will be applied in 3 schools and physical activity intervention among another 3 schools. A total of 9750 primary students (grade 1 to grade 5, aged 7-13 years) will participate in baseline and intervention measurements, including weight, height, waist circumference, body composition (bioelectrical impendence device), physical fitness, 3 days dietary record, physical activity questionnaire, blood pressure, plasma glucose and plasma lipid profiles. Data concerning investments will be collected in our study, including costs in staff training, intervention materials, teachers and school input and supervising related expenditure.

DISCUSSION

Present study is the first and biggest multi-center comprehensive childhood obesity intervention study in China. Should the study produce comprehensive results, the intervention strategies would justify a national school-based program to prevent childhood obesity in China.

A quantitative analysis of body mass index and colorectal cancer: findings from 56 observational studies

To perform a systematic review of studies reporting on the association between body mass index (BMI) and the risk of colorectal cancer, we conducted a meta-analysis and meta-regression analysis. The identified 56 studies were conducted among 7 213 335 individuals including 93 812 cases. Compared with BMI < 23.0 kg m(-2), BMI of 23.0-24.9, 25.0-27.4, 27.5-29.9 and > or = 30.0 kg m(-2) were associated with 14%, 19%, 24% and 41% increased risks, respectively. Asians and premenopausal women had sharply increased risk from BMI < 23 kg m(-2) to general 'normal' range (23-25 kg m(-2)). Each 5 kg m(-2) increment was associated with 18% increased risk. Meta-regression analysis indicated that the association was stronger for colon than rectal cancer (P < 0.001), for men than women (P < 0.001), for self-reported BMI than directly measured BMI (P < 0.001), and for studies adjusting for physical activity than not adjusting (P < 0.001). The variation of the reported risk estimates for the association can be partly explained by cancer site, sex, women menopausal status, BMI assessment and adjustment of confounding variables.

Risk factors for sporadic colorectal cancer in southern Chinese

AIM: To investigate the role of smoking, alcohol drinking, family history of cancer, and body mass index (BMI) in sporadic colorectal cancer in southern Chinese.

METHODS: A hospital-based case-control study was conducted from July 2002 to December 2008. There were 706 cases and 723 controls with their sex and age (within 5 years) matched. An unconditional logistic regression model was used to analyze the association between smoking, alcohol drinking, family history of cancer, BMI and sporadic colorectal cancer.

RESULTS: No positive association was observed between smoking status and sporadic colorectal cancer risk. Compared with the non alcohol drinkers, the current and former alcohol drinkers had an increased risk of developing sporadic colorectal cancer (CRC) (adjusted OR = 8.61 and 95% CI = 6.15-12.05; adjusted OR = 2.30, 95% CI = 1.27-4.17). Moreover, the increased risk of developing sporadic CRC was significant in those with a positive family history of cancer (adjusted OR = 1.62, 95% CI = 1.12-3.34) and in those with their BMI ≥ 24.0 kg/m² (adjusted OR = 1.39, 95% CI = 1.10-1.75). Stratification analysis showed that the risk of developing both colon and rectal cancers was increased in current alcohol drinkers (adjusted OR = 7.60 and 95% CI = 5.13-11.25; adjusted OR = 7.52 and 95% CI = 5.13-11.01) and in those with their BMI ≥ 24.0 kg/m² (adjusted OR = 1.38 and 95% CI = 1.04-1.83; adjusted OR = 1.35 and 95% CI = 1.02-1.79). The risk of developing colon cancer, but not rectal cancer, was found in former alcohol drinkers and in those with a positive family history of cancer (adjusted OR = 2.51 and 95% CI = 1.24-5.07; adjusted OR = 1.82 and 95% CI = 1.17-2.82).

CONCLUSION: Alcohol drinking, high BMI (≥ 24.0 kg/m²) and positive family history of cancer are the independent risk factors for colorectal cancer in southern Chinese.

Association between body mass index and colorectal neoplasia at follow-up colonoscopy: a pooling study

A direct relation between body mass index (BMI) and risk of colorectal adenomas and cancer has been reported, but few studies have had adequate sample size for conducting stratified analyses by sex, family history, colorectal subsite, or features of metachronous lesions. Data from 8,213 participants in 7 prospective studies of metachronous colorectal adenomas were pooled to assess whether the association between BMI and metachronous neoplasia varied by these factors. A statistically significant direct association between BMI and the odds of nonadvanced adenomas (P(trend) < 0.001) was observed, while the relation for advanced adenomas was of marginal significance (P(trend) < 0.07). In sex-stratified analyses, obesity was statistically significantly associated with the odds of any metachronous lesion among men (odds ratio = 1.36, 95% confidence interval: 1.17, 1.58) but not among women (odds ratio = 1.10, 95% confidence interval: 0.89, 1.37). The associations with BMI appeared to be limited to proximal neoplasia, with statistically significant results for BMI and proximal (P(trend) < 0.001), but not distal (P(trend) < 0.85), neoplasia. Exploratory analyses indicated that BMI was significantly related to most histologic characteristics of metachronous adenomas among men but not among women. Our results provide further support for the association between BMI and metachronous colorectal adenomas, particularly among men, thereby indicating that body size may affect colorectal carcinogenesis at comparatively early stages.

Energy intake, physical activity, energy balance, and cancer: epidemiologic evidence

Energy intake, physical activity, and obesity are modifiable lifestyle factors. This chapter reviews and summarizes the epidemiologic evidence on the relation of energy intake, physical activity, and obesity to cancer. High energy intake may increase the risk of cancers of colon-rectum, prostate (especially advanced prostate cancer), and breast. However, because physical activity, body size, and metabolic efficiency are highly related to total energy intake and expenditure, it is difficult to assess the independent effect of energy intake on cancer risk. There are sufficient evidences to support a role of physical activity in preventing cancers of the colon and breast, whereas the association is stronger in men than in women for colon cancer and in postmenopausal than in premenopausal women for breast cancer. The evidence also suggests that physical activity likely reduces the risk of cancers of endometrium, lung, and prostate (to a lesser extent). On the other hand, there is little or no evidence that the risk of rectal cancer is related to physical activity, whereas the results have been inconsistent regarding the association between physical activity and the risks of cancers of pancreas, ovary and kidney. Epidemiologic studies provide sufficient evidence that obesity is a risk factor for both cancer incidence and mortality. The evidence supports strong links of obesity with the risk of cancers of the colon, rectum, breast (in postmenopausal women), endometrium, kidney (renal cell), and adenocarcinoma of the esophagus. Epidemiologic evidence also indicates that obesity is probably related to cancers of the pancreas, liver, and gallbladder, and aggressive prostate cancer, while it seems that obesity is not associated with lung cancer. The role of obesity in other cancer risks is unclear.

Clinical and molecular mechanism of the relationship between obesity and colorectal adenoma

AIM: To investigate the relationship between obesity and the colorectal precancerous lesion-adenoma, and to further investigate relationship between obesity and colon cancer and its prevention and treatment.

METHODS: A total of 539 subjects who underwent colonoscopy in Tongji Hospital from December 2006 to December 2007 were selected, and divided into the adenoma group (n = 250) and the control group (n = 289). Body height, weight, waist and hip circumference were measured, respectively. All data were analyzed using logistic multi-factors regression. Four adenomatous tissues, pathologically-confirmed as tubular adenoma or tubulovillous adenoma, 2 with BMI > 24, WC > 85 cm, and the others with BMI < 24, WC < 85 cm, were selected from adenoma group, and used to screen the differentially expressed gene by Oligo Signal Transduction Pathway Microarray.

RESULTS: Obesity (by using BMI cut-offs) (ORadj = 2.48, 95% CI = 1.19-5.20, P = 0.016) and abdominal adiposity (by using WC cut-offs) (ORadj = 1.75, 95% CI = 1.15-2.66, P = 0.009) were significantly associated with an increased risk of colorectal adenomas, especially in men(ORadj = 4.10 and 1.70, 95% CI = 1.26-13.31 and 1.00-2.88, P = 0.019 and 0.019, respectively), but there was no association in overweight group. Abdominal adiposity based on WHR showed no significant difference. Genomic hybridization showed 23 differentially expressed genes between the two groups. Among them, there were 6 genes up-regulated in BMI > 24 group, and 17 genes down-regulated in BMI < 24 group. Foxa2 was up-regulated, and IL-8 and Leptin were down-regulated.

CONCLUSION: Obesity or abdominal adiposity is positively associated with colorectal adenomas; the risk is highly increased in men. It is presumed that there are several abnormally expressed factors in the colorectal adenomous tissues of obesity.

The effect of body weight reduction on the incidence of colorectal adenoma

OBJECTIVES

Obesity is thought to be associated with colorectal cancer and adenoma. We aimed to investigate the effect of body weight on the risk of colorectal adenoma both in cross-sectional and longitudinal analyses.

METHODS

This is a retrospective cohort study in a large-scale health appraisal institution in Japan. A total of 7,963 asymptomatic, average-risk Japanese were enrolled at initial examinations, and 2,568 subjects who underwent a second colonoscopy after 1 yr were investigated. The association with the prevalence of colorectal adenoma was evaluated according to the body mass index (BMI) at the initial examination. The incidence of colorectal adenoma at the second colonoscopy was investigated according to the initial BMI and body weight changes during the year.

RESULTS

The prevalence of colorectal adenoma increased in relation to increases in the BMI: 15.4%, 20.6%, 22.7%, and 24.2%, respectively, in the first (BMI < 21.350), second (21.350 < or = BMI < 23.199), third (23.199 < or = BMI < 25.156), and fourth (25.156 < or = BMI) quartiles. The adjusted odds ratios in reference to Group Q1 were 1.15 (95% CI 0.97-1.37, P= 0.1) for Group Q2, 1.19 (1.01-1.41, P= 0.04) for Group Q3, and 1.32 (1.12-1.56, P= 0.001) for Group Q4. The incidence rates of colorectal adenoma after 1 yr also increased proportionally according to the initial BMI: Group Q1 (12.9%), Group Q2 (15.7%), Group Q3 (18.3%), and Group Q4 (19.0%).

CONCLUSIONS

Obesity was associated with the risk for colorectal adenoma, and body weight reduction was suggested to decrease this risk.

Obesity and Risk of Cancer in Postmenopausal Korean Women

Purpose

To evaluate an association between obesity, measured by body mass index (BMI; kg/m2), and risk of cancer at individual and all sites in postmenopausal women.

Methods

A cohort of 170,481 postmenopausal Korean women who were age 40 to 64 years at baseline measurement of BMI was observed prospectively from 1994 to 2003 for cancer incidence. Multivariable adjusted proportional hazard models were used for evaluating the association.

Results

Women with a BMI of 30 kg/m2 or higher had a 23% higher risk of cancer than women with a BMI between 21.0 and 22.9 kg/m2 (hazard ratio = 1.23; 95% CI, 1.08 to 1.41). According to the increase in BMI level, significant positive trends existed in cancers of colon, breast, corpus uteri, and kidney with hazard ratios of 1.05 (95% CI, 1.02 to 1.08), 1.07 (95% CI, 1.05 to 1.10), 1.13 (95% CI, 1.07 to 1.20), and 1.08 (95% CI, 1.02 to 1.15), respectively, for the increase of BMI by 1 kg/m2. When the analysis was limited to never-smokers, women with a BMI of 25 kg/m2 or higher showed a significantly increased risk of cancers of the colon, breast, corpus uteri, and kidney and leukemia compared with the normal BMI (18.5 to 22.9 kg/m2) group.

Conclusion

Although variations exist between the individual cancer sites, obesity was associated with an overall increased risk of cancer in postmenopausal Korean women. To reduce the risk of cancer, active strategies to prevent obesity should be implemented in postmenopausal women.

Bone mass density, subsequent risk of colon cancer and survival in postmenopausal women

OBJECTIVES

To test the hypothesis that high bone mass density (BMD), a potential marker for cumulative exposure to endogenous estrogen, calcium and vitamin D intake, is associated with a lower risk of colon cancer, and that women with a lower BMD are likely to develop a more aggressive form of colon cancer, as defined by mortality.

STUDY DESIGN AND SETTING

BMD was measured in three different sites (Ward's triangle, trochanter, femoral neck) in 1,471 women 60 years of age. All incident cases of colon cancers were identified through record-linkage of cancer registry. The women were followed for a mean of 9.5 years.

RESULTS

Overall 31 cases of colon cancer were observed among 28.6 expected (standardized incidence ratio (SIR) = 1.09, 95% confidence interval: 0.79-1.25). The SIR decreased with increasing BMD showing a significantly decreasing risk of 20% for women who were at the higher BMD comparatively to women who were at the lower BMD in all the skeletal sites. The 10-year survival rates showed that survival was increasing with increased BMD, but not significantly.

CONCLUSION

The findings suggest that postmenopausal women with lower BMD have an increased risk of colon cancer. The biological mechanisms linking bone mass to colon cancer risk are not clear.

Obesity and risk of colorectal cancer: a meta-analysis of 31 studies with 70,000 events

BACKGROUND

Colorectal cancer is the second most common cause of death and illness in developed countries. Previous reviews have suggested that obesity may be associated with 30% to 60% greater risk of colorectal cancer, but little consideration was given to the possible effect of publication bias on the reported association.

METHODS

Relevant studies were identified through EMBASE and MEDLINE. Studies were included if they had published quantitative estimates of the association between general obesity [defined here as body mass index (BMI) > or = 30 kg/m(2)] and central obesity (measured using waist circumference) and colorectal cancer. Random-effects meta-analyses were done, involving 70,000 cases of incident colorectal cancer from 31 studies, of which 23 were cohort studies and 8 were case-control studies.

RESULTS

After pooling and correcting for publication bias, the estimated relative risk of colorectal cancer was 1.19 [95% confidence interval (95% CI), 1.11-1.29], comparing obese (BMI > or = 30 kg/m(2)) with normal weight (BMI <25 kg/m(2)) people; and 1.45 (95% CI, 1.31-1.61), comparing those with the highest, to the lowest, level of central obesity. After correcting for publication bias, the risk of colorectal cancer was 1.41 (95% CI, 1.30-1.54) in men compared with 1.08 (95% CI, 0.98-1.18) for women (P(heterogeneity) <0.001). There was evidence of a dose-response relationship between BMI and colorectal cancer: for a 2 kg/m(2) increase in BMI, the risk of colorectal cancer increased by 7% (4-10%). For a 2-cm increase in waist circumference, the risk increased by 4% (2-5%).

CONCLUSIONS

Obesity has a direct and independent relationship with colorectal cancer, although the strength of the association with general obesity is smaller than previously reported.

Excess body weight and colorectal cancer risk in Canada: associations in subgroups of clinically defined familial risk of cancer

Overweight and obesity are linked with several chronic diseases, including colorectal cancer, among men, but results among women are equivocal. Previous evidence suggests that menopausal status, postmenopausal hormone use, and family history of cancer may modify the link between adiposity and colorectal cancer. In data from two population-based case-control studies (cases: 1,292 males and 1,404 females; controls: 1,465 males and 1,203 females) in Ontario and Newfoundland, Canada, we examined the link between colorectal cancer and body mass index (BMI) at two reference periods (BMI 2 years prior and BMI at age 20 years), weight gain since age 20 years, and height. Based on recent BMI indices among men, obesity (BMI >/=30 kg/m(2)) was associated with an 80% [95% confidence interval (95% CI), 1.43-2.27] increased risk of colorectal cancer relative to a normal BMI (18.5-24.9 kg/m(2)). The same comparison for BMI at age 20 years suggested a 94% increased risk of colorectal cancer (95% CI, 1.19-3.16). Odds ratios were similar among subgroups of men with and without a clinically defined familial risk of cancer (according to the Amsterdam or revised Bethesda criteria for Lynch syndrome). Associations were moderately stronger for cancer of the colon than cancer of the rectum. Among women, BMI and weight gain were not linked with colorectal cancer; the null associations were persistent in subgroups of familial risk of cancer, menopausal status, estrogenic status, and subsite. Tall height (>1.75 m), however, was linked with increased risk of colorectal cancer among women (odds ratio, 2.27; 95% CI, 1.46-3.59) but not among men. This study suggests that obesity is associated with increased risk of sporadic and Lynch syndrome-related colon and rectal cancers among men but not among women, whereas height is directly linked with all such cancers among women but not among men.

Hormone replacement therapy, body mass, and the risk of colorectal cancer among postmenopausal women from Germany

Previous studies have reported inconsistent results regarding the modifying effect of hormone replacement therapy (HRT) on the association of body mass index (BMI) and the risk of colorectal cancer (CRC) among postmenopausal women. We assessed the use of HRT and BMI in 208 postmenopausal women with histologically confirmed incident CRC and 246 controls in a population-based case–control study in Germany (DACHS study). Ever use of HRT was strongly associated with reduction of CRC risk (adjusted odds ratio 0.41, 95% confidence interval 0.25–0.67). Among nonusers of HRT, risk of CRC was strongly increased in women with BMI 27 to <30 kg m⁻² (2.76, 1.07–7.12) and obese women (3.30, 1.25–8.72), when compared with women with BMI <23 kg m⁻² (P for trend <0.01). BMI was not associated with risk of CRC among HRT users (P for interaction <0.01). In contrast to most other studies, a positive association of BMI and CRC risk was found among nonusers of HRT, but not among users of HRT. The reasons for the inconsistency of results regarding the potential risk modifying effect of postmenopausal hormones in the association of BMI with CRC remain inconclusive and require further study.

Overweight/obesity and cancer genesis: more than a biological link

The classical view according to which overweight/obesity is related to cancer considers adipose tissue as an active and metabolic "organ", acting through endocrine, autocrine and paracrine processes. Consequently, it has been hypothesized, that genesis and progression of cancer may be caused by different biological factors acting through diverse mechanisms including changes in the synthesis and bioavailability of sex hormones, insulin resistance, release of growth factors and/or proinflammatory cytokines and abnormal energetic disposal and expenditure. We have shown that overweight/obesity can be experimentally induced by benzo[a]pyrene, a universal well characterized chemical pollutant and that overweight/obesity may in fact be caused by several types of chemical pollutants. In this paper we propose that in addition to the above hypothetical biological mechanisms, adipose tissue acts as a reservoir for lipophilic, liposoluble environmental carcinogens, so that chemical pollution may in fact generate both overweight/obesity and cancer. More precisely, we propose that many carcinogens, be they mutagens or promotors can be stored in the adipose tissue, be released at convenient dose in the blood circulation and therefore target peripheral tissues to induce carcinogenesis. Such carcinogens mainly include organochlorine pesticides and PCBs. Their association with an increased risk of cancer seems to be demonstrated for breast and prostate carcinoma, as well as for lymphoma, not only in obese patients, but also in normal weight or even leaner patients suggesting that the adipose tissue may act as a reservoir for environmental carcinogens in obese as well as in non-obese patients.

Diet, gender, and colorectal neoplasia

The association between diet and colorectal cancer has been studied in depth for many decades, with equivocal results. It has been hypothesized that cancers arising in the distal and proximal colon have different pathologies, and therefore different risk factors. As such, it is possible that diet-related factors might influence colorectal neoplasia differently depending on the subsite. Recent evidence indicates that women may be more likely to develop proximal cancers than men. Additionally, the link between certain dietary factors and colorectal neoplasia in women seems to vary by menopausal status. Given these observations, women may be affected differently than men by diet-related factors. The objective of this article was therefore to review the data for diet and colorectal adenomas and cancer, and then attempt to address the potential differences in the association of diet-related factors and colorectal neoplasia in men and women. For total energy intake, selenium, and fiber, it seems that there may be slightly stronger effects in men as compared with women, whereas calcium and folate seem to affect both sexes similarly. With regard to vitamin D and colorectal cancer, women may exhibit stronger associations than men. Perhaps the most evidence for a sex-specific effect is observed for obesity, where more substantial direct relationships between body size and colorectal neoplasia have been reported for men than for women. However, this observation may be influenced by the differential effects in women by menopausal status. Further research on sex-specific dietary effects is warranted.

Obesity and colorectal cancer risk: A meta-analysis of cohort studies

AIM: To evaluate the association between obesity and colorectal cancer risk.

METHODS: We searched PubMed, EMBASE, and the Cochrane Library up to January 1, 2007. Cohort studies permitting the assessment of causal association between obesity and colorectal cancer, with clear definition of obesity and well-defined outcome of colorectal cancer were eligible. Study design, sample size at baseline, mean follow-up time, co-activators and study results were extracted. Pooled standardized effect sizes were calculated.

RESULTS: The pooled relative risk (RR) of colorectal cancer was 1.37 (95% CI: 1.21-1.56) for overweight and obese men, 1.07 (95% CI: 0.97-1.18) for women measured by body mass index (BMI). The pooled RR for the highest vs the lowest quantiles of BMI was 1.59 (95% CI: 1.35-1.86) for men and 1.22 (95% CI: 1.08-1.39) for women at risk of colon cancer, 1.16 (95% CI: 0.93-1.46) for men and 1.23 (95% CI: 0.98-1.54) for women at risk of rectal cancer. The pooled RR for the highest vs the lowest quantiles of waist circumference was 1.68 (95% CI: 1.36-2.08) for men and 1.48 (95% CI: 1.19-1.84) for women at risk of colon cancer, 1.26 (95% CI: 0.90-1.77) for men and 1.23 (95% CI: 0.81-1.86) for women at risk of rectal cancer. The pooled RR for the highest quantiles vs the lowest quantiles of waist-to-hip ratio was 1.91 (95% CI: 1.46-2.49) for men and 1.49 (95% CI 1.23-1.81) for women at risk of colon cancer, 1.93 (95% CI: 1.19-3.13) for men and 1.20 (95% CI: 0.81-1.78) for women at risk of rectal cancer. Compared with 'normal range', the pooled RR for proximal colon cancer was 1.14 (95% CI : 0.88-1.47) for the overweight and 1.41 (95% CI: 0.66-3.01) for the obese. The pooled RR for the highest quantiles vs the lowest quantiles was 2.05 (95% CI: 1.23-3.41) with waist circumference, 1.66 (95% CI: 0.69-3.99) with waist-to-hip ratio. Compared with 'normal range', the pooled RR for distal colon cancer was 1.38 (95% CI: 1.02-1.87) for the overweight and 1.23 (95% CI: 0.80-1.90) for the obese. The pooled RR for the highest quantiles vs the lowest quantiles was 1.86 (95% CI: 1.05-3.30) with waist circumference, and 1.79 (95% CI: 0.82-3.90) with waist-to-hip ratio.

CONCLUSION: Obesity is a statistically significant risk factor for colorectal cancer and the relationship is more significant in men than in women among different cancer subsites. Indexes of abdominal obesity are more sensitive than those of overall obesity.

Lack of evidence for effect modification by estrogen of association between body mass index and colorectal cancer risk among postmenopausal women

OBJECTIVE

Previous studies of the association between body mass index (BMI) and colorectal cancer among women found increased risk only among women who were premenopausal or used hormone replacement therapy (HRT). These results led to the hypothesis that BMI may increase risk more strongly among women with higher levels of circulating estrogen. We examined the association between BMI and colorectal cancer incidence by use of HRT, and number of postmenopausal years without HRT, a measure of duration of exposure to lower levels of estrogen.

METHODS

During follow-up from 1992-2003, 814 incident colorectal cancer cases were identified among 73,842 postmenopausal women in the Cancer Prevention Study-II Nutrition Cohort. Information on BMI and other risk factors was obtained from questionnaires completed at enrollment in 1992-1993 and during follow-up. Hazard ratios were calculated using proportional hazards modeling.

RESULTS

The association between BMI and colorectal cancer incidence was similar among never-users of HRT (hazard ratio 1.13, 95% confidence interval 1.02-1.25 per 5-unit increase in BMI) and current-users of HRT (hazard ratio 1.08, 95% confidence interval 0.92-1.27 per 5-unit increase in BMI). Among women not currently using HRT, the association between BMI and colorectal cancer did not differ by postmenopausal years without HRT.

CONCLUSIONS

Our results do not support the hypothesis that BMI increases risk of colorectal cancer more strongly among women with higher levels of estrogen.

Do Factors Related to Endogenous and Exogenous Estrogens Modify the Relationship between Obesity and Risk of Colorectal Adenomas in Women?

Obesity has consistently been associated with increased colorectal cancer risk in men, but not in women. In the absence of postmenopausal hormone use (PMH), adipose-derived estrogen is the primary determinant of circulating estrogen levels in postmenopausal women, perhaps ameliorating the mitogenic effects of obesity in this group. Using data from a case-control study in the United States, we examined associations among obesity, potential modifying effects of factors related to endogenous and exogenous estrogen levels, and risk of colorectal adenoma. Cases (n = 219) were women of ages 30 to 74 years with colonoscopy proven, incident, sporadic, pathology-confirmed, adenomatous polyps of the colon and rectum. Two control groups were recruited: colonoscopy-confirmed polyp-free women (n = 438) and age- and zip code frequency-matched women randomly selected from the community (n = 247). Multivariate odds ratios and 95% confidence intervals (95% CI) for obese [body mass index (BMI) >or=30.0; compared with nonobese, BMI <25.0] premenopausal women were 2.09 (95% CI, 0.81-5.41) versus colonoscopy controls, and 5.18 (95% CI, 1.40-19.32) versus population controls. For PMH users, the corresponding odds ratios were 0.29 (95% CI, 0.12-0.70) versus colonoscopy controls and 0.64 (95% CI, 0.23-1.83) versus population controls. There was no significant association of BMI with adenoma risk for PMH nonusers. Findings for waist-to-hip ratio were similar to those for BMI. These data support the hypothesis that risk for colorectal adenoma may be increased with obesity among premenopausal women but decreased among postmenopausal women, especially if they also take PMH.

The metabolic syndrome: A high-risk state for cancer?

The metabolic syndrome is composed of cardiovascular risk factors including increased body mass index/waist circumference, blood pressure, plasma glucose, and triglycerides, as well as decreased high-density lipoprotein cholesterol. The essence of the metabolic syndrome lies in the clustering of these risk factors, which are associated with cardiovascular disease. Interestingly, most of the components of the metabolic syndrome have individually been linked in some way to the development of cancer. However, epidemiological studies linking the metabolic syndrome to cancer are scarce. Nevertheless, two such studies indicate that the clustering of metabolic syndrome components significantly increases the risk of colon cancer mortality compared with the individual components. The purpose of this review is to further explore the potential relationship between the metabolic syndrome and cancer risk. Specifically, we examine the hypothesis that individual components of the metabolic syndrome contribute to the development of several processes, including insulin resistance, aromatase activity, adipokine production, angiogenesis, glucose utilization, and oxidative stress/DNA damage, which can work together to increase cancer risk beyond that of the individual components alone. We propose that the metabolic syndrome be considered as a high-risk state for certain types of cancer and that this relationship should be systematically explored across cancer types.

Colorectal cancer in middle-aged women in relation to hormonal status: a report from the Women's Health in the Lund Area (WHILA) study

OBJECTIVE

To delineate a perceived association of estradiol versus estradiol plus norethisterone hormone therapy on the prevalence of colorectal cancer in postmenopausal women.

METHODS

The Women's Health in the Lund Area (WHILA) project covers 10,766 women aged 50-60 years, living in the Lund area, Sweden. Out of this population, 6908 (64%) women completed questionnaires, underwent physical and laboratory assessments and had self-reported information regarding colorectal cancer. Four hundred and twenty-two (6%) were premenopausal (PM), 3600 (52%) were postmenopausal without hormone therapy (PM0), 2452 (36%) were postmenopausal with combined hormone therapy (PMT-HT) and 364 (5%) were postmenopausal with estrogen monotherapy (PMT-E).

RESULTS

There were 21 cases of colorectal cancer (0.3%), one in the PM group, 16 in the PM0 group, two in the PMT-HT group and another two in the PMT-E group. Colorectal cancer prevalence was lower in the PMT-HT than in the PM0 group (odds ratio (OR) = 0.18, 95% confidence interval (CI) = 0.04-0.80). However, for the PMT-E group, the OR (95% CI) was 1.02 (0.86-1.20). There was a positive association between low physical activity (p = 0.04), low parity (p = 0.02) and risk of colorectal cancer.

CONCLUSION

Combined hormone therapy seemed to be associated with a lower risk of colorectal cancer in postmenopausal women in contrast to estrogen monotherapy. Hence the progestin might have a protective role.