Vasectomy and prostate cancer risk

Vasectomy and Risk of Prostate Cancer: A Systematic Review and Meta-analysis

Context

Previous reports have shown an association between vasectomy and prostate cancer (PCa). However, there exist significant discrepancies between studies and systematic reviews due to a lack of strong causal association and residual confounding factors such as prostate-specific antigen (PSA) screening.

Objective

To assess the association between vasectomy and PCa, in both unadjusted and PSA screen-adjusted studies.

Evidence acquisition

We performed a systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses. The PubMed, Scopus, and Web of Science databases were searched in January 2022 for studies that analyzed the association between vasectomy and PCa.

Evidence synthesis

A total of 37 studies including 16 931 805 patients met our inclusion criteria. A pooled analysis from all studies showed a significant association between vasectomy and any-grade PCa (odds ratio [OR] 1.23; 95% confidence interval [CI], 1.10–1.37; p < 0.001; I² = 96%), localized PCa (OR 1.08; 95% CI, 1.06–1.11; p < 0.00001; I² = 31%), or advanced PCa (OR 1.07; 95% CI, 1.02–1.13; p = 0.006; I² = 0%). The association with PCa remained significant when the analyses were restricted to studies with a low risk of bias (OR 1.06; 95% CI, 1.02–1.10; p = 0.02; I² = 48%) or cohort studies (OR 1.09; 95% CI, 1.04–1.13; p < 0.0001; I² = 64%). Among studies adjusted for PSA screening, the association with localized PCa (OR 1.06; 95% CI, 1.03–1.09; p < 0.001; I² = 0%) remained significant. Conversely, vasectomy was no longer associated with localized high-grade (p = 0.19), advanced (p = 0.22), and lethal (p = 0.42) PCa.

Conclusions

Our meta-analysis found an association between vasectomy and any, mainly localized, PCa. However, the effect estimates of the association were increasingly close to null when examining studies of robust design and high quality. On exploratory analyses including studies, which adjusted for PSA screening, the association for aggressive and/or advanced PCa diminished.

Patient summary

In this study, we found an association between vasectomy and the risk of developing localized prostate cancer without being able to determine whether the procedure leads to a higher prostate cancer incidence.

Association between vasectomy and risk of prostate cancer: a meta-analysis

BACKGROUND

The debate over the association between vasectomy and prostate cancer has been lasted about 40 years and there is no sign of stopping. In the present study, we aimed to evaluate whether vasectomy is associated with prostate cancer based on the most comprehensive and up-to-date evidence available.

METHODS

The PubMed, Cochrane Library, and EMBASE databases were systematically searched inception to March 14, 2021 without year or language restriction. Multivariable adjusted risk ratios (RRs) were used to assess each endpoint. Risk of bias was assessed using the Newcastle-Ottawa scale.

RESULTS

A total of 58 studies involving 16,989,237 participants fulfilled inclusion criteria. There was significant association of vasectomy with risk of any prostate cancer (risk ratio, 1.18, 95% CI, 1.07-1.31). Association between vasectomy and advanced prostate cancer (risk ratio, 1.06, 95% CI, 1.01-1.12), low-grade prostate cancer (risk ratio, 1.06, 95% CI, 1.02-1.10), and intermediate-grade prostate cancer (risk ratio, 1.12, 95% CI, 1.03-1.22) were significant. There was no significant association between vasectomy and prostate cancer-specific mortality (risk ratio, 1.01, 95% CI, 0.93-1.10).

CONCLUSIONS

This study found that vasectomy was associated with the risk of any prostate cancer and advanced prostate cancer. From the current evidence, patients should be fully informed of the risk of prostate cancer before vasectomy.

Impact of Vasectomy on the Development and Progression of Prostate Cancer: Preclinical Evidence

Some observational studies have implied a link between vasectomy and an elevated risk of prostate cancer. We investigated the impact of vasectomy on prostate cancer outgrowth, mainly using preclinical models. Neoplastic changes in the prostate were compared in transgenic TRAMP mice that underwent vasectomy vs. sham surgery performed at 4 weeks of age. One of the molecules identified by DNA microarray (i.e., ZKSCAN3) was then assessed in radical prostatectomy specimens and human prostate cancer lines. At 24 weeks, gross tumor (p = 0.089) and poorly differentiated adenocarcinoma (p = 0.036) occurred more often in vasectomized mice. Vasectomy significantly induced ZKSCAN3 expression in prostate tissues from C57BL/6 mice and prostate cancers from TRAMP mice. Immunohistochemistry showed increased ZKSCAN3 expression in adenocarcinoma vs. prostatic intraepithelial neoplasia (PIN), PIN vs. non-neoplastic prostate, Grade Group ≥3 vs. ≤2 tumors, pT3 vs. pT2 tumors, pN1 vs. pN0 tumors, and prostate cancer from patients with a history of vasectomy. Additionally, strong (2+/3+) ZKSCAN3 expression (p = 0.002), as an independent prognosticator, or vasectomy (p = 0.072) was associated with the risk of tumor recurrence. In prostate cancer lines, ZKSCAN3 silencing resulted in significant decreases in cell proliferation/migration/invasion. These findings suggest that there might be an association between vasectomy and the development and progression of prostate cancer, with up-regulation of ZKSCAN3 expression as a potential underlying mechanism.

Infectious, inflammatory and 'autoimmune' male factor infertility: how do rodent models inform clinical practice?

BACKGROUND

Infection and inflammation of the reproductive tract are significant causes of male factor infertility. Ascending infections caused by sexually transmitted bacteria or urinary tract pathogens represent the most frequent aetiology of epididymo-orchitis, but viral, haematogenous dissemination is also a contributory factor. Limitations in adequate diagnosis and therapy reflect an obvious need for further understanding of human epididymal and testicular immunopathologies and their contribution to infertility. A major obstacle for advancing our knowledge is the limited access to suitable tissue samples. Similarly, the key events in the inflammatory or autoimmune pathologies affecting human male fertility are poorly amenable to close examination. Moreover, the disease processes generally have occurred long before the patient attends the clinic for fertility assessment. In this regard, data obtained from experimental animal models and respective comparative analyses have shown promise to overcome these restrictions in humans.

OBJECTIVE AND RATIONALE

This narrative review will focus on male fertility disturbances caused by infection and inflammation, and the usefulness of the most frequently applied animal models to study these conditions.

SEARCH METHODS

An extensive search in Medline database was performed without restrictions until January 2018 using the following search terms: 'infection' and/or 'inflammation' and 'testis' and/or 'epididymis', 'infection' and/or 'inflammation' and 'male genital tract', 'male infertility', 'orchitis', 'epididymitis', 'experimental autoimmune' and 'orchitis' or 'epididymitis' or 'epididymo-orchitis', antisperm antibodies', 'vasectomy'. In addition to that, reference lists of primary and review articles were reviewed for additional publications independently by each author. Selected articles were verified by each two separate authors and discrepancies discussed within the team.

OUTCOMES

There is clear evidence that models mimicking testicular and/or epididymal inflammation and infection have been instructive in a better understanding of the mechanisms of disease initiation and progression. In this regard, rodent models of acute bacterial epididymitis best reflect the clinical situation in terms of mimicking the infection pathway, pathogens selected and the damage, such as fibrotic transformation, observed. Similarly, animal models of acute testicular and epididymal inflammation using lipopolysaccharides show impairment of reproduction, endocrine function and histological tissue architecture, also seen in men. Autoimmune responses can be studied in models of experimental autoimmune orchitis (EAO) and vasectomy. In particular, the early stages of EAO development showing inflammatory responses in the form of peritubular lymphocytic infiltrates, thickening of the lamina propria of affected tubules, production of autoantibodies against testicular antigens or secretion of pro-inflammatory mediators, replicate observations in testicular sperm extraction samples of patients with 'mixed atrophy' of spermatogenesis. Vasectomy, in the form of sperm antibodies and chronic inflammation, can also be studied in animal models, providing valuable insights into the human response.

WIDER IMPLICATIONS

This is the first comprehensive review of rodent models of both infectious and autoimmune disease of testis/epididymis, and their clinical implications, i.e. their importance in understanding male infertility related to infectious and non-infectious/autoimmune disease of the reproductive organs.

Association between vasectomy and risk of testicular cancer: A systematic review and meta-analysis

Objectives

A number of researchers have reported that vasectomy is a risk factor for testicular cancer. However, this conclusion is inconsistent with a number of other published articles. Hence, we conducted this meta-analysis to assess whether vasectomy increases the risk of testicular cancer.

Materials and methods

We identified all related studies by searching the PubMed, Embase, and Cochrane Library database from January 01, 1980 to June 01, 2017. The Newcastle-Ottawa Scale (NOS) checklist was used to assess all included non-randomized studies. Summarized odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the difference in outcomes between case and control groups. Subgroup analyses were performed according to the study design and country.

Results

A total of eight studies (2176 testicular cancer patients) were included in this systematic review and meta-analysis. Six articles were case-control studies, and two were cohort studies. The pooled estimate of the OR was 1.10 (95% CI: 0.93–1.30) based on the eight studies in a fixed effects model. Two subgroup analyses were performed according to the study design and country. The results were consistent with the overall findings. Publication bias was detected by Begg’s test and Egger’s test and p values > 0.05, respectively.

Conclusions

Our meta-analysis suggested that there was no association between vasectomy and the development of testicular cancer. More high-quality studies are warranted to further explore the association between vasectomy and risk of testicular cancer.

The Effect of Vasectomy Reversal on Prostate Cancer Risk: International Meta-Analysis of 684,660 Vasectomized Men

PURPOSE

Evidence of the effect of vasectomy on prostate cancer is conflicting with the issue of detection bias a key criticism. We examined the effect of vasectomy reversal on prostate cancer risk in a cohort of vasectomized men. Evidence of a protective effect would be consistent with a harmful effect of vasectomy on prostate cancer risk while nullifying the issue of detection bias.

MATERIALS AND METHODS

Data were sourced from a total of 5 population level linked health databases in Australia, Canada and the United Kingdom. Cox proportional hazards regression analysis was used to compare the risk of prostate cancer in 9,754 men with vasectomy reversal to the risk in 684,660 with vasectomy but no reversal. Data from each jurisdiction were combined in a meta-analysis.

RESULTS

The combined analysis showed no protective effect of vasectomy reversal on the incidence of prostate cancer compared to that in men with vasectomy alone (HR 0.92, 95% CI 0.70-1.21).

CONCLUSIONS

These results align with those of previous studies showing no evidence of a link between vasectomy and prostate cancer.

The Association Between Vasectomy and Prostate Cancer: A Systematic Review and Meta-analysis

Importance

Despite 3 decades of study, there remains ongoing debate regarding whether vasectomy is associated with prostate cancer.

Objective

To determine if vasectomy is associated with prostate cancer.

Data Sources

The MEDLINE, EMBASE, Web of Science, and Scopus databases were searched for studies indexed from database inception to March 21, 2017, without language restriction.

Study Selection

Cohort, case-control, and cross-sectional studies reporting relative effect estimates for the association between vasectomy and prostate cancer were included.

Data Extraction and Synthesis

Two investigators performed study selection independently. Data were pooled separately by study design type using random-effects models. The Newcastle-Ottawa Scale was used to assess risk of bias.

Main Outcomes and Measures

The primary outcome was any diagnosis of prostate cancer. Secondary outcomes were high-grade, advanced, and fatal prostate cancer.

Results

Fifty-three studies (16 cohort studies including 2 563 519 participants, 33 case-control studies including 44 536 participants, and 4 cross-sectional studies including 12 098 221 participants) were included. Of these, 7 cohort studies (44%), 26 case-control studies (79%), and all 4 cross-sectional studies were deemed to have a moderate to high risk of bias. Among studies deemed to have a low risk of bias, a weak association was found among cohort studies (7 studies; adjusted rate ratio, 1.05; 95% CI, 1.02-1.09; P < .001; I2 = 9%) and a similar but nonsignificant association was found among case-control studies (6 studies; adjusted odds ratio, 1.06; 95% CI, 0.88-1.29; P = .54; I2 = 37%). Effect estimates were further from the null when studies with a moderate to high risk of bias were included. Associations between vasectomy and high-grade prostate cancer (6 studies; adjusted rate ratio, 1.03; 95% CI, 0.89-1.21; P = .67; I2 = 55%), advanced prostate cancer (6 studies; adjusted rate ratio, 1.08; 95% CI, 0.98-1.20; P = .11; I2 = 18%), and fatal prostate cancer (5 studies; adjusted rate ratio, 1.02; 95% CI, 0.92-1.14; P = .68; I2 = 26%) were not significant (all cohort studies). Based on these data, a 0.6% (95% CI, 0.3%-1.2%) absolute increase in lifetime risk of prostate cancer associated with vasectomy and a population-attributable fraction of 0.5% (95% CI, 0.2%-0.9%) were calculated.

Conclusions and Relevance

This review found no association between vasectomy and high-grade, advanced-stage, or fatal prostate cancer. There was a weak association between vasectomy and any prostate cancer that was closer to the null with increasingly robust study design. This association is unlikely to be causal and should not preclude the use of vasectomy as a long-term contraceptive option.

Vasectomy and Risk of Prostate Cancer in a Screening Trial

Background: Vasectomy has been implicated as a risk factor for prostate cancer in multiple epidemiologic studies over the past 25 years. Whether this relationship is causal remains unclear. This study examines the association between vasectomy and prostate cancer in the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, which randomized men to usual care or annual prostate cancer screening.Methods: We performed a retrospective analysis of 13-year screening and outcomes data from the PLCO trial. Multivariable Cox proportional hazards regression stratified by study arm and age at vasectomy was performed.Results: There was an increased risk of prostate cancer in men who had undergone a vasectomy and were randomized to the usual care arm of the study (adjusted HR, 1.11; 95% confidence interval, 1.03-1.20; P = 0.008). There was no association between vasectomy and diagnosis of prostate cancer in men randomized to the prostate cancer screening arm. Only men undergoing vasectomy at an older age in the usual care arm of the study, but not the prostate cancer screening arm, were at increased risk of being diagnosed with prostate cancer.Conclusions: Vasectomy was not associated with prostate cancer risk among men who were screened for prostate cancer as part of a clinical trial, but was associated with prostate cancer detection in men receiving usual care.Impact: The positive association between vasectomy and prostate cancer is likely related to increased detection of prostate cancer based on patterns of care rather than a biological effect of vasectomy on prostate cancer development. Cancer Epidemiol Biomarkers Prev; 26(11); 1653-9. ©2017 AACR.

Vasectomy and risk of prostate cancer: population based matched cohort study

OBJECTIVE

 To determine the association between vasectomy and prostate cancer, adjusting for measures of health seeking behaviour.

DESIGN

 Population based matched cohort study.

SETTING

 Multiple validated healthcare databases in Ontario, Canada, 1994-2012.

PARTICIPANTS

 326 607 men aged 20 to 65 who had undergone vasectomy were identified through physician billing codes and matched 1:1 on age (within two years), year of cohort entry, comorbidity score, and geographical region to men who did not undergo a vasectomy.

MAIN OUTCOMES MEASURES

 The primary outcome was incident prostate cancer. Secondary outcomes were prostate cancer related grade, stage, and mortality.

RESULTS

 3462 incident cases of prostate cancer were identified after a median follow-up of 10.9 years: 1843 (53.2%) in the vasectomy group and 1619 (46.8%) in the non-vasectomy group. In unadjusted analysis, vasectomy was associated with a slightly increased risk of incident prostate cancer (hazard ratio 1.13, 95% confidence interval 1.05 to 1.20). After adjustment for measures of health seeking behaviour, however, no association remained (adjusted hazard ratio 1.02, 95% confidence interval 0.95 to 1.09). Moreover, no association was found between vasectomy and high grade prostate cancer (adjusted odds ratio 1.05, 95% confidence interval 0.67 to 1.66), advanced stage prostate cancer (adjusted odds ratio 1.04, 0.81 to 1.34), or mortality (adjusted hazard ratio 1.06, 0.60 to 1.85).

CONCLUSION

 The findings do not support an independent association between vasectomy and prostate cancer.

Vasectomy and prostate cancer risk: a historical synopsis of undulating false causality

The potential influence of vasectomy being a risk factor for the development of prostate cancer is not a new concept, with more than 30 publications addressing the topic. Given the global frequency of vasectomy and the prevalence of prostate cancer, this subject justifiably deserves scrutiny. Several articles have claimed that vasectomy puts men at risk for future development of prostate cancer. We explore articles that have shown the contrary (no link), explore the studies’ strengths and weaknesses, describe possible prostate cancer pathophysiologic mechanisms, and apply Bradford Hill criteria to help discern correlation with causation. The risk and interest of association of prostate cancer with vasectomy has waxed and waned over the last three decades. Based on our review, vasectomy remains a safe form of sterilization and does not increase prostate cancer risk.

Vasectomy and prostate cancer risk: a meta-analysis of cohort studies

Some studies have suggested that vasectomy is associated with the increased risk of prostate cancer, however, this conclusion is not supported by all the published studies. In order to examine the relationship between vasectomy and prostate cancer risk, we conducted a meta-analysis of cohort studies to clarify this controversial association. PubMed and Medline were used to identify the cohort studies that reported the association of vasectomy with prostate cancer risk from 1980 to January 2015. Based on a random effects model, the RR and 95% CI were used to assess the combined risk. In total, 10 cohort studies involving more than 7027 cases and 429914 participants were included. There was no significant relationship between vasectomy and prostate cancer risk, the pooled RR (95%CI) was 1.11[0.98, 1.27] (P = 0.109). In subgroup-analysis, the relationship between vasectomy and prostate cancer risk was not significantly modified by the length of follow-up and population distribution except Americans. Omission of any single study had little effect on the pooled risk estimate. Little evidence of publication bias was found. In conclusion, our meta-analysis suggests that vasectomy is not associated with the increased risk of prostate cancer. More studies based on other populations including the Chinese are needed.

Regulatory T cells and vasectomy

CD4+ CD25+ regulatory T cells (Tregs) strongly influence the early and late autoimmune responses to meiotic germ cell antigens (MGCA) and the gonadal immunopathology in vasectomized mice. This is supported by the published and recently acquired information presented here. Within 24h of unilateral vasectomy (uni-vx) the ipsilateral epididymis undergoes epithelial cell apoptosis followed by necrosis, severe inflammation, and granuloma formation. Unexpectedly, vasectomy alone induced MGCA-specific tolerance. In contrast, uni-vx plus simultaneous Treg depletion resulted in MGCA-specific autoimmune response and bilateral autoimmune orchitis. Both tolerance and autoimmunity were strictly linked to the early epididymal injury. We now discovered that testicular autoimmunity in uni-vx mice did not occur when Treg depletion was delayed by one week. Remarkably, this delayed Treg depletion also prevented tolerance induction. Therefore, tolerance depends on a rapid de novo Treg response to MGCA exposed after vasectomy. Moreover, tolerance was blunted in mice genetically deficient in PD-1 ligand, suggesting the involvement of induced Treg. We conclude that pre-existing natural Treg prevents post-vasectomy autoimmunity, whereas vasectomy-induced Treg maintains post-vasectomy tolerance. We further discovered that vasectomized mice were still resistant to autoimmune orchitis induction for at least 12-16 months; thus, tolerance is long-lasting. Although significant sperm autoantibodies of low titers became detectable in uni-vx mice at 7 months, the antibody titers fluctuated over time, suggesting a dynamic "balance" between the autoimmune and tolerance states. Finally, we observed severe epididymal fibrosis and hypo-spermatogenesis at 12 months after uni-vx: findings of highly critical clinical significance.

Reported family history of cancer in 1,271 prostate cancer cases and 1,909 controls

Prostate cancer risk has been associated with a family history of the disease. A two- to three-fold increase in risk has been observed in several studies. Details concerning modification of this risk by age, type of familial history of prostate cancer, and possible involvement of history of cancer at other sites have been less well documented. This case-control study of 1,271 prostate cancer patients and 1,909 control subjects admitted to Roswell Park Cancer Institute in Buffalo, NY, found age-adjusted increased risk associated with reporting a history of prostate cancer in a father (RR = 2.3, 95% Cl 1.4-3.3) or brother (RR = 2.5, 95% Cl 1.6-3.9). Subjects with both a father and brother affected had a 6.5-fold (95% Cl 1.4-30.5) increased risk of prostate cancer. Greater risk were observed at younger ages of diagnosis. Risks associated with reporting a father or a brother affected were not significantly elevated for patients over age 70 at diagnosis. No significant differences in patients reporting histories of cancer other than prostate cancer were observed regardless of relationship, age at diagnosis, or type of cancer examined. These observations from a large cancer patient population may be useful when making recommendations for cost-effective prostate cancer screening and for directing investigators to the potentially most informative subjects.

Regulatory T cells control tolerogenic versus autoimmune response to sperm in vasectomy

Vasectomy is a well accepted global contraceptive approach frequently associated with epididymal granuloma and sperm autoantibody formation. To understand the long-term sequelae of vasectomy, we investigated the early immune response in vasectomized mice. Vasectomy leads to rapid epithelial cell apoptosis and necrosis, persistent inflammation, and sperm granuloma formation in the epididymis. Vasectomized B6AF1 mice did not mount autoimmune response but instead developed sperm antigen-specific tolerance, documented as resistance to immunization-induced experimental autoimmune orchitis (EAO) but not experimental autoimmune encephalomyelitis. Strikingly, tolerance switches over to pathologic autoimmune state following concomitant CD4(+)CD25(+)Foxp3(+) regulatory T cell (Treg) depletion: unilaterally vasectomized mice produce dominant autoantibodies to an orchitogenic antigen (zonadhesin), and develop CD4 T-cell- and antibody-dependent bilateral autoimmune orchitis. Therefore, (i) Treg normally prevents spontaneous organ-specific autoimmunity induction by persistent endogenous danger signal, and (ii) autoantigenic stimulation with sterile autoinflammation can lead to tolerance. Finally, postvasectomy tolerance occurs in B6AF1, C57BL/6, and A/J strains. However, C57BL/6 mice resisted EAO after 60% Treg depletion, but developed EAO after 97% Treg reduction. Therefore, variance in intrinsic Treg function--a possible genetic trait--can influence the divergent tolerogenic versus autoimmune response to vasectomy.

Medical history, body size, and cigarette smoking in relation to fatal prostate cancer

OBJECTIVES

Prostate cancer has few known risk factors. As part of a population-based case-control study conducted in four health maintenance organizations, the authors examined the associations between fatal prostate cancer and several medical and behavioral characteristics.

METHODS

Cases were 768 health plan members who died of prostate adenocarcinoma during the period 1997-2001. We randomly selected controls (929) from the health plan membership and matched them to cases on health plan, age, race, and pattern of health plan membership. We examined medical records to obtain information on potential risk factors during the 10 years before the date on which prostate cancer was first suspected; the same reference date was used for the matched controls.

RESULTS

Anthropometric characteristics, as well as personal histories of benign prostatic hypertrophy, transurethral prostatectomy, cancer, diabetes, prostatitis, hypertension, and vasectomy were largely similar for cases and controls. Men who died from prostate cancer were more likely than controls to have been cigarette smokers according to the most recent smoking notation before the reference date (odds ratio 1.5, 95% confidence interval 1.1-2.0).

CONCLUSIONS

The observed increase in risk associated with recent cigarette smoking is consistent with the findings of several other studies. However, in contrast with some reports, we observed no connection between fatal prostate cancer and some prior health conditions or measures of body size.

Putative health risks associated with vasectomy

Vasectomy is widely regarded as a safe method of contraception, but over the years there have been many reports suggesting putative health risks associated with the procedure. Concerns over the possible association of vasectomy with a number of medical conditions, including cardiovascular disease, testicular cancer, prostate cancer, psychologic distress, and a variety of immune complex-mediated disease processes have been reported. Most recently, a manuscript from the neurology literature has described an association between vasectomy and primary progressive aphasia, a rare variety of frontotemporal dementia. This article reviews the literature surrounding each of these purported health concerns. Because the ultimate findings have important ramifications for both informed consent of vasectomy patients and for public health, the reported health risks in question should be critically evaluated.

Prostate cancer and vasectomy: a hospital-based case-control study in China, Nepal and the Republic of Korea

BACKGROUND

The study of a possible relationship between vasectomy and prostate cancer has yielded mixed results. Data from developing countries are limited.

STUDY DESIGN

We conducted a hospital-based case-control study in China, Nepal and the Republic of Korea to evaluate the risk of prostate cancer after vasectomy.

RESULTS

Prostate cancer in 294 cases (confirmed by independent pathologists) and 879 matched controls were included. The odds ratio of prostate cancer in men with a history of vasectomy was 1.21 [95% confidence interval (95% CI)=0.79, 1.87]. No significant trend was observed in risk by time since vasectomy or age at vasectomy. The odds ratio for localized disease was 1.02 (95% CI=0.53, 1.95); the odds ratio for later stages was 1.41 (95% CI=0.78, 2.53). No confounding factor was identified. The study illustrated differential misclassification of disease by vasectomy status; reference pathologists determined that 28% of men with a history of vasectomy, compared with 17% of men without a history of vasectomy, were misdiagnosed with prostate cancer by local pathologists.

CONCLUSION

Vasectomy is not associated with an increased risk of prostate cancer in developing countries where the rate of the disease is low.

Vasectomy and the risk of prostate cancer

PURPOSE

While the weight of evidence shows no association overall between vasectomy and prostate cancer, there has been some suggestion that an association may exist in subgroups, such as men who have a family history of prostate cancer, men who undergo vasectomy at a younger age or when several decades have passed since the procedure. Studies of risk with long latency periods have been hampered by small sample sizes in subgroups since vasectomy only became widely used in the 1960s and generally prostate cancer has a long latency period.

MATERIALS AND METHODS

We analyzed data from a recent population based case-control study that was designed specifically to address this issue of risk in subgroups. Interviews were completed with 1,001 men diagnosed with prostate cancer from January 1, 2002 through December 31, 2005 in the Seattle-Puget Sound region and in 942 matched control men. Subjects were black and white men between the ages of 35 and 74 years. Data were analyzed using unconditional logistic regression to calculate the OR as an estimate of the relative risk of prostate cancer associated with various vasectomy parameters.

RESULTS

The prevalence of vasectomy was similar in cases and controls (36.2% and 36.1%, respectively, adjusted OR 1.0, 95% CI 0.8-1.2). There were also no associations between prostate cancer and age at vasectomy, years elapsed since vasectomy or calendar year of vasectomy.

CONCLUSIONS

These findings indicate that there is no association between vasectomy and the risk of prostate cancer.

Risk of ovarian cancer associated with BMI varies by menopausal status

Obesity has been linked to increased risk of several malignancies, but the role of obesity in the etiology of ovarian cancer remains unclear. Therefore, a hospital-based case-control study was conducted to investigate the association between body size and risk of ovarian cancer. Participants included 427 women with primary, incident ovarian cancer and 854 cancer-free controls. All participants received medical services at Roswell Park Cancer Institute in Buffalo, NY between 1982 and 1998 and completed a comprehensive epidemiological questionnaire. The instrument included questions regarding height and usual wt prior to survey. Participants were classified as underweight/normal (BMI < or = 24.9 kg/m2), overweight (BMI 25.0-29.9 kg/m2), or obese (BMI > or = 30.0 kg/m2). Compared with underweight/normal participants, being overweight (adjusted odds ratio [OR] = 1.02; 95% CI 0.77-1.36) or obese (adjusted OR = 1.17; 95% CI 0.84-1.65) was not significantly associated with an elevated risk of ovarian cancer. After stratification by menopausal status, BMI showed no significant association to ovarian cancer risk among postmenopausal women (> or = 50 y old). However, among premenopausal women (<50 y old), those classified as obese had a significantly increased risk (adjusted OR = 2.19; 95% CI 1.19-4.04) compared with women classified as normal/underweight. These findings suggest a potential influence of menopausal status on the total endogenous hormonal environment, including estrogens, androgens, and insulin-like growth factors, when considering the association between body size and ovarian cancer risk. In light of the fact that obesity is a modifiable risk factor, further investigation on this topic is warranted.

Intakes of selected food groups and beverages and adult acute myeloid leukemia

Few studies have explored the association between diet and adult acute myeloid leukemia (AML). In a hospital-based case-control study among 111 cases and 439 controls, AML risk was negatively associated with milk intake among women (OR 0.25, 95% CI 0.08-0.73) and tea (OR 0.50, 95% CI 0.23-1.09), and positively associated among women with beer (OR 2.48, 95% CI 1.05-5.85), wine (OR 2.32, 95% CI 1.05-5.09), and beef (OR 4.78, 95% CI 1.35-16.94). Our findings support a role of diet in adult AML; however, further research is needed to explore gender differences in risk.

Regular Use of Aspirin and Prostate Cancer Risk (United States)

It has been hypothesized that aspirin and other nonsteroidal anti-inflammatory drugs can decrease the risk of developing prostate and other cancers, although observational studies have not been very conclusive. The current study examined the effects of regular aspirin use on prostate cancer risk in 1,029 patients with primary, incident cancer of the prostate and 1,029 hospital controls frequency-matched to cases by 5-year age group and period of questionnaire completion. Patients who reported use of aspirin for at least once a week for at least 6 months were classified as regular users, with others classified as non-users. Results indicate that regular aspirin use may not be associated with decreased prostate cancer risk [odds ratio (OR) 1.05, 95% confidence interval (CI) 0.89-1.25], frequency of use (OR for at least seven/week 0.91, 95% CI 0.73-1.13), duration of use (OR for at least 10 years of use 1.17 95% CI 0.93-1.46) or tablet years (defined as tablets per day x years of use). A similar lack of association was observed when analyses were performed examining stage of the cancer. These data suggest that aspirin use may not be associated with reduced risk of prostate cancer.

Opposing effects of aspirin and acetaminophen use on risk of adult acute leukemia

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been hypothesized to be associated with reduced risk of hematologic cancer, although previous results have been inconsistent. The current study investigated the effects of aspirin or acetaminophen use on adult acute leukemia risk among 169 individuals with leukemia and 676 age and sex matched hospital controls with non-neoplastic conditions who completed a comprehensive epidemiologic questionnaire. Results indicate that regular aspirin use may be associated with a modest decrease in leukemia risk [adjusted odds ratio (aOR), 0.84; 95% confidence interval (CI), 0.59-1.21]. In contrast, ever using acetaminophen was associated with elevated leukemia risk (aOR, 1.53; 95% CI, 1.03-2.26). Results did not differ between men and women. Other studies have demonstrated that acetaminophen is associated with transient decreases in DNA repair, and lymphocytes may be particularly susceptible to DNA damage, suggesting a mechanism for the elevated acute leukemia risk observed among acetaminophen users.

Active and passive smoking and risk of ovarian cancer

It is unclear whether smoking is a risk factor for epithelial ovarian cancer, although some studies have suggested that it may be associated with an increased risk of mucinous tumors. This study investigated the effect of smoking and environmental tobacco smoke (ETS) on ovarian cancer risk among 434 women with primary epithelial ovarian, peritoneal, or fallopian cancers and 868 age- and region-matched hospital controls with nonneoplastic conditions. All participants completed a comprehensive epidemiologic questionnaire. Results indicate that decreased risk of ovarian cancer was associated with being a nonsmoker exposed to ETS (adjusted odds ratio [aOR] 0.68, 95% confidence interval [CI] 0.46-0.99), a former smoker (aOR 0.76, 95% CI 0.53-1.10), or a current smoker (aOR 0.53, 95% CI 0.32-0.88). A similar protective effect was noted for smokers with moderate or high exposure based on smoking intensity, duration, and cumulative exposure, as well as for never smokers exposed to ETS. Results did not differ substantially by histologic subtype. Although prevailing theories of ovarian cancer etiology implicate incessant ovulation, characteristics of the study population suggest that anovulation was not the protective mechanism in this study. Immunosuppression by nicotine or upregulation of enzymes that metabolize carcinogens may be responsible for the effects observed.

Consumption of coffee, but not black tea, is associated with decreased risk of premenopausal breast cancer

Caffeine has been suggested as a possible risk factor for breast cancer, potentially through its effect of facilitating the development of benign breast disease. However, coffee and tea also contain polyphenols, which exhibit anticarcinogenic properties. A hospital-based, case-control study was conducted to evaluate the role of coffee, decaffeinated coffee, and black tea in breast cancer etiology. Study participants included 1932 cases with primary, incident breast cancer and 1895 hospital controls with nonneoplastic conditions. All participants completed a comprehensive epidemiological questionnaire. Among premenopausal women, consumption of regular coffee was associated with linear declines in breast cancer risk (P for trend = 0.03); consumers of >or=4 cups/d experienced a 40% risk reduction (odds ratio = 0.62, 95% CI 0.39-0.98). No clear associations between intake of black tea or decaffeinated coffee and breast cancer risk were noted among premenopausal women, although black tea was associated with a protective effect unique to a subsample of cases with lobular histology. Among postmenopausal women, breast cancer risk was not associated with consumption of coffee, tea, or decaffeinated coffee. Results among postmenopausal women did not differ by histologic subtype. Our findings support a protective effect of coffee intake on premenopausal, but not postmenopausal breast cancer risk. Further studies are warranted to confirm these findings.

Regular Analgesic Use and Risk of Endometrial Cancer

BACKGROUND

Analgesic use has been implicated in the chemoprevention of a number of solid tumors, but thus far, no previous research has focused on the role of aspirin in endometrial cancer etiology.

METHODS

We conducted a hospital-based case-control study of 427 women with primary, incident endometrial cancer, and 427 age- and residence-matched controls without benign or malignant neoplasms. All participants received medical services at Roswell Park Cancer Institute in Buffalo, NY, and completed a comprehensive epidemiologic questionnaire. Women who reported analgesic use at least once a week for at least 6 months were classified as regular users and served as the reference group throughout the analyses. We used unconditional logistic regression analyses to compute crude and adjusted odds ratios (OR) with corresponding 95% confidence intervals (CI).

RESULTS

Compared with nonusers, regular aspirin users were not at reduced risk of endometrial cancer (adjusted OR, 0.91; 95% CI, 0.66-1.26), nor were women with the highest frequency, duration, or cumulative lifetime aspirin use. When the sample was divided by body mass index status, regular aspirin use was not associated with risk among women classified as normal weight or overweight, but a significant risk reduction was seen for obese women (adjusted OR, 0.50; 95% CI, 0.27-0.92). Significant decreases in risk were also observed for obese women with the greatest frequency, duration, and cumulative aspirin use. No significant associations in the overall sample or among obese women were noted for acetaminophen use.

CONCLUSION

We observed no evidence of an overall chemoprotective effect of aspirin on endometrial cancer risk, but the significant risk reductions among obese women warrant further investigation.

Associations Between Black Tea and Coffee Consumption and Risk of Lung Cancer Among Current and Former Smokers

Although cigarette smoking is a clear risk factor for lung cancer, the other determinants of lung cancer risk among smokers are less clear. Tea and coffee contain catechins and flavonoids, which have been shown to exhibit anticarcinogenic properties. Conversely, caffeine may elevate cancer risk through a variety of mechanisms. The current study investigated the effects of regular consumption of black tea and coffee on lung cancer risk among 993 current and former smokers with primary incident lung cancer and 986 age-, sex-, and smoking-matched hospital controls with non-neoplastic conditions. Results indicated that lung cancer risk was not different for those with the highest black tea consumption (>or=2 cups/day) compared with nondrinkers of tea [adjusted odds ratio (aOR)=0.90; 95% confidence interval (CI)=0.66-1.24]. However, elevated lung cancer risk was observed for participants who consumed 2-3 cups of regular coffee daily (aOR=1.34; 95% CI=0.99-1.82) or >or=4 cups of regular coffee daily (aOR=1.51, 95% CI=1.11-2.05). In contrast, decaffeinated coffee drinking was associated with decreased lung cancer risk for both participants who consumed <or=1 cup/day (aOR=0.67; 95% CI=0.54-0.84) and those who consumed >or=2 cups/day (aOR=0.64; 95% CI=0.51-0.80). These results suggest that any chemoprotective effects of phytochemicals in coffee and tea may be overshadowed by the elevated risk associated with caffeine in these beverages.

Sexually transmitted diseases and other urogenital conditions as risk factors for prostate cancer: a case–control study in Wayne County, Michigan

OBJECTIVE To investigate associations between prostate cancer and sexually transmitted diseases (STDs), prostatitis, benign prostatic hyperplasia (BPH), and vasectomy in a population-based case-control study in Wayne County, Michigan, among African American and white men aged 50--74 years.

METHODS

Incident prostate cancer cases (n=700) from 1996--1998 were identified from the Metropolitan Detroit Cancer Surveillance System. Controls (n=604) were identified through random digit dialing and Medicare recipient lists, and frequency matched to cases on age and race. History of potential prostate cancer risk factors was ascertained through in-person interview.

RESULTS

Prostate cancer was not associated with STD or vasectomy history. History of prostatitis was associated with prostate cancer among all subjects (odds ratio [OR]=1.8, 95% confidence interval [CI]: 1.1, 2.9) and in African American men (OR=2.2, 95% CI: 1.1, 4.6). History of BPH was associated with prostate cancer among all subjects (OR=2.4, 95% CI: 1.8, 3.3); significant associations were observed in both African American (OR=2.7, 95% CI: 1.6, 4.4) and white (OR=2.3, 95% CI: 1.5, 3.4) men.

CONCLUSIONS

Among all subjects, prostate cancer was associated with prostatitis and BPH history, but not with STD or vasectomy history. Prevention efforts could be enhanced if inflammatory or infectious etiologies are found to be of importance in the subsequent development of prostate cancer.

Regular use of aspirin or acetaminophen and risk of non-Hodgkin lymphoma

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been hypothesized to be associated with reduced risk of non-Hodgkin lymphoma (NHL), although previous results have been inconsistent. The current study investigated the effects of regular aspirin or acetaminophen use on non-Hodgkin lymphoma risk among 625 individuals with primary, incident NHL and 2512 age and sex matched hospital controls with non-neoplastic conditions who completed a comprehensive epidemiologic questionnaire. Results indicate that regular aspirin use may be associated with decreased NHL risk among men [adjusted odds ratio (aOR) 0.82, 95% confidence interval (CI), 0.65--1.04], but not among women (aOR 0.93, 95% CI, 0.71--1.23). In contrast, regular acetaminophen use was associated with elevated NHL risk among women (aOR 1.71, 95% CI, 1.18--2.50) but not among men (aOR 0.75, 95% CI, 0.48--1.17). Other studies have demonstrated that acetaminophen is associated with transient decreases in DNA repair, and lymphocytes may be particularly susceptible to DNA damage, suggesting a mechanism for the elevated NHL risk observed.

Association of regular aspirin use and breast cancer risk

Of the limited number of epidemiological investigations on aspirin (and other nonsteroidal anti-inflammatory drugs) and breast cancer, the majority observe a protective role, yet only a few report dose-response effects for frequency or duration of use. We studied aspirin use among 1,478 breast cancer patients diagnosed from 1982 to 1998, and 3,383 cancer-free hospital controls at the Roswell Park Cancer Institute. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression. Compared to never use,both regular (> or =1 tablet per week for > or =1 year) and occasional use were inversely associated with breast cancer (adjusted OR = 0.84, 95% CI 0.64-0.97; adjusted OR = 0.80, 95% CI 0.67-0.96, respectively). Among regular users, an inverse trend was found for number of tablets consumed per week (1, 2-6, or > or =7) with corresponding ORs of 0.95, 0.80, and 0.74 (P(trend) = 0.01). Daily use spanning 10 or more years was associated with a more pronounced reduction in risk (P(trend) = 0.005). Our findings corroborate the growing body of observational evidence that regular aspirin use may be associated with reduced risk of breast cancer.

[Vasectomy: study of 300 interventions. Review of the national literature and of its complications]

OBJECTIVES

The aims of this paper are: 1. To study the demand and reasons why of the vasectomy in area 12 of Valencian Community. 2. To analyse the adverse effects of our series and the predictable risk factors. 3. To review the adverse effects in the national series. 4. To review the adverse effects referred to in international publications.

PATIENTS AND METHODS

A retrospective study was made of 300 patients who had submitted themselves to a vasectomy between january 1992 and december 2000. All the clinical dossiers were reviewed according to 10 pre-established variables. age, number of offspring, reasons why, pre-vasectomy anticontraceptives; date of operation, type of anaesthesia used, pathologic anatomy, semen analysis after vasectomy, adverse effects and their possible causes (risk factors). The basic statistic study was done using a data base of Microsoft Access and the interpretations of the different variables using a table of Excel.

RESULTS

The demand for contraceptive attention (vasectomy) is the 8th cause for external urological consulting and the 4th for urological local ambulatory surgery of our area. 300 operations were done during that period. The average age of the patients was 37.5 years old (ranging from 25 to 51). The number of offspring ranged from 1 to 7, with a promedia of 2.41 children/patient. The reasons why were: voluntary family planning (86%), medical illnesses of the female which contraindicated gestation (9%), genetic reasons (4.33%) and social-sanitary problems (0.66%). Contraceptive methods used by 71.63% are known: The widest-used method being IUD (49.74%) and the preservative (25.88%). 30 patients (10%) had adverse effects, 29 patients having light adverse effects. The most frequent were: 12 orchiepididymitis (4%), 5 spermatic granulomas (1.66%), 3 chronic scrotal pain (1%), 2 scrotal haematoma (0.66%) and 2 bleeding (0.66%). There was one serious complications and of all the cases mentioned above only one needed hospitalization (impetigo-sepsis) and another needed surgery due to a spermatic granuloma. There were no pregnancies or post-vasectomy court cases. 81% of the patients had been declared azoospermic within 45 to 60 days after the vasectomy in one or two consecutive semen analysis.

CONCLUSIONS

The vasectomy is a safe and simple way for male sterilization. It's the most widely done urologic operation in Spain. The technique isn't extent of adverse effects (0 to 18%) and its seriousness varies from a simple ecchymosis to Fournier's gangrene, endocarditis or sepsis. A doctor would be considered negligent if he/she didn't inform the patient about the remote possibility of a spontaneous recanalisation of the vas deferens leading to renewed fertility (failure of the vasectomy). It is imperative to give post-vasectomy information where the patient must continue using his habitual anticonceptive method until the azoospermia shown in 2 semen analysis confirm the sterility of the patient so that the urologist has no legal problem.

Canadian Contraception Consensus

This document has been archived because it contains outdated information. It should not be consulted for clinical use, but for historical research only. Please visit the journal website for the most recent guidelines.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Vasectomy and the risk of prostate cancer: a meta-analysis examining vasectomy status, age at vasectomy, and time since vasectomy

The aim of this study was to conduct a quantitative review of prostate cancer studies to pool relative risk (RR) estimates on the association between prostate cancer and vasectomy, in an attempt to determine whether there is an association, and if so, its magnitude. Random-effects models were examined along with a linear model for time since vasectomy. The pooled RR estimate was 1.37 (95% CI=1.15-1.62) based on five cohort studies and 17 case-control studies. The RR estimate varied by study design with the lowest risk for population-based case-control studies. No difference was seen in risk by age at vasectomy. A linear trend based on the 16 studies reporting time since vasectomy suggested an 10% increase for each additional 10 y or a RR of 1.32 (95% CI=1.17-1.50) for 30 y since vasectomy. When null effects were assumed for the six studies not reporting information, the linear RR for the 22 studies was 1.07 (1.03-1.11) and 1.23 (1.11-1.37) for 10 and 30 y since vasectomy, respectively. These results suggest that men with a prior vasectomy may be at an increased risk of prostate cancer, however, the increase may not be causal since potential bias cannot be discounted. The overall association was small and therefore could be explained by bias. The latency effect shown here for time since vasectomy should be examined further.

Regular aspirin use and lung cancer risk

BACKGROUND

Although a large number of epidemiological studies have examined the role of aspirin in the chemoprevention of colon cancer and other solid tumors, there is a limited body of research focusing on the association between aspirin and lung cancer risk.

METHODS

We conducted a hospital-based case-control study to evaluate the role of regular aspirin use in lung cancer etiology. Study participants included 868 cases with primary, incident lung cancer and 935 hospital controls with non-neoplastic conditions who completed a comprehensive epidemiological questionnaire. Participants were classified as regular aspirin users if they had taken the drug at least once a week for at least one year.

RESULTS

Results indicated that lung cancer risk was significantly lower for aspirin users compared to non-users (adjusted OR = 0.57; 95% CI 0.41-0.78). Although there was no clear evidence of a dose-response relationship, we observed risk reductions associated with greater frequency of use. Similarly, prolonged duration of use and increasing tablet years (tablets per day x years of use) was associated with reduced lung cancer risk. Risk reductions were observed in both sexes, but significant dose response relationships were only seen among male participants. When the analyses were restricted to former and current smokers, participants with the lowest cigarette exposure tended to benefit most from the potential chemopreventive effect of aspirin. After stratification by histology, regular aspirin use was significantly associated with reduced risk of small cell lung cancer and non-small cell lung cancer.

CONCLUSIONS

Overall, results from this hospital-based case-control study suggest that regular aspirin use may be associated with reduced risk of lung cancer.

Vasectomy and prostate cancer characteristics of patients referred for prostate biopsy

PURPOSE

The prospect of an association between vasectomy and prostate cancer has gained widespread attention and has potentially influenced patterns of referral. In patients referred for prostate needle biopsies we compared the incidence and characteristics of prostate cancer in those reporting a history of vasectomy to those denying prior vasectomy.

MATERIALS AND METHODS

A total of 585 consecutive prostate biopsy procedures were performed on 522 veterans during a 42-month period. Upon questioning 101 patients (19.3%) reported prior vasectomy. From the remaining 421 patients 202 consecutive age matched controls were selected. Pre-procedure prostate specific antigen levels, digital examination findings, incidence of prostate cancer, cancer grade and tumor length on biopsy cores were compared between the patients with and without a history of vasectomy.

RESULTS

Of the 101 patients who reported a history of vasectomy 46 (45.5%) had prostate cancer compared to 98 (48.5%) of the 202 age matched controls, and this difference was not statistically significant. Of the patients with prostate cancer those with prior vasectomy less frequently had an abnormal digital examination and lower prostate specific antigen levels, lower Gleason grade, lower clinical stage and shorter length of cancer on biopsies.

CONCLUSIONS

We found no increase in prostate cancer incidence or severity in patients referred for prostate biopsy who had undergone prior vasectomy. In fact, prostate cancer was less common with fewer poor prognostic indicators in patients with previous vasectomy. These findings may be secondary to either selection bias, as patients with a vasectomy may seek more routine medical care, or a greater tendency of primary providers to refer these patients for evaluation.

Regular use of aspirin and pancreatic cancer risk

BACKGROUND

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been consistently associated with reduced risk of colorectal cancer and adenoma, and there is some evidence for a protective effect for other types of cancer. As experimental studies reveal a possible role for NSAIDs is reducing the risk of pancreatic cancer, epidemiological studies examining similar associations in human populations become more important.

METHODS

In this hospital-based case-control study, 194 patients with pancreatic cancer were compared to 582 age and sex-matched patients with non-neoplastic conditions to examine the association between aspirin use and risk of pancreatic cancer. All participants received medical services at the Roswell Park Cancer Institute in Buffalo, NY and completed a comprehensive epidemiologic questionnaire that included information on demographics, lifestyle factors and medical history as well as frequency and duration of aspirin use. Patients using at least one tablet per week for at least six months were classified as regular aspirin users. Unconditional logistic regression was used to compute crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

Pancreatic cancer risk in aspirin users was not changed relative to non-users (adjusted OR = 1.00; 95% CI 0.72-1.39). No significant change in risk was found in relation to greater frequency or prolonged duration of use, in the total sample or in either gender.

CONCLUSIONS

These data suggest that regular aspirin use may not be associated with lower risk of pancreatic cancer.

Intakes of selected nutrients and food groups and risk of ovarian cancer

In a hospital-based case-control study, we examined dietary intakes of selected nutrients and food groups and ovarian cancer risk among 496 women with primary, histologically confirmed epithelial ovarian cancer and 1,425 women with nonneoplastic diagnoses, ages 20-87 years, admitted to Roswell Park Cancer Institute between 1982 and 1998. Data on diet and other relevant risk factors in the few years before admission were collected with a self-administered questionnaire. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression adjusting for age, education, region of residence, regularity of menstruation, family history of ovarian cancer, parity, age at menarche, oral contraceptive use, and energy intake. Women in the highest vs. the lowest quartile of total energy had a weak increase in risk (OR = 1.25, 95% CI = 0.90-1.73). Significantly reduced risks were associated with higher intakes of dietary fiber (OR = 0.57, 95% CI = 0.38-0.87), vitamin A (OR = 0.66, 95% CI = 0.45-0.98), carotenoid (OR = 0.64, 95% CI = 0.43-0.93), vitamin E (OR = 0.58, 95% CI = 0.38-0.88), beta-carotene (OR = 0.68, 95% CI = 0.46-0.98), and total fruit and vegetable intake (OR = 0.62, 95% CI = 0.42-0.92). Our findings suggest that a diet high in plant foods may be important in reducing risk of ovarian cancer.

Vasectomy and prostate cancer in Québec, Canada

The present investigation measured the association between vasectomy and prostate cancer (PC) in the male population of Québec, Canada. The Québec Health Insurance Board and the Québec Cancer Registry were our principal sources of information. Lung cancer cases and the male population of Québec served as controls for comparative purposes. Within a retrospective design, our preliminary results indicate an association between vasectomy and PC. Among the 1925-39 birth cohort of individuals diagnosed with PC in 1990--93, the global odds ratio was 2.6 (95% CI=1.7--4.3) while it was compared with lung cancer as the control group. This risk increased with the length of time between vasectomy and the diagnosis of cancer. An historical design indicated strong cohesion of the results. Besides, the risk does not vary when we control for the place of residence of the individuals. Vasectomy seems to increase the risk of PC at least 10 years after the operation, but we cannot exclude the impact of a possible detection bias among vasectomized individuals.

Vasectomy

Vasectomy is regarded as the safest method now available for male fertility control. Almost 100 million men worldwide have relied on vasectomy for family planning. This review discusses all currently relevant operative techniques, including no-scalpel vasectomy, complications, possible long-term effects on the testis and epididymis, and diseases for which associations with vasectomy have been suggested, such as arteriosclerosis, autoimmune diseases and cancer of the prostate and testis. Other topics of discussion include the timing of post-operative semen analysis, patient noncompliance concerning post-operative controls, persistent cryptozoospermia and transient reappearance of spermatozoa after vasectomy, vasectomy failure and legal aspects.

Safety and effectiveness of vasectomy

OBJECTIVE

To recommend further research on vasectomy based on a systematic review of the effectiveness and safety of vasectomy.

DESIGN

A systematic MEDLINE review of the literature on the safety and effectiveness of vasectomy between 1964 and 1998.

MAIN OUTCOME MEASURE(S)

Early failure rates are <1%; however, effectiveness and complications vary with experience of surgeons and surgical technique. Early complications, including hematoma, infection, sperm granulomas, epididymitis-orchitis, and congestive epididymitis, occur in 1%-6% of men undergoing vasectomy. Incidence of epididymal pain is poorly documented. Animal and human data indicate that vasectomy does not increase atherosclerosis and that increases in circulating immune complexes after vasectomy are transient in men with vasectomies. The weight of the evidence regarding prostate and testicular cancer suggests that men with vasectomy are not at increased risk of these cancers.

CONCLUSION(S)

Publications to date continue to support the conclusion that vasectomy is a highly effective form of contraception. Future studies should include evaluations of the long-term effectiveness of vasectomy, evaluating criteria for postvasectomy discontinuation of alternative contraception for use in settings where semen analysis is not practical, and characterizing complications including chronic epididymal pain syndrome.

The association between vasectomy and prostate cancer: a systematic review of the literature

OBJECTIVE

To evaluate the possible association between vasectomy and prostate cancer.

DESIGN

Systematic review of the literature.

PATIENT(S)

Fourteen original studies published between January 1985 and December 1996 that addressed the association between vasectomy and prostate cancer.

MAIN OUTCOME MEASURE(S)

The strength of the association was estimated with the use of a meta-analysis (DerSimonian and Laird method). A sensitivity analysis was conducted to assess the impact of different sources of heterogeneity.

RESULT(S)

Fourteen original papers were reviewed (5 cohort and 9 case-control studies). Relative risks ranged between 0.44 (95% confidence interval [CI] = 0.1-4.0) and 6.70 (95% CI = 2.1-21.6). The overall relative risk (DerSimonian and Laird estimate) was 1.23 (95% CI = 1.01-1.49). The sensitivity analysis showed that this measure was very sensitive to the study base, the type of design used, and the possibility of bias. Further, the funnel plot demonstrated the probable existence of publication bias.

CONCLUSION(S)

No causal association was found between vasectomy and prostate cancer. Individuals who have undergone vasectomy are not at high risk for the development of prostate cancer.

Male genital cancers

Each type of male genital cancer has features that are unique in diagnosis and treatment. The incidences of these cancers are related to age, race, and environment. Early diagnosis and treatment are documented as important for all male genital cancers except prostate cancer, where this remains a subject of controversy.