Vasectomy and prostate cancer risk: methodological review of the evidence

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.

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.

[Male and female sterilization techniques: Summary of ANAES assessments (May 2005)]

OBJECTIVE

To summarize assessments carried out by ANAES on male and female sterilization techniques. The summary was requested by the French Health Directorate after the law authorizing sterilization as a means of contraception was passed.

RESULTS (FEMALE STERILIZATION)

(i) EFFICACY of tubal ligation, electrocoagulation, clips or rings: the annual pregnancy rate is 0-2% depending on the study, with no significant difference between techniques. No data were found on fimbriectomy. (ii) EFFICACY of a hysteroscopically placed micro-insert device: no pregnancies were observed in patients with bilateral tube obstruction diagnosed by hysterosalpingography at 3 or at 6 months after placement (placement rate: 87-89%). (iii) SAFETY of tubal ligation, electrocoagulation, clips or rings: (a) By approach: There was no difference in the incidence of major complications between laparoscopy and minilaparotomy but there were significantly fewer minor complications with laparoscopy than with minilaparotomy. There were significantly more major complications with culdoscopy than with minilaparotomy and significantly more minor complications than with laparoscopy. (b) By operative technique: major and minor complications were significantly more common with the Pomeroy technique than with electrocoagulation; the difference could be due to the approach used. No data were available on fimbriectomy. (iv) SAFETY of a hysteroscopically placed micro-insert device: there were 11 cases of myometrial or tubal perforation among 734 patients (with device displacement into the peritoneal cavity in 3 cases).

RESULTS (MALE STERILIZATION)

(i)

EFFICACY

efficacy varied from 84% to 100% depending on the approach and the mode of vas deferens obstruction. There was no significant difference in efficacy according to approach (transcutaneous or scrotal). However, no conclusion could be drawn on the comparative efficacy of the occlusion techniques used from published data. (ii)

SAFETY

the rate of postoperative complications was low, below 10% in most series. Complications were benign and only rarely necessitated surgical revision.

CONCLUSION

The advantage of sterilization methods is that they lack any permanent contraindication. They should be presented as being generally irreversible. Fimbriectomy is not recommended for female sterilization. Laparoscopy is the preferred approach. Sterilization by hysteroscopic placement of a micro-insert device should be restricted to cases presenting a risk on laparoscopy; the technique should be re-assessed in 2006. The two approaches used for male sterilization are technically similar and do not seem to differ in efficacy. The Public Health Code states that "Fallopian tube or deferens duct ligation for contraceptive purposes is not allowed in minors" and that ligation "cannot be performed unless the adult involved has given his/her informed and motivated consent, expressed after taking into consideration clear, complete information on the consequences of the procedure". A waiting period of four months must follow the moment the decision to sterilize is taken and consent is given. An informed consent form must be signed. Sterilization in young or nulliparous women should be proposed with the greatest prudence and with many reservations.

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.

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.

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.

A psychometric experiment in causal inference to estimate evidential weights used by epidemiologists

A psychometric experiment in causal inference was performed on 159 Australian and New Zealand epidemiologists. Subjects each decided whether to attribute causality to 12 summaries of evidence concerning a disease and a chemical exposure. The 1,748 unique summaries embodied predetermined distributions of 19 characteristics generated by computerized evidence simulation. Effects of characteristics of evidence on causal attribution were estimated from logistic regression, and interactions were identified from a regression tree analysis. Factors with the strongest influence on the odds of causal attribution were statistical significance (odds ratio = 4.5 if 0.001 < or = P < 0.05 and 7.2 if P < 0.001, vs P > or = 0.05); refutation of alternative explanations (odds ratio = 8.1 for no known confounder vs none adjusted); strength of association (odds ratio = 2.0 if 1.5 < relative risk < or = 2.0 and 3.6 if relative risk > 2.0, vs relative risk < or = 1.5); and adjunct information concerning biological, factual, and theoretical coherence. The refutation of confounding reduced the cutpoint in the regression tree for decision-making based on strength of association. The effect of the number of supportive studies reached saturation after it exceeded 12 studies. There was evidence of flawed logic in the responses concerning specificity of effects of exposure and a tendency to discount evidence if the P-value was a "near miss" (0.050 < P < 0.065). Evidential weights based on regression coefficients for causal criteria can be applied to actual scientific evidence.

Population-based outcomes after 28,246 in-hospital vasectomies and 1,902 vasovasostomies in Western Australia

OBJECTIVES

To examine trends in vasectomy and vasovasostomy, and the surgical complications and factors associated with reversal after vasectomy, and paternity after vasovasostomy.

PATIENTS AND METHODS

Procedure rates were estimated from 1980 to 1996 in the population of Western Australia. Linked hospital morbidity records were used in the follow-up of men after vasectomy to estimate the risks of complications and reversals. Records of vasovasostomies were linked to the paternity field on birth registrations. Independent effects of the study factors were examined using Cox regression.

RESULTS

There was little net change in vasectomy rates, whereas vasovasostomy rates increased in men aged 30-49 years. Risks of surgical complications were low and decreased for vasovasostomy. At 12-15 years after vasectomy, the risk of reversal levelled at 2. 4% in the total cohort and at 11.1% in men aged 20-24 years. The risk of vasovasostomy was 69% greater after vasectomy performed in 1994-96 than in 1980-84 (P = 0.011). The factors strongly associated with reversal were age < 30 years and being single, divorced or separated at the time of vasectomy. Paternity was achieved after an estimated 53% of vasovasostomies. Successful reversal was more likely if the man was younger at vasectomy and the time elapsed was comparatively short. Compared with vasovasostomies performed in 1980-84, the success rate of those in 1994-96 was almost four times higher.

CONCLUSION

Population rates of vasectomy are stable but the risk of seeking a reversal has increased. Outcomes after vasovasostomy have improved. Care should be taken during the counselling of men before vasectomy, and especially in those aged <30 years.

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.

Vasectomy in the United States, 1991

OBJECTIVES

Recent conflicting findings on possible health risks related to vasectomy have underscored the need for reliable and representative estimates of numbers and rates of vasectomies in the United States. The purpose of this study was to estimate the annual US number, rate, and characteristics of vasectomies in 1991.

METHODS

A national survey of urology, general surgery, and family practice physician practices was conducted with probability sampling methods (n = 1685 physicians).

RESULTS

An estimated 493,487 (95% confidence interval = 450,480, 536,494) vasectomies were performed in 1991, for a rate of 10.3 procedures per 1000 men aged 25 through 49 years. Most vasectomies were performed by urologists, and most were done in physicians' offices with local anesthesia and ligation as the method of occlusion. The rate of vasectomies was highest in the Midwest.

CONCLUSIONS

This survey provides the first national estimates of the number and rate of vasectomies in the United States, as well as the first estimates of occlusion method used. Results confirm previous findings that urologists perform most vasectomies and that most vasectomies are performed with local anesthesia. Recommendations include the monitoring of vasectomy numbers and rates as well as demographic studies of men obtaining vasectomies.

Vasectomy and vasectomy reversal

Vasectomy remains the safest method of birth control and there is much to commend it in the setting of a stable family relationship. However, some aspects of this operation have been wrongly presented in an attempt to widen its popularity and increase public acceptance. A simple procedure it may be but it is not totally free of complications; sometimes the operation has to be repeated and rarely it may reverse spontaneously even after the most stringent precautions. The family planning officer who counsels a prospective candidate and the surgeon who undertakes the procedure must ensure that these facts are understood by the patient with crystal clarity and that this fact is duly recorded on a signed and witnessed permission slip. Any organization which includes vasectomy in its programme of family planning should include advice and referral for vasectomy reversal in exactly the same way that the pill may be stopped or a coil can be removed. Fertility can be successfully restored by vasovasostomy in 50% of men who wish to have their vasectomies reversed, which often is due to a change in circumstances beyond their direct control.

Alcohol consumption, smoking, and other risk factors and prostate cancer in a large health plan cohort in California (United States)

Alcohol consumption and cigarette smoking have been suggested as possible causes of prostate cancer. We therefore examined this relation in a cohort of 43,432 men who were members of a prepaid health plan in northern California (United States) and who had received a health examination in the period from 1979 through 1985. Detailed information on demographic variables, alcohol consumption, smoking habits, medical complaints and conditions, occupation, and surgery (including vasectomy) was assessed. Symptoms of prostatism and a history of sexually transmitted diseases were abstracted from the medical records of all prostate cancer patients and of a matched subsample of randomly selected control-subjects. Alcohol consumption was associated with no elevated prostate cancer risk for the 238 men in our study in whom prostate cancer developed, but smoking one or more packs of cigarettes per day was associated with an adjusted relative risk (RR) of 1.9 (95 percent confidence interval [CI] = 1.2-3.1). Prostate cancer risk for Black men was 2.2 (CI = 1.6-3.1) when compared with that for White men, and education level was associated positively in an increasing trend (P < 0.020) up to an RR of 1.4 (CI = 0.9-2.1) among men with postgraduate education. Symptoms of prostate hypertrophy were not associated with elevated risk of prostate cancer if they occurred two or more years before the diagnosis. The finding that smoking increased the risk of prostate cancer confirms the observations of others but needs cautious interpretation because we were unable to adjust for the potential confounding effect of dietary and hormonal factors.