Concordance on the recording of cancer in the Saskatchewan Cancer Agency Registry, hospital charts and death registrations

The effect of statin use on the incidence of prostate cancer: A population-based nested case-control study

Preclinical studies suggest statins may help prevent prostate cancer (PC), but epidemiologic results are mixed. Many epidemiological studies have relatively short prediagnosis drug exposure data, which may miss some statin use. We completed a nested case-control study investigating the impact of statin use on PC diagnosis and clinically significant PC using data from men aged ≥40 years in the Canadian province of Saskatchewan between 1990 and 2010. Drug exposure histories were derived from a population-based prescription drug database. We used conditional logistic regression to model use of statins as a class and stratified analyses for groups defined by lipophilicity. Clinically significant PC was defined as Gleason score 8-10 OR stage C or D or III or IV at diagnosis. 12,745 cases of PC were risk-set matched on age and geographic location to 50,979 controls. Greater than 90% of subjects had prediagnosis drug exposure histories >15 years. 2,064 (16.2%) cases and 7,956 (15.6%) controls were dispensed one or more statin prescriptions. In multivariable models, ever prescription of statins was not associated with PC diagnosis (OR 0.97; 95% CI 0.90-1.05). Neither lipophilic statins (OR 0.96, 95% CI 0.88-1.04) nor hydrophilic statins (OR 1.06, 95% CI 0.95-1.20) impacted PC diagnosis. There was no effect of the dose or duration of statin use. Diagnosis of clinically significant PC decreased with statin use (OR 0.84, 95% CI 0.73-0.97). Statin use is not associated with overall PC risk, regardless of duration or dose of statin exposure. Statin use is associated with a decreased risk of clinically significant PC.

Risk of prostate cancer death in long-term users of warfarin: a population-based case-control study

PURPOSE

Recent evidence suggests that warfarin use may be associated with a reduced risk of prostate cancer. We aimed to determine whether exposure to warfarin is also associated with a reduced risk of prostate cancer death.

METHODS

A nested case-control study was conducted within a population-based cohort of 10,012 men aged ≥50 years with newly diagnosed prostate cancer between 1985 and 2002 and with no history of cancer since 1970 using the linked records of Saskatchewan Health and Saskatchewan Cancer Agency registry. We identified 2,309 cases who died of prostate cancer during follow-up. For each case, one control alive at the time of the case's death and matched for length of follow-up (±6 months) was randomly selected. Prescription counts were used to define warfarin exposure. Multivariate conditional logistic regression analysis was used to calculate the adjusted incidence rates of prostate cancer death in relation to warfarin use while adjusting for confounding by age, year of prostate cancer diagnosis, clinical stage and grade of cancer at diagnosis, Chronic Disease Score, and use of warfarin before diagnosis.

RESULTS

Ever use of warfarin following a diagnosis of prostate cancer was associated with an adjusted rate ratio of 1.44 (95 % confidence interval (CI) 1.33-1.84) for prostate cancer death. The adjusted rate ratio with one-year use of warfarin was 1.77 (95 % CI 1.25-2.50) compared to never use. The unadjusted rate ratio with five-year use of warfarin was 0.64 (95 % CI 0.40-1.00) and remained unchanged in the adjusted analysis (0.65, 95 % CI 0.37-1.13), although no longer statistically significant.

CONCLUSION

Our study does not provide conclusive evidence for a protective effect of long-term warfarin on prostate cancer-specific mortality. Moreover, short-term warfarin use may be associated with an increased risk of prostate cancer death.

A population-based case-control study of Selective Serotonin Reuptake Inhibitors (SSRIs) and breast cancer: the impact of duration of use, cumulative dose and latency

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs), a popular class of antidepressants, may increase breast cancer risk by stimulating the secretion of prolactin, a potential tumour promoter. We evaluated the effects of duration of SSRI use, cumulative dose, and latency on the risk of breast cancer by conducting a population-based case-control study utilizing Saskatchewan health databases.

METHODS

Cases included 1,701 women with primary invasive breast cancer diagnosed from 2003 to 2006, and controls consisted of 17,017 women, randomly selected from the population registry. Use of SSRIs was compiled using the Saskatchewan prescription database. Unconditional logistic regression was conducted to evaluate the impact of duration of combined SSRI use (total number of prescriptions dispensed), cumulative dose (total dosage received) and timing of use (two or more years, two to seven years and more than seven years prior to index date) on the risk of breast cancer.

RESULTS

Overall, SSRI use was not associated with an increased risk of breast cancer regardless of our definition of cumulative use (total number of prescriptions dispensed and total dosage). In addition, our results indicate that prolonged SSRI use does not have a latent effect on breast cancer risk. Also, our findings are not suggestive of an increased risk of breast cancer with the use of individual SSRIs.

CONCLUSIONS

Our study improved upon most previous studies by having a longer follow-up period, a larger sample size of long-term SSRI users and consideration of risk during specific exposure time windows that take latency into account. Given the potential health benefits of using SSRIs, our results suggest that the issue of breast cancer risk may no longer be a concern for women requiring long-term SSRIs.

A population-based study of age inequalities in access to palliative care among cancer patients

BACKGROUND

Inequalities in access to palliative care programs (PCP) by age have been shown to exist in Canada and elsewhere. Few studies have been able to provide greater insight by simultaneously adjusting for multiple demographic, health service, and socio-cultural indicators.

OBJECTIVE

To re-examine the relationship between age and registration to specialized community-based PCP programs among cancer patients and identify the multiple indicators contributing to these inequalities.

METHODS

This retrospective, population-based study was a secondary data analysis of linked individual level information extracted from 6 administrative health databases and contextual (neighborhood level) data from provincial and census information. Subjects included all adults who died due to cancer between 1998 and 2003 living within 2 District Health Authorities in the province of Nova Scotia, Canada. The relationship between registration in a PCP and age was examined using hierarchical nonlinear regression modeling techniques. Identification of potential patient and ecologic contributing indicators was guided by Andersen's conceptual model of health service utilization.

RESULTS

Overall, 66% of 7511 subjects were registered with a PCP. Older subjects were significantly less likely than those <65 years of age to be registered with a PCP, in particular those aged 85 years and older (adjusted odds ratio: 0.4; 95% confidence interval: 0.3-0.5). Distance to the closest cancer center had a major impact on registration.

CONCLUSIONS

Age continues to be a significant predictor of PCP registration in Nova Scotia even after controlling for the confounding effects of many new demographic, health service, and ecologic indicators.

Quantifying data quality for clinical trials using electronic data capture

Background

Historically, only partial assessments of data quality have been performed in clinical trials, for which the most common method of measuring database error rates has been to compare the case report form (CRF) to database entries and count discrepancies. Importantly, errors arising from medical record abstraction and transcription are rarely evaluated as part of such quality assessments. Electronic Data Capture (EDC) technology has had a further impact, as paper CRFs typically leveraged for quality measurement are not used in EDC processes.

Methods and Principal Findings

The National Institute on Drug Abuse Treatment Clinical Trials Network has developed, implemented, and evaluated methodology for holistically assessing data quality on EDC trials. We characterize the average source-to-database error rate (14.3 errors per 10,000 fields) for the first year of use of the new evaluation method. This error rate was significantly lower than the average of published error rates for source-to-database audits, and was similar to CRF-to-database error rates reported in the published literature. We attribute this largely to an absence of medical record abstraction on the trials we examined, and to an outpatient setting characterized by less acute patient conditions.

Conclusions

Historically, medical record abstraction is the most significant source of error by an order of magnitude, and should be measured and managed during the course of clinical trials. Source-to-database error rates are highly dependent on the amount of structured data collection in the clinical setting and on the complexity of the medical record, dependencies that should be considered when developing data quality benchmarks.

Assessing the concordance of trauma registry data and hospital records

This study examined the concordance of trauma registry and hospital records in Queensland in 1998. The design involved a retrospective review of records and documentation comparison. Demographic variables from the registry were matched to hospital data to obtain admission/diagnoses data. There were four main types of error identified which included: failure to identify relevant patients, inappropriate inclusion of patients, insufficient/inaccurate data in hospital records, and insufficient/inaccurate data in the trauma registry. Of the 87 cases with data quality issues, 63% were due to Queensland Trauma Registry (QTR) data errors, 5% were due to hospital data errors, and in 32% of cases the source of errors was undetermined. Of the potential 1759 trauma cases from 1998, 12 cases should have been included in the registry that were not, 71 cases should not have been included in the registry, and 4 cases were removed from the study due to insufficient or inaccurate hospital record data. Overall, a concordance rate of approximately 95% was found between the trauma registry records and the hospital records.

Use of warfarin and risk of urogenital cancer: a population-based, nested case-control study

BACKGROUND

Indirect evidence suggests that prolonged treatment with warfarin might be associated with a decreased incidence of urogenital cancer. We aimed to assess this association in a large population-based study.

METHODS

Beneficiaries of Saskatchewan Health who were eligible for prescription drug benefits and aged 50 years or over with no history of cancer since 1967 were enrolled into a nested, matched case-control study. 19 412 new cases of urogenital cancer diagnosed between Jan 1, 1981, and Dec 31, 2002, were identified by use of information from the Saskatchewan Cancer Agency registry. For each case, six controls, totalling 116 470, who were matched for age, sex, and time of diagnosis were selected randomly. Conditional logistic regression analysis was used to calculate adjusted incidence rates of urogenital cancer in relation to warfarin use.

FINDINGS

Compared with men who never used warfarin, men with 4 years of warfarin use had an adjusted incidence rate of 0.80 (95% CI [0.65-0.99]). For warfarin use 76-100% of the time, the adjusted rate ratios were 0.80 (0.66-0.96) during year 2 preceding diagnosis of prostate cancer, 0.76 (0.62-0.94) during year 3, and 0.67 (0.53-0.86) during year 4. No significant association was found between warfarin and risk of other urogenital cancers.

INTERPRETATION

Our results suggest that warfarin has an antitumour effect that is specific to prostate cancer. Further investigation, with more complete assessment of confounders and that addresses the effect of warfarin on mortality of prostate cancer, is warranted.

Increased cancer-related mortality for patients with type 2 diabetes who use sulfonylureas or insulin

OBJECTIVE

Numerous studies have identified an increased risk of cancer in type 2 diabetes. We explored the association between antidiabetic therapies and cancer-related mortality in patients with type 2 diabetes, postulating that agents that increase insulin levels might promote cancer.

RESEARCH DESIGN AND METHODS

This was a population-based cohort study using administrative databases from Saskatchewan Health. Cancer-related mortality was compared among inception cohorts of metformin users and sulfonylurea monotherapy users. Multivariate Cox regression was used to estimate the hazard ratio (HR) of cancer-related mortality, after adjusting for age, sex, insulin use, and chronic disease score. All statistical tests were two-sided.

RESULTS

We identified 10,309 new users of metformin or sulfonylureas with an average follow-up of 5.4 +/- 1.9 years (means +/- SD). The mean age for the cohort was 63.4 +/- 13.3 years, and 55% were men. Cancer mortality over follow-up was 4.9% (162 of 3,340) for sulfonylurea monotherapy users, 3.5% (245 of 6,969) for metformin users, and 5.8% (84 of 1,443) for subjects who used insulin. After multivariate adjustment, the sulfonylurea cohort had greater cancer-related mortality compared with the metformin cohort (adjusted HR 1.3 [95% CI 1.1-1.6]; P = 0.012). Insulin use was associated with an adjusted HR of cancer-related mortality of 1.9 (95% CI 1.5-2.4; P < 0.0001).

CONCLUSIONS

Patients with type 2 diabetes exposed to sulfonylureas and exogenous insulin had a significantly increased risk of cancer-related mortality compared with patients exposed to metformin. It is uncertain whether this increased risk is related to a deleterious effect of sulfonylurea and insulin or a protective effect of metformin or due to some unmeasured effect related to both choice of therapy and cancer risk.

Bayesian modelling of imperfect ascertainment methods in cancer studies

Tumour registry linkage, chart review and patient self-report are all commonly used ascertainment methods in cancer epidemiology. These methods are used for estimating the incidence or prevalence of different cancer types in a population, and for investigating the effects of possible risk factors for cancer. Tumour registry linkage is often treated as a gold standard, but in fact none of these methods is error free, and failure to adjust for imperfect ascertainment can lead to biased estimates. This is true both if the goal of the study is to estimate the properties of each ascertainment type, or if it is to estimate cancer incidence or prevalence from one or more of these methods. Although rarely applied in the literature to date, when cancer is ascertained by three or more methods, standard latent class models can be used to estimate cancer incidence or prevalence while adjusting for the estimated imperfect sensitivities and specificities of each ascertainment method. These models, however, do not account for variations in these properties across different cancer sites. To address this problem, we extend latent class methodology to include a hierarchical component, which accommodates different ascertainment properties across cancer sites. We apply our model to a data set of 169 lupus patients with three ascertainment methods and eight cancer types. This allows us to estimate the properties of each ascertainment method without assuming any to be a gold standard, and to calculate a standardized incidence ratio for cancer for lupus patients compared to the general population. As our data set is small, we also illustrate the effects as more data become available. We show that our model produces parameter estimates that are substantially different from the currently most popular method of ascertainment, which uses tumour registry data alone.

Exploring the Links Between Systemic Lupus Erythematosus and Cancer

For decades, concern has been mounting that individuals with systemic lupus erythematosus (SLE) have increased susceptibility to cancer. Recent data confirm that certain cancers, particularly hematologic, occur more frequently in SLE than in the general population. Numerous pathogenic mechanisms are possible, but hypotheses remain largely speculative. In particular, data are inadequate on how cancer risk in SLE may be related to medication exposures. To evaluate the impact of medication exposures on cancer risk in SLE, cooperative efforts of Systemic Lupus International Collaborating Clinics and Canadian Network for Improved Outcomes in Systemic Lupus are currently in progress. This should provide much-needed insight into the pathogenesis of the association between cancer and SLE.

The effects of transdermal and oral oestrogen replacement therapy on colorectal cancer risk in postmenopausal women

The aim of this study was to examine the effects of oral and transdermal oestrogen replacement therapy on the risk of colorectal cancer. Data from a nested case–control study, designed to investigate the effect of hormone replacement therapy (HRT) on colorectal cancer were analysed. New cases of colorectal cancer, diagnosed between 1992 and mid-1998 (N=1197), were identified using the Saskatchewan Cancer Agency cancer registry. Women ⩾50 years of age, eligible for coverage by the Saskatchewan Prescription Drug Plan, were included in the study. Four controls per case were age matched to cases, using incidence density sampling. The outpatient prescription drug plan database was used to ascertain oestrogen prescriptions. Women were classified according to history of transdermal (TDE) and oral (OE) oestrogen use. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Compared with women who had never used HRT, ORs for <3 and ⩾3 years of TDE use and colorectal cancer were 0.69 (95% CI: 0.43–1.10) and 0.33 (95% CI: 0.12–0.95), and for OE use were 0.90 (95% CI: 0.73–1.01) and 0.75 (95% CI: 0.60–0.93), respectively. The risk reduction for colorectal cancer with TDE may be greater in magnitude than that which has been reported for oral HRT.