Laboratory survey of prostate specific antigen testing in Ontario

Trends in prostate cancer incidence and mortality in Canada during the era of prostate-specific antigen screening

BACKGROUND

Widespread use of prostate-specific antigen (PSA) to screen for prostate cancer began in the early 1990s. Advocates for screening assert that this has caused a decrease in prostate cancer mortality. We sought to describe secular changes in prostate cancer incidence and mortality in Canada in relation to the onset of PSA screening.

METHODS

Age-standardized and age-specific prostate cancer incidence (1969-2007) and mortality (1969-2009) from Public Health Agency of Canada databases were analyzed by joinpoint regression. Changes in incidence and mortality were related to introduction of PSA screening.

RESULTS

Prior to PSA screening, prostate cancer incidence increased from 54.2 to 99.8 per 100 000 between 1969 and 1990. Thereafter, incidence increased sharply (12.8% per year) to peak at 140.8/100 000 in 1993. After decreasing in all age groups between 1993 and 1996, incidence continued to increase for men aged less than 70 years, but decreased for older men. Age-standardized mortality was stable from 1969 to 1977, increased 1.4% per year to peak in 1995 and subsequently decreased at 3.3% per year; the decline started from 1987 in younger men (age < 60 yr).

INTERPRETATION

Incidence was increasing before PSA screening occurred, but rose further after it was introduced. Reductions in prostate cancer mortality began before PSA screening was widely used and were larger than could be anticipated from screening alone. These findings suggest that screening caused artifactual increase in incidence, but no more than a part of reductions in prostate cancer mortality. The reduction may be due to changing treatment or certification of death.

Feasibility and utility of mapping disease risk at the neighbourhood level within a Canadian public health unit: an ecological study

Background

We conducted spatial analyses to determine the geographic variation of cancer at the neighbourhood level (dissemination areas or DAs) within the area of a single Ontario public health unit, Wellington-Dufferin-Guelph, covering a population of 238,326 inhabitants. Cancer incidence data between 1999 and 2003 were obtained from the Ontario Cancer Registry and were geocoded down to the level of DA using the enhanced Postal Code Conversion File. The 2001 Census of Canada provided information on the size and age-sex structure of the population at the DA level, in addition to information about selected census covariates, such as average neighbourhood income.

Results

Age standardized incidence ratios for cancer and the prevalence of census covariates were calculated for each of 331 dissemination areas in Wellington-Dufferin-Guelph. The standardized incidence ratios (SIR) for cancer varied dramatically across the dissemination areas. However, application of the Moran's I statistic, a popular index of spatial autocorrelation, suggested significant spatial patterns for only two cancers, lung and prostate, both in males (p < 0.001 and p = 0.002, respectively). Employing Bayesian hierarchical models, areas in the urban core of the City of Guelph had significantly higher SIRs for male lung cancer than the remainder of Wellington-Dufferin-Guelph; and, neighbourhoods in the urban and surrounding rural areas of Orangeville exhibited significantly higher SIRs for prostate cancer. After adjustment for age and spatial dependence, average household income attenuated much of the spatial pattern of lung cancer, but not of prostate cancer.

Conclusion

This paper demonstrates the feasibility and utility of a systematic approach to identifying neighbourhoods, within the area served by a public health unit, that have significantly higher risks of cancer. This exploratory, ecologic study suggests several hypotheses for these spatial patterns that warrant further investigations. To the best of our knowledge, this is the first Canadian study published in the peer-reviewed literature estimating the risk of relatively rare public health outcomes at a very small areal level, namely dissemination areas.

Has there been a change in practice of screening for prostate cancer with prostate-specific antigen in Ontario?

OBJECTIVE

To determine whether there has been a change in the rate of screening in Ontario in 2002 compared to 1995.

METHODS

A questionnaire was mailed to 520 physicians, associated with PSA records selected randomly from the database of a large community laboratory. Physicians were asked to consult their records as to the reasons for PSA testing.

RESULTS

There were 285 usable responses from 520 mailings (response rate 55%), mostly (91%) from family or general practice. Reasons for testing, expressed as proportions of responses, were as follows (this study, 1995 study and P value for the differences): screening for prostate cancer (74%, 63%; P = 0.059), diagnosis of urinary symptoms (30%, 40%; P = 0.027), follow-up of a medical procedure or drug therapy (14%, 32%; P = 0.001), confirmation of a previous PSA result (14%, 6%; P = 0.015) and other reasons (7%, 8%; P = 0.73). Of those records with screening as one reason for testing, 80% vs. 66% (P = 0.003) indicated it was the only reason; 86% vs. 73% (P = 0.003) indicated that it was part of a routine examination, and 54% vs. 64% (P = 0.052) indicated that the test was requested by the patient.

CONCLUSION

These findings are consistent with increased screening for prostate cancer with PSA.

Prostate cancer mortality reduction by screening: power and time frame with complete enrollment in the European Randomised Screening for Prostate Cancer (ERSPC) trial

From 1992-2001, 7 countries in Europe gradually recruited men for the European Randomised Screening for Prostate Cancer (ERSPC) trial. Centres recruit different age groups and have different designs for recruiting and countries have different underlying risks for prostate cancer. Recruitment has reached 163,126 men aged 55-69 at entry now. Our purpose was to calculate the power of the trial and at what point in time can statistically significant differences in prostate cancer mortality be expected. Recruitment data were collected from the screening centres. We calculated the expected number of prostate cancer deaths in each follow-up year, based on national statistics and expected rate in trial entrants. The power was calculated using different assumptions on intervention effect and contamination rate and also if the ERSPC trial would cooperate with other trials. With an assumed 25% intervention effect in men actually screened and a 20% contamination rate, the trial will reach a power of 0.86 in 2008. With an assumed intervention effect of 40%, the power reaches 0.90 in 2003-2004. Pooling data with those of the Prostate, Lung, Colorectal and Ovary (PLCO) trial early is expected to improve the power to 79% (20% intervention effect) to 92% (40% intervention effect PLCO). Adding more centres with compliance rates lower than 45% decreases the power of the trial. The ERSPC trial has sufficient power to detect a significant difference in prostate cancer mortality between the 2 arms if the true reduction in mortality by screening is 25% or more or if contamination remains limited to 10% if the true effect is 20% or more. If early detection and treatment turns out to have a stronger effect as may be suggested by observational data, the ERSPC trial is likely to conclusively show that within the next 5 years.

PSA-use in a Spanish industrial area

OBJECTIVES

To document the extent of prostate-specific antigen (PSA)-testing in the general population at Getafe (Spain) outside our prostate cancer (PC) screening program, and to check its performance in terms of PC detection.

METHODS

A total of 5371 PSA-test records (1997-1999) were reviewed and testing rates estimated per 1000 person-years. The extent of patient referral (men referred to our facilities) was calculated adjusting for PSA levels. To approach the performance of testing in the general population, our PC screening program acted as a standard for comparison. The probability of missing one PC in the general population was estimated in terms of number of men necessary to screen (NNS). Calculations were made adjusting for PSA levels.

RESULTS

PSA-testing rate in the general population was 21.6/1000 person-years. In the age-group 55-69 years, this rate was 86.8/1000 (152.6 in men >70 years). Referral rates were 67.9 and 39.5% for men with PSA 4-10 and >10 ng/ml, respectively. Overall PC detection rate was 1.76%. Detection rates for PSA 4-10 and >10 ng/ml were 4.66 and 12.94%, respectively. When compared with the performance of the screening program, for every 17 men with a PSA in the range 4-10 ng/ml one cancer was missed (95% confidence interval (CI), 9-580). Similarly, one cancer was lost for every four men with a PSA >10 ng/ml (95% CI, 2-8).

CONCLUSIONS

The extent of opportunistic testing in our setting is very high, particularly in the older age groups. Opportunistic screening renders PC detection rates lower than expected for every PSA level and cannot be encouraged.

[Analysis of the use of prostate specific antigen (PSA) in a health area of the Community of Madrid]

OBJECTIVES

To approach the local extent of PSA-use, and to check its yield in terms of prostate cancer (PC) detection.

METHODS

All PSA-test records (1997-1999) were reviewed and testing rates calculated per 1000 person-years. Detection rate (PC) was also estimated and referred to our PC prevalence study using the odds ratio as instrument for comparison.

RESULTS

Testing rate in the general population was 21.6/1000 person-years. PC detection rate was 1.76% (1.28 inside the prevalence study). For every CP detected in the general population with a PSA ranging 4-10 ng/ml, 2.39 (OR = 2.39) were detected in the prevalence study (OR = 4.48 for the PSA range > 10 ng/ml).

CONCLUSIONS

PSA-testing in our setting is high. PC detection rates were lower than expected.

Prostate-specific antigen utilization in Ontario: extent of testing in patients with and without cancer

OBJECTIVES

To ascertain the extent of prostate-specific antigen (PSA) testing in patients with prostate cancer (PC), with other cancers (OC), and with no cancer (NC) in two clinical laboratory databases.

DESIGN AND METHODS

PSA test records were obtained from a tertiary care hospital, Sunnybrook Health Science Centre (SHSC) and from a private laboratory, Gamma-Dynacare Medical Laboratories (GDL), during the period 1988 to 1995. These records were linked with the Ontario Cancer Registry (OCR) to establish a diagnosis of PC, OC, or NC. Trends in PSA testing according to diagnostic category, testing laboratory, patient age (by decade), and PSA value (in microgram/L) were determined.

RESULTS

Major cancer sites identified in the patients tested for PSA were prostate (60%), bladder and colon (7% each), lung (5%), kidney (3%), and rectum (3%). There were 11,867 patients (8.5%) with PC, 8,002 (5.9%) with OC, and 118,954 (86%) with NC. The total number of PSA tests performed on these patients was 230,756, of which 21% were on PC, 5% on OC, and 74% on NC; of these tests, 64% were performed through GDL and 36% through SHSC. The mean (median) number of tests per patient was: PC, 4.0 (2); OC, 1.4 (1); and NC, 1.5 (1). For PC 89% and for OC 72% of all tests occurred after diagnosis. Between 1990 and 1995 the number of PSA tests increased two-fold in PC and OC, and 20-fold in NC. We estimate that about one-half of the PSA tests in the NC group were for screening purposes. The proportion of PSA tests occurring in PC, OC, and NC for patients 50 to 70 years of age was 41%, 50%, and 63%, respectively; for patients over 70 years of age, this proportion was 58%, 46%, and 22% respectively; and for patients under 50 it was 1%, 4%, and 15%, respectively. Between 1990 and 1995, the largest increase in testing frequency was in the NC group, particularly in patients 50 to 70 years of age, which was accompanied by a decrease in patients over 70. Less than 10% of testing occurred in patients under 50 in all diagnostic groups. We estimate that about 26% of PSA screening tests in NC occurred outside the guidelines for patient age. Between 1988 and 1995, the proportion of PSA results below our detection limit (< 0.2 micrograms/L) showed a steady rise in the PC group, as did the proportion between 0.2 and 3.9 micrograms/L; these were accompanied by a fall in the proportion > 20.0 micrograms/L. However, the proportion of PSA results within these ranges did not change much during the same time period for the OC and NC groups. At cutoffs of PSA = 4.0 micrograms/L (or PSA = 10.0 micrograms/L), estimates of clinical specificity were 84.0% (or 96.3%), and of clinical sensitivity were 83.4% (or 47.1%).

CONCLUSIONS

Most (86%) PSA testing occurred in men with NC, consistent with diagnosis or screening. There were more PSA tests per patient in PC than in OC, and most testing occurred after diagnosis. PSA testing in the NC group continues to increase rapidly. The proportion of PSA tests in patients over age 70 decreased in the order of PC > NC > OC. Between 1990 and 1995, there was an increase in the proportion of patients tested who were between 50 and 70 in the NC group, which may suggest more screening in this group. Over this same time period, there was an increase in the proportion of undetectable PSA values, possibly suggesting increased use of radical therapy; there was also a decrease in the proportion of PSA > 20 micrograms/L, possibly suggesting a decrease in the prevalence of advanced stage PC.