|Cost-effectiveness analysis in early detection of prostate cancer: an evaluation of six screening strategies in a randomly selected population of 2,400 men
|Gustafsson O, Carlsson P, Norming U, Nyman C R, Svensson H
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
The early detection of prostate cancer: a cost-effectiveness analysis of six screening strategies using different combinations of digital rectal examinations (DRE), transrectal ultrasound (TRUS), and prostate-specific antigen (PSA).
Economic study type
A hypothetical cohort of men 55-70 years of age.
The practice setting was hospital. The study was carried out in the Urology Department of Soder Hospital, Stockholm, Sweden.
Dates to which data relate
The effectiveness and resource data were taken from January 1988 to June 1989. The price date was 1990.
Source of effectiveness data
Link between effectiveness and cost data
Costing was undertaken alongside the effectiveness study and using the same patient sample.
From the 26,602 men in the catchment area, 2,400 men (9%) were randomly selected for examination. Written information was mailed to those selected, followed by further information and an appointment for examination. Of the 2,400 men invited to participate, 1,782 (74%) underwentDRE, TRUS and PSA. In 17% of the study population, 80% of the detected cancers were found.
Case series from a single centre. The follow-up re-examination and repeat biopsies to patients in strategies 3, 5, and 6, took 6 hours, 23 hours, and 9 hours, respectively.
Analysis of effectiveness
The results did not depend on the principle used in the data analysis. The primary health outcomes were positive predictive values (PPVs) for different combinations of findings by DRE, TRUS, and PSA. The reference test was biopsy.
Of the 1,782 (74%) men who underwent DRE, TRUS and PSA analysis, 65 (3.6%) were detected for prostate cancer.42 (2.4%) of the cancers were detected by DRE, 20 (1.1%) at TRUS, and the number detected at stage T2A or less was doubled.371 individuals underwent biopsy, resulting in 413 biopsies performed (11.5% repeat biopsy).
The DRE Positive Predictive Values for prostate cancer were:
22% for PSA unknown,
6% for PSA values 0-3.9 ng/ml,
49% for PSA values >=4 ng/ml,
64% for PSA values >=7 ng/ml.
The DRE with positive findings plus a negative TRUS result had Positive Predictive Value figures:
4% for PSA unknown,
1% for PSA values 0-3.9 ng/ml,
16% for PSA values >=4 ng/ml,
29% for PSA values >=7 ng/ml.
The PPV of a negative DRE result plus a TRUS positive finding was
14% for PSA unknown,
6% for PSA values 0-3.9 ng/ml,
39% for PSA values >=4 ng/ml,
43% for PSA values >=7 ng/ml.
A positive result in both DRE and TRUS examinations had a PPV:
38% for PSA unknown,
12% for PSA values 0-3.9 ng/ml,
62% for PSA values >=4 ng/ml,
71% for PSA values >=7 ng/ml.
A decision tree structure was used showing the costs and clinical outcomes of the 6 different screening strategies. The model incorporated the detection rates and resource use in each phase, based on the study data.
Measure of benefits used in the economic analysis
The measure of benefits was the number of cancers detected, number of small cancers diagnosed (T2A or less), and number of patients given treatment for cure. A decision model was used in the estimation of these benefits.
Cost calculations were based on the actual annual costs for 1990. The mean exchange rate used was $1=SEK5.90 for 1990. Capital costs included depreciation and running costs. Quantities and costs were analysed separately. Total costs included capital costs, direct costs, travel costs and costs due to complications. Direct costs for both the programme and the patient were included in the analysis. Estimation of the quantities and costs were based on actual data. The sources of quantity/cost data were the Swedish Cancer Registry and the internal hospital accounts for 1990. Total costs were calculated using a model. The price year was 1990.
Indirect costs comprised participants' costs due to absence from work and loss of leisure time. The calculations were estimated from distributed questionnaires and based on the average age-related hourly income. Quantities and costs were calculated for the patient and were based on actual data from Statistics Sweden (Stockholm 1990) and unpublished background data for the 1990 yearbook.45% of the study population were gainfully employed. The value of foregone leisure time was estimated to be 25% of working time. Indirect costs were incorporated into total costs using a model. The price year was 1990.
Sensitivity analysis was not performed.
Estimated benefits used in the economic analysis
For every 1,000 individuals examined results were as follows for each of the sub-groups 1 to 6:
Number of individuals who had biopsy: 109, 137, 90, 22, 49, and 20,
Total number of biopsies performed: 122, 153, 100, 24, 55, and 22,
Total cancers detected: 24, 33, 36, 20, 26, and 32,
Number of tumours of stage T2A or less detected: 6, 10, 12, 4, 6, and 9,
Treatment for cure was given to: 15, 20, 23, 12, 18, and 21 individuals.
For strategies 1 to 6 the total costs per 1,000 patients examined were $74,5000, $97,500, $160,900, $71,200, $82,600, and $116,100, respectively.
Synthesis of costs and benefits
Using a baseline strategy with the lowest total costs (i.e. strategy 4) for comparison, by performing strategy 1 the number potentially cured increased from 12 to 15 and the incremental cost for each additional case was $1,100.
Compared to strategy 5 the number increased from 15 (with DRE) to 18 and the incremental cost was $2,700. Strategy 2 further increased the number of patients from 18 to 20 at an incremental cost of $7,450.
Performing strategy 6 increased the number from 20 to 21 and the incremental costs increased steeply to $18,600. Strategy 3 compared to strategy 6, increased the number of patients given treatment for cure from 21 to 23 and the incremental costs increased to $22,400.
Extrapolated from the outcome in the study to a nationwide Swedish screening, strategy 4 would detect roughly 9,500 prostate cancers at a cost of $35.2 million in the first screening round, while the most effective strategy (strategy 6), would detect 17,000 prostate cancers at a cost of $76.1 million.
The cost-effectiveness of strategies 1 and 2 is in the same range and may seem favourable. However, strategy 1 might seem less appropriate since it detects only two thirds of cancers treated for cure, while strategy 2 would probably occupy too many urological resources and would raise problems concerning availability. Strategy 4 detects only 50% of the tumours treated for cure, and has a lower cost-effectiveness than strategies 1 and 2. Strategy 3 had the highest diagnostic yield and also a lower cost-effectiveness due to total costs. Strategy 5 was the most cost-effectiveness strategy and detected 80% of the cancers actually treated for cure. Strategy 6 had a somewhat lower cost-effectiveness, but detected 90% of the cancers treated for cure.
This was a well conducted study as regards sample representation and cost description. However the study design is likely to introduce bias to the results. The authors' assumption that the ratios between various costs are independent of the general cost level and that comparison between various screenings strategies might therefore be valid for the Western world in general, does not take into consideration the social, cultural and economic conditions of those countries.
Source of funding
Supported by grants from the Gunvor and Josef Aner Foundation, the Sigurd and Elsa Golje Memory Trust and the Maud and Birger Gustafsson Trust.
Gustafsson O, Carlsson P, Norming U, Nyman C R, Svensson H. Cost-effectiveness analysis in early detection of prostate cancer: an evaluation of six screening strategies in a randomly selected population of 2,400 men. Prostate 1995; 26(6): 299-309
Subject indexing assigned by NLM
Aged; Cost-Benefit Analysis; Humans; Male; Mass Screening /economics /methods; Middle Aged; Physical Examination; Predictive Value of Tests; Prostate-Specific Antigen /blood; Prostatic Neoplasms /diagnosis /economics /immunology /ultrasonography; Rectum; Sweden; Time and Motion Studies
Date bibliographic record published
Date abstract record published