Breast cancer mortality in organised mammography screening in Denmark: comparative study

Contribution of early detection and adjuvant treatments to breast cancer mortality reduction in Catalonia, Spain

Background

Reductions in breast cancer (BC) mortality in Western countries have been attributed to the use of screening mammography and adjuvant treatments. The goal of this work was to analyze the contributions of both interventions to the decrease in BC mortality between 1975 and 2008 in Catalonia.

Methodology/Principal Findings

A stochastic model was used to quantify the contribution of each intervention. Age standardized BC mortality rates for calendar years 1975–2008 were estimated in four hypothetical scenarios: 1) Only screening, 2) Only adjuvant treatment, 3) Both interventions, and 4) No intervention. For the 30–69 age group, observed Catalan BC mortality rates per 100,000 women-year rose from 29.4 in 1975 to 38.3 in 1993, and afterwards continuously decreased to 23.2 in 2008. If neither of the two interventions had been used, in 2008 the estimated BC mortality would have been 43.5, which, compared to the observed BC mortality rate, indicates a 46.7% reduction. In 2008 the reduction attributable to screening was 20.4%, to adjuvant treatments was 15.8% and to both interventions 34.1%.

Conclusions/Significance

Screening and adjuvant treatments similarly contributed to reducing BC mortality in Catalonia. Mathematical models have been useful to assess the impact of interventions addressed to reduce BC mortality that occurred over nearly the same periods.

Trends in incidence and detection of advanced breast cancer at biennial screening mammography in The Netherlands: a population based study

Introduction

The aims of this study were to determine trends in the incidence of advanced breast cancer at screening mammography and the potential of screening to reduce it.

Methods

We included a consecutive series of 351,009 screening mammograms of 85,274 women aged 50-75 years, who underwent biennial screening at a Dutch breast screening region in the period 1997-2008. Two screening radiologists reviewed the screening mammograms of all advanced screen detected and advanced interval cancers and determined whether the advanced cancer (tumor > 20 mm and/or lymph node positive tumor) had been visible at a previous screen. Interval cancers were breast cancers diagnosed in women after a negative screening examination (defined as no recommendation for referral) and before any subsequent screen. Patient and tumor characteristics were compared between women with advanced cancer and women with non-advanced cancer, including ductal carcinoma in situ.

Results

A total of 1,771 screen detected cancers and 669 interval cancers were diagnosed in 2,440 women. Rates of advanced cancer remained stable over the 12-year period; the incidence of advanced screen-detected cancers fluctuated between 1.5 - 1.9 per 1,000 screened women (mean 1.6 per 1,000) and of advanced interval cancers between 0.8 - 1.6 per 1,000 screened women (mean 1.2 per 1,000). Of the 570 advanced screen-detected cancers, 106 (18.6%) were detected at initial screening; 265 (46.5%) cancers detected at subsequent screening had been radiologically occult at the previous screening mammogram, 88 (15.4%) had shown a minimal sign, and 111 (19.5%) had been missed. Corresponding figures for advanced interval cancers were 50.9% (216/424), 24.3% (103/424) and 25.1% (105/424), respectively. At multivariate analysis, women with a ≥ 30 months interval between the latest two screens had an increased risk of screen-detected advanced breast cancer (OR 1.63, 95%CI: 1.07-2.48) and hormone replacement therapy increased the risk of advanced disease among interval cancers (OR 3.04, 95%CI: 1.22-7.53).

Conclusion

We observed no decline in the risk of advanced breast cancer during 12 years of biennial screening mammography. The majority of these cancers could not have been prevented through earlier detection at screening.

Balancing harms and benefits of service mammography screening programs: a cohort study

INTRODUCTION

The use of screening mammography is still under debate within the medical community. The aim of this study is to define a balance sheet of benefits (breast cancer mortality reduction) and harms (overdiagnosis) for mammography screening programs.

METHODS

We compared breast cancer incidence and mortality in two cohorts of women, defined as 'attenders' or 'non-attenders' on the basis of the individual attitudes towards screening, who were invited to the first round of the Florentine screening program. The effects of screening exposure on breast cancer incidence and mortality were evaluated by fitting Poisson regression models adjusted for age at entry, marital status and deprivation index. We performed a sensitivity analysis excluding 34 women not responding to the invitation with a breast cancer diagnosis in the following six months.

RESULTS

In total, we included 51,096 women aged 50 to 69 years invited at the first screening round (1991 to 1993) and followed-up for breast cancer incidence and mortality until 31 December 2007 and 31 December 2008, respectively The estimate of mortality reduction varies from 45% among 50 to 59 year-old women up to 51% among 60 to 69 year-old women. The estimate of overdiagnosis, according to the cumulative-incidence method, is an additional 10% of all breast cancer cases among 60 to 69 year-old women screened.

CONCLUSIONS

Comparing the breast cancer mortality and breast cancer incidence between attenders and non-attenders, we have determined that the overall cost to save one life corresponds to no more than one over-diagnosed tumor (from 0.6 to 1 depending on the selection criteria of the cohort), even if a residual self-selection bias cannot be excluded.

Health beliefs as predictors of breast cancer screening behaviour in a group of female employees in shiraz

BACKGROUND

The purpose of the present study was to investigate the frequency of getting such health screenings as mammography and breast self-examination among a group of women and also to identify the role of health beliefs in predicting mammography practice.

METHODS

The data were collected from a convenience sample of 113 female staff at the University of Shiraz and Shiraz University of Medical Sciences. The participants completed the Champion Health Beliefs Scale (CHBS) designed to measure patients' perception on mammography of breast cancer screening. The scale assesses health beliefs components such as perceived susceptibility, perceived benefits of mammography screening, and perceived barriers to mammography screening. The participants also answered several questions on practicing Breast Self-Examination (BSE), mammography screening behaviours and health factors such as family history of cancer, and physicians' recommendation for mammography.

RESULTS

The results indicated that 51% of women had BSE, and only 21% had a mammogram. Logistic regression showed that physician's recommendation, and the perceived barriers significantly predicted mammography screening, explaining 27% of the total variance of mammography practice. The participants who saw fewer barriers to have a mammogram and those who had been recommended to have one by their physician were more likely to get it. The present study provides some supports for the health beliefs model.

CONCLUSIONS

Data indicated that perceived barriers to have a mammogram predicted not getting one, and physicians' recommendation predicted getting a mammogram by women.

Overdiagnosis from non-progressive cancer detected by screening mammography: stochastic simulation study with calibration to population based registry data

OBJECTIVE

To quantify the magnitude of overdiagnosis from non-progressive disease detected by screening mammography, after adjustment for the potential for lead time bias, secular trend in the underlying risk of breast cancer, and opportunistic screening.

DESIGN

Approximate bayesian computation analysis with a stochastic simulation model designed to replicate standardised incidence rates of breast cancer. The model components included the lifetime probability of breast cancer, the natural course of breast cancer, and participation in organised and opportunistic mammography screening.

SETTING

Isère, a French administrative region with nearly 1.2 million inhabitants.

PARTICIPANTS

All women living in Isère and aged 50-69 during 1991-2006.

MAIN OUTCOME MEASURES

Overdiagnosis, defined as the proportion of non-progressive cancers among all cases of invasive cancer and carcinoma in situ detected 1991-2006.

RESULTS

In 1991-2006, overdiagnosis from non-progressive disease accounted for 1.5% of all cases of invasive cancer (95% credibility interval 0.3% to 2.9%) and 28.0% of all cases of carcinoma in situ (2.2% to 59.8%) detected either clinically or by screening mammography in Isère. When analysis was restricted to the cancers detected by screening mammography only, the estimates of overdiagnosis were 3.3% (0.7% to 6.5%) and 31.9% (2.9% to 62.3%) for invasive cancer and carcinomas in situ, respectively.

CONCLUSION

Overdiagnosis from the detection of non-progressive disease by screening mammography was limited in 1991-2006 in Isère. Because carcinoma in situ accounted for less than 15% of all incident breast cancer cases, its contribution to overdiagnosis was relatively limited and imprecise.

The breast screening programme and misinforming the public

The information provided to the public by the NHS Breast Screening Programme has been criticized for lack of balance, omission of information on harms and substantially exaggerated estimates of benefit. These shortcomings have been particularly evident in the various invitation leaflets for breast screening and in the Programme's own 2008 Annual Review, which celebrated 20 years of screening. The debate on screening has been heated after new data published in the last two years questioned the benefit and documented substantial harm. We therefore analysed whether the recent debate and new pivotal data about breast screening has had any impact on the contents of the new 2010 leaflet and on the 2010 Annual Review. We conclude that spokespeople for the Programme have stuck to the beliefs about benefit that prevailed 25 years ago. Concerns about over-diagnosis have not been addressed either and official documents still downplay this most important harm of breast cancer screening.

Why mammography screening has not lived up to expectations from the randomised trials

We analysed the relation between tumour sizes and stages and the reported effects on breast cancer mortality with and without screening in trials and observational studies. The average tumour sizes in all the trials suggest only a 12% reduction in breast cancer mortality, which agrees with the 10% reported in the most reliable trials. Recent studies of tumour sizes and tumour stages show that screening has not lowered the rate of advanced cancers. In agreement with this, recent observational studies of breast cancer mortality have failed to find an effect of screening. In contrast, screening leads to serious harms in healthy women through overdiagnosis with subsequent overtreatment and false-positive mammograms. We suggest that the rationale for breast screening be urgently reassessed by policy-makers. The observed decline in breast cancer mortality in many countries seems to be caused by improved adjuvant therapy and breast cancer awareness, not screening. We also believe it is more important to reduce the incidence of cancer than to detect it 'early.' Avoiding getting screening mammograms reduces the risk of becoming a breast cancer patient by one-third.

Systematic skin cancer screening in Northern Germany

BACKGROUND

The incidence of skin cancer is increasing worldwide. For decades, opportunistic melanoma screening has been carried out to respond to this burden. However, despite potential positive effects such as reduced morbidity and mortality, there is still a lack of evidence for feasibility and effectiveness of organized skin cancer screening.

OBJECTIVE

The main aim of the project was to evaluate the feasibility of systematic skin cancer screening.

METHODS

In 2003, the Association of Dermatological Prevention was contracted to implement the population-based SCREEN project (Skin Cancer Research to Provide Evidence for Effectiveness of Screening in Northern Germany) in the German state of Schleswig-Holstein. A two-step program addressing malignant melanoma and nonmelanocytic skin cancer was implemented. Citizens (aged ≥ 20 years) with statutory health insurance were eligible for a standardized whole-body examination during the 12-month study period. Cancer registry and mortality data were used to assess first effects.

RESULTS

Of 1.88 million eligible citizens, 360,288 participated in SCREEN. The overall population-based participation rate was 19%. A total of 3103 malignant skin tumors were found. On the population level, invasive melanoma incidence increased by 34% during SCREEN. Five years after SCREEN a substantial decrease in melanoma mortality was seen (men: observed 0.79/100,000 and expected 2.00/100,000; women: observed 0.66/100,000 and expected 1.30/100,000).

LIMITATIONS

Because of political reasons (resistance as well as lack of support from major German health care stakeholders), it was not possible to conduct a randomized controlled trial.

CONCLUSIONS

The project showed that large-scale systematic skin cancer screening is feasible and has the potential to reduce skin cancer burden, including mortality. Based on the results of SCREEN, a national statutory skin cancer early detection program was implemented in Germany in 2008.

Mammography Screening: Keeping Women Alive

Evaluation of: Tabár L, Vitak B, Chen TH et al. Swedish Two-County Trial: impact of mammographic screening on breast cancer mortality during 3 decades. Radiology 260(3), 658–663 (2011). In the 1980s, the periodic invitation of women aged 40–69 years for mammographic screening in the Swedish Two-County Trial showed a strong 30% reduction in breast cancer mortality. The result of 2–3-yearly mammographic examinations has persisted throughout the long follow-up of three decades. Through the richness of the collected and verified data, the trial has also demonstrated a substantial and absolute reduction in mortality risk. For each 414 women screened for 7 years (approximately four screening examinations), one breast cancer death was prevented. Transferring these outcomes to, for example, the national program of the UK, for every 1000 women aged 47–73 years attending the 3-yearly screenings (nine screening examinations) at least five to seven breast cancer deaths would be prevented. In recent follow-up papers by the Swedish trial group, the major human cost of screening (false-positive outcome, occurrence of interval cancer, overdiagnosis and radiation exposure) were judged to be in balance with the accurately demonstrated mortality benefit.

Adjuvant therapy, not mammographic screening, accounts for most of the observed breast cancer specific mortality reductions in Australian women since the national screening program began in 1991

There has been a 28% reduction in age-standardised breast cancer mortality in Australia since 1991 when the free national mammographic program (BreastScreen) began. Therefore, a comparative study between BreastScreen participation and breast cancer age specific mortality trends in Australia was undertaken for two time periods between 1991 and 2007, where women aged 50-59 and 60-69 years, who were invited to screen, were compared to women aged 40-49 and 70-79 years who were not invited, but who did have access to the program. There were mortality reductions in all four age groups between 1991-1992 and 2007, resulting in 5,849 (95% CI 4,979 to 6,718) fewer women dying of breast cancer than would have otherwise been the case. Women aged 40-49 years, who had the lowest BreastScreen participation (approximately 20%), had the largest mortality reduction: 44% (95% CI 34.8-51.2). Women aged 60-69 years, who had the highest BreastScreen participation (approximately 60%), had the smallest mortality reduction: 19% (95% CI 10.5-26.9). As BreastScreen participation by invited women aged 50-69 years only reached a maximum of about 55-60% in 1998-1999, a decline in mortality in Australian women cannot be attributed to BreastScreen prior to this time. Thus, almost 60% of the Australian decline in breast cancer mortality since 1991 cannot be attributed to BreastScreen. Therefore, mammographic screening cannot account for most of the reductions in breast cancer mortality that have occurred in Australian women since 1991 and may have contributed to over-diagnosis. Most, if not all, of the reductions can be attributed to the adjuvant hormonal and chemotherapy, which Australian women have increasingly received since 1986.

Register-based studies of cancer screening effects

INTRODUCTION

There are two organised cancer screening programmes in Denmark, against cervical and breast cancers. The aim with this study was to give an overview of the available register-based research regarding these two programmes, to demonstrate the usefulness of data from the national registers.

RESEARCH TOPICS

The register-based studies on cancer screening in Denmark could be grouped into research concerning effectiveness, in terms of mortality and incidence reduction, short-term indicators, e.g. in relation to recommended quality assurance indicators, and side effects, e.g. as false-positive results and overdiagnosis.

CONCLUSION

The results indicate that registers have proven to be a valuable tool in evaluating the effects of ongoing screening activities. As they cannot be systematically used to test new screening technologies, register-based studies should not be seen as an alternative to randomised controlled trials, but as a supplement.

An investigation of the apparent breast cancer epidemic in France: screening and incidence trends in birth cohorts

BACKGROUND

Official descriptive data from France showed a strong increase in breast-cancer incidence between 1980 to 2005 without a corresponding change in breast-cancer mortality. This study quantifies the part of incidence increase due to secular changes in risk factor exposure and in overdiagnosis due to organised or opportunistic screening. Overdiagnosis was defined as non progressive tumours diagnosed as cancer at histology or progressive cancer that would remain asymptomatic until time of death for another cause.

METHODS

Comparison between age-matched cohorts from 1980 to 2005. All women residing in France and born 1911-1915, 1926-1930 and 1941-1945 are included. Sources are official data sets and published French reports on screening by mammography, age and time specific breast-cancer incidence and mortality, hormone replacement therapy, alcohol and obesity. Outcome measures include breast-cancer incidence differences adjusted for changes in risk factor distributions between pairs of age-matched cohorts who had experienced different levels of screening intensity.

RESULTS

There was an 8-fold increase in the number of mammography machines operating in France between 1980 and 2000. Opportunistic and organised screening increased over time. In comparison to age-matched cohorts born 15 years earlier, recent cohorts had adjusted incidence proportion over 11 years that were 76% higher [95% confidence limits (CL) 67%, 85%] for women aged 50 to 64 years and 23% higher [95% CL 15%, 31%] for women aged 65 to 79 years. Given that mortality did not change correspondingly, this increase in adjusted 11 year incidence proportion was considered as an estimate of overdiagnosis.

CONCLUSIONS

Breast cancer may be overdiagnosed because screening increases diagnosis of slowly progressing non-life threatening cancer and increases misdiagnosis among women without progressive cancer. We suggest that these effects could largely explain the reported "epidemic" of breast cancer in France. Better predictive classification of tumours is needed in order to avoid unnecessary cancer diagnoses and subsequent procedures.

Breast cancer screening for women ages 50 to 69 years a systematic review of observational evidence

OBJECTIVE

To systematically review the observational evidence concerning the effect of screening on breast cancer mortality in actual populations of women ages 50-69 years.

METHODS

We searched MEDLINE and multiple reference lists for relevant cohort and ecologic studies. At least 2 authors reviewed abstracts and full texts of studies meeting eligibility criteria. We rated each accepted study on standard quality criteria and developed a Summary Evidence Table.

RESULTS

Seventeen studies met eligibility criteria. Five studies found no to small effect of screening (0-12% relative risk reduction [RRR] in breast cancer mortality), 4 found a large effect (greater than 33% RRR), and 8 found a moderate effect (13% to 33% reduction). The authors found concerns about quality in all studies. There was insufficient evidence to determine whether the effectiveness of screening is decreasing over time.

CONCLUSIONS

Current observational evidence shows that breast cancer screening in actual populations of women ages 50 to 69 reduces breast cancer mortality; the magnitude of the effect is probably smaller than predicted in the randomized controlled trials. Because the magnitude may change (either increase or decrease) in the future, further ecologic studies are needed. The methodology and infrastructure for these studies should be improved.

Clinical breast examination: preliminary results from a cluster randomized controlled trial in India

A cluster randomized controlled trial was initiated in the Trivandrum district (Kerala, India) on January 1, 2006, to evaluate whether three rounds of triennial clinical breast examination (CBE) can reduce the incidence rate of advanced disease incidence and breast cancer mortality. A total of 275 clusters that included 115,652 healthy women, aged 30-69 years, were randomly allocated to intervention (CBE; 133 clusters; 55,844 women) or control (no screening; 142 clusters; 59,808 women) groups. Performance characteristics (sensitivity, specificity, false-positive rate, and positive predictive value) of CBE were evaluated. An intention-to-treat analysis was performed for comparison of incidence rates between the intervention and control groups. Preliminary results for incidence are based on follow-up until May 31, 2009, when the first round of screening was completed. Of the 50,366 women who underwent CBE, 30 breast cancers were detected among 2880 women with suspicious findings in CBE screening that warranted further investigations. Sensitivity, specificity, false-positive rate, and positive predictive value of CBE were 51.7% (95% confidence interval [CI] = 38.2% to 65.0%), 94.3% (95% CI = 94.1% to 94.5%), 5.7% (95% CI = 5.5% to 5.9%), and 1.0% (95% CI = 0.7% to 1.5%), respectively. The age-standardized incidence rates for early-stage (stage IIA or lower) breast cancer were 18.8 and 8.1 per 100,000 women and for advanced-stage (stage IIB or higher) breast cancer were 19.6 and 21.7 per 100,000 women, in the intervention and control groups, respectively.

Breast cancer mortality in neighbouring European countries with different levels of screening but similar access to treatment: trend analysis of WHO mortality database

OBJECTIVE

To compare trends in breast cancer mortality within three pairs of neighbouring European countries in relation to implementation of screening.

DESIGN

Retrospective trend analysis.

SETTING

Three country pairs (Northern Ireland (United Kingdom) v Republic of Ireland, the Netherlands v Belgium and Flanders (Belgian region south of the Netherlands), and Sweden v Norway).

DATA SOURCES

WHO mortality database on cause of death and data sources on mammography screening, cancer treatment, and risk factors for breast cancer mortality.

MAIN OUTCOME MEASURES

Changes in breast cancer mortality calculated from linear regressions of log transformed, age adjusted death rates. Joinpoint analysis was used to identify the year when trends in mortality for all ages began to change.

RESULTS

From 1989 to 2006, deaths from breast cancer decreased by 29% in Northern Ireland and by 26% in the Republic of Ireland; by 25% in the Netherlands and by 20% in Belgium and 25% in Flanders; and by 16% in Sweden and by 24% in Norway. The time trend and year of downward inflexion were similar between Northern Ireland and the Republic of Ireland and between the Netherlands and Flanders. In Sweden, mortality rates have steadily decreased since 1972, with no downward inflexion until 2006. Countries of each pair had similar healthcare services and prevalence of risk factors for breast cancer mortality but differing implementation of mammography screening, with a gap of about 10-15 years.

CONCLUSIONS

The contrast between the time differences in implementation of mammography screening and the similarity in reductions in mortality between the country pairs suggest that screening did not play a direct part in the reductions in breast cancer mortality.

Frank words about breast screening

A growing body of evidence suggests that the benefits achieved by screening for breast cancer are small, that the harm from the over-diagnosis of breast cancer arising from screening is substantial, and that, where screening is available, the observed reductions in breast cancer mortality arise largely from increased awareness and improved chemo- and hormone therapyIt is reasonable for women to choose to be screened, but only if they are completely informed about the probability of benefit versus the probability of harm. For 2000 women aged 40–49 who undergo screening for 10 years, the benefit is much smaller in terms of avoiding death from breast cancer than is the harm arising from over-diagnosis and unnecessary treatment for breast cancer, to say nothing of the increased rates of mastectomy associated with screening.These issues are not widely known to the general public.

Mammography Screening: Evidence, History and Current Practice in Germany and Other European Countries

SUMMARY: In this review, we describe the history, evidence, and current practice of mammography screening in Europe and the newly implemented screening program in Germany. We report results of the first screening rounds in North Rhine-Westphalia and compare these with reference values set by the European Guidelines for Quality Assurance in Breast Cancer Screening and Diagnosis. Finally, we summarize and compare performance indicators of the organized screening program in England, Italy, North Rhine-Westphalia and The Netherlands. Based on results of the first screening rounds, we conclude that the digital mammography screening program in North Rhine-Westphalia performs well and complies with the European guidelines. Besides relatively low attendance rates of approximately 53%, implementation of the German organized breast cancer screening program was successful.

Increasingly strong reduction in breast cancer mortality due to screening

BACKGROUND

Favourable outcomes of breast cancer screening trials in the 1970s and 1980s resulted in the launch of population-based service screening programmes in many Western countries. We investigated whether improvements in mammography and treatment modalities have had an influence on the effectiveness of breast cancer screening from 1975 to 2008.

METHODS

In Nijmegen, the Netherlands, 55,529 women received an invitation for screening between 1975 and 2008. We designed a case-referent study to evaluate the impact of mammographic screening on breast cancer mortality over time from 1975 to 2008. A total number of 282 breast cancer deaths were identified, and 1410 referents aged 50-69 were sampled from the population invited for screening. We estimated the effectiveness by calculating the odds ratio (OR) indicating the breast cancer death rate for screened vs unscreened women.

RESULTS

The breast cancer death rate in the screened group over the complete period was 35% lower than in the unscreened group (OR=0.65; 95% CI=0.49-0.87). Analysis by calendar year showed an increasing effectiveness from a 28% reduction in breast cancer mortality in the period 1975-1991 (OR=0.72; 95% CI=0.47-1.09) to 65% in the period 1992-2008 (OR=0.35; 95% CI=0.19-0.64).

CONCLUSION

Our results show an increasingly strong reduction in breast cancer mortality over time because of mammographic screening.

Rational and irrational issues in breast cancer screening

Evidence on the efficacy of breast screening from randomized controlled trials conducted in the last decades of the 1900s is reviewed. For decades, controversy about their results has centered on the magnitude of benefit in terms of breast cancer mortality reduction that can be achieved. However more recently, several expert bodies have estimated the benefits to be smaller than initially expected and concerns have been raised about screening consequences such as over-diagnosis and unnecessary treatment. Trials with substantial mortality reduction have been lauded and others with null effects have been critiqued. Critiques of the Canadian National Breast Screening Study are refuted. Extreme responses by screening advocates to the United States Preventive Services Task Force 2009 guidelines are described. The role vested interests play in determining health policy is clearly revealed in the response to the guidelines and should be more generally known. A general reluctance to explore unexpected results or to accept new paradigms is briefly discussed.

Descriptive epidemiology of breast cancer in Vojvodina

The main aim of our study was to perform the epidemiological analysis of the breast cancer in Autonomous Province of Vojvodina, Republic of Serbia, in 15 years period (1987-2001). Descriptive method was used in epidemiological analysis of the data from the Vojvodina cancer registry. According to our results the breast cancer is the most frequent neoplasm in women in Vojvodina (26.54% of all cancers), and the leading cause of mortality (20.97%). Linear trend for both incidence and mortality crude and standardized rates showed the significant and unfavorable increase from 1987 to 2001.

Population-based screening for colorectal cancer with faecal occult blood test--do we really have enough evidence?

INTRODUCTION

Population-based randomised controlled trials (RCT) have shown that invitation to biennial screening with faecal occult blood testing (FOBT) during 10 or more years reduced colorectal cancer-specific mortality. These results have stimulated plans to introduce mass screening in various countries; however, none of these trials has been able to show any reduction of total mortality, which should be expected with reduced disease-specific mortality in a RCT.

METHODS

The aim of this review is to analyse, in more detail, the findings in these trials. The results of the trials have, in this review, been systematised and discussed in the context of potential bias, validity and effectiveness.

RESULTS

It is found that the reduced cancer-specific mortality is modest and that the clinical significance may be discussed. The number of persons needed to be invited for multiple screening rounds to avoid one death in colorectal cancer (CRC) is high, ranging from about 600 to 1,200. A remarkable finding is that only one fourth of the carcinomas in those invited to the screening were actually detected by this intervention. The absence of reduced total mortality in all series is a serious problem and evokes questions about the validity in determination of cause of death. None of these trials showed any effect on incidence of CRC by removal of precancerous adenomas.

CONCLUSIONS

It seems reasonable to conclude that the scientific evidence to support introduction of population-based screening programmes with FOBT appears not yet strong enough. In addition, harm/benefit and cost/effectiveness ratios are not well determined.