Recognizing the Limitations of Cancer Overdiagnosis Studies: A First Step Towards Overcoming Them

Do doctors and other healthcare professionals know overdiagnosis in screening and how are they dealing with it? A protocol for a mixed methods systematic review

INTRODUCTION

Overdiagnosis is the diagnosis of a disease that would never have caused any symptom or problem. It is a harmful side effect of screening and may lead to unnecessary treatment, costs and emotional drawbacks. Doctors and other healthcare professionals (HCPs) have the opportunity to mitigate these consequences, not only by informing their patients or the public but also by adjusting screening methods or even by refraining from screening. However, it is unclear to what extent HCPs are fully aware of overdiagnosis and whether it affects their screening decisions. With this systematic review, we aim to synthesise all available research about what HCPs know and think about overdiagnosis, how it affects their position on screening policy and whether they think patients and the public should be informed about it.

METHODS AND ANALYSIS

We will systematically search several databases (MEDLINE, Embase, Web of Science, Scopus, CINAHL and PsycArticles) for studies that directly examine HCPs' knowledge and subjective perceptions of overdiagnosis due to health screening, both qualitatively and quantitatively. We will optimise our search by scanning reference and citation lists, contacting experts in the field and hand searching abstracts from the annual conference on 'Preventing Overdiagnosis'. After selection and quality appraisal, we will analyse qualitative and quantitative findings separately in a segregated design for mixed-method reviews. The data will be examined and presented descriptively. If the retrieved studies allow it, we will review them from a constructivist perspective through a critical interpretive synthesis.

ETHICS AND DISSEMINATION

For this type of research, no ethical approval is required. Findings from this systematic review will be published in a peer-reviewed journal and presented at the annual congress of 'Preventing Overdiagnosis'. In addition, the results will serve as guidance for further research on this topic.

PROSPERO REGISTRATION NUMBER

CRD42021244513.

National, sub-national, and risk-attributed burden of thyroid cancer in Iran from 1990 to 2019

An updated exploration of the burden of thyroid cancer across a country is always required for making correct decisions. The objective of this study is to present the thyroid cancer burden and attributed burden to the high Body Mass Index (BMI) in Iran at national and sub-national levels from 1990 to 2019. The data was obtained from the GBD 2019 study estimates. To explain the pattern of changes in incidence from 1990 to 2019, decomposition analysis was conducted. Besides, the attribution of high BMI in the thyroid cancer DALYs and deaths were obtained. The age-standardized incidence rate of thyroid cancer was 1.57 (95% UI: 1.33–1.86) in 1990 and increased 131% (53–191) until 2019. The age-standardized prevalence rate of thyroid cancer was 30.19 (18.75–34.55) in 2019 which increased 164% (77–246) from 11.44 (9.38–13.85) in 1990. In 2019, the death rate, and Disability-adjusted life years of thyroid cancer was 0.49 (0.36–0.53), and 13.16 (8.93–14.62), respectively. These numbers also increased since 1990. The DALYs and deaths attributable to high BMI was 1.91 (0.95–3.11) and 0.07 (0.04–0.11), respectively. The thyroid cancer burden and high BMI attributed burden has increased from 1990 to 2019 in Iran. This study and similar studies’ results can be used for accurate resource allocation for efficient management and all potential risks’ modification for thyroid cancer with a cost-conscious view.

Harm-to-Benefit of Three Decades of Prostate Cancer Screening in Black Men

BACKGROUND

Prostate-specific antigen screening has profoundly affected the epidemiology of prostate cancer in the United States. Persistent racial disparities in outcomes for Black men warrant re-examination of the harms of screening relative to its cancer-specific mortality benefits in this population.

METHODS

We estimated overdiagnoses and overtreatment of prostate cancer for men of all races and for Black men 50 to 84 years of age until 2016, the most recent year with treatment data available, using excess incidence relative to 1986 based on the Surveillance, Epidemiology, and End Results registry and U.S. Census data as well as an established microsimulation model of prostate cancer natural history. Combining estimates with plausible mortality benefit, we calculated numbers needed to diagnose (NND) and treat (NNT) to prevent one prostate cancer death.

RESULTS

For men of all races, we estimated 1.5 to 1.9 million (range between estimation approaches) overdiagnosed and 0.9 to 1.5 million overtreated prostate cancers by 2016. Assuming that half of the 270,000 prostate cancer deaths avoided by 2016 were attributable to screening, the NND and the NNT would be 11 to 14 and 7 to 11 for men of all races and 8 to 12 and 5 to 9 for Black men, respectively. Alternative estimates incorporating a lag between incidence and mortality resulted in a NND and a NNT for Black men that reached well into the low single digits.

CONCLUSIONS

Complementary approaches to quantifying overdiagnosis indicate a harm-benefit tradeoff of prostate-specific antigen screening that is more favorable for Black men than for men of all races considered together. Our findings highlight the need to account for the increased value of screening in Black men in clinical guidelines. (Funded by the Patient-Centered Outcomes Research Institute, the National Cancer Institute, the Bristol Myers Squibb Foundation, and the Damon Runyon Cancer Research Foundation.).

Overdetection of Breast Cancer

Overdetection (often referred to as overdiagnosis) of cancer is the detection of disease, such as through a screening program, that would otherwise remain occult through an individual’s life. In the context of screening, this could occur for cancers that were slow growing or indolent, or simply because an unscreened individual would have died from some other cause before the cancer had surfaced clinically. The main harm associated with overdetection is the subsequent overdiagnosis and overtreatment of disease. In this article, the phenomenon is reviewed, the methods of estimation of overdetection are discussed and reasons for variability in such estimates are given, with emphasis on an analysis using Canadian data. Microsimulation modeling is used to illustrate the expected time course of cancer detection that gives rise to overdetection. While overdetection exists, the actual amount is likely to be much lower than the estimate used by the Canadian Task Force on Preventive Health Care. Furthermore, the issue is of greater significance in older rather than younger women due to competing causes of death. The particular challenge associated with in situ breast cancer is considered and possible approaches to avoiding overtreatment are suggested.

A simple framework to identify optimal cost-effective risk thresholds for a single screen: Comparison to Decision Curve Analysis

Decision Curve Analysis (DCA) is a popular approach for assessing biomarkers and risk models, but does not require costs and thus cannot identify optimal risk thresholds for actions. Full decision analyses can identify optimal thresholds, but typically used methods are complex and often difficult to understand. We develop a simple framework to calculate the Incremental Net Benefit for a single-time screen as a function of costs (for tests and treatments) and effectiveness (life-years gained). We provide simple expressions for the optimal cost-effective risk-threshold and, equally importantly, for the monetary value of life-years gained associated with the risk-threshold. We consider the controversy over the risk-threshold to screen women for mutations in BRCA1/2. Importantly, most, and sometimes even all, of the thresholds identified by DCA are infeasible based on their associated dollars per life-year gained. Our simple framework facilitates sensitivity analyses to cost and effectiveness parameters. The proposed approach estimates optimal risk thresholds in a simple and transparent manner, provides intuition about which quantities are critical, and may serve as a bridge between DCA and a full decision analysis.

Increasing Gap Between Thyroid Cancer Incidence and Mortality in Urban Shanghai, China: An Analysis Spanning 43 Years

OBJECTIVE

To examine the secular trends of thyroid cancer incidence and mortality and to estimate the proportion of thyroid cancer cases potentially attributable to overdiagnosis.

METHODS

Data on thyroid cancer cases from 1973 to 2015 were obtained from the Shanghai Cancer Registry. The average annual percent change (AAPC) was evaluated using the joinpoint regression analysis. The age, period, and birth cohort effects were assessed using an age-period-cohort model. The overdiagnosis of thyroid cancer cases was estimated based on the difference between observed and expected incidences using the rates of Nordic countries as reference.

RESULTS

From 1973 to 2015, the number of thyroid cancer cases was 23 117, and 75% of the patients were women. The age-standardized rates were seven- to eightfold higher from 2013 to 2015 than from 1973 to 1977. Compared with relatively stable mortality, thyroid cancer incidence was dramatically increased from 2002 to 2015 in both sexes, with significant trends (men: AAPC = 21.84%, 95% CI: 18.77%-24.98%, P < .001; women: AAPC = 18.55%, 95% CI: 16.49%-20.64%, P < .001). The proportion of overdiagnosis has gradually increased over time, rising from 68% between 2003 and 2007 to more than 90% between 2013 and 2015. This increasing trend appeared to be similar between men and women.

CONCLUSION

An increasing gap between thyroid cancer incidence and mortality was observed in Shanghai, and overdiagnosis has contributed substantially to the rise of incidence, which calls for an urgent update on the practice of thyroid examination.

Overdiagnosis: one concept, three perspectives, and a model

Defining, estimating, communicating about, and dealing with overdiagnosis is challenging. One reason for this is because overdiagnosis is a complex phenomenon. In this article we try to show that the complexity can be analysed and addressed in terms of three perspectives, i.e., that of the person, the professional, and the population. Individuals are informed about overdiagnosis based on population-based estimates. These estimates depend on professionals' conceptions and models of disease and diagnostic criteria. These conceptions in turn depend on individuals' experience of suffering, and on population level outcomes from diagnostics and treatment. As the personal, professional, and populational perspectives are not easy to reconcile, we must address them explicitly and facilitate interaction. Population-based estimates of overdiagnosis must be more directly informed by personal need for information. So must disease definitions and diagnostic criteria. Only then can individuals be appropriately informed about overdiagnosis.

Personalized early detection and prevention of breast cancer: ENVISION consensus statement

The European Collaborative on Personalized Early Detection and Prevention of Breast Cancer (ENVISION) brings together several international research consortia working on different aspects of the personalized early detection and prevention of breast cancer. In a consensus conference held in 2019, the members of this network identified research areas requiring development to enable evidence-based personalized interventions that might improve the benefits and reduce the harms of existing breast cancer screening and prevention programmes. The priority areas identified were: 1) breast cancer subtype-specific risk assessment tools applicable to women of all ancestries; 2) intermediate surrogate markers of response to preventive measures; 3) novel non-surgical preventive measures to reduce the incidence of breast cancer of poor prognosis; and 4) hybrid effectiveness-implementation research combined with modelling studies to evaluate the long-term population outcomes of risk-based early detection strategies. The implementation of such programmes would require health-care systems to be open to learning and adapting, the engagement of a diverse range of stakeholders and tailoring to societal norms and values, while also addressing the ethical and legal issues. In this Consensus Statement, we discuss the current state of breast cancer risk prediction, risk-stratified prevention and early detection strategies, and their implementation. Throughout, we highlight priorities for advancing each of these areas.

Thyroid Cancer Incidence in India Between 2006 and 2014 and Impact of Overdiagnosis

CONTEXT/OBJECTIVE

Increases of thyroid cancer (TC) incidence emerged in the past several decades in several countries. This study aimed to estimate time trends of TC incidence in India and the proportion of TC cases potentially attributable to overdiagnosis by sex, age, and area.

DESIGN

TC cases aged 0 to 74 years reported to Indian cancer registries during 2006 through 2014 were included. Age-standardized incidence rates (ASR) and TC overdiagnosis were estimated by sex, period, age, and area.

RESULTS

Between 2006 to 2008 and 2012 to 2014, the ASRs for TC in India increased from 2.5 to 3.5/100,000 women (+37%) and from 1.0 to 1.3/100,000 men (+27%). However, up to a 10-fold difference was found among regions in both sexes. Highest ASRs emerged in Thiruvananthapuram (14.6/100,000 women and 4.1/100,000 men in 2012-2014), with 93% increase in women and 64% in men compared with 2006 to 2008. No evidence of overdiagnosis was found in Indian men. Conversely, overdiagnosis accounted for 51% of TC in Indian women: 74% in those aged < 35 years, 50% at ages 35 to 54 years, and 30% at ages 55 to 64 years. In particular, 80% of TC overdiagnosis in women emerged in Thiruvananthapuram, whereas none or limited evidence of overdiagnosis emerged in Kamrup, Dibrugarh, Bhopal, or Sikkim.

CONCLUSIONS

Relatively high and increasing TC ASRs emerged in Indian regions where better access to health care was reported. In India, as elsewhere, new strategies are needed to discourage opportunistic screening practice, particularly in young women, and to avoid unnecessary and expensive treatments. Present results may serve as a warning also for other transitioning countries.

Global Burden of Thyroid Cancer From 1990 to 2017

IMPORTANCE

Thyroid cancer is the most pervasive endocrine cancer worldwide. Studies examining the association between thyroid cancer and country, sex, age, sociodemographic index (SDI), and other factors are lacking.

OBJECTIVE

To examine the thyroid cancer burden and variation trends at the global, regional, and national levels using data on sex, age, and SDI.

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study, epidemiologic data were gathered using the Global Health Data Exchange query tool, covering persons of all ages with thyroid cancer in 195 countries and 21 regions from January 1, 1990, to December 31, 2017; data analysis was completed on October 1, 2019. All participants met the Global Burden of Disease Study inclusion criteria.

MAIN OUTCOMES AND MEASURES

Outcomes included incidence, deaths, and disability-adjusted life-years (DALYs) of thyroid cancer. Measures were stratified by sex, region, country, age, and SDI. The estimated annual percentage changes (EAPCs) and age-standardized rates were calculated to evaluate the temporal trends.

RESULTS

Increases of thyroid cancer were noted in incident cases (169%), deaths (87%), and DALYs (75%). Age-standardized incidence rate (ASIR) showed an upward trend over time, with an EAPC of 1.59 (95% CI, 1.51-1.67); decreases were noted in EAPCs of age-standardized death rate (-0.15; 95% CI, -0.19 to -0.12) and age-standardized DALY rate (-0.11; 95% CI, -0.15 to -0.08). Almost half (41.73% for incidence, 50.92% for deaths, and 54.39% for DALYs) of the thyroid cancer burden was noted in Southern and Eastern Asia. In addition, females accounted for most of the thyroid cancer burden (70.22% for incidence, 58.39% for deaths, and 58.68% for DALYs) and increased by years in this population, although the ASIR of males with thyroid cancer (EAPC, 2.18; 95% CI, 2.07-2.28) increased faster than that of females (EAPC, 1.38; 95% CI, 1.30-1.46). A third (34%) of patients with thyroid cancer resided in countries with a high SDI, and most patients were aged 50 to 69 years, which was older than the age in other quintiles (high SDI quintile compared with all other quintiles, P<.05). The most common age at onset of thyroid cancer worldwide was 15 to 49 years in female individuals compared with 50 to 69 years in male individuals (P<.05). Death from thyroid cancer was concentrated in participants aged 70 years or older and increased by years (average annual percentage change, 0.10; 95% CI, 0.01-0.21; P<.05). Furthermore, people in lower SDI quintiles developed thyroid cancer and died from it earlier than those in other quintiles (high and high-middle SDI vs low and low-middle SDI, P<.05).

CONCLUSIONS AND RELEVANCE

Data from this study suggest considerable heterogeneity in the epidemiologic patterns of thyroid cancer across sex, age, SDI, region, and country, providing information for governments that may help improve national and local cancer control policies.

An exploration for quantification of overdiagnosis and its effect for breast cancer screening

Objective

To redefine overdiagnosis and reestimate the proportion of overdiagnosis of breast cancer caused by screening based on the Surveillance, Epidemiology, and End Results (SEER, 1973−2015) Program data.

Methods

The breast cancer diagnosed before 1977 was defined as the no-screening cohort since America had initiated breast cancer screening from 1977. The breast cancer diagnosed in 1999 was defined as the screening cohort due to no increases in both the proportion of early-stage breast cancer until 1999 and the overall survival of early-stage breast cancer diagnosed over the three years since 1999. The magnitude of overdiagnosis was calculated as the difference in the proportions of early-stage breast cancer patients with long-time (15-year) survival to all breast cancer patients between two cohorts.

Results

Over 23 years before and after widespread screening in America, the proportion of early-stage breast cancer patients increased from 52.1% (16,891/32,443) to 72.7% (16,021/22,025) (P<0.001). The 15-year survival rate of early-stage breast cancer patients increased from 51.1% to 61.5% (P<0.001), while the proportions of early-stage breast cancer patients with long-time survival to all breast cancer patients increased from 26.6% (52.1%×51.1%) to 44.7% (72.7%×61.5%). Assuming no improvements in cancer screening technology and treatment technology, 18.1% (44.7%−26.6%) of breast cancer patients were overdiagnosed associated with screening. The age-specific overdiagnosis rates were 18.9%, 24.7%, 24.5%, 20.5%, and 8.3% for breast cancer patients aged 40−49, 50−59, 60−69, 70−74, and ≥75 years old, respectively.

Conclusions

Overdiagnosis caused by mammographic screening is probably overestimated in current screening practices. Further trials with more sophisticated designs and analyses are needed to validate our findings in the future.

Cluster miRNAs and cancer: Diagnostic, prognostic and therapeutic opportunities

MiRNAs are class of noncoding RNA important for gene expression regulation in many plants, animals and viruses. MiRNA clusters contain a set of two or more miRNA encoding genes, transcribed together as polycistronic miRNAs. Currently, there are approximately 159 miRNA clusters reported in the human genome consisting of miRNAs ranging from two or more miRNA genes. A large proportion of clustered miRNAs resides in and around the fragile sites or cancer associated genomic hotspots and plays an important role in carcinogenesis. Altered expression of miRNA cluster can be pro-tumorigenic or anti-tumorigenic and can be targeted for clinical management of cancer. Over the past few years, manipulation of miRNA clusters expression is attempted for experimental purpose as well as for diagnostic, prognostic and therapeutic applications in cancer. Re-expression of miRNAs by epigenetic therapy, genome editing such as clustered regulatory interspaced short palindromic repeats (CRISPR) and miRNA mowers showed promising results in cancer therapy. In this review, we focused on the potential of miRNA clusters as a biomarker for diagnosis, prognosis, targeted therapy as well as strategies for modulating their expression in a therapeutic context. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Processing > Processing of Small RNAs RNA in Disease and Development > RNA in Disease Regulatory RNAs/RNAi/Riboswitches > Biogenesis of Effector Small RNAs.

Thyroid cancer in Friuli Venezia Giulia, northeastern Italy: incidence, overdiagnosis, and impact of type of surgery on survival

BACKGROUND

Incidence rates of thyroid cancer (TC) increased in the last decades worldwide. This study aimed to describe TC incidence in the Friuli Venezia Giulia (FVG) region, to estimate the quota of overdiagnosis, and to investigate the impact of surgery on long-term survival after TC diagnosis.

METHODS

TC cases reported to the FVG population-based cancer registry during 2002-2013, aged <85 years, were included. Age standardized rates (ASR) on the European population were computed, while proportion of TC overdiagnosis was estimated in comparison with expected age-specific incidence rates from published time series. Adjusted hazard ratios of death, with 95% confidence intervals, were also estimated.

RESULTS

During 2002-2013, 1701 TC cases were reported to the FVG cancer registry, with papillary TC (78.2%) as the most frequent histologic type. ASR increased from 12.4 to 16.5 in women and from 4.3 to 6.2 in men (+33.1% and +44.2%, respectively). Overdiagnosis was estimated as 79% of TC cases in women and 64% in men. Almost all TC cases (97.1%) underwent surgery, including 84.6% of women and 78.9% of men who underwent total thyroidectomy. Up to 10 years after TC diagnosis, the type of surgery did not appear to influence survival.

CONCLUSIONS

This study documented an increase in TC incidence in FVG in the last decade, with overdiagnosis accounting for a large proportion of TC diagnoses and total thyroidectomy in more than 80% of cases. These findings suggest reconsidering thyroid screening practice and aggressive therapeutic strategies, as recommended by new TC guidelines.

As you like it: How the same data can support manifold views of overdiagnosis in breast cancer screening

Overdiagnosis estimates have varied substantially, causing confusion. The discussions have been complicated by the fact that population and study design have varied substantially between studies. To help assess the impact of study design choices on the estimates, we compared them on a single population. A cohort study from Funen County, Denmark, recently suggested little (∼1%) overdiagnosis. It followed previously screened women for up to 14 years after screening had ended. Using publically available data from Funen, we recreated the designs from five high-estimate, highly cited studies from various countries. Selected studies estimated overdiagnosis to be 25-54%. Their designs were adapted only to the extent that they reflect the start of screening in Funen in 1993. The reanalysis of the Funen data resulted in overdiagnosis estimates that were remarkably similar to those from the original high-estimate age-period studies, 21-55%. In additional analyses, undertaken to elucidate the effect of the individual components of the study designs, overdiagnosis estimates were more than halved after the most likely changes in the background risk were accounted for and decreased additionally when never-screened birth cohorts were excluded from the analysis. The same data give both low and high estimates of overdiagnosis, it all depends on the study design. This stresses the need for a careful scrutiny of the validity of the assumptions underpinning the estimates. Age-period analyses of breast cancer overdiagnosis suggesting very high frequencies of overdiagnosis rested on unmet assumptions. This study showed that overdiagnosis estimates should in the future be requested to adequately control for the background risk and include an informative selection of the studied population to achieve valid and comparable estimates of overdiagnosis.

Long-Term Active Surveillance of Screening Detected Subsolid Nodules is a Safe Strategy to Reduce Overtreatment

INTRODUCTION

Lung cancer presenting as subsolid nodule (SSN) can show slow growth, hence treating SSN is controversial. Our aim was to determine the long-term outcome of subjects with unresected SSNs in lung cancer screening.

METHODS

Since 2005, the Multicenter Italian Lung Detection (MILD) screening trial implemented active surveillance for persistent SSN, as opposed to early resection. Presence of SSNs was related to diagnosis of cancer at the site of SSN, elsewhere in the lung, or in the body. The risk of overall mortality and lung cancer mortality was tested by Cox proportional hazards model.

RESULTS

SSNs were found in 16.9% (389 of 2303) of screenees. During 9.3 ± 1.2 years of follow-up, the hazard ratio of lung cancer diagnosis in subjects with SSN was 6.77 (95% confidence interval: 3.39-13.54), with 73% (22 of 30) of cancers not arising from SSN (median time to diagnosis 52 months from SSN). Lung cancer-specific mortality in subjects with SSN was significantly increased (hazard ratio = 3.80; 95% confidence interval: 1.24-11.65) compared to subjects without lung nodules. Lung cancer arising from SSN did not lead to death within the follow-up period.

CONCLUSIONS

Subjects with SSN in the MILD cohort showed a high risk of developing lung cancer elsewhere in the lung, with only a minority of cases arising from SSN, and never representing the cause of death. These results show the safety of active surveillance for conservative management of SSN until signs of solid component growth and the need for prolonged follow-up because of high risk of other cancers.

The impact of overdiagnosis on thyroid cancer epidemic in Italy,1998-2012

AIMS

In Italy, incidence rates of thyroid cancer (TC) are among the highest worldwide with substantial intracountry heterogeneity. The aim of the study was to examine time trends of TC incidence in Italy and to estimate the proportion of TC cases potentially attributable to overdiagnosis.

METHODS

Data on TC cases reported to Italian cancer registries during 1998-2012 aged <85 years were included. Age-standardised incidence rates (ASR) were computed by sex, period, and histology. TC overdiagnosis was estimated by sex, period, age, and Italian region.

RESULTS

In Italy between 1998-2002 and 2008-2012, TC ASR increased of 74% in women (from 16.2 to 28.2/100,000) and of 90% in men (from 5.3 to 10.1/100,000). ASR increases were nearly exclusively due to papillary TC (+91% in women, +120% in men). In both sexes, more than three-fold differences emerged between regions with highest and lowest ASR. Among TC cases diagnosed in 1998-2012 in Italy, we estimated that overdiagnosis accounted for 75% of cases in women and 63% in men and increased over the study period leading to overdiagnosis of 79% in women and 67% in men in 2008-2012. Notably, overdiagnosis was over 80% among women aged <55 years, and substantial variations were documented across Italian regions, in both genders.

CONCLUSION(S)

Incidence rates of TC are steadily increasing in Italy and largely due to overdiagnosis. These findings call for an update of thyroid gland examination practices in the asymptomatic general population, at national and regional levels.

Cancer Screening in the Elderly: A Review of Breast, Colorectal, Lung, and Prostate Cancer Screening

There are relatively limited data on outcomes of screening older adults for cancer; therefore, the decision to screen older adults requires balancing the potential harms of screening and follow-up diagnostic tests with the possibility of benefit. Harms of screening can be amplified in older and frail adults and include discomfort from undergoing the test itself, anxiety, potential complications from diagnostic procedures resulting from a false-positive test, false reassurance from a false-negative test, and overdiagnosis of tumors that are of no threat and may result in overtreatment. In this paper, we review the evidence and guidelines on breast, colorectal, lung and prostate cancer as applied to older adults. We also provide a general framework for approaching cancer screening in older adults by incorporating evidence-based guidelines, patient preferences, and patient life expectancy estimates into shared screening decisions.

Estimating the frequency of indolent breast cancer in screening trials

Cancer screening can detect cancer that would not have been detected in a patient's lifetime without screening. Standard methods for analyzing screening data do not explicitly account for the possibility that a fraction of tumors may remain latent indefinitely. We extend these methods by representing cancers as a mixture of those that progress to symptoms (progressive) and those that remain latent (indolent). Given sensitivity of the screening test, we derive likelihood expressions to simultaneously estimate (1) the rate of onset of preclinical cancer, (2) the average preclinical duration of progressive cancers, and (3) the fraction of preclinical cancers that are indolent. Simulations demonstrate satisfactory performance of the estimation approach to identify model parameters subject to precise specifications of input parameters and adequate numbers of interval cancers. In application to four breast cancer screening trials, the estimated indolent fraction among preclinical cancers varies between 2% and 35% when assuming 80% test sensitivity and varying specifications for the earliest time that participants could plausibly have developed cancer. We conclude that standard methods for analyzing screening data can be extended to allow some indolent cancers, but accurate estimation depends on correctly specifying key inputs that may be difficult to determine precisely in practice.

Quantifying Overdiagnosis in Cancer Screening: A Systematic Review to Evaluate the Methodology

Background

Overdiagnosis is the main harm of cancer screening programs but is difficult to quantify. This review aims to evaluate existing approaches to estimate the magnitude of overdiagnosis in cancer screening in order to gain insight into the strengths and limitations of these approaches and to provide researchers with guidance to obtain reliable estimates of overdiagnosis in cancer screening.

Methods

A systematic review was done of primary research studies in PubMed that were published before January 1, 2016, and quantified overdiagnosis in breast cancer screening. The studies meeting inclusion criteria were then categorized by their methods to adjust for lead time and to obtain an unscreened reference population. For each approach, we provide an overview of the data required, assumptions made, limitations, and strengths.

Results

A total of 442 studies were identified in the initial search. Forty studies met the inclusion criteria for the qualitative review. We grouped the approaches to adjust for lead time in two main categories: the lead time approach and the excess incidence approach. The lead time approach was further subdivided into the mean lead time approach, lead time distribution approach, and natural history modeling. The excess incidence approach was subdivided into the cumulative incidence approach and early vs late-stage cancer approach. The approaches used to obtain an unscreened reference population were grouped into the following categories: control group of a randomized controlled trial, nonattenders, control region, extrapolation of a prescreening trend, uninvited groups, adjustment for the effect of screening, and natural history modeling.

Conclusions

Each approach to adjust for lead time and obtain an unscreened reference population has its own strengths and limitations, which should be taken into consideration when estimating overdiagnosis.

Second opinion strategies in breast pathology: a decision analysis addressing over-treatment, under-treatment, and care costs

PURPOSE

To estimate the potential near-term population impact of alternative second opinion breast biopsy pathology interpretation strategies.

METHODS

Decision analysis examining 12-month outcomes of breast biopsy for nine breast pathology interpretation strategies in the U.S. health system. Diagnoses of 115 practicing pathologists in the Breast Pathology Study were compared to reference-standard-consensus diagnoses with and without second opinions. Interpretation strategies were defined by whether a second opinion was sought universally or selectively (e.g., 2nd opinion if invasive). Main outcomes were the expected proportion of concordant breast biopsy diagnoses, the proportion involving over- or under-interpretation, and cost of care in U.S. dollars within one-year of biopsy.

RESULTS

Without a second opinion, 92.2% of biopsies received a concordant diagnosis. Concordance rates increased under all second opinion strategies, and the rate was highest (95.1%) and under-treatment lowest (2.6%) when all biopsies had second opinions. However, over-treatment was lowest when second opinions were sought selectively for initial diagnoses of invasive cancer, DCIS, or atypia (1.8 vs. 4.7% with no 2nd opinions). This strategy also had the lowest projected 12-month care costs ($5.907 billion vs. $6.049 billion with no 2nd opinions).

CONCLUSIONS

Second opinion strategies could lower overall care costs while reducing both over- and under-treatment. The most accurate cost-saving strategy required second opinions for initial diagnoses of invasive cancer, DCIS, or atypia.

Missteps in Current Estimates of Cancer Overdiagnosis

The balance between the benefits and harms of imaging-based cancer screening continues to be an area of controversy and widespread media attention. Of the potential harms, overdiagnosis from screening is likely the most elusive in estimating and quantifying. This article describes the major methodological issues with recently reported estimates of overdiagnosis that are based on excess cancer incidence, and suggests that modeling focused on tumor lead-time can serve as a complementary method for excess incidence-based overdiagnosis estimates. Radiologists should be conversant on the topic of overdiagnosis and understand the limitations of different methods used to estimate its magnitude.

Decision-Making Regarding Mammography Screening for Older Women

The population is aging, and breast cancer incidence increases with age, peaking between the ages of 75 and 79. However, it is not known whether mammography screening helps women aged 75 and older live longer because they have not been included in randomized controlled trials evaluating mammography screening. Guidelines recommend that older women with less than a 10-year life expectancy not be screened because it takes approximately 10 years before a screen-detected breast cancer may affect an older woman's survival. Guidelines recommend that clinicians discuss the benefits and risks of screening with women aged 75 and older with a life expectancy of 10 years or longer to help them elicit their values and preferences. It is estimated that two of 1,000 women who continue to be screened every other year from age 70 to 79 may avoid breast cancer death, but 12% to 27% of these women will experience a false-positive test, and 10% to 20% of women who experience a false-positive test will undergo a breast biopsy. In addition, approximately 30% of screen-detected cancers would not otherwise have shown up in an older woman's lifetime, yet nearly all older women undergo treatment for these breast cancers, and the risks of treatment increase with age. To inform decision-making, tools are available to estimate life expectancy and to educate older women about the benefits and harms of mammography screening. Guides are also available to help clinicians discuss stopping screening with older women with less than a 10-year life expectancy. Ideally, screening decisions would consider an older woman's life expectancy, breast cancer risk, and her values and preferences.

Conditions for Valid Empirical Estimates of Cancer Overdiagnosis in Randomized Trials and Population Studies

Cancer overdiagnosis is frequently estimated using the excess incidence in a screened group relative to that in an unscreened group. However, conditions for unbiased estimation are poorly understood. We developed a mathematical framework to project the effects of screening on the incidence of relevant cancers-that is, cancers that would present clinically without screening. Screening advances the date of diagnosis for a fraction of preclinical relevant cancers. Which diagnoses are advanced and by how much depends on the preclinical detectable period, test sensitivity, and screening patterns. Using the model, we projected incidence in common trial designs and population settings and compared excess incidence with true overdiagnosis. In trials with no control arm screening, unbiased estimates are available using cumulative incidence if the screen arm stops screening and using annual incidence if the screen arm continues screening. In both designs, unbiased estimation requires waiting until screening stabilizes plus the maximum preclinical period. In continued-screen trials and population settings, excess cumulative incidence is persistently biased. We investigated this bias in published estimates from the European Randomized Study of Screening for Prostate Cancer after 9-13 years. In conclusion, no trial or population setting automatically permits unbiased estimation of overdiagnosis; sufficient follow-up and appropriate analysis remain crucial.