Impressive time-related influence of the Dutch screening programme on breast cancer incidence and mortality, 1975-2006

Interpreting Breast Cancer Mortality Trends Related to Introduction of Mammography Screening: A Simulation Study

Background. Several studies have evaluated the effect of mammography screening on breast cancer mortality based on overall breast cancer mortality trends, with varied conclusions. The statistical power of such trend analyses is, however, not carefully studied. Methods. We estimated how the effect of screening on overall breast cancer mortality is likely to unfold. Because a screening effect is based on earlier treatment, screening can affect only new incident cases after screening introduction. To evaluate the likelihood of detecting screening effects on overall breast cancer mortality time trends, we calculated the statistical power of joinpoint regression analysis on breast cancer mortality trends around screening introduction using simulations. Results. We found that a very gradual increase in population-level screening effect is expected due to prescreening incident cases. Assuming 25% effectiveness of a biennial screening program in reducing breast cancer mortality among women 50 to 69 y of age, the expected reduction in overall breast cancer mortality was 3% after 2 y and reached a long-term effect of 18% after 20 y. In common settings, the statistical power to detect any screening effects using joinpoint regression analysis is very low (<50%), even in an artificial setting of constant risk of baseline breast cancer mortality over time. Conclusions. Population effects of screening on breast cancer mortality emerge very gradually and are expected to be considerably lower than the effects reported in trials excluding women diagnosed before screening. Studies of overall breast cancer mortality time trends have too low statistical power to reliably detect screening effects in most populations. Implications. Researchers and policy makers evaluating mammography screening should avoid using breast cancer mortality trend analysis that does not separate pre- and postscreening incident cases.

HIGHLIGHTS

Population-level mammography screening effects on breast cancer mortality emerge gradually following screening introduction, resulting in very low statistical power of trend analysis.Researchers and policy makers evaluating mammography screening should avoid relying on population-wide breast cancer mortality trends.Expected mammography screening effects at population level are lower than those from screening trials, as many cases of breast cancer fall outside the screening age range.

Are there employment and income gains of a national breast cancer screening program?

BACKGROUND

The Dutch national breast cancer screening program invites women aged 50-75 for screening. By detecting the disease in an early phase, the program aims to achieve lower breast cancer mortality and improve breast cancer survivors' health. Arguably, the latter also improves the employability of diagnosed women.

OBJECTIVE

This study investigates the effects of the Dutch national breast cancer screening program on diagnosed women's employment and income.

METHODS

The empirical analysis uses data of 229,357 women aged 40-59, of whom 10,515 were diagnosed with breast cancer at an age in the range 47-53. A regression-based difference-in-differences estimator is used to identify program effects by comparing outcomes for women diagnosed at ages 47-49 with the outcomes for those diagnosed at ages 50-53. The empirical models account for individual fixed effects, and for age and year fixed effects by using a control group of women who were not diagnosed with breast cancer.

RESULTS

Women's employment rates declined in the six-year period after a breast cancer diagnosis with, on average, about 3 percentage points and their incomes declined with, on average, about 5% over this period. The empirical evidence, based on a comparison of outcomes for women diagnosed at ages 47-49 with the outcomes for those diagnosed at ages 50-53 when covered by the breast cancer screening program, does not support that these declines in employment and income were affected by the program. The evidence also does not support short or medium-term survival gains of the program.

CONCLUSIONS

The findings of this study suggest that the Dutch national breast cancer screening program yields no discernible short or medium-term employment and income gains for women diagnosed with breast cancer.

Cancer incidence trends in the Czech Republic

BACKGROUND

Evaluation of time trends is an integral part of a comprehensive analysis of cancer data. Our study aimed to assess trends in cancer incidence in the period 1977-2018 in the Czech Republic.

METHODS

Cancer data were obtained from the Czech National Cancer Registry. Incidence trends were evaluated using the joinpoint regression. The overall trend for the entire analysed period and the current trend for the last 10 years were determined using the average annual percentage change.

RESULTS

In the period 1977-2018, the age-standardised incidence (European standard) of malignant neoplasms excluding non-melanoma skin cancers increased from 518.2 to 681.9 cases per 100,000 population in men, and from 320.9 to 467.2 in women. The largest increase in trend in the analysed period was observed for melanoma, which showed an average annual increase of 4.0 % in men and 3.3 % in women. Over the last decade, a significant increase has been observed for head and neck cancer and oesophageal cancer, mainly in women. On the contrary, the largest decrease in trend in the analysed period was observed for stomach cancer, with an average decrease of 2.9 % in men and 2.8 % in women. Over the last 10 years, a highly significant decrease has also been observed for colorectal cancer: 3.2 % in men and 2.8 % in women. The largest difference in trend between the sexes was recorded in lung cancer: a steady decline of 1.3 % per year was observed for men, but an increase of 3.1 % per year was demonstrated for women. After the introduction of colorectal and cervical cancer screening programmes, a significant decrease of incidence rates for these diagnoses was observed.

CONCLUSIONS

Knowledge of the current cancer burden in the population and its time trends will help to prioritise targets and future resource allocation to cancer control.

Breast cancer screening program in Lithuania: trends in breast cancer mortality before and during the introduction of the mammography screening programme

Abstract. Background.

Breast cancer is the most frequent oncological disease as well as the leading cause of cancer death among women worldwide. Decline in mortality in economically strong countries is observed. This decline is mostly related to early diagnosis (an improvement in breast cancer awareness and the mammography screening program (MSP)) and a more effective treatment. In the end of 2005, MSP started in Lithuania. The main aim of this article is to evaluate the breast cancer mortality during 22 years in Lithuania, as well as changes before the start of the MSP and during its implementation, in order to assess the influence of the MSP on mortality.

Materials and methods.

Analysis is based on data from the population-based Lithuanian Cancer Registry. Analysis of changes in mortality includes the period from 1998 to 2019. Age standardized mortality rates are calculated for assessment of changes. Joinpoint regression analysis is used.

Results.

Applying the segmental regression model, it was found that during the study period mortality was statistically significantly decreasing by -1.1% each year. Mortality among women under the age of 50 decreased both before and during the implementation of MSP. Mortality in the target population also was already decreasing until the implementation of the program, but a significant reduction in mortality was observed in this group since 2006.

Conclusions.

Overall breast cancer mortality is decreasing in Lithuania. After the implementation of MSP the largest reduction in mortality was observed in the target population, however, it is not as pronounced as it could be with the well-organized MSP.

Comprehensive trends in incidence, treatment, survival and mortality of first primary invasive breast cancer stratified by age, stage and receptor subtype in the Netherlands between 1989 and 2017

Our study aimed to provide a comprehensive overview of trends in incidence, survival, mortality and treatment of first primary invasive breast cancer (BC), according to age, stage and receptor subtype in the Netherlands between 1989 and 2017. Data from all women diagnosed with first primary stage I to IV BC (N = 320 249) were obtained from the Netherlands Cancer Registry. BC mortality and general population data were retrieved from Statistics Netherlands. Age-standardised incidence and mortality rates were calculated with annual percentage change (APC) and average annual percentage change (AAPC) statistics. The relative survival (RS) was used as estimator for disease-specific survival. The BC incidence for all BC patients combined significantly increased until 2013 from 126 to 158 per 100 000 person-years, after which a declining trend was observed. Surgery became less extensive, but (neo-)adjuvant systemic treatments and their combinations were given more frequently. The RS improved for all age groups and for most stages and receptor subtypes, but remained stable for all subtypes since 2012 to 2013 and since 2000 to 2009 for Stage IV BC at 15 years of follow-up. Overall, the 5- and 10-year RS increased from 76.8% (95% confidence interval [CI]: 76.1, 77.4) and 55.9% (95% CI: 54.7, 57.1) in 1989 to 1999 to 91.0% (95% CI: 90.5, 91.5) and 82.9% (95% CI: 82.2, 83.5), respectively, in 2010 to 2016. BC mortality improved regardless of age and overall decreased from 57 to 35 per 100 000 person-years between 1989 and 2017. In conclusion, the BC incidence in the Netherlands has steadily increased since 1989, but the latest trends show promising declines. Survival improved markedly for most patients and the mortality decreased regardless of age.

Symptoms in long-term breast cancer survivors: A cross-sectional study in primary care

Purpose

Various long-term symptoms can manifest after breast cancer treatment, but we wanted to clarify whether these are more frequent among long-term breast cancer survivors than matched controls and if they are associated with certain diagnoses.

Methods

This was a cross-sectional, population-based study of 350 breast cancer survivors treated with chemo- and/or radiotherapy ≥5 years (median 10) after diagnosis and 350 women without cancer matched by age and primary care physician. All women completed a questionnaire enquiring about symptoms, underwent echocardiography to assess the left ventricle ejection fraction, and completed the Hospital Anxiety and Depression Scale. Cardiovascular diseases were diagnosed from primary care records. In a multivariable logistic regression analysis, symptoms were adjusted for the long-term effects and compared between cohorts and within the survivor group.

Results

Concentration difficulties, forgetfulness, dizziness, and nocturia were more frequent among breast cancer survivors compared with controls, but differences could not be explained by cardiac dysfunction, cardiovascular diseases, depression, or anxiety. Intermittent claudication and appetite loss were more frequent among breast cancer survivors than controls and associated with cardiac dysfunction, depression, and anxiety. Breast cancer survivors treated with chemotherapy with/without radiotherapy were at significantly higher odds of forgetfulness and nocturia, but significantly lower odds of dizziness, compared with breast cancer survivors treated with radiotherapy alone.

Conclusions

Intermittent claudication and appetite loss are common among breast cancer survivors and are associated with cardiac dysfunction and mood disorders. Other symptoms varied by whether the patient underwent chemotherapy with/without radiotherapy (forgetfulness and nocturia) radiotherapy alone (dizziness).

•

Even 10 years after diagnosis, breast cancer survivors experience various long-term symptoms.

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Some symptoms are more common among breast cancer survivors than among controls without cancer.

•

Not all symptoms are associated with known cardiovascular or psychological diagnoses.

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A symptom-specific approach may be appropriate.

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This study does not evaluate a causal relation.

Reliability of MRI tumor size measurements for minimal invasive treatment selection in small breast cancers

INTRODUCTION

Due to the shift towards minimal invasive treatment, accurate tumor size estimation is essential for small breast cancers. The purpose of this study was to determine the reliability of MRI-based tumor size measurements with respect to clinical, histological and radiomics characteristics in small invasive or in situ carcinomas of the breast to select patients for minimal invasive therapy.

MATERIALS AND METHODS

All consecutive cases of cT1 invasive breast carcinomas that underwent pre-operative MRI, treated in two hospitals between 2005 and 2016, were identified retrospectively from the Dutch cancer registry and cross-correlated with local databases. Concordance between MRI-based measurements and final pathological size was analyzed. The influence of clinical, histological and radiomics characteristics on the accuracy of MRI size measurements were analyzed.

RESULTS

Analysis included 343 cT1 breast carcinomas in 336 patients (mean age, 55 years; range, 25-81 years). Overall correlation of MRI measurements with pathology was moderately strong (ρ = 0.530, P < 0.001), in 42 cases (12.2%) MRI underestimated the size with more than 5 mm. Underestimation occurs more often in grade 2 and grade 3 disease than in low grade invasive cancers. In DCIS the frequency of underestimation is higher than in invasive breast cancer. Unfortunately, none of the patient, imaging or biopsy characteristics appeared predictive for underestimation.

CONCLUSION

Size measurements of small breast cancers on breast MRI are within 5 mm of pathological size in 88% of patients. Nevertheless, underestimation cannot be adequately predicted, particularly for grade 2 and grade 3 tumors, which may hinder patient selection for minimal invasive therapy.

Psychosocial well-being at time of diagnosis of breast cancer affects the decision whether or not to undergo breast reconstruction

OBJECTIVES

Numerous studies have shown that breast reconstruction after mastectomy improves QoL in breast cancer survivors. However, still about half of the patients does not opt for reconstruction. In order to accommodate suitable counseling, we should elucidate the factors that play a role in the decision-making process. This study aimed to evaluate the influence of QoL, among women diagnosed with breast cancer before the start of any treatment, on their decision whether or not to undergo breast reconstruction.

MATERIALS AND METHODS

BREAST-Q surveys were provided to breast cancer patients at the specialized breast care outpatient clinic after their first consultation with a surgical oncologist, between June 2017 and March 2019. The Q-scores of the subdomains physical well-being, psychosocial well-being, sexual well-being, and satisfaction with breasts of patients that underwent mastectomy were statistically analyzed.

RESULTS

Sixty-seven patients, undergoing mastectomy, completed the questionnaire. Fifty-four percent received reconstructive surgery. Mean age of patients seeking breast reconstruction was significantly lower than patients who did not opt for a reconstruction (53.5 vs. 63.7). Mean follow-up after mastectomy was 18.1 months. Except for satisfaction with breasts, mean Q-scores were higher in the group of patients who did not choose for reconstructive surgery. Psychosocial well-being was significantly higher in the non-reconstruction group (p = 0.012).

CONCLUSIONS

Psychosocial well-being at time of diagnosis of breast cancer was significantly higher in patients refraining from breast reconstructive surgery after mastectomy. Psychosocial characteristics might be essential for the decision-making process as well. Further prospective research should evaluate this.

Effect of screening mammography on breast cancer mortality: Quasi-experimental evidence from rollout of the Dutch population-based program with 17-year follow-up of a cohort

There is uncertainty about the magnitude of the effect of screening mammography on breast cancer mortality. The relevance and validity of evidence from dated randomized controlled trials has been questioned, whereas observational studies often lack a valid comparison group. There is no estimate of the effect of one screening invitation only. We exploited the geographic rollout of the Dutch screening mammography program across municipalities to estimate the effects of one additional biennial screening invitation on breast cancer and all‐cause mortality. Population administrative data provided vital status and cause of death of a cohort of women aged 49–63 in 1995 over 17 years. Linear probability models were used to estimate the mortality effects. We estimated 154 fewer breast cancer deaths (95% confidence interval: 40–267; p = 0.01) over 17 years in a population of 100,000 women aged 49–63 who received one additional biennial screening invitation, which corresponds to an 9.6% risk reduction for a woman of age 56. The estimated effect on all‐cause mortality was negative but not close to statistical significance. Our study shows that one single invitation for breast cancer screening is effective in reducing breast cancer mortality, which is important for health policy. The effect is smaller than previous estimates of the effect of invitation for multiple screens, which further emphasizes the importance of achieving regular participation.

What's new?

To date, there is still uncertainty about the magnitude of the effect of screening mammography on breast cancer mortality. Here, the authors exploited the geographic rollout of the Dutch screening mammography program and high‐quality national population, cancer, and death registries to avoid limitations of observational research by comparing breast cancer mortality across groups of women of the same age who joined the mammography program at different dates. The analysis provides a unique estimate of the effect of one additional invitation for screening mammography on breast cancer mortality (around 10%) and delivers evidence in favour of the effectiveness of such screening.

Development of breast cancer mortality considering the implementation of mammography screening programs - a comparison of western European countries

Background

Triggered by the successive implementation of organized mammography screening programs (MSPs) throughout western European countries over the last decades, there is an ongoing debate questioning their effectiveness. Since it is difficult to assess the effect of MSPs on a population level, we rather aim to assess the impact of the implementation itself on breast cancer mortality rates utilizing an ecological study design.

Methods

We analyzed age group-specific (50–59, 60–69 and 70–79 years) female breast cancer mortality rates in 14 western European countries between 1980 and 2017 using Joinpoint regression, interrupted time series (ITS) regression and multivariable Poisson regression.

Results

The Joinpoint analysis demonstrated decreasing trends resulting in annual percentage changes ranging from − 1.5% to − 5.4% (50–59), − 0.2% to − 8.1% (60–69) and 0% to − 7.1% (70–79) depending on the country within 3 years after MSP implementation. The ITS analysis results in highly significant interaction terms (calendar year * binary MSP indicator) for all age groups. The multivariable regression using “calendar year”, “year of MSP implementation” and “years with MSP” as independent variables yielded a significant yearly decrease for “years with MSP” ranging from 0.9 to 1.2%.

Conclusions

The results of this study suggest a positive association between the implementation of MSPs and the (accelerated) reduction of breast cancer mortality rates. Measuring and quantifying the isolated effect of MSPs on a population level will require additional studies using individual data.

A systematic review on the use of the breast lesion excision system in breast disease

Purpose

To outline the current status of and provide insight into possible future research on the breast lesion excision system (BLES) as a diagnostic and therapeutic device.

Methods

A systematic search of the literature was performed using PubMed, Embase, and the Cochrane databases to identify relevant studies published between January 2002 and April 2018. Studies were considered eligible for inclusion if they evaluated the diagnostic or therapeutic accuracy or safety of BLES.

Results

Ultimately, 17 articles were included. The reported underestimation rates of atypical ductal hyperplasia and ductal carcinoma in situ (DCIS) ranged from 0 to 14.3% and from 0 to 22.2%, respectively. Complete excision rates for invasive ductal carcinoma and DCIS ranged from 5.3 to 76.3%. Bleeding was the most frequently reported complication (0–11.8%). Device-related complications may arise, with an empty basket being the most common (0.6–3.6%). Thermal damage of the specimen, caused by the use of a radiofrequency cutting wire, was reported in eight of the included studies. Most thermal artifacts were reported as superficial and small (0.1–1.9 mm).

Conclusions

The BLES, an automated, image-guided, single-pass biopsy system for breast lesions using radiofrequency is designed to excise and retrieve an intact tissue specimen. It is an efficient and safe breast biopsy method with acceptable complication rates, which may be used as an alternative to vacuum-assisted biopsies. The variable rate of complete excision raises questions about the possibility to use BLES as a therapeutic device for the excision of small lesions. Further research should focus on this aspect of BLES.

Absence of sustained breast cancer incidence inflation in a national mammography screening programme

OBJECTIVE

To investigate the impact of population mammography screening on breast cancer incidence trends in New Zealand.

METHODS

Trends in age-specific rates of invasive breast cancer incidence (1994-2014) were assessed in relation to screening in women aged 50-64 from 1999 and 45-69 following the programme age extension in mid-2004.

RESULTS

Breast cancer incidence increased significantly by 18% in women aged 50-64 compared with 1994-98 (p<0.0001), coinciding with the 1999 introduction of mammography screening, and remained elevated for four years, before declining to pre-screening levels. Increases over 1994-99 incidence occurred in the 45-49 (21%) and 65-69 (19%) age groups following the 2004 age extension (p<0.0001). Following establishment of screening (2006-10), elevated incidence in the screening target age groups was compensated for by lower incidence in the post-screening ⩾70 age groups than in 1994-98. Incidence in women aged ⩾45 was not significantly higher (+5%) after 2006 than in 1994-98. The cumulated risk of breast cancer in women aged 45-84 for 1994-98 was 10.7% compared with 10.8% in 2006-10.

CONCLUSIONS

Increases in breast cancer incidence following introduction of mammography screening in women aged 50-64 did not persist. Incidence inflation also occurred after introduction of screening for age groups 45-49 and 65-69. The cumulated incidence for women aged 45-84 over 2006-10 after screening was well established, compared with 1994-98 prior to screening, shows no increase in diagnosis. Over-diagnosis is not inevitable in population mammography screening programmes.

Octreotide-modified liposomes containing daunorubicin and dihydroartemisinin for treatment of invasive breast cancer

Tumor invasion is considered a major promoter in the initiation of tumor metastasis, which is supposed to cause most cancer-related deaths. In the present study, octreotide (OCT)-modified daunorubicin plus dihydroartemisinin liposomes were developed and characterized. Evaluations were undertaken on breast cancer MDA-MB-435S cells and MDA-MB-435S xenografts nude mice. The liposomes were ∼100 nm in size with a narrow polydispersity index. In vitro results showed that the OCT-modified daunorubicin plus dihydroartemisinin liposomes could enhance cytotoxicity and cellular uptake by OCT-SSTRs (somatostatin receptors)-mediated active targeting, block on tumor cell wound healing and migration by incorporating dihydroartemisinin. The action mechanism might be related to regulations on E-cadherin, α5β1-integrin, TGF-β1, VEGF and MMP2/9 in breast cancer cells. In vivo, the liposomes displayed a prolonged circulating time, more accumulation in tumor location, and a robust overall antitumor efficacy with no obvious toxicity at the test dose in MDA-MB-435S xenograft mice. In conclusion, the OCT-modified daunorubicin plus dihydroartemisinin liposomes could prevent breast cancer invasion, hence providing a possible strategy for treatment of metastatic breast cancer.

The effect of population-based mammography screening in Dutch municipalities on breast cancer mortality: 20 years of follow-up

Long-term follow-up data on the effects of screening are scarce, and debate exists on the relative contribution of screening versus treatment to breast cancer mortality reduction. Our aim was therefore to assess the long-term effect of screening by age and time of implementation. We obtained data on 69,630 breast cancer deaths between 1980 and 2010 by municipality (N = 431) and age of death (40-79) in the Netherlands. Breast cancer mortality trends were analyzed by defining the municipality-specific calendar year of introduction of screening as Year 0. Additionally, log-linear Poisson regression was used to estimate the turning point in the trend after Year 0, per municipality, and the annual percentage change (APC) before and after this point. Twenty years after introduction of screening breast cancer mortality was reduced by 30% in women aged 55-74 and by 34% in women aged 75-79, compared to Year 0. A similar and significant decrease was present in municipalities that started early (1987-1992) and late (1995-1997) with screening, despite the difference in availability of effective adjuvant treatment. In the age groups 55-74 and 75-79, the turning point in the trend in breast cancer mortality was estimated in Years 2 and 6 after the introduction of screening, respectively, after which mortality decreased significantly by 1.9% and 2.6% annually. These findings show that the implementation of mammography screening in Dutch municipalities is associated with a significant decline in breast cancer mortality in women aged 55-79, irrespective of time of implementation.

Imaging Surveillance for Survivors of Breast Cancer: Correlation between Cancer Characteristics and Method of Detection

Purpose

The aim of our study was to investigate the characteristics of primary and recurrent breast cancers and the correlation between cancer subtypes and detection modes.

Methods

Between 2003 and 2013, 147 cases of recurrent breast cancer in 137 women (mean age, 45.30±10.78 years) were identified via an annual clinical examination using radiological studies among 6,169 patients with a breast cancer history (mean follow-up period, 13.26±1.78 years). Clinical, radiological, and pathological findings including immunohistochemistry findings of primary and recurrent cancers were reviewed. The size of the tumor in primary and recurrent cancers, disease-free survival, methods of surgery, and the recurrence detection modalities were analyzed with respect to the breast cancer subtype.

Results

Ipsilateral and contralateral in-breast recurrence occurred in 105, 21 had axillary lymph node recurrence, and 21 had chest wall recurrences. The subtypes of the primary cancers were hormone receptor (HR) positive and human epidermal growth factor receptor 2 (HER2) negative (HR+HER2−) in 57, HER2 positive (HER2+) in 39, and triple-negative type in 51, and the recurrent cancers in each subtype showed the same type as the primary cancer in 84.3% of cases. In the in-breast recurrent cancers, the HR+HER2− cancers were most frequently detected using ultrasonography (15/43) followed by mammography (MG) (11/43). The HER2+ recurrent cancers were most commonly detected using MG (14/31, 45.2%), whereas triple-negative type recurrent cancers most commonly presented as symptomatic masses (15/31) (p=0.028).

Conclusion

Most recurrent breast cancers showed the same cancer subtype as the primary tumor, and recurrent breast cancer subtypes correlated with the detection modality. Imaging surveillance of survivors of breast cancer might be more beneficial in cases of HR+HER2− type breast cancer or HER2+ type breast cancer than in cases of triple-negative type breast cancer.

[Cardiovascular risk of androgen deprivation therapy for treatment of hormone-dependent prostate cancer : Differences between GnRH antagonists and GnRH agonists]

BACKGROUND

Several studies have indicated that reduction of testosterone levels in patients with prostate cancer undergoing androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) agonists can be associated with an increased risk of cardiovascular events. The GnRH antagonists have a different mode of action compared with GnRH agonists and may be preferred in ADT for patients with cardiovascular disease.

OBJECTIVE

This review article discusses potential mechanisms underlying the development of cardiovascular events associated with ADT when using GnRH agonists and explains the differences in mode of action between GnRH agonists and GnRH antagonists. Additionally, relevant studies are presented and practical recommendations for the clinical practice are provided.

MATERIAL AND METHODS

A literature search was performed. Full publications and abstracts published in the last 10 years up to September 2015 were considered to be eligible.

RESULTS

The GnRH antagonists were associated with a decreased risk of cardiovascular events compared with GnRH agonists in prostate cancer patients undergoing ADT and particularly in patients with cardiovascular risk factors or a history of cardiovascular disease. This decrease may be due to the different mode of action of GnRH antagonists compared with GnRH agonists.

CONCLUSION

Prostate cancer patients with either cardiovascular disease or an increased risk of experiencing a cardiovascular event undergoing ADT should be preferentially treated with GnRH antagonists.

Predicting the stage shift as a result of breast cancer screening in low- and middle-income countries: a proof of concept

OBJECTIVE

To provide proof of concept for a simple model to estimate the stage shift as a result of breast cancer screening in low- and middle-income countries (LMICs). Stage shift is an essential early detection indicator and an important proxy for the performance and possible further impact of screening programmes. Our model could help LIMCs to choose appropriate control strategies.

METHODS

We assessed our model concept in three steps. First, we calculated the proportional performance rates (i.e. index number Z) based on 16 screening rounds of the Nijmegen Screening Program (384,884 screened women). Second, we used linear regression to assess the association between Z and the amount of stage shift observed in the programme. Third, we hypothesized how Z could be used to estimate the stage shift as a result of breast cancer screening in LMICs.

RESULTS

Stage shifts can be estimated by the proportional performance rates (Zs) using linear regression. Zs calculated for each screening round are highly associated with the observed stage shifts in the Nijmegen Screening Program (Pearson's R: 0.798, R square: 0.637).

CONCLUSIONS

Our model can predict the stage shifts in the Nijmegen Screening Program, and could be applied to settings with different characteristics, although it should not be straightforwardly used to estimate the impact on mortality. Further research should investigate the extrapolation of our model to other settings. As stage shift is an essential screening performance indicator, our model could provide important information on the performance of breast cancer screening programmes that LMICs consider implementing.

Screening mammography benefit controversies: sorting the evidence

Numerous clinical studies have confirmed that screening women age 40 years and older reduces breast cancer mortality by 30% to 50%. Several factors including faster breast cancer growth rates and lower breast cancer incidence among younger women, as well as shorter life expectancy and more comorbid conditions among older women, should also be considered in screening guidelines. Annual screening beginning at age 40 years and continuing with no upper age limit, as long as a woman has a life expectancy of at least 5 years and no significant comorbid conditions, is currently recommended.

Immediate and delayed effects of mammographic screening on breast cancer mortality and incidence in birth cohorts

BACKGROUND

Trend studies investigating the impact of mammographic screening usually display age-specific mortality and incidence rates over time, resulting in an underestimate of the benefit of screening, that is, mortality reduction, and an overestimate of its major harmful effect, that is, overdiagnosis. This study proposes a more appropriate way of analysing trends.

METHODS

Breast cancer mortality (1950-2009) and incidence data (1975-2009) were obtained from Statistics Netherlands, 'Stg. Medische registratie' and the National Cancer Registry in the Netherlands for women aged 25-85 years. Data were visualised in age-birth cohort and age-period figures.

RESULTS

Birth cohorts invited to participate in the mammographic screening programme showed a deflection in the breast cancer mortality rates within the first 5 years after invitation. Thereafter, the mortality rate increased, although less rapidly than in uninvited birth cohorts. Furthermore, invited birth cohorts showed a sharp increase in invasive breast cancer incidence rate during the first 5 years of invitation, followed by a moderate increase during the following screening years and a decline after passing the upper age limit.

CONCLUSION

When applying a trend study to estimate the impact of mammographic screening, we recommend using a birth cohort approach.

Breast cancer phenotype, nodal status and palpability may be useful in the detection of overdiagnosed screening-detected breast cancers

BACKGROUND

Breast cancer remains the leading cause of female cancer death despite improvements in treatment and screening. Screening is often criticized for leading to overdiagnosis and overtreatment. However, few have attempted to identify overdiagnosed cases.

PATIENTS AND METHODS

A large, consecutive series of patients treated for primary operable, screening-detected, breast cancer (n = 1610). Details from pathology and clinical reports, treatment and follow-up were available from our prospectively managed database. Univariate and multivariate Cox proportional models were used to study the prognostic variables in screening-detected breast cancers for distant metastatic and breast cancer-specific survival.

RESULTS

We included 1610 patients. The mean/median follow-up was 6.0/6.0 years. Univariate analysis: tumor size, palpability, breast cancer phenotype and nodal status were predictors of distant metastasis and breast cancer-specific death. Multivariate analysis: palpability, breast cancer phenotype and nodal status remained independent prognostic variables. Palpability differed by breast cancer phenotype.

CONCLUSION

Screening-detected breast cancer is associated with excellent outcome. Palpability, nodal status and breast cancer phenotype are independent prognostic variables that may select patients at increased risk for distant metastatic relapse and breast cancer-specific death. Overdiagnosed cases reside most likely in the nonpalpable node negative subgroup with a Luminal A phenotype.

The impact of mammographic screening on breast cancer mortality in Europe: a review of observational studies

OBJECTIVES

To assess the impact of population-based mammographic screening on breast cancer mortality in Europe, considering different methodologies and limitations of the data.

METHODS

We conducted a systematic literature review of European trend studies (n = 17), incidence-based mortality (IBM) studies (n = 20) and case-control (CC) studies (n = 8). Estimates of the reduction in breast cancer mortality for women invited versus not invited and/or for women screened versus not screened were obtained. The results of IBM studies and CC studies were each pooled using a random effects meta-analysis.

RESULTS

Twelve of the 17 trend studies quantified the impact of population-based screening on breast cancer mortality. The estimated breast cancer mortality reductions ranged from 1% to 9% per year in studies reporting an annual percentage change, and from 28% to 36% in those comparing post- and prescreening periods. In the IBM studies, the pooled mortality reduction was 25% (relative risk [RR] 0.75, 95% confidence interval [CI] 0.69-0.81) among invited women and 38% (RR 0.62, 95% CI 0.56-0.69) among those actually screened. The corresponding pooled estimates from the CC studies were 31% (odds ratio [OR] 0.69, 95% CI 0.57-0.83), and 48% (OR 0.52, 95% CI 0.42-0.65) adjusted for self-selection.

CONCLUSIONS

Valid observational designs are those where sufficient longitudinal individual data are available, directly linking a woman's screening history to her cause of death. From such studies, the best 'European' estimate of breast cancer mortality reduction is 25-31% for women invited for screening, and 38-48% for women actually screened. Much of the current controversy on breast cancer screening is due to the use of inappropriate methodological approaches that are unable to capture the true effect of mammographic screening.

Breast cancer screening: evidence of benefit depends on the method used

In this article, we discuss the most common epidemiological methods used for evaluating the ability of mammography screening to decrease the risk of breast cancer death in general populations (effectiveness). Case-control studies usually find substantial effectiveness. However when breast cancer mortality decreases for reasons unrelated to screening, the case-control design may attribute to screening mortality reductions due to other causes. Studies based on incidence-based mortality have obtained contrasted results compatible with modest to considerable effectiveness, probably because of differences in study design and statistical analysis. In areas where screening has been widespread for a long time, the incidence of advanced breast cancer should be decreasing, which in turn would translate into reduced mortality. However, no or modest declines in the incidence of advanced breast cancer has been observed in these areas. Breast cancer mortality should decrease more rapidly in areas with early introduction of screening than in areas with late introduction of screening. Nonetheless, no difference in breast mortality trends has been observed between areas with early or late screening start. When effectiveness is assessed using incidence-based mortality studies, or the monitoring of advanced cancer incidence, or trends in mortality, the ecological bias is an inherent limitation that is not easy to control. Minimization of this bias requires data over long periods of time, careful selection of populations being compared and availability of data on major confounding factors. If case-control studies seem apparently more adequate for evaluating screening effectiveness, this design has its own limitations and results must be viewed with caution.See related Opinion article: http://www.biomedcentral.com/1741-7015/10/106 and Commentary http://www.biomedcentral.com/1741-7015/10/164.

Endocrine-disrupting chemicals: associated disorders and mechanisms of action

The incidence and/or prevalence of health problems associated with endocrine-disruption have increased. Many chemicals have endocrine-disrupting properties, including bisphenol A, some organochlorines, polybrominated flame retardants, perfluorinated substances, alkylphenols, phthalates, pesticides, polycyclic aromatic hydrocarbons, alkylphenols, solvents, and some household products including some cleaning products, air fresheners, hair dyes, cosmetics, and sunscreens. Even some metals were shown to have endocrine-disrupting properties. Many observations suggesting that endocrine disruptors do contribute to cancer, diabetes, obesity, the metabolic syndrome, and infertility are listed in this paper. An overview is presented of mechanisms contributing to endocrine disruption. Endocrine disruptors can act through classical nuclear receptors, but also through estrogen-related receptors, membrane-bound estrogen-receptors, and interaction with targets in the cytosol resulting in activation of the Src/Ras/Erk pathway or modulation of nitric oxide. In addition, changes in metabolism of endogenous hormones, cross-talk between genomic and nongenomic pathways, cross talk with estrogen receptors after binding on other receptors, interference with feedback regulation and neuroendocrine cells, changes in DNA methylation or histone modifications, and genomic instability by interference with the spindle figure can play a role. Also it was found that effects of receptor activation can differ in function of the ligand.

Impact of mammographic screening on the detection of good and poor prognosis breast cancers

We sought to compare the molecular signature of node negative cancers from two cohorts 15 years apart, to determine if there is molecular evidence of increase in low and ultralow risk cancers over time. We studied the impact of age, time period of diagnosis, and mammographic screening on biology of tumors where The Netherlands Cancer Institute 70-gene prognosis signature was generated as part of 2 validation series, one retrospective (1984-1992), Cohort 1, and one prospective (2004-2006), Cohort 2. A total of 866 patients were analyzed. Regardless of time period of diagnosis, the proportion of T1, grade 1, hormone receptor positive (HR) tumors, and good prognosis by 70-gene signature significantly increases as age increases (P < 0.01). In women aged 49-60, the time period of diagnosis significantly affects the proportion of cancers that were NKI 70-gene low risk: 40.6% (67/165) compared with 58% (119/205) for Cohorts 1 and 2, respectively. This is in contrast to the absence of a significant change for women under age 40, where 25% (17/68) and 30% (17/56) were low risk in Cohorts 1 and 2, respectively. In women aged 49-60, using an ultralow risk threshold of the 70-gene signature, 10% of tumors in Cohort 1 were ultralow risk compared with 30% for women with screen-detected cancers in Cohort 2. Older age and method of detection (screening) are associated with a higher likelihood of a biologically low risk tumor. In women over age 50, biologically low risk tumors are frequent and tools that classify risk may minimize overtreatment.

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.

Interpreting overdiagnosis estimates in population-based mammography screening

Estimates of overdiagnosis in mammography screening range from 1% to 54%. This review explains such variations using gradual implementation of mammography screening in the Netherlands as an example. Breast cancer incidence without screening was predicted with a micro-simulation model. Observed breast cancer incidence (including ductal carcinoma in situ and invasive breast cancer) was modeled and compared with predicted incidence without screening during various phases of screening program implementation. Overdiagnosis was calculated as the difference between the modeled number of breast cancers with and the predicted number of breast cancers without screening. Estimating overdiagnosis annually between 1990 and 2006 illustrated the importance of the time at which overdiagnosis is measured. Overdiagnosis was also calculated using several estimators identified from the literature. The estimated overdiagnosis rate peaked during the implementation phase of screening, at 11.4% of all predicted cancers in women aged 0–100 years in the absence of screening. At steady-state screening, in 2006, this estimate had decreased to 2.8%. When different estimators were used, the overdiagnosis rate in 2006 ranged from 3.6% (screening age or older) to 9.7% (screening age only). The authors concluded that the estimated overdiagnosis rate in 2006 could vary by a factor of 3.5 when different denominators were used. Calculations based on earlier screening program phases may overestimate overdiagnosis by a factor 4. Sufficient follow-up and agreement regarding the chosen estimator are needed to obtain reliable estimates.

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.

Independent prognostic value of screen detection in invasive breast cancer

BACKGROUND

Mammographic screening has led to a proportional shift toward earlier-stage breast cancers at presentation. We assessed whether the method of detection provides prognostic information above and beyond standard prognostic factors and investigated the accuracy of predicted overall and breast cancer-specific survival by the computer tool Adjuvant! among patients with screen-detected, interval, and nonscreening-related carcinomas.

METHODS

We studied 2592 patients with invasive breast cancer who were treated at the Netherlands Cancer Institute from January 1, 1990, through December 31, 2000. Overall and breast cancer-specific survival probabilities among patients with mammographically screen-detected (n = 958), interval (n = 417), and nonscreening-related (n = 1217) breast carcinomas were compared. Analyses were adjusted for clinicopathologic characteristics and adjuvant systemic therapy. Because of gradual implementation of population-based screening in the Netherlands, analyses were stratified a priori according to two periods of diagnosis. All statistical tests were two-sided.

RESULTS

Screen detection was associated with reduced mortality (adjusted hazard ratio for all-cause mortality = 0.74, 95% confidence interval = 0.63 to 0.87, P < .001, and adjusted hazard ratio for breast cancer-specific mortality = 0.62, 95% confidence interval = 0.50 to 0.78, P < .001, respectively) compared with nonscreening-related detection. The absolute adjusted reduction in breast cancer-specific mortality was 7% at 10 years. The prognostic value of the method of detection was independent of the period of diagnosis and was similar across tumor size and lymph node status categories, indicating its prognostic value beyond stage migration. Adjuvant! underestimated breast cancer-specific survival in patients with screen-detected (-3.2%) and interval carcinomas (-5.4%).

CONCLUSIONS

Screen detection was found to be independently associated with better prognosis for overall and breast cancer-specific survival and to provide prognostic information beyond stage migration among patients with invasive breast cancer. We propose that the method of detection should be taken into account when estimating individual prognosis.

Preoperative MRI and surgical management in patients with nonpalpable breast cancer: the MONET - randomised controlled trial

BACKGROUND

We evaluated whether performing contrast-enhanced breast MRI in addition to mammography and/or ultrasound in patients with nonpalpable suspicious breast lesions improves breast cancer management.

METHODS

The MONET - study (MR mammography of nonpalpable breast tumours) is a randomised controlled trial in patients with a nonpalpable BIRADS 3-5 lesion. Patients were randomly assigned to receive routine medical care, including mammography, ultrasound and lesion sampling by large core needle biopsy or additional MRI preceding biopsy. Patients with cancer were referred for surgery. Primary end-point was the rate of additional surgical procedures (re-excisions and conversion to mastectomy) in patients with a nonpalpable breast cancer.

FINDINGS

Four hundred and eighteen patients were randomised, 207 patients were allocated to MRI, and 211 patients to the control group. In the MRI group 74 patients had 83 malignant lesions, compared to 75 patients with 80 malignant lesions in the control group. The primary breast conserving surgery (BCS) rate was similar in both groups; 68% in the MRI group versus 66% in the control group. The number of re-excisions performed because of positive resection margins after primary BCS was increased in the MRI group; 18/53 (34%) patients in the MRI group versus 6/50 (12%) in the control group (p=0.008). The number of conversions to mastectomy did not differ significantly between groups. Overall, the rate of an additional surgical intervention (BCS and mastectomy combined) after initial breast conserving surgery was 24/53 (45%) in the MRI group versus 14/50 (28%) in the control group (p=0.069).

INTERPRETATION

Addition of MRI to routine clinical care in patients with nonpalpable breast cancer was paradoxically associated with an increased re-excision rate. Breast MRI should not be used routinely for preoperative work-up of patients with nonpalpable breast cancer.

A remarkable reduction of breast cancer deaths in screened versus unscreened women: a case-referent study

OBJECTIVE

We designed a case-referent study to investigate the effect of mammographic screening at the individual level, looking at the association of breast cancer death with screening history.

METHODS

The study population included all women aged 50-75 in the province of Limburg, the Netherlands who had been invited to the screening program from 1989 to 2006. From this population, 118 cases originated who died of breast cancer in 2004 or 2005. The screening history of these cases was collected and compared with a sample of the invited population. The breast cancer death rate in the screened relative to the unscreened women was estimated as the odds ratio (OR). This OR was adjusted for self-selection bias, the difference in baseline risk for breast cancer death between screened and unscreened women.

RESULTS

Analysis of the data showed a breast cancer mortality reduction of 70% in the screened versus the unscreened women (OR = 0.30, 95% CI 0.14-0.63). The magnitude of self-selection was estimated specifically for Limburg. After correction for self-selection bias, the effect of screening increased to 76% (OR = 0.24, 95% CI 0.10-0.58).

CONCLUSION

Screening resulted in a remarkable reduction in breast cancer mortality. Contrary to findings in other countries, adjustment for self-selection in Limburg had no influence on the impact of screening. Thanks to a well-organized centralized screening program, similar results are expected in other regions of the Netherlands.

The attendance of migrant women at the national breast cancer screening in the Netherlands 1997-2008

The attendance of migrant women at the national breast cancer screening in the Netherlands is high; however, a much lower attendance was found in a study carried out in one region of the Netherlands some years ago. An increase in the attendance rates of migrant women over time was assumed, but no national data were available until now. The aim of this study is to provide national data about the attendance of migrant women at the national breast cancer screening in the Netherlands and the development of these attendance rates over time. The attendance rates at the national breast cancer screening program in the years 1997-1998 and 2007-2008 of women of all nationalities are compared and the differences are tested with the chi test. The attendance of Dutch women at the breast cancer screening in 2007-2008 was high (83%). The attendance rates of migrant women originating from Africa, Asia or Latin America (63%), such as Turkish women (62%) and especially Moroccan women (54%), were significantly lower (P=0.00). Compared with 10 years before, the overall attendance in 2007-2008 stayed almost constant, and changed only from 80 to 83%. The attendance rate of migrant women from Africa, Asia or Latin America increased from 51% in 1997-1998 to 63% in 2007-2008. These national figures show that the attendance rates of migrant women at the breast cancer screening have increased substantially over the past 10 years. However, specific efforts to increase the attendance rates of this target group are needed because the current attendance rates of this group are still far below the overall attendance rates.

Evaluation of cancer service screening: case referent studies recommended

Various cancer screening trials, randomised or otherwise controlled, have demonstrated reductions in cancer mortality. As a consequence, population screening programmes have been implemented. In the mean time, major advances are being made in early detection and treatment modalities of specific cancers and pre-cancers. The impact of these improvements should have bearing on the beneficial effect of periodical screening in preventing cancer death. To monitor these dynamics in the effectiveness of screening, case-referent studies are designed. The effectiveness is estimated by calculating an odds ratio indicating the cancer death rate in screened versus not screened invitees. The major criticisms of case referent studies are potential selection bias and confounding bias of the odds ratio. By properly designing and applying sensitivity analyses these biases can be minimised.

Life expectancy of screen-detected invasive breast cancer patients compared with women invited to the Nijmegen screening program

BACKGROUND

Screening can lead to earlier detection of breast cancer and thus to an improvement in survival. The authors studied the life expectancy of women with screen-detected invasive breast cancer (patients) compared with women invited to the breast cancer screening program in Nijmegen, the Netherlands (comparison group).

METHODS

Each patient diagnosed between 1975 and 2006 was randomly age-matched with a woman invited in the same calendar year and free from breast cancer at the time of diagnosis of the patient. Survival analyses were performed to study differences in life expectancy.

RESULTS

The life expectancy for 858 patients was 6 years shorter than for the comparison group. However, for 360 patients with small (<15 mm) invasive breast cancer, life expectancy was similar to that of the comparison group. In contrast, for patients detected with larger tumors (> or = 15 mm) the life expectancy was 6 to 12 years shorter, depending on tumor size. Furthermore, life expectancy was modified by screening history. For patients who had a negative screening examination 2 years before the detection of their breast cancer, the difference in life expectancy from the comparison group became smaller for the larger tumor sizes (> or = 15 mm).

CONCLUSIONS

In conclusion, about 40% (360 of 858) of all women with invasive screen-detected breast cancer have the same life expectancy as women from the comparison group (reflecting the general population). For women diagnosed with larger tumors at diagnosis, life expectancy diminishes with increasing tumor size and is modified by screening history.

The other side of technology: risk of overdiagnosis of breast cancer with mammography screening

Estimates of overdiagnosis of breast cancer with mammography screening differ between studies. The estimate of overdiagnosis obtained using the cumulative incidence approach with data from randomized clinical trials ranges from 10 to 14%. In observational studies, where statistical adjustment for lead-time was utilized, the estimate was lower than 5% in two Italian studies, while it was quite higher in a Swedish study. Most of the differences are explained by different methodology, study design and measures. In this review we discuss the concept and the definition of the measure of overdiagnosis, and present different study methods to estimate overdiagnosis of breast cancer with mammography screening.

By invitation only - the case for breast cancer screening reminders for women over 69 years

BACKGROUND

Breast cancer is the leading cause of cancer death in women in Australia. Early detection provides the best chance of reducing mortality and morbidity from the disease. Mammographic screening is a population health strategy for the early detection of breast cancer in Australia. Recruitment strategies such as regular advertising and biannual screening invitations are exclusively targeted at women aged 50 - 69 years. Even though they can participate, women 70 years or over are not invited or actively encouraged to undertake screening. Research has found that a routine letter of invitation increases the number of women participating in breast cancer screening.

METHODS

Cancer data analysis and a literature and policy review was conducted to assess age specific breast cancer mortality rates and the legitimacy of rationale used to limit invitations for breast cancer screening to women younger than 70 years.

RESULTS

The proportion of women over 69 years participating in the BreastScreen program is significantly less than rate of screening in the target age range (50-69 years). Evidence and data indicate that common justifications for limiting screening reminders to the target age range including life expectancy, comorbidities, effectiveness, treatment and cost are, for many women, unreasonable.

CONCLUSION

There is now sufficient data to support a change in the targeted upper age range for breast cancer screening to improve the existing suboptimal surveillance in women aged over 69 years.

Binding site of activators of the cystic fibrosis transmembrane conductance regulator in the nucleotide binding domains

The use of substances that could activate the defective chloride channels of the mutant cystic fibrosis transmembrane conductance regulator (CFTR) has been suggested as possible therapy for cystic fibrosis. Using epithelia formed by cells stably transfected with wildtype or mutant (G551D, G1349D) CFTR, we estimated the apparent dissociation constant, K(D), of a series of CFTR activators by measuring the increase in the apical membrane current. Modification of apparent K(D) of CFTR activators by mutations of the nucleotide-binding domains (NBDs) suggests that the binding site might be in these regions. The human NBD structure was predicted by homology with murine NBD1. An NBD1-NBD2 complex was constructed by overlying monomers to a bacterial ABC transporter NBD dimer in the "head-to-tail" conformation. Binding sites for CFTR activators were predicted by molecular docking. Comparison of theoretical binding free energy estimated in the model to free energy estimated from the apparent dissociation constants, K(D), resulted in a remarkably good correlation coefficient for one of the putative binding sites, located in the interface between NBD1 and NBD2.