Histopathology and growth rate of interval breast carcinoma. Characterization of different subgroups

Interval breast cancer: Analysis of occurrence, subtypes and implications for breast cancer screening in a model region

PURPOSE

Interval breast carcinomas (IBC) constitute a subgroup of malignancies in women participating in a breast cancer screening programme, yet diagnosed outside of a screening appointment. Tyrol is an Austrian screening model region with a dedicated IBC board. We analysed IBC subtype distribution, demographic and biological parameters and implications for screening programmes.

METHOD

161 patients with an IBC diagnosed from 2014 to 2017 were retrospectively analysed and grouped into true, occult, minimal-signs, and false negative (due to reading or technical error) IBCs cases by three independent readers. The influence of demographic and disease-related covariates were assessed.

RESULTS

The median interval from screening to diagnostic diagnosis was 12.8 months (range 1.1 to 23.9 months). Most cases were true (36.02%), occult (31.06%) and false-negative IBCs due to reading errors (29.81%). Interobserver agreement was rated as 'high' between all readers. Higher breast density was associated with true and occult IBCs. The rate of invasive subtypes was highest in true IBCs. Regardless of smaller tumour size in true and occult IBCs, doubling time was lower and ki-67 index higher in true and occult compared to false-negative IBCs.

CONCLUSIONS

True and occult IBCs present with a more aggressive biological phenotype and are associated with younger age and higher breast density. Additional yearly ultrasound examinations in women at risk may aid in the earlier detection.

Survival among women diagnosed with screen-detected or interval breast cancer classified as true, minimal signs, or missed through an informed radiological review

OBJECTIVES

"True" breast cancers, defined as not being visible on prior screening mammograms, are expected to be more aggressive than "missed" cancers, which are visible in retrospect. However, the evidence to support this hypothesis is limited. We compared the risk of death from any cause for women with true, minimal signs, and missed invasive screen-detected (SDC) and interval breast cancers (IC).

METHODS

This nation-wide study included 1022 SDC and 788 IC diagnosed through BreastScreen Norway during 2005-2016. Cancers were classified as true, minimal signs, or missed by five breast radiologists in a consensus-based informed review of prior screening and diagnostic images. We used multivariable Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of death from any cause associated with true, minimal signs, and missed breast cancers, adjusting for age at diagnosis, histopathologic tumour diameter and grade, and subtype. Separate models were created for SDC and IC.

RESULTS

Among SDC, 463 (44%) were classified as true and 242 (23%) as missed; among IC, 325 (39%) were classified as true and 235 (32%) missed. Missed SDC were associated with a similar risk of death as true SDC (HR = 1.20, 95% CI (0.49, 2.46)). Similar results were observed for missed versus true IC (HR = 1.31, 95% CI (0.77, 2.23)).

CONCLUSIONS

We did not observe a statistical difference in the risk of death for women diagnosed with true or missed SDC or IC; however, the number of cases reviewed and follow-up time limited the precision of our estimates.

KEY POINTS

• An informed radiological review classified screen-detected and interval cancers as true, minimal signs, or missed based on prior screening and diagnostic mammograms. • It has been hypothesised that true cancers, not visible on the prior screening examination, may be more aggressive than missed cancers. • We did not observe a statistical difference in the risk of death from any cause for women with missed versus true screen-detected or interval breast cancers.

Mammographic sensitivity as a function of tumor size: A novel estimation based on population-based screening data

Background

Instead of a single value for mammographic sensitivity, a sensitivity function based on tumor size more realistically reflects mammography’s detection capability. Because previous models may have overestimated size-specific sensitivity, we aimed to provide a novel approach to improve sensitivity estimation as a function of tumor size.

Methods

Using aggregated data on interval and screen-detected cancers, observed tumor sizes were back-calculated to the time of screening using an exponential tumor growth model and a follow-up time of 4 years. From the observed number of detected cancers and an estimation of the number of false-negative cancers, a model for the sensitivity as a function of tumor size was determined. A univariate sensitivity analysis was conducted by varying follow-up time and tumor volume doubling time (TVDT). A systematic review was conducted for external validation of the sensitivity model.

Results

Aggregated data of 22,915 screen-detected and 10,670 interval breast cancers from the Dutch screening program were used. The model showed that sensitivity increased from 0 to 85% for tumor sizes from 2 to 20 mm. When TVDT was set at the upper and lower limits of the confidence interval, sensitivity for a 20-mm tumor was 74% and 93%, respectively. The estimated sensitivity gave comparable estimates to those from two of three studies identified by our systematic review.

Conclusion

Derived from aggregated breast screening outcomes data, our model’s estimation of sensitivity as a function of tumor size may provide a better representation of data observed in screening programs than other models.

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Mammographic sensitivity is a key indicator of screening effectiveness.

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Previous model using logistic function might overestimate size-specific sensitivity.

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Our model showed that sensitivity increased from 0 to 85% for tumor sizes from 2 to 20 mm.

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Our model may provide a better representation of data observed in screening programs.

Radiological audit of interval breast cancers: Estimation of tumour growth rates

INTRODUCTION

This multicentre, retrospective study aimed to establish correlation between estimated tumour volume doubling times (TVDT) from a series of interval breast cancers with their clinicopathological features. The potential impact of delayed diagnosis on prognosis was also explored.

MATERIALS AND METHODS

Interval cancers, where screening mammograms demonstrated changes that were retrospectively classified as either uncertain or suspicious, were reviewed from five screening units within the UK NHS Breast Screening Programme (NHSBSP). Data collected included the time interval between screening mammogram and cancer diagnosis, the size of the initial mammographic abnormality and of the subsequent cancer, demographics, mammographic density and tumour biology. We estimated volume doubling times and the estimated change in size and node status, which would have followed if these cancers had been detected at the previous screen.

RESULTS

306 interval cancers meeting the inclusion criteria were identified. Average time from screening to diagnosis was 644 days (SD 276 days). 19% were diagnosed in the first twelve months, 42% in the subsequent twelve months and 39% thereafter. Overall average estimated TVDT was 167 days (95% CI 151-186). Significant differences were noted with age (p = 0.01), grade (p < 0.001) and ER status (p < 0.001) with women under 60, grade 3 cancers and ER negative cancers having shorter TVDTs. HER2 positive tumours had shorter doubling times than HER2 negative, but this difference was not statistically significant. It was estimated that diagnosing these cancers at the previous screen would have increased ten-year survival from 82% to 86%.

CONCLUSION

High grade, ER negativity and younger age were associated with shorter durations of TVDT. The role of HER2 status on interval cancer growth rate requires further assessment. It is likely that the delayed diagnosis of interval cancers confers a 4% reduction in ten-year survival.

Machine learning-based prediction of breast cancer growth rate in vivo

Background

Determining the rate of breast cancer (BC) growth in vivo, which can predict prognosis, has remained elusive despite its relevance for treatment, screening recommendations and medicolegal practice. We developed a model that predicts the rate of in vivo tumour growth using a unique study cohort of BC patients who had two serial mammograms wherein the tumour, visible in the diagnostic mammogram, was missed in the first screen.

Methods

A serial mammography-derived in vivo growth rate (SM-INVIGOR) index was developed using tumour volumes from two serial mammograms and time interval between measurements. We then developed a machine learning-based surrogate model called Surr-INVIGOR using routinely assessed biomarkers to predict in vivo rate of tumour growth and extend the utility of this approach to a larger patient population. Surr-INVIGOR was validated using an independent cohort.

Results

SM-INVIGOR stratified discovery cohort patients into fast-growing versus slow-growing tumour subgroups, wherein patients with fast-growing tumours experienced poorer BC-specific survival. Our clinically relevant Surr-INVIGOR stratified tumours in the discovery cohort and was concordant with SM-INVIGOR. In the validation cohort, Surr-INVIGOR uncovered significant survival differences between patients with fast-growing and slow-growing tumours.

Conclusion

Our Surr-INVIGOR model predicts in vivo BC growth rate during the pre-diagnostic stage and offers several useful applications.

A suprasellar colloid cyst over an 11-year follow-up: case report and literature review

BACKGROUND

Colloid cysts (CCs) are rare cystic lesions derived from the endoderm of the central nervous system. Although they appear most commonly in the anterior roof of the third ventricle, there are only a few reports of CCs located in the suprasellar region. Although CCs are considered to be slow-growing benign tumors, their developmental process remains unclear.

CASE DESCRIPTION

A 6-year-old boy was referred to our hospital for a mild head injury. Head computed tomography scan revealed a round, hyperdense suprasellar lesion, while magnetic resonance (MR) imaging depicted the mass as an isointense lesion with multiple highly hypointense spots on T2-weighted imaging. Although this lesion had been managed conservatively with annual MR imaging follow up, its size gradually increased, resulting in an increase in diameter by a factor of 1.5 over an 11-year period. The doubling time of this tumor was estimated to be approximately a 7 years. Despite its asymptomatic nature, the cystic lesion was totally resected when the patient was 17 years of age using an endoscopic endonasal approach to make a definitive histological diagnosis and prevent the occurrence of neurological symptoms. The postoperative course was uneventful, and the histological diagnosis of the surgical specimen was consistent with CC.

CONCLUSIONS

This case suggests that CC may be one of several possible diagnoses in patients who present with suprasellar cystic lesions. Even if CCs in the suprasellar region remain asymptomatic, radiological follow-up is required due to possible progressive enlargement of the cyst.

Estimation of the benefit and harms of including clinical breast examination in an organized breast screening program

BACKGROUND

There is controversy about the value of clinical breast examination (CBE) in addition to mammography for breast screening. The study investigates the associations between risk factors such as mammographic density, hormone therapy use and family history and the effectiveness of screening mammography with or without CBE.

METHODS

The cohort consists of women 50-69 years old screened at the Ontario Breast Screening Program. The associations of the risk factors were investigated using a joint logistic regression model that accommodates the partially unobserved disease status, clustered data structures, individual risk factors, and the dependence between true and false detection.

RESULTS

Having high mammographic density, a first degree relative with breast cancer and using hormone therapy generally increased a woman's probability of being referred correctly. For low risk group (defined as without dense breasts, family history, and not currently using hormone therapy), the average loss of specificity ranged from 3.6% to 5.7% and the gain of sensitivity was between 10.6% and 21.2% with the addition of CBE.

CONCLUSIONS

The addition of CBE to mammography would increase the overall sensitivity and decrease the specificity. CBE can be targeted to those women in which it has the highest net benefit.

Mammographic density and risk of breast cancer by mode of detection and tumor size: a case-control study

BACKGROUND

Risk of screen-detected breast cancer mostly reflects inherent risk, while risk of interval cancer reflects inherent risk and risk of masking (risk of the tumor not being detected due to increased dense tissue). Therefore the predictors of whether a breast cancer is interval or screen-detected include those that predict masking. Our aim was to investigate the associations between mammographic measures and (1) inherent risk, and (2) masking.

METHODS

We conducted a case-control study nested within the Melbourne collaborative cohort study of 244 screen-detected cases (192 small tumors (<2 cm)) matched to 700 controls and 148 interval cases (76 small tumors) matched to 446 controls. Dense area (DA), percent dense area (PDA), and non-dense area (NDA) were measured using the Cumulus software. Conditional and unconditional logistic regression were applied as appropriate to estimate the odds per adjusted standard deviation (OPERA) adjusted for age and body mass index (BMI), allowing for the association with BMI to be a function of age at diagnosis. Tests of fit were performed using the Bayesian information criterion (BIC) and the area under the receiver operating characteristic curve.

RESULTS

For screen-detected cancer, the association with BMI had a marginally significant dependence on age at diagnosis, and after adjustment both DA and PDA were associated with risk (OPERA approximately 1.2) and gave a similar fit. NDA was not associated with risk. For interval cancer, the BMI risk association was not dependent on age at diagnosis and the best fitting model was PDA alone (OPERA = 2.24, 95 % confidence interval 1.75, 2.86). Prediction of interval versus screen-detected cancer was best achieved by PDA alone (OPERA = 1.76, 95 % confidence interval 1.39, 2.22) with no association with BMI. When the analysis was restricted to small tumors to reduce the influence of tumor growth, we obtained similar results.

CONCLUSIONS

Inherent breast cancer risk is predicted by BMI and DA or PDA, but not NDA. Masking is predicted by PDA, and not by BMI. Understanding risk and masking could help tailor mammographic screening.

A comparison of clinical-pathological characteristics between symptomatic and interval breast cancer

BACKGROUND

An association between interval breast cancers (cancer detected after a normal mammogram and before the next scheduled mammogram) and tumour aggressiveness has been postulated which may reflect their relatively poor overall prognosis. The aim of this study was to evaluate known prognostic features of screen detected breast cancers compared to interval breast cancers.

METHODS

Patients diagnosed with breast cancer between January 2010 and 2013 at a single unit of the National Breast Screening Program (NBSP) in Ireland and those between the ages of 50 and 65 diagnosed at a symptomatic breast clinic were included in the study. Patients who had not had a screening mammogram within the proceeding two years or had a previous history of breast cancer were excluded. Data were retrospectively collected on patient demographics, tumour type, grade, hormone receptor status and stage of disease at presentation.

RESULTS

There were 915 patients included in the study, with 92% (n = 844) diagnosed through the NBSP. Ductal carcinoma in-situ accounted for 19% (n = 160) of screen-detected breast cancers but only 2.8% of interval cancers (p < 0.05). The most common type of invasive cancer was invasive ductal carcinoma. Tumour grade was significantly higher in interval breast cancers (p < 0.05). Interval cancers were identified at a significantly higher stage (Stage 1 versus 2; p < 0.001) than screen-detected cancers. Interval breast cancers were less likely to be ER positive (76% versus 81%; p < 0.05) and significantly more likely to over-express HER2 (20% vs 10%, p < 0.05) than screen-detected cancers.

CONCLUSION

This study highlights the fact that interval cancers appear to have a number of adverse prognostic markers for overall breast cancer survival when compared to women with screen-detected breast cancers. Interval cancers were more likely to be invasive, of a higher grade and stage and with a greater predominance of HER2 and triple negative molecular subtypes. Therefore this heterogeneous group of tumours may be biologically more aggressive and account disproportionately to overall breast cancer mortality.

Digital compared to screen-film mammography: breast cancer prognostic features in an organized screening program

Our previous study found cancer detection rates were equivalent for direct radiography compared to screen-film mammography, while rates for computed radiography were significantly lower. This study compares prognostic features of invasive breast cancers by type of mammography. Approved by the University of Toronto Research Ethics Board, this study identified invasive breast cancers diagnosed among concurrent cohorts of women aged 50-74 screened by direct radiography, computed radiography, or screen-film mammography from January 1, 2008 to December 31, 2009. During the study period, 816,232 mammograms were performed on 668,418 women, and 3,323 invasive breast cancers were diagnosed. Of 2,642 eligible women contacted, 2,041 participated (77.3 %). The final sample size for analysis included 1,405 screen-detected and 418 interval cancers (diagnosed within 24 months of a negative screening mammogram). Polytomous logistic regression was performed to evaluate the association between tumour characteristics and type of mammography, and between tumour characteristics and detection method. Odds ratios (OR) and 95 % confidence intervals (CI) were recorded. Cancers detected by computed radiography compared to screen-film mammography were significantly more likely to be lymph node positive (OR 1.94, 95 %CI 1.01-3.73) and have higher stage (II:I, OR 2.14, 95 %CI 1.11-4.13 and III/IV:I, OR 2.97, 95 %CI 1.02-8.59). Compared to screen-film mammography, significantly more cancers detected by direct radiography (OR 1.64, 95 %CI 1.12-2.38) were lymph node positive. Interval cancers had worse prognostic features compared to screen-detected cancers, irrespective of mammography type. Screening with computed radiography may lead to the detection of cancers with a less favourable stage distribution compared to screen-film mammography that may reflect a delayed diagnosis. Screening programs should re-evaluate their use of computed radiography for breast screening.

Impact of the transition from screen-film to digital screening mammography on interval cancer characteristics and treatment - a population based study from the Netherlands

INTRODUCTION

In most breast screening programmes screen-film mammography (SFM) has been replaced by full-field digital mammography (FFDM). We compared interval cancer characteristics at SFM and FFDM screening mammography.

PATIENTS AND METHODS

We included all 297 screen-detected and 104 interval cancers in 60,770 SFM examinations and 427 screen-detected and 124 interval cancers in 63,182 FFDM examinations, in women screened in the period 2008-2010. Breast imaging reports, biopsy results and surgical reports of all cancers were collected. Two radiologists reviewed prior and diagnostic mammograms of all interval cancers. They determined breast density, described mammographic abnormalities and classified interval cancers as missed, showing a minimal sign abnormality or true negative.

RESULTS

The referral rate and cancer detection at SFM were 1.5% and 4.9‰ respectively, compared to 3.0% (p<0.001) and 6.6‰ (p<0.001) at FFDM. Screening sensitivity was 74.1% at SFM (297/401, 95% confidence interval (CI)=69.8-78.4%) and 77.5% at FFDM (427/551, 95% CI=74.0-81.0%). Significantly more interval cancers were true negative at prior FFDM than at prior SFM screening mammography (65.3% (81/124) versus 47.1% (49/104), p=0.02). For interval cancers following SFM or FFDM screening mammography, no significant differences were observed in breast density or mammographic abnormalities at the prior screen, tumour size, lymph node status, receptor status, Nottingham tumour grade or surgical treatment (mastectomy versus breast conserving therapy).

CONCLUSION

FFDM resulted in a significantly higher cancer detection rate, but sensitivity was similar for SFM and FFDM. Interval cancers are more likely to be true negative at prior FFDM than at prior SFM screening mammography, whereas their tumour characteristics and type of surgical treatment are comparable.

Specific expression of k63-linked ubiquitination of calmodulin-like protein 5 in breast cancer of premenopausal patients

PURPOSE

Posttranslational modifications such as ubiquitination regulate many functions of proteins by affecting their interaction with other molecules, their activity, and their subcellular localization. In cancer biology, the ubiquitin network has gained major interest. K63-linked ubiquitination has emerged as a posttranslational modification with functional consequences, as it acts in several processes such as protein trafficking, DNA repair, and inflammation. Moreover, k63-linked ubiquitination is involved in the regulation of carcinogenesis. Based on previous findings, the aim of this study was to evaluate the ubiquitination of CALML5 in breast cancer patients.

PATIENTS AND METHODS

The breast cancer cell lines SkBr3, MCF7, HCC1937, and BT474 as well as 23 tumor samples of patients with primary breast cancer and the normal adjacent breast tissue were analyzed by one-dimensional immunoblot.

RESULTS

Using specific antibodies against CALML5 and k63-linked ubiquitin, we demonstrate a k63-linked ubiquitination in the nuclear fraction of premenopausal breast cancer patients. K63-linked ubiquitination of CALML5 was found in breast cancer tissue, but not found in surrounding healthy tissue.

CONCLUSION

Our findings support the concept that ubiquitination of CALML5 in the nucleus is involved in the carcinogenesis of breast cancer in premenopausal women.

Outcomes of surveillance for contralateral breast cancer in patients less than age 60 at the time of initial diagnosis

BACKGROUND

After an initial diagnosis of breast cancer, the risk of contralateral breast cancer is approximately 0.5% per year. Annual mammography is recommended to identify local recurrences and contralateral new primaries. Because the sensitivity of mammography tends to be lower in younger women, we conducted a retrospective review of the method of detection and pathologic stage of metachronous contralateral primary breast cancers according to age at diagnosis in a cohort of breast cancer patients.

METHODS

The Henrietta Banting Database contains information on cases of breast cancer diagnosed at Women's College Hospital from 1987 to 2004. From among 1992 women in the database, 71 patients were identified who were initially diagnosed before age 60 and who subsequently developed a contralateral breast cancer. Medical records were obtained for 53 of the 71 patients.

RESULTS

Of the 53 contralateral cancers, 33 (62%) were detected by mammography, including 4 in 16 patients (25%) diagnosed before age 50 and 29 in 37 patients (78%) diagnosed at age 50 or older (p ≤ 0.001).

CONCLUSIONS

Mammography has poor sensitivity for the surveillance of contralateral breast cancer in early-onset breast cancer patients. Other imaging modalities should be evaluated in this setting.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Clinical and self breast examination remain important in the era of modern screening

BACKGROUND

Breast cancer screening recommendations are in flux. We reviewed the methods of detecting newly diagnosed breast neoplasms at our institution.

METHODS

A retrospective review of patients stratified by age was performed to compare mammography with self- (SBE) and clinical (CBE) breast examination methods of cancer detection from 2005 to 2009.

RESULTS

We identified 782 patients. Patients aged <50 years were more likely to present with palpable disease (P < 0.001). Overall, 75% of patients had a mammogram within 24 months. There was a higher incidence of Tis tumors and lower incidence of T1 tumors if patients had mammography performed within 12 months versus 13-24 months (P < 0.01); tumor size, hormonal status, and lymph node (LN) status were comparable between these two groups. Patients diagnosed by SBE/CBE who had mammography performed within 12 months versus 13-24 months did not differ statistically according to tumor characteristics. In the screened cohort (mammography within 24 months), the majority of patients (64%) were diagnosed by mammography. Cancers detected by SBE/CBE were larger tumors (2.4 vs. 1.3 cm), higher grade, more frequently ER- (29 vs. 16%), triple-negative (21 vs. 10%), and lymph node-positive (39 vs. 18%; all P ≤ 0.01). There were no statistically significant differences in tumor size, T stage, or hormonal status in patients who had analog versus digital mammography.

CONCLUSIONS

Whereas the majority of patients had image-detected breast cancer, a significant number of image-screened patients presented with palpable disease, which were more aggressive cancers. Until imaging techniques are refined, SBE and CBE remain important for breast cancer diagnosis.

Differential expression of prognostic biomarkers between interval and screen-detected breast cancers: does age or family history matter?

The aim of this study was to compare tumor expression of prognostic biomarkers between interval breast cancers and screen-detected breast cancers overall, and according to age at diagnosis and familial risk. Tissue micro-arrays were constructed from 98 breast cancers (47 interval and 51 screen-detected) diagnosed in women in the Cancer Genetics Network. Arrays were immuno-stained to compare protein expression of six biomarkers including estrogen and progesterone receptor (ER/PR), Her2/neu, EGFR, cytokeratin 5/6, and Ki67. Fisher's Exact test was used to compare expression between interval and screen-detected cancers. Interval cancers were larger (P = 0.04), higher stage (P < 0.001), and more likely to have lobular histology (P = 0.01) than screen-detected cancers. Overall, interval cancers more often overexpressed EGFR (P = 0.01) and were somewhat more likely to be ER- (55% vs. 43%, P = 0.3), and triple negative (ER-/PR-/Her2-) (21 vs. 12%, P = 0.26). A greater difference in the proportion of interval versus screen-detected tumors that were ER- (53 vs. 35%; P = 0.29), PR- (35 vs. 21%; P = 0.25) and EGFR+ (17 vs. 0%; P = 0.02) was evident among women over 50. There was a trend toward differential expression among women with familial risk for PR- (P = 0.005) and triple negative status (P = 0.02). This study provides new data indicating that EGFR may be important in the etiology of interval cancer and be a possible therapeutic target. Our data also suggest that biological differences between interval and screen-detected cancers are more defined in older women. Future studies to confirm this finding and to elucidate novel markers for characterizing interval cancers may be more beneficial to this subgroup.

Diagnostic delay of breast cancer - an analysis of claims to Swedish Board of Malpractice (LÖF)

AIM

Delay in the diagnosis of breast cancer may have important clinical and medico-legal implications. This study examined the decisions made by reviewers at the Swedish agency (LÖF) that handles claims of medical malpractice where claimants seek compensation for alleged suffering and/or negative clinical impacts of diagnostic delays.

MATERIAL AND METHODS

In 1995-2006 a total of 134 women filed claims for negative effects resulting from delays in the diagnosis of breast cancer. Review of the claims led to approval of delay in the primary diagnosis for 62 women and of recurrence for 28 women. The clinical symptoms that were overlooked and other causes of delay that had any relation to therapy, prognosis and economic compensation were identified. The verdicts reached were analysed.

RESULTS

The median delay in the diagnosis of the primary disease was 11 months and for recurrent disease 3.5 months. Delay in diagnosis of the primary disease was considered to have an impact on the therapy in 23%. The prognosis was postulated to have been adversely affected 11% of the patients for whom the delay was longer than 12 months. Delay in diagnosing the recurrence was contributing to delay in starting therapy and to unnecessary suffering in 32%. The delay in diagnosis was mainly caused by incomplete clinical or radiological examination and by misinterpretations of the examination results. Economic compensation was given in 90%. There was a warning or admonition to the responsible doctor in a third of the cases referred to the judgement court.

CONCLUSION

This study demonstrates that claims for compensation for delay in diagnosis of breast cancer in Sweden occur in about 1/1000 new patient. The delay in the diagnosis of the primary tumour was considered to have an impact on the magnitude of therapeutic measures in almost 25% of the women who filed claims. Economic compensation for the patients' injuries was given in ninety percent of the cases. In women for whom there was a delay in diagnosing the recurrence there was consequently a delay in starting the palliative therapy.

Tumor characteristics associated with mammographic detection of breast cancer in the Ontario breast screening program

BACKGROUND

Few studies have compared the prognostic value of tumor characteristics by type of breast cancer diagnosed in the interval between mammographic screenings with screen-detected breast cancers.

METHODS

We conducted a case-case study within the cohort of women (n = 431 480) in the Ontario Breast Screening Program who were aged 50 years and older and were screened between January 1, 1994, and December 31, 2002. Interval cancers, defined as breast cancers diagnosed within 24 months after a negative screening mammogram, were designated as true interval cancers (n = 288) or missed interval cancers (n = 87) if they were not identified at the time of screening but were identified in retrospect. Screen-detected breast cancers (n = 450) were selected to match interval cancers. Tumors were evaluated for stage, grade, mitotic index, histology, and expression of hormone receptors and odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by conditional logistic regression.

RESULTS

Both true and missed interval cancers were of higher stage and grade than matched screen-detected breast cancers. However, true interval cancers had a higher mitotic index (OR = 3.13, 95% CI = 1.81 to 5.42), a higher percentage of nonductal histology (OR = 1.94, 95% CI = 1.05 to 3.59), and were more likely to be both estrogen receptor-negative (OR = 2.09, 95% CI = 1.32 to 3.30) and progesterone receptor-negative (OR = 2.49, 95% CI = 1.68 to 3.70) compared with matched screen-detected tumors.

CONCLUSIONS

In this study, interval cancers were of higher stage and grade compared with screen-detected cancers. True interval cancers were more likely to have additional adverse prognostic features of estrogen and progesterone receptor negativity and nonductal morphology. The findings suggest a need for more sensitive screening modalities to detect true interval breast cancers and different approaches for early detection of fast-growing tumors.

Non-invasive proteomics-thinking about personalized breast cancer screening and treatment

The early diagnosis of breast cancer in potentially curable stages improves prognosis and consecutively reduces mortality of breast cancer patients. Established screening programs have an unfavorable connotation due to significant rates of false negative as well as false positive results leading to overdiagnosis and overtherapy. The combination of a non-invasive breast-cancer-suspectability-biomarker with established clinical diagnostics could help to increase the acceptance of population based breast cancer screening programs by creating an individual risk profile, which is irrespective of mammography quality and interpretation. Recently, non-invasive proteomic biomarkers obtained from blood, saliva or nipple aspiration fluid have been extensively investigated and might play a future role in the personalized management of breast cancer screening. A simple, robust and inexpensive, non-invasive test for screening and diagnosis could easily be performed in every medical practice leading to an affordable, high-throughput instrument. This review describes recently investigated proteomic screening biomarkers that could improve the early diagnosis of breast cancer in the following years.

A pooled analysis of interval cancer rates in six European countries

The objective of this study was to assess detection rates and interval breast cancer (IC) rates from eight programmes in the European Breast Cancer Screening Network. A common data collection protocol was used to explore differences in IC rates among programmes and discuss their potential determinants. Pooled analysis was used to describe IC rates by age, compliance in screening, recall rate, screening detection (SD) rate and expected breast cancer incidence. Participation in screening averaged 77.9% (range 42.6-88.7%), recall rate 5.4% (range 3.3-17.7%) in the initial and 3.4% (range 1.8-8.9%) in the subsequent screening rounds, and SD rate was 60.4 (range 41.6-91) per 10 000 women in initial and 38.5 (range 31.3-62.6) in subsequent screens. IC rate during first 12 months after screening was 5.9 (range 2.1-7.3) per 10 000 women screened negative and 12.6 (range 6.3-15) in the second year of the interval. IC comprised 28% of the IC and SD cancers. The ratio between IC rate and expected incidence was 0.29 for the first 12 months and 0.63 for the 13-24 months period. Sensitivity was higher for the ages 60-69 years and for initial tests than subsequent tests. There were distinct differences in the IC rates between programmes. The results of this study reveal large variations in screening sensitivity and performance. Pooled evaluation of some process indicators within the European breast cancer screening programmes proved to be feasible and is likely to be useful for the future, particularly if it is performed regularly and extensively.

Aggressiveness of 'true' interval invasive ductal carcinomas of the breast in postmenopausal women

There is debate whether interval carcinomas differ from screen-detected tumours biologically. In this study, clinico-pathological parameters and the expression of well-validated biological markers were compared between 'true' interval carcinomas and screen-detected/missed carcinomas hypothesising that 'true' interval carcinomas show a more aggressive biological behaviour. The study group consisted of 92 consecutive postmenopausal women attending the breast screening programme and presenting with an invasive ductal carcinoma. All screening mammograms were re-reviewed. Sixteen patients had a 'true' interval carcinoma. Seven carcinomas were missed at screening, but detected on re-reviewing of the screening mammogram. Radiological characteristics were assessed from diagnostic mammograms. Data on patient- and tumour characteristics and follow-up data were recorded from hospital records. Median follow-up was 61 months. Immunohistochemistry for ER, PR, Her2/neu and p53 was performed on TMA sections. Univariate and multivariate logistic regression analyses were performed. In univariate analysis, 'true' interval carcinomas were significantly larger (odd ratios (OR) 7.2, 95% CI 1.8-28.1) and less frequently ER (OR 0.3, 95% CI 0.1-0.9) and PR (OR 0.3, 95% CI 0.1-1.0) positive. In multivariate analysis, 'true' interval carcinoma was independently associated with larger tumours (OR 7.0, 95% CI 1.4-36.2). A trend toward ER negativity was found (OR 0.3, 95% CI 0.1-1.1). 'True' interval carcinomas showed a trend toward a decreased relapse-free survival (HR 1.7 95% CI 0.9-3.1). Although 'true' interval carcinomas were significantly larger than screen-detected/missed interval carcinomas, it remains challenging to observe parameters that determine this difference between 'true' interval carcinomas and screen-detected lesions.

Mammographic features and histopathological findings of interval breast cancers

BACKGROUND

Interval cancers are considered a shortcoming in screening mammography due to less favorable prognostic tumor characteristics compared to screening-detected cancers and consequently a lower chance of survival from the disease.

PURPOSE

To describe the mammographic features and prognostic histopathological tumor characteristics of interval breast cancers.

MATERIAL AND METHODS

A total of 231 interval breast cancer cases diagnosed in prevalently screened women aged 50-69 years old were examined. Thirty-five percent of the cases were retrospectively classified as missed cancers, 23% as minimal sign, and 42% as true negative (including occult cancers) in a definitive classification performed by six experienced breast radiologists. The retrospective classification described the mammographic features of the baseline screening mammograms in missed and minimal-sign interval cancers, while histopathological reports were used to describe the tumor characteristics in all the subgroups of interval cancers.

RESULTS

Fifty percent of the missed and minimal-sign interval cancers combined presented poorly defined mass or asymmetric density, and 26% calcifications with or without associated density or mass at baseline screening. Twenty-seven percent of invasive tumors were <15 mm for missed and 47% for true interval cancers (P<0.001). Lymph node involvement was more common in missed (49%) compared with the true cases (33%, P<0.05).

CONCLUSION

Missed interval cancers have less prognostically favorable histopathological tumor characteristics compared with true interval cancers. Improving the radiologist's perception and interpretation by establishing systematic collection of features and implementation of organized reviews may decrease the number of interval cancers in a screening program.

A comparative proteinomic analysis of nipple aspiration fluid from healthy women and women with breast cancer

This pilot study examines the feasibility of nipple aspiration to distinguish women with breast cancer from healthy women using surface-enhanced laser desorption ionisation time-of-flight mass spectrometry (SELDI-TOF/MS). Nipple aspiration fluid (NAF) was collected from each breast in 21 women newly diagnosed with unilateral breast cancer and 44 healthy women. No differences were found when proteomic profiles of NAF from the cancer-bearing breast and the contralateral non-cancerous breast were compared. In contrast, 9 protein peaks were significantly different between the cancer-bearing breast compared with healthy women and 10 peaks were significantly different between the contralateral healthy breast and healthy women (P<0.05). These data suggest that invasive breast cancer may result in a field change across both breasts and that proteomic profiling of NAF may have more value in breast cancer risk assessment than as a diagnostic or screening tool.

Influence of Patterns of Hormone Replacement Therapy Use and Mammographic Density on Breast Cancer Detection

BACKGROUND

There is evidence that factors such as current hormone replacement therapy (HRT) use and mammographic density may each lower the sensitivity of mammography and are associated with a greater risk of developing an interval cancer. This study explores this relationship further by examining the influence of patterns of HRT use and the percentage of mammographic density on the detection of breast cancer by classification of interval cancer.

METHODS

This study uses a case-case design nested within a cohort of women screened by the Ontario Breast Screening Program between 1994 and 2002. Interval cancers, both those missed at screening but seen on retrospective review (n = 87) or true intervals without visible tumor signs at screening (n = 288) were matched to 450 screen-detected cancers. The association between the percentage of mammographic density, measured by radiologists and a computer-assisted method, and HRT use, ascertained from a mailed questionnaire, and the risk of being diagnosed with an interval cancer was estimated using conditional logistic regression.

RESULTS

A monotonic gradient of increasing risk for interval cancers was found for each 25% increase in mammographic density [odds ratio (OR), 1.77; 95% confidence intervals (95% CI), 1.07-2.95 for missed intervals and OR, 2.16; 95% CI, 1.59-2.94 for true intervals]. After adjusting for mammographic density, a significantly increased risk for true-interval cancers remained for women taking estrogen alone (OR, 1.75; 95% CI, 1.11-2.83) as well as for missed- (OR, 2.84; 95% CI, 1.32-6.13) and true-interval cancers (OR, 1.79; 95% CI, 1.10-2.90) for women taking combined HRT.

CONCLUSIONS

Information on mammographic density and HRT use should routinely be collected at the time of screening. Women at risk should be made aware of the lower sensitivity of mammography and offered alternative procedures for screening.

Role of Detection Method in Predicting Breast Cancer Survival: Analysis of Randomized Screening Trials

BACKGROUND

Screening mammography detects breast cancers earlier than those detected symptomatically, and so mammographically detected breast cancers tend to have better prognoses. The so-called stage shift that results from screen detection is subject to lead-time and length biases, and so earlier detection may not translate into longer survival. We used data from three large breast cancer screening trials--Health Insurance Plan (HIP) of New York and two Canadian National Breast Cancer Screening Studies (CNBSS)--to investigate survival benefits of breast cancer screening beyond stage shift. We also address whether method of detection is an independent prognostic factor in breast cancer.

METHODS

The HIP trial randomly assigned approximately 62,000 women to screening and control groups. The two CNBSS trial cohorts CNBSS-1 and CNBSS-2 included a total of 44,970 women in the screening group and 44,961 in the control group. After adjusting for stage and other tumor characteristics in a Cox proportional hazards model, survival distributions were compared by method of breast cancer detection with both univariate and multivariable analyses. All P values are two-sided.

RESULTS

Breast cancers detected by screening mammography had a shift in stage distribution to earlier stages (for HIP, P < .001; for CNBSS-1, P = .03; and for CNBSS-2, P < .001). After adjusting for tumor size, lymph node status, and disease stage in a Cox proportional hazards model, method of detection was a statistically significant independent predictor of disease-specific survival. Patients with interval cancers had a 53% (95% confidence interval [CI] = 17% to 100%) greater hazard of death from breast cancer than patients with screen-detected cancers, and patients with cancer in the control groups had a 36% (95% CI = 10% to 68%) greater hazard of death than patients with screen-detected cancer.

CONCLUSION

There was an apparent survival benefit beyond stage shift for patients with screen-detected breast cancers compared with patients with breast cancers detected otherwise. Method of detection appears to be an important prognostic factor, even after adjusting for known tumor characteristics. This finding suggests that clinical trialists should routinely collect information about method of detection.

A Basal Epithelial Phenotype Is More Frequent in Interval Breast Cancers Compared with Screen Detected Tumors

Interval breast cancer reduce the effectiveness of mammography screening programs. We studied 95 interval cancers, diagnosed during 1996 to 2001 as part of the population-based Norwegian Breast Cancer Screening Program. These cases were matched on size (+/-2.0 mm) to 95 screen-detected breast cancers, and the tumors were compared by immunohistochemical methods using tissue microarrays. Patients with interval cancers were more likely to be younger [odds ratio (OR), 4.7; P = 0.0001], to have dense breasts (OR, 3.4; P = 0.004), and to have estrogen receptor-negative tumors (OR, 2.6, P = 0.01), and p53 expression was more frequent (OR, 4.0; P = 0.001). Notably, interval cancers were more likely to have a basal epithelial phenotype, in that expression of cytokeratin 5/6 (OR, 2.3; P = 0.04) and P-cadherin (OR, 2.5; P = 0.04) was more frequent in interval cases than in size-matched, screen-detected tumors. In a logistic regression model, p53 expression, age, and breast density were independent predictors of interval cancers. Our data suggest that breast cancers with a basal epithelial phenotype are more likely than nonbasal breast cancers to present between regular mammograms.

Coexistence of lactating adenoma and invasive ductal adenocarcinoma of the breast in a pregnant woman

A 36 year old pregnant woman was admitted to hospital complaining of an enlarging mass in her left breast. Histopathological examination of the mastectomy specimen revealed a high grade infiltrating ductal adenocarcinoma intermixed with a lactating adenoma. Lactating adenomas are rare entities but are the most common masses that occur during pregnancy. Although they are not thought to carry an increased risk of cancer there are two other case reports in the literature of a lactating adenoma associated with an infiltrating carcinoma. In this case, areas where the lactating adenoma and the infiltrating carcinoma were intermixed could be identified. This case could simply be a collision tumour, although the possibility of an invasive carcinoma arising within a lactating adenoma cannot be ruled out. Because of the relative lack of experience with lactating adenomas, the question of an increased association with carcinoma development remains unclear.

Factors Contributing to Mammography Failure in Women Aged 40-49 Years

BACKGROUND

Younger women (40-49 years) have lower mammographic sensitivity (i.e., greater proportion of cancers detected after a negative mammogram) than older women (> or =50 years). We explored the effect of tumor growth rate, breast density, mammographic image quality, and breast cancer risk factors on mammographic sensitivity in younger and older women.

METHODS

We studied 576 women (n = 73 aged 40-49 years and n = 503 aged 50 years or older) who were diagnosed with invasive breast cancer between 1988 and 1993. Interval cancers were defined as those diagnosed within 12 or 24 months after a negative screening mammogram and before a subsequent mammogram. Tumor growth rate was assessed by mitotic figure count and Ki-67 positivity. The main outcome measures were percentage of women with interval cancer (1 -mammographic sensitivity) by age, odds ratio (OR) of interval cancer by age, and excess odds (i.e., the percentage of the odds ratio for age that was explained by individual covariates).

RESULTS

Interval cancers occurred in 27.7% of younger women and 13.9% of older women within 12 months (OR = 2.36, 95% confidence interval [CI] = 1.14 to 4.77) and in 52.1% of younger women and 24.7% of older women within 24 months (OR = 3.58, 95% CI = 2.15 to 5.97). Greater breast density explained 67.6% of the decreased mammographic sensitivity in younger women at 12 months, whereas rapid tumor growth explained 30.6% and breast density explained 37.6% of the decreased sensitivity in younger women at 24 months.

CONCLUSIONS

Breast density largely explained decreased mammographic sensitivity at 12 months, whereas rapid tumor growth contributed to decreased mammographic sensitivity at 24 months. A 12-month versus a 24-month mammography screening interval may therefore reduce the adverse impact of faster growing tumors on mammographic sensitivity in younger women.

Hormonal Factors and Breast Tumor Proliferation: Do Factors that Affect Cancer Risk also Affect Tumor Growth?

BACKGROUND

Tumor cell proliferation is one of the most significant predictors of prognosis for women with breast cancer. Personal characteristics that affect hormonal exposure have been implicated in breast tumor etiology, and it is possible that they may also influence tumor cell proliferation. We examined the association between hormone-related breast cancer risk factors and breast tumor proliferation, as reflected in two proliferation measures, Ki-67 and mitotic count.

METHODS

The study population was 484 women 40 years of age and older, who were members of a managed care organization's breast cancer screening program and were diagnosed with invasive breast cancer between 1988 and 1995. The percent of Ki-67 positive tumor cells averaged over four high powered fields (Ki-67) was log transformed and analyzed in a linear regression model. Mitotic count was dichotomized into high versus low (<or=10), and analyzed in an unconditional logistic regression model with the odds ratio (OR) as the measure of association.

RESULTS

Consistent with other studies, there was a significant trend of decreased tumor cell proliferation with increasing age ( p for trend <0.05 for both measures). Higher body weight was associated with higher Ki-67 ( p for trend <0.05), but not with higher mitotic count. We found no significant associations between any reproductive factors (age at menarche, parity, age at first birth, menopausal status and age at menopause) and either measure of tumor cell proliferation. We observed an association between reduced tumor proliferation, as measured by mitotic count and former/current use of hormone replacement therapy (HRT) in comparison to never use (adjusted OR's: former HRT use: 0.40 (95% CI 0.19-0.85); current HRT use: 0.52 (95% CI 0.26-1.04).

CONCLUSION

Certain factors related to hormonal exposure that influence breast tumor etiology, for example, age, also appear to increase tumor growth. Conversely HRT use, which clearly increases breast cancer risk, may not adversely affect, and possibly may diminish cell proliferation once tumors are established.

Mammography screening and breast cancer biology in African American women--a review

This review examines some of the key issues in early detection and breast cancer biology for African American (AA) women which contribute to their diagnoses at more advanced stages than white women, and poorer long-term prognoses. While screening mammography is considered an essential factor in eliminating these disparities, its optimal application for AAs is not fully understood. There is a paucity of information on the success with which mammography screening programs are maintained over time in the AA population, and on screening guidelines with regard to age of initiation and frequency. No randomized clinical trials targeting AA women have been reported. This type of information is critical since breast cancer in AA women occurs at younger ages, and frequently demonstrates aggressive tumor biology at diagnosis. Studies are required to determine the incidence of interval cancers in current screening programs, and the influence of the biological characteristics which are known to differ in the breast tumors of AA and white women. Recognition of molecular and cellular characteristics which identify the potential invasiveness of ductal carcinomas in situ is also required. These studies would assist in establishing the criteria for identifying the subpopulation of younger pre-menopausal AA women who would benefit from early initiation of screening. Finally, the epidemiology and biology of mammographic densities, a risk factor for breast cancer and, perhaps, markers of aggressive disease require further study in both AA and white women.

Comparison of breast mammography, sonography and physical examination for screening women at high risk of breast cancer in taiwan

Recommended surveillance for screening breast cancer, which includes regular mammography and clinical breast examination, has long been established in Western countries. This strategy may be too costly and unnecessary for countries with low incidences of breast cancer. The purpose of the present study is to compare breast mammography, sonography and physical examination in screening female relatives of breast cancer index cases from the hospital, and their relative efficiency. A total of 935 women over 35 years old, who were relatives of breast cancer patients, were invited to an annual screening by means of a combination of mammography, sonography and physical examination on a single day. A biopsy was performed when any of the three investigations indicated a possibility of malignancy. A total of 21 breast cancers, including sixteen invasive cancers and 5 noninvasive cancers, were detected among the 935 high-risk women. Of the cancers, 18, including 16 invasive cancers and 3 noninvasive cancers, were detected by sonography. In contrast, only 11 invasive cancers were detected by mammography, and 7 by physical examination. There were only 14 cancers detected by a combination of mammography and physical examination. The 7 (33.3%) additional cancers were detected when sonography was added. The sensitivity of sonography was 90.4%, which was higher than mammography (52.4%) and physical examination (33.3%), or even a combination of these two modalities (66.7%). This indicates that sonography is a more accurate screening tool for breast cancer in the high-risk group. Although breast sonography has not yet been recommended as a routine screening tool for breast cancer in Western countries, it may be superior to mammography and physical examination for the screening of Taiwanese high-risk female relatives of breast cancer index cases. If it should also be considered as a routine adjunct screening modality for Taiwanese women with lower rates of breast cancer will need further study.

Screening mammography: clinical image quality and the risk of interval breast cancer

OBJECTIVE

We evaluated the association between clinical image quality and breast cancer occurrence within 24 months of a negative mammogram.

MATERIALS AND METHODS

We identified women with breast cancer who were younger than 40 years old and older and screened from January 1, 1988, through December 31, 1993. We retrospectively assigned Breast Imaging Reporting and Data System (BI-RADS) assessments to their screening mammogram. We classified cancers (invasive or ductal in situ) as "screen-detected" when found after positive assessments (BI-RADS codes 3, 4, and 5) and "interval-detected" when found after negative assessments (BI-RADS codes 1 and 2). One reviewer evaluated mediolateral oblique and craniocaudal views for all cancer cases using a 3-point scale (failure, borderline, pass) for each measure of clinical image quality (positioning, breast compression, contrast, exposure, noise, sharpness, artifacts, overall quality). We used separate logistic regression models and evaluated the odds of interval invasive cancer or invasive plus in situ cancer as a function of each measure of quality using "pass" as the referent group.

RESULTS

We found 492 screen-detected and 164 interval-detected cancers that met study criteria. Cancer detection (sensitivity) was highest (84%) among patients with proper breast positioning, but when images failed this measure (33.4%), sensitivity fell to 66.3%. After adjustment for age, film date, and breast density, interval-detected invasive cancers were more likely after images failing positioning (odds ratio, 2.57; 95% confidence interval, 1.28-5.52%). Failures in overall quality were also associated with interval cancers when cases of ductal carcinoma in situ (p = 0.037) were included.

CONCLUSION

Invasive breast cancer detection by mammography may be improved through attention to correct positioning.

Interval breast cancer: is it a different type of breast cancer?

We have compared tumour type, tumour size, tumour grade and axillary lymph node status in three groups of women, 230 interval breast cancers (IC) in the West Sussex Breast Screening programme and 625 screen detected (SD) cancers and 916 symptomatic (S) cancers treated at Worthing Hospital between July 1989 to April 1996. Our true interval cancer detection rates were 5.28, 11.28 and 15.3 per 10,000 screened women for the 1st, 2nd and 3rd year after screening. The proportionate incidences of true interval cancer were 29%, 61% and 82% for the 1st, 2nd and 3rd year, similar to others' programmes in UK. In our programme a large proportion (42%) of IC and more than half of the true IC presented in the 3rd year after screening. Out of 230 interval cancers, 40% (90) were unclassifiable, the remaining 60% (140) were classified as: True interval cancers (T) 54% (76), False Negative Subtle (FNS) 12% (16), Occult (O) 12% (17), and 22% (31) as False Negative (FN). Analysis of interval cancers according to their classification did not demonstrate any significant difference with respect to tumour size (chi2 5.59, df 4, P=0.22), tumour grade (chi2 5.29, df 4, P=0.25) and axillary node status (chi2 3.16, df 4, P=0.53) thus establishing interval cancers as a single group. Invasive ductal carcinoma of no specific type was the main tumour type in all three groups. Analysis of variance (ANOVA) showed significant differences in size between the groups (df 2, F=71.36, p<0.0001). Symptomatic cancers were 1.19 times the size of IC while SD were 0.83 times the size of IC. The difference in groups in terms of tumour grade was significant (Kruskal-Wallis test chi2 33.31, df 2, P<0.0001). The incidence of grade 2 tumours was similar in the three groups while a third of the IC and S were grade 3 tumours. Comparison of axillary node status showed a significant difference between the three groups (chi2 26.59, df 2, P<0.0001). When means and 75th percentiles were compared IC had the greatest number of positive nodes while SD had the smallest number of positive nodes. Interval cancers are the middle spectrum between symptomatic and screen detected breast cancers and represent small cancers (<10 mm) not detected at the time of screening and de novo cancers developing in the screening interval. The need for improving the sensitivity of current screening methods and identifying newer methods of breast cancer detection is highlighted by our study.

A study of interval breast cancer within the NHS breast screening programme

AIM

To define the biological nature and malignant potential of interval cancers presenting to a breast unit within the NHS breast screening programme.

METHODS

112 interval cancers were compared with matched, screen detected and symptomatic cancers in terms of their radiographic, histopathological, and immunohistochemical features.

RESULTS

Interval cancers, strictly defined, showed no characteristic radiographic pattern. In terms of size, vascular invasion, lymph node status, and prognosis they were intermediate between screen detected and symptomatic cancers. Within the interval cancers there was an excess of grade 1 and grade 3 tumours, and lesions with a high Ki67 index but immunohistochemistry otherwise failed to discriminate between the three groups. Inclusion of data from false negative "interval cancers" did not significantly alter the results.

CONCLUSIONS

Interval cancers are more aggressive than screen detected cancers but in general less aggressive than symptomatic cancers. However, within a heterogeneous group, occasional interval cancers are exceptionally malignant.

Breast tumor characteristics as predictors of mammographic detection: comparison of interval- and screen-detected cancers

BACKGROUND

Although mammographic screening is useful for detecting early breast cancer, some tumors are detected in the interval between screening examinations. This study attempted to characterize fully the tumors detected in the two different manners.

METHODS

Our study utilized a case-control design and involved a cohort of women undergoing mammographic screening within the defined population of a health maintenance organization (the Group Health Cooperative of Puget Sound). Women were classified as having "interval" or "interval-detected" cancers (n = 150) if their diagnosis was made within 24 months after a negative-screening mammogram or one that indicated a benign condition. Cancers were classified as "screen detected" (n = 279) if the diagnosis occurred after a positive assessment by screening mammography. Tumors from women in each group were evaluated for clinical presentation, histology, proliferative characteristics, and expression of hormone receptors, p53 tumor suppressor protein, and c-erbB-2 protein.

RESULTS

Interval-detected cancers occurred more in younger women and were of larger tumor size than screen-detected cancers. In unconditional logistic regression models adjusted for age and tumor size, tumors with lobular (odds ratio [OR] = 1.9; 95% confidence interval [CI] = 0.9-4.2) or mucinous (OR = 5.5; 95% CI = 1.5-19.4) histology, high proliferation (by either mitotic count [OR = 2.9; 95% CI = 1.5-5.7] or Ki-67 antigen expression [OR = 2.3; 95% CI = 1.3-4.1]), high histologic grade (OR = 2.1; 95% CI = 1.2-4.0), high nuclear grade (OR = 2.0; 95% CI = 1.0-3.7), or negative estrogen receptor status (OR = 1.8; 95% CI = 1.0-3.1) were more likely to surface in the interval between screening examinations. Tumors with tubular histology (OR = 0.2; 95% CI = 0.0-0.8) or with a high percentage of in situ components (50%) (OR = 0.5; 95% CI = 0.2-1.2) were associated with an increased likelihood of screen detection.

CONCLUSIONS

Our data from a large group of women in a defined population indicate that screening mammography may miss tumors of lobular or mucinous histology and some rapidly proliferating, high-grade tumors.