Interval cancers and cancers in non-attenders in the Ostergötland Mammographic Screening Programme. Duration between screening and diagnosis, S-phase fraction and distant recurrence

Interval Cancers in Understanding Screening Outcomes

Interval breast cancers are not detected at routine screening and are diagnosed in the interval between screening examinations. A variety of factors contribute to interval cancers, including patient and tumor characteristics as well as the screening technique and frequency. The interval cancer rate is an important metric by which the effectiveness of screening may be assessed and may serve as a surrogate for mortality benefit.

Genetic landscape of interval and screen detected breast cancer

Interval breast cancers (IBCs) are cancers diagnosed between screening episodes. Understanding the biological differences between IBCs and screen-detected breast-cancers (SDBCs) has the potential to improve mammographic screening and patient management. We analysed and compared the genomic landscape of 288 IBCs and 473 SDBCs by whole genome sequencing of paired tumour-normal patient samples collected as part of the UK 100,000 Genomes Project. Compared to SDBCs, IBCs were more likely to be lobular, higher grade, and triple negative. A more aggressive clinical phenotype was reflected in IBCs displaying features of genomic instability including a higher mutation rate and number of chromosomal structural abnormalities, defective homologous recombination and TP53 mutations. We did not however, find evidence to indicate that IBCs are associated with a significantly different immune response. While IBCs do not represent a unique molecular class of invasive breast cancer they exhibit a more aggressive phenotype, which is likely to be a consequence of the timing of tumour initiation. This information is relevant both with respect to treatment as well as informing the screening interval for mammography.

Combining method of detection and 70-gene signature for enhanced prognostication of breast cancer

PURPOSE

Studies have shown that screen detection by national screening programs is independently associated with better prognosis of breast cancer. The aim of this study is to evaluate the association between tumor biology according to the 70-gene signature (70-GS) and survival of patients with screen-detected and interval breast cancers.

METHODS

All Dutch breast cancer patients enrolled in the MINDACT trial (EORTC-10041/BIG3-04) accrued 2007-2011, who participated in the national screening program (biennial screening, ages 50-75) were included (n = 1102). Distant Metastasis-Free Interval (DMFI) was evaluated according to the 70-GS for patients with screen-detected (n = 754) and interval cancers (n = 348).

RESULTS

Patients with screen-detected cancers had 8-year DMFI rates of 98.2% for 70-GS ultralow-, 94.6% for low-, and 93.8% for high-risk tumors (p = 0.4). For interval cancers, there was a significantly lower 8-year DMFI rate for patients with 70-GS high-risk tumors (85.2%) compared to low- (92.2%) and ultralow-risk tumors (97.4%, p = 0.0023). Among patients with 70-GS high-risk tumors, a significant difference in 8-year DMFI rate was observed between interval (85.2%, n = 166) versus screen-detected cancers (93.8%, n = 238; p = 0.002) with a HR of 2.3 (95%CI 1.2-4.4, p = 0.010) adjusted for clinical-pathological characteristics and adjuvant systemic treatment.

CONCLUSION

Among patients with 70-GS high-risk tumors, a significant difference in DMFI was observed between screen-detected and interval cancers, suggesting that method of detection is an additional prognostic factor in this subgroup and should be taken into account when deciding on adjuvant treatment strategies.

Differences between screen-detected and interval breast cancers among BRCA mutation carriers

BACKGROUND

BRCA mutation carriers have an elevated lifetime breast cancer risk and remain at risk for interval cancer development. We sought to compare BRCA mutation carriers with screen-detected versus interval breast cancers.

METHODS

Women with a known BRCA mutation prior to a breast cancer diagnosis were identified. Clinical and pathologic factors, and imaging within 18 months of diagnosis were compared among screen-detected versus interval cancers. Interval cancers were those detected by physical exam among women undergoing regular screening.

RESULTS

Of 124 breast cancers, 92 were screen and 22 clinically detected, of which 11 were interval cancers among regular screeners, and 10 were incidentally found on prophylactic mastectomy. Women with interval cancers were younger, had lower body mass indexes, and were more likely to be Black than those with screen-detected cancers (p < 0.05). Interval cancers were all invasive, larger, more likely to be node positive, and more likely to require axillary lymph node dissection and chemotherapy (p < 0.05). No significant differences were seen by BRCA mutation, mammographic density, MRI background parenchymal enhancement, tumor grade, or receptor status between cohorts. Women screened with both mammogram and MRI had significantly lower proportions of interval cancers compared to women screened with only mammogram or MRI alone (p < 0.05).

CONCLUSIONS

Interval breast cancers among BRCA mutation carriers have worse clinicopathologic features than screen-detected tumors, and require more-aggressive medical and surgical therapy. Imaging with mammogram and MRI is associated with lower interval cancer development and should be utilized among this high-risk population.

Prognosis in women with interval breast cancer: population based observational cohort study

OBJECTIVE

To compare the prognosis in women with interval breast cancer (cancer detected after a normal screening mammogram and before the next scheduled mammogram) with breast cancer detected among women not yet invited to mammography screening (non-screened).

DESIGN

Population based observational study.

SETTING

Norwegian breast cancer screening programme, implemented in different counties from 1996 to 2005.

PARTICIPANTS

7116 women with a diagnosis of breast cancer at age 50 to 72 years; 1816 had interval breast cancer and 5300 had a diagnosis of breast cancer but had not yet been invited to screening.

MAIN OUTCOME MEASURES

Characteristics of the breast tumours, and survival of the women using Kaplan Meier curves and multivariable Cox proportional hazard models.

RESULTS

Although interval cancers on average were slightly larger than the cancers in women not invited to screening, the histological type or status of axillary lymph nodes did not differ noticeably between the two groups. Among interval cancers, there were no appreciable trends in size, nodal status, grade, or hormone receptor positivity associated with time since the last normal mammogram as a marker of growth rate. After 10 years of follow-up, the survival rates were 79.1% (95% confidence interval 75.4% to 82.3%) among women with interval cancers and 76.8% (75.3% to 78.2%) among women in the non-screened cancer group (hazard ratio 0.98, 95% confidence interval 0.84 to 1.15; P=0.53). Analyses stratified by time since last normal mammogram, age at diagnosis, or screening round showed similar results.

CONCLUSION

The prognosis of women with interval breast cancers was the same as that of women with breast cancers diagnosed without mammography screening.

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.

Women's patterns of participation in mammography screening in Denmark

The objective of the study is to analyse individual women's participation patterns in mammography screening in Denmark. The study is set in the capital of Copenhagen and the county of Fyn representing around 95,000 women aged 50-69. The Central Population Register (CPR) was used to define the total target group, and supply information on migrations and deaths. Invitation and participation data came from the mammography screening programmes in Copenhagen (1991-1999) and Fyn (1993-2001), containing personal identification number, data on invitation date, participation and examination date for each screening round. In Copenhagen the coverage went from 70.5% in the first round to 63.1% in the fourth round, and the equivalent data for Fyn is 84.6% in the first round and 82.8% in the fourth round. Of the women eligible for at least three invitation rounds, 52.6% in Copenhagen and 76.4% in Fyn were faithful users, i.e. had participated in all screenings they were invited to. The conclusion is that the programme participation rates tend to overestimate the protection of the individual women covered by the programme. Behind the urban-rural gradient in programme participation is an even greater gradient in programme protection.

Survival from invasive breast cancer among interval cases in the mammography screening programmes of northern Sweden

The aim of this study was to estimate breast cancer survival according to detection mode for 5120 women with invasive breast cancer, in particular for those detected in the screening intervals. We found a significant survival difference in favour of women with cancer detected in the screening intervals (n=729) compared with those uninvited (n=1879) during the 13-year follow-up. Detection mode was proven to modify the prognostic effect of stage. Women with stage I interval cancer had shorter survival and those with stage II had longer survival than expected. It is suggested that interval cancers might consist of two subgroups with different behaviour: one of fast-growing tumours presenting as stage I cases and another of slow-growing tumours presenting as stage II+ cases. A hypothesis related to this observation is discussed.

Episode sensitivity in association with process indicators in the Finnish breast cancer screening program

We assessed the episode sensitivity of the Finnish mammography program for women aged 50-59 (partly 60-64) years and explored associations between the episode sensitivity and the screening process indicators from 1991 to 1999. For the study period, data were available from 10 screening centers. Records of 721,000 screening visits were linked to the files of the nationwide Finnish Cancer Registry from 1991 to 2001 at an individual level. The rates of screen-detected and interval breast cancers were calculated at the first and at the subsequent screens. The episode sensitivity was determined by contrasting the incidence of interval cancers with the expected population incidence rate without screening (incidence method) and as a proportion of interval cancers out of all cancers detected (detection method). At the subsequent screens, the episode sensitivity determined by the incidence method was 54% and by the detection method 65%. The sensitivity 0-11 and 12-23 months after the screening was 70% and 38%, respectively. The episode sensitivity decreased toward the end of the study period and increased with age. The center-specific sensitivity increased 13% per 1% absolute increase in the recall rate. In general, our study provides further information on the effectiveness of screening programs. The sensitivity estimates were comparable with those from other European service screening programs. The variability in the episode sensitivity suggests potential for variations in the future screening outcome.

Early breast cancer deaths in women aged 40–74 years diagnosed during the first 5 years of organised mammography service screening in north Sweden

The aim of this study was to analyse individual cases of lethal breast cancer and not to evaluate the screening programme. Women aged 40-74 years who were diagnosed with breast cancer in 1990-94 and died on or before 31 December 1998, during the gradual introduction of organised mammography service screening in north Sweden, were included in the study. Out of 342 breast cancer deaths, 280 (82%) were in symptomatic patients whose cancers were clinically detected. Most breast cancers that proved fatal were already in an advanced stage and/or of high histological grade at the time of detection. A shift towards a lower stage was seen among screen-detected and interval-detected fatal cases. In a few of the cases with fatal outcome, in patients primarily presenting with histological grade I tumours of various sizes or small screen-detected tumours less than 10mm in size, early diagnosis by mammography followed by state-of-the-art treatment did not seem to have been enough to prevent death.

Reporting of performance indicators of mammography screening in Europe

We compared short-term indicators for service mammography screening in Europe. Data were available from 17 programmes, although not all programmes provided a comprehensive reporting. More than 90% of the target population had been screened within the last 3 years in the WE trial, whereas only two-thirds of women in England and Copenhagen had been screened within the last 3 years, which will delay or reduce the effect of screening compared with the trial. Participation was highest in sparsely populated areas. Detection rates at first screen reached three times the baseline in Copenhagen, the Netherlands and North-West England. The clinical characteristics of screen-detected cases were badly reported. Given their importance for the long-term effect of screening, further data are warranted. Sensitivity and specificity could be measured only indirectly; they showed, however, considerable variation between programmes. Fyn, Florence and Stockholm had succeeded in combining high specificity with high sensitivity. With different recall policies, different proportions of women will experience a false-positive test; expected numbers after three screens were 14%, 10% and 1%, for England, Copenhagen and the Netherlands, respectively. Based on the observed wide variation in short-term indicators, a similar wide variation is expected in the effect of screening on breast cancer mortality.

Non-attendance in breast cancer screening is associated with unfavourable socio-economic circumstances and advanced carcinoma

Our first objective was to assess changes in non-attendance, proportion of advanced breast cancer and survival in Malmö Mammographic Service Screening Program, MMSSP, compared to a former trial, Malmö Mammographic Screening Trial, MMST. Our second objective was to describe non-attenders in MMSSP in socio-economic terms and risk for advanced breast cancer compared to attenders. Information from hospital and national registers was used to identify 33,800 women invited to service screening in MMSSP 1990-93. Attendance rates at first screening, the proportion of advanced breast cancers (Stage II-IV) and survival among non-attenders in MMSSP were compared to the non-attenders and with the control group of the former trial, MMST. Various socio-economic factors were assessed as potential predictors of non-attendance in MMSSP. Odds ratios (OR) and 95% confidence interval (CI) were computed. Incidence of breast cancer during a 10-year-period, relative risks and 95% CI among non-attenders compared to attenders in MMSSP were computed. Attendance rates were significantly lower in MMSSP but a lower proportion of advanced breast cancers and a somewhat better survival among breast cancer cases (not significant) was seen in non-attenders in MMSSP compared to MMST. In MMSSP non-attendance was associated with being unmarried, being born abroad, being not currently employed, crowded housing conditions and low income. Incidence of advanced breast cancer was significantly higher among non-attenders than among attenders. Attendance has decreased over time and potential reasons are discussed. Stage distribution and survival among non-attenders seem to have improved. Several socio-economic factors predict non-attendance and non-attenders are at higher risk for advanced breast cancer.

Interval cancers in a French breast cancer-screening programme (Somme Department)

The objective of this study is to analyse the detection rates and tumour diameter of interval cancers in the breast cancer mass-screening programme of Somme Department (France), launched in 1990. Interval cancers are defined as breast cancers diagnosed within 36 months after a negative screening assessment, for women attending the programme between December 1990 to December 1993. Age-adjusted incidence rates were 0.51 per 1000 woman-years of follow-up in the 3-year interval after initial and subsequent screens. Diagnosis is made at early stage (sizes < or = 10 mm) in 20% of interval cancers. This stage is higher than that in screened women (9% of in situ cases and 35% of very small tumours). Interval cancer rates are low during the first year (0.18 per 1000 woman-years of follow-up) but higher in the second and third years.

Interval cancers in the Dutch breast cancer screening programme

The nationwide breast cancer screening programme in The Netherlands for women aged 50-69 started in 1989. In our study we assessed the occurrence and stage distribution of interval cancers in women screened during 1990-1993. Records of 0.84 million screened women were linked to the regional cancer registries yielding a follow-up of at least 2.5 years. Age-adjusted incidence rates and relative (proportionate) incidences per tumour size including ductal carcinoma in-situ were calculated for screen-detected and interval cancers, and cancers in not (yet) screened women, comparing them with published data from the UK regions North West and East Anglia. In total 1527 interval cancers were identified: 0.95 and 0.99 per 1000 woman-years of follow-up in the 2-year interval after initial and subsequent screens respectively. In the first year after initial screening interval cancers amounted to 27% (26% after subsequent screens) of underlying incidence, and in the second year to 52% (55%). Generally, interval cancers had a more favourable tumour size distribution than breast cancer in not (yet) screened women. The Dutch programme detected relatively less (favourable) invasive cancers in initial screens than the UK programme, whereas the number of interval cancers confirms UK findings. Measures should be considered to improve the detection of small invasive cancers and to reduce false-negative rates, even if this will lead to increasing referral rates.