Are mammography image acquisition factors, compression pressure and paddle tilt, associated with breast cancer detection in screening?

OBJECTIVES: To assess the associations between objectively measured mammographic compression pressure and paddle tilt and breast cancer (BC) detected at the same ("contemporaneous") screen, subsequent screens, or in-between screens (interval cancers). METHODS: Automated pressure and paddle tilt estimates were derived for 80,495 mammographic examinations in a UK population-based screening programme. Adjusted logistic regression models were fitted to estimate the associations of compression parameters with BC detected at contemporaneous screen (777 cases).Nested case-control designs were used to estimate associations of pressure and tilt with: (a) interval cancer (148 cases/625 age-matched controls) and (b) subsequent screen-detected cancer (344/1436), via conditional logistic regression. RESULTS: Compression pressure was negatively associated with odds of BC at contemporaneous screen (odds ratio (OR) for top versus bottom third of the pressure distribution: 0.74; 95% CI 0.60, 0.92; P-for-linear-trend (Pt) = 0.007). There was weak evidence that moderate pressure at screening was associated with lower odds of interval cancer (OR for middle versus bottom third: 0.63; 95% CI 0.38, 1.05; p = 0.079), but no association was found between pressure and the odds of BC at subsequent screen. There was no evidence that paddle tilt was associated with the odds of contemporaneous, subsequent screen or interval cancer detection. CONCLUSIONS: Findings are consistent with compression pressure, but not paddle tilt, affecting the performance of mammographic screening by interfering with its ability to detect cancers. ADVANCES IN KNOWLEDGE: Inadequate or excessive compression pressure at screening may contribute to a reduced ability to detect cancers, resulting in a greater number of interval cancer cases.

To what extent are objectively measured mammographic imaging techniques associated with compression outcomes.

OBJECTIVE: To describe the association between objectively measurable imaging techniques and the resulting compression thickness and dose. METHODS: The study included 80,495 routine screens from the South-West London Breast Screening Service between March 2013 and July 2017. Average compression force, paddle tilt and dose were calculated. The Volpara® DensityTM algorithm was used to estimate pressure, breast volume and density.Linear regression models, using generalized estimating equations (GEEs) to account for clustering by practitioner, assessed the strength of the associations between the imaging compression outcomes, (thickness, dose) and imaging techniques (force, pressure and paddle tilt), adjusting for the subject's characteristics (age, ethnicity, breast volume and percent mammographic density). RESULTS: Fully adjusted linear regression models showed that compression thickness decreased by ~1 mm (~2% of mean thickness) for every 1daN increase in force and decreased by ~0.8 mm with an increase of 1 kPa of pressure (at median pressure). Increasing pressure above 15 kPa resulted in minimal reduction in thickness. Dose increased with increased force but decreased by ~1% of mean dose with every increase in 1 kPa of pressure. For 1o increase in paddle tilt, the compression thickness increased by ~1.5 mm (~2.5%) and dose increased by ~2.5%, (Pt <0.001 in all cases). CONCLUSION: Differences in imaging technique are associated with imaging outcome measures (thickness and dose). A better understanding of the association between objective image acquisition parameters and tumour conspicuity could lead to clearer guidelines for practitioners. ADVANCES IN KNOWLEDGE: Increased paddle tilt is associated with increased compression thickness and increased dose after adjustment for breast volume and force applied.

Did the use of open invitations in place of timed appointment invitations reduce the uptake of breast screening in the London region during the COVID-19 recovery?

OBJECTIVE: The Covid-19 pandemic created a backlog of women awaiting an invitation for breast screening in the UK. To recover in a timely fashion, the National Health Service programme opted to issue open invitations (OI) to women rather than the standard pre-booked timed appointments (TA). Historically, OIs have been shown to result in lower uptake. The aim of this study was to make use of a natural experiment to compare uptake in groups sent an OI with those sent a TA during a period when both invitation methods were in use. METHODS: Women invited for routine screening at one of the six London breast screening services from September 2020 to March 2021 were included and grouped according to the type of invitation they had received (TA or OI). The outcome was attendance within 6 months of opening the screening episode. Data were analysed by logistic regression. RESULTS: During the period of the study, 78,192 (32.5%) women received a TA and 162,680 (67.5%) received an OI. In the TA group, 47,391 (60.6%) attended within six months of offered appointment and in the OI group 86,430 (53.1%) attended. This difference was significant (p < 0.001). The odds ratio (95% CI) for the attended outcome was 1.44 (1.33-1.55) adjusted for differences in deprivation and for invitation category (first invitation or subsequent invitation). CONCLUSIONS: This study supports the view that TA delivers a higher uptake than OI. It suggests that during this period over 12,000 women in London, who would have been expected to attend if given the standard TA, did not attend their appointment having received an OI.

Left-right breast asymmetry and risk of screen-detected and interval cancers in a large population-based screening population.

OBJECTIVES: To assess the associations between automated volumetric estimates of mammographic asymmetry and breast cancers detected at the same ("contemporaneous") screen, at subsequent screens, or in between (interval cancers). METHODS: Automated measurements from mammographic images (N = 79,731) were used to estimate absolute asymmetry in breast volume (BV) and dense volume (DV) in a large ethnically diverse population of attendees of a UK breast screening programme. Logistic regression models were fitted to assess asymmetry associations with the odds of a breast cancer detected at contemporaneous screen (767 cases), adjusted for relevant confounders.Nested case-control investigations were designed to examine associations between asymmetry and the odds of: (a) interval cancer (numbers of cases/age-matched controls: 153/646) and (b) subsequent screen-detected cancer (345/1438), via conditional logistic regression. RESULTS: DV, but not BV, asymmetry was positively associated with the odds of contemporaneous breast cancer (P-for-linear-trend (Pt) = 0.018). This association was stronger for first (prevalent) screens (Pt = 0.012). Both DV and BV asymmetry were positively associated with the odds of an interval cancer diagnosis (Pt = 0.060 and 0.030, respectively). Neither BV nor DV asymmetry were associated with the odds of having a subsequent screen-detected cancer. CONCLUSIONS: Increased DV asymmetry was associated with the risk of a breast cancer diagnosis at a contemporaneous screen or as an interval cancer. BV asymmetry was positively associated with the risk of an interval cancer diagnosis. ADVANCES IN KNOWLEDGE: The findings suggest that DV and BV asymmetry may provide additional signals for detecting contemporaneous cancers and assessing the likelihood of interval cancers in population-based screening programmes.

Ethnic and age differences in right-left breast asymmetry in a large population-based screening population.

OBJECTIVE: Exposure to sex hormones is important in the pathogenesis of breast cancer and inability to tolerate such exposure may be reflected in increased asymmetrical growth of the breasts. This study aims to characterize, for the first time, asymmetry in breast volume (BV) and radiodense volume (DV) in a large ethnically diverse population. METHODS: Automated measurements from digital raw mammographic images of 54,591 cancer-free participants (aged 47-73) in a UK breast screening programme were used to calculate absolute (cm3) and relative asymmetry in BV and DV. Logistic regression models were fitted to assess asymmetry associations with age and ethnicity. RESULTS: BV and DV absolute asymmetry were positively correlated with the corresponding volumetric dimension (BV or DV). BV absolute asymmetry increased, whilst DV absolute asymmetry decreased, with increasing age (P-for-linear-trend <0.001 for both). Relative to Whites, Blacks had statistically significantly higher, and Chinese lower, BV and DV absolute asymmetries. However, after adjustment for the corresponding underlying volumetric dimension the age and ethnic differences were greatly attenuated. Median relative (fluctuating) BV and DV asymmetry were 2.34 and 3.28% respectively. CONCLUSION: After adjusting for the relevant volumetric dimension (BV or DV), age and ethnic differences in absolute breast asymmetry were largely resolved. ADVANCES IN KNOWLEDGE: Previous small studies have reported breast asymmetry-breast cancer associations. Automated measurements of asymmetry allow the conduct of large-scale studies to further investigate these associations.