Identification of key components in the irreversibility of salmon calcitonin binding to calcitonin receptors

This study investigates the poor reversibility of salmon calcitonin (sCT) binding to rat and human calcitonin receptors. Efficacy of CT and analogue peptides in (125)I-sCT binding competition and cAMP assays was compared with the dissociation kinetics of (125)I-labelled peptides. Assessment was performed on cells stably expressing either rat or human calcitonin receptors. Dissociation kinetics of the antagonists, sCT(8-32) and AC512, revealed that binding was rapidly and completely reversible at the receptors, despite high affinity binding, suggesting that poor reversibility required the active conformation of the receptor. G protein coupling was not essential as the dissociation kinetics of (125)I-sCT binding to cell membranes did not significantly alter in the presence of GTP gamma S. Time course experiments established that the transition to irreversibility was slow, while the reversible component of binding appeared to involve a single population of either receptor states or binding sites. Pre-bound (125)I-human CT dissociated rapidly from the receptors, indicating that not all agonists bound irreversibly. To identify structural features of sCT that contribute to its poor reversibility, dissociation kinetics of sCT analogues with various structural modifications were examined. Increasing truncation of N-terminal residues of sCT analogues led to a corresponding increase in the rate of peptide dissociation. Salmon CT peptides which had been substituted at the N-terminus by 13-21 residues of human CT (hCT) were equipotent with sCT in binding competition and cAMP accumulation assays but exhibited a dissociation rate similar to hCT. In contrast, despite lower affinity and efficacy at the receptors, the chimeric analogue sCT(1-16)-hCT(17-32) displayed poorly reversible binding, similar to sCT. Analysis of the dissociation kinetics of sCT analogues with differing alpha-helix forming potential indicated that the ability to form alpha-helical secondary structure was an important factor in the rate of ligand dissociation. We hypothesise that poor reversibility results from a conformational change in the receptor and/or ligand and that this is dependent, at least in part, on interaction with residues constrained within the alpha-helix of the peptide.     

The Association of Surgical Margins and Local Recurrence in Women with Early-Stage Invasive Breast Cancer Treated with Breast-Conserving Therapy: A Meta-Analysis

Purpose

There is no consensus on what constitutes adequate negative margins in breast-conserving therapy (BCT). We systematically review the evidence on surgical margins in BCT for invasive breast cancer to support the development of clinical guidelines.

Methods

Study-level meta-analysis of studies reporting local recurrence (LR) data relative to final microscopic margin status and the threshold distance for negative margins. LR proportion was modeled using random-effects logistic meta-regression.

Results

Based on 33 studies (LR in 1,506 of 28,162), the odds of LR were associated with margin status [model 1: odds ratio (OR) 1.96 for positive/close vs negative; model 2: OR 1.74 for close vs. negative, 2.44 for positive vs. negative; (P < 0.001 both models)] but not with margin distance [model 1: >0 mm vs. 1 mm (referent) vs. 2 mm vs. 5 mm (P = 0.12); and model 2: 1 mm (referent) vs. 2 mm vs. 5 mm (P = 0.90)], adjusting for study median follow-up time. There was little to no statistical evidence that the odds of LR decreased as the distance for declaring negative margins increased, adjusting for follow-up time [model 1: 1 mm (OR 1.0, referent), 2 mm (OR 0.95), 5 mm (OR 0.65), P = 0.21 for trend; and model 2: 1 mm (OR 1.0, referent), 2 mm (OR 0.91), 5 mm (OR 0.77), P = 0.58 for trend]. Adjustment for covariates, such as use of endocrine therapy or median-year of recruitment, did not change the findings.

Conclusions

Meta-analysis confirms that negative margins reduce the odds of LR; however, increasing the distance for defining negative margins is not significantly associated with reduced odds of LR, allowing for follow-up time. Adoption of wider relative to narrower margin widths to declare negative margins is unlikely to have a substantial additional benefit for long-term local control in BCT.     

Breast cancer--new and emerging technologies for diagnosis and management

Part six of this series discusses established and emerging technologies in breast cancer care, with an emphasis on technologies in diagnosis and treatment supported by evidence. These include percutaneous core biopsy techniques and breast imaging in diagnosis. From the surgical perspective, we discuss the emerging role of sentinel node biopsy as a potentially less invasive method of staging the axilla in women with breast cancer. We also review advances in radiotherapy techniques that have allowed delivery of radiotherapy with more precision and improved safety.     

Hormone replacement therapy use dramatically increases breast oestrogen receptor expression in obese postmenopausal women

Background

It is known that use of hormone replacement therapy (HRT) by postmenopausal women increases the risk of breast cancer.

Method

In this study, oestrogen receptor (ER)-α expression is examined using standard immunoperoxidase technique.

Results

Normal breast samples of 11 Australian postmenopausal women have been included in the ER-α study; the result showed a strong correlation (r ² = 0.80) between ER-α expression in normal breast epithelial cells and body mass index (BMI) in normal women who currently use HRT.

Conclusion

This finding confirms that the possibility of increased risk of breast cancer associated with increased ER-α expression in normal breast epithelial cells, in turn associated with high BMI and the use of HRT.     

Medical tests: women's reported and preferred decision-making roles and preferences for information on benefits, side-effects and false results

Objective To determine women's preferences for and reported experience with medical test decision‐making. Design Computer‐assisted telephone survey. Setting and participants Six hundred and fifty‐two women resident in households randomly selected from the New South Wales electronic white pages. Main outcome measures Reported and preferred test and treatment (for comparison) decision‐making, satisfaction with and anxiety about information on false results and side‐effects; and effect of anxiety on desire for such information. Results Overall most women preferred to share test (94.6%) and treatment (91.2%) decision‐making equally with their doctor, or to take a more active role, with only 5.4–8.9% reporting they wanted the doctor to make these decisions on their behalf. This pattern was consistent across all age groups. In general, women reported experiencing a decision‐making role that was consistent with their preference. Women who had a usual doctor were more likely to report experiencing an active role in decision‐making. More women reported receiving as much information as they wanted about the benefits of tests and treatment than about the side‐effects of tests and treatment. Most women wanted information about the possibility of false test results (91.5%) and test side‐effects (95.6%), but many reported the doctor never provided this information (false results = 40.0% and side‐effects = 31.3%). A substantial proportion said this information would make them anxious (false results = 56.6% and side‐effects = 43.1%), but reported they wanted the information anyway (false results = 77.6% and side‐effects = 88.1%). Conclusions Women prefer an active role in test and treatment decision‐making. Many women reported receiving inadequate information. If so, this may jeopardize informed decision‐making.     

Evidence of the effect of adjunct ultrasound screening in women with mammography-negative dense breasts: interval breast cancers at 1 year follow-up

Surveillance of interval cancers (IC) provides a measure of breast screening efficacy. Increased breast density is a predictor of breast cancer risk and of the risk of IC in screening. Improving screening sensitivity in women with dense breasts, through adjunct ultrasound (US), may potentially reduce IC; however this has not been proven. We report on first-year IC in a retrospective cohort of 8865 women who had 19,728 screening examinations (2001-2006): women with non-dense (D1-D2) breasts received mammography (M) screening, and women with dense (D3-D4) breasts also received ultrasound. Data linkage with both hospital discharge records and cancer registry databases was used to identify IC.Underlying cancer rates (cancers observed within 1-year from screening) were 6.3/1000 screens in the D1-D2 group and 8.3/1000 screens in the D3-D4 group. Cancer detection rate (CDR) was 5.98/1000 in all screening examinations; in D3-D4 breasts ultrasound had an additional CDR of 4.4/1000 screens. There were 21 first-year IC, an overall interval cancer rate (ICR) of 1.07/1000 negative screens: 0.95/1000 in women <50 years and 1.16/1000 screens in women ?50 years. ICR by breast density were 1.0/1000 negative screens in D1-D2, and 1.1/1000 negative screens in D3-D4. Interval cancers were early stage (in situ or small invasive) cancers, almost all were node-negative. Screening sensitivity was 83.5% for mammography alone in D1-D2 breasts relative to 86.7% for mammography with ultrasound in D3-D4 breasts.Our study shows that including ultrasound as adjunct screening in women with D3-D4 breasts brings the IC rate to similar levels as IC in non-dense breasts - this suggests that additional cancer detection by ultrasound is likely to improve screening benefit in dense breasts, and supports the implementation of a randomised trial of adjunct ultrasound in women with increased breast tissue density.     

Reliability of sparing Papanicolaou test conventional reading in cases reported as No Further Review at AutoPap-assisted cytological screening: survey of 30,658 cases with follow-up cytological screening

BACKGROUND: AutoPap-assisted smear reading has been proposed prior to conventional manual reading; the latter may be unnecessary for cases reported as No Further Review (NFR) and would be required for cases reported as Review (REV). METHODS: The authors evaluated comparable concurrent screening cohorts who were undergoing a conventional manual (CONV) or an AutoPap-assisted smear reading within the same screening program. The authors evaluated the prevalence of CIN2+ at repeat screening in subjects 1) with a negative report at conventional Papanicolaou test (CONV- = 9605), 2) with a REV report at AutoPap, followed by a negative conventional reading (REV- = 17,576), and 3) with a NFR report at AutoPap, followed by a negative rapid review (NFR- = 3477) at previous (baseline) screening. RESULTS: Crude CIN2+ detection rate was 0.176% (17 of 9605), 0.187% (33 of 17,576), or 0.02% (1 of 3477) among baseline CONV-, REV-, or NFR- subjects, respectively. No significant difference in CIN2+ detection rates was evident when comparing the whole baseline CONV- and AutoPap- cohorts (0.176% versus 0.161%; chi(2) ((df=1)) = 2.48, P = .87), or baseline CONV- with baseline REV- subjects (chi(2) ((df=1)) = 2.49, P = .96), whereas a borderline difference was evident when comparing baseline NFR- with CONV- (chi(2) ((df=1)) = 3.07, P = .079) or with REV- (chi(2) ((df=1)) = 3.61, P = .057) subjects. CONCLUSIONS: The authors' findings suggested that AutoPap assisted reading is comparable to conventional reading, as the frequency of CIN2+ detected at repeat screening did not differ between baseline CONV- or AutoPap- cohorts. The baseline NFR- subgroups showed a lower, borderline significant CIN2+ detection rate when compared to the CONV- cohort. The very low observed negative predictive value of an NFR report (0.02%) suggested that these subjects may safely return to periodic screening and that quality control measures such as rapid review or full manual reading of a random sample are probably not necessary.     

Proportional incidence and radiological review of large (T2+) breast cancers as surrogate indicators of screening programme performance

Objectives

Surrogate measures of screening performance [e.g. interval cancer (IC) proportional incidence] allow timely monitoring of sensitivity and quality. This study explored measures using large (T2+) breast cancers as potential indicators of screening performance.

Methods

The proportional incidence of T2+ cancers (observed/expected cases) in a population-based screening programme (Trento, 2001–2009) was estimated. A parallel review of ‘negative’ preceding mammograms for screen-detected T2+ and for all ICs, using ‘blinded’ independent readings and case-mixes (54?T2+, 50 ICs, 170 controls) was also performed.

Results

T2+ cancers were observed in 168 screening participants: 48 at first screen, 67 at repeat screening and 53 ICs. The T2+ estimated proportional incidence was 68% (observed/expected?=?168/247), corresponding to an estimated 32% reduction in the rate of T2+ cancers in screening participants relative to that expected without screening. Majority review classified 27.8% (15/54) of T2+ and 28% (14/50) of ICs as screening error (P?=?0.84), with variable recall rates amongst radiologists (8.8–15.2%).

Conclusions

T2+ review could be integrated as part of quality monitoring and potentially prove more feasible than IC review for some screening services.

Key Points

? Interval breast cancers, assumed as screening failures, are monitored to estimate screening performance ? Large (T2+) cancers at screening may also represent failed prior screening detection ? Analysis of T2+ lesions may be more feasible than assessing interval cancers ? Analysis of T2+ cancers is a potential further measure of screening performance     

Evaluation of the evidence on staging imaging for detection of asymptomatic distant metastases in newly diagnosed breast cancer

While guidelines recommend against routine use of staging imaging to detect asymptomatic distant metastases (DM) in newly diagnosed breast cancer (BC), modern imaging technologies may have improved detection capability and may have a role in some cases. We performed a systematic review of studies (1995-2011) evaluating the prevalence of DM and the accuracy of staging imaging for detection of asymptomatic DM. Twenty-two studies reporting on 14,824 BC subjects (median age 53 years) undergoing staging imaging were eligible. Median prevalence of DM was 7.0% (range 1.2-48.8%); prevalence increased with increasing BC stage. Conventional imaging studies had lower DM prevalence than studies of PET(PET/CT). Imaging median sensitivity/specificity respectively were: combined conventional imaging 78.0%/91.4%; bone scintigraphy 98.0%/93.5%; chest X-ray 100%/97.9%; liver ultrasound 100%/96.7%; CT chest/abdomen 100%/93.1%; FDG-PET 100.0%/96.5%; FDG-PET/CT 100%/98.1%. Low prevalence of DM was seen in Stage I-II BC with much higher prevalence in more advanced disease. Accuracy of PET modalities was very high however the high proportion of detected asymptomatic DM partly reflects selection bias.