A retrospective study of the effect of participation in screening mammography on the use of chemotherapy and breast conserving surgery

Screening for breast cancer: a systematic review update to inform the Canadian Task Force on Preventive Health Care guideline

OBJECTIVE

This systematic review update synthesized recent evidence on the benefits and harms of breast cancer screening in women aged ≥ 40 years and aims to inform the Canadian Task Force on Preventive Health Care's (CTFPHC) guideline update.

METHODS

We searched Ovid MEDLINE® ALL, Embase Classic + Embase and Cochrane Central Register of Controlled Trials to update our searches to July 8, 2023. Search results for observational studies were limited to publication dates from 2014 to capture more relevant studies. Screening was performed independently and in duplicate by the review team. To expedite the screening process, machine learning was used to prioritize relevant references. Critical health outcomes, as outlined by the CTFPHC, included breast cancer and all-cause mortality, treatment-related morbidity and overdiagnosis. Randomized controlled trials (RCTs), non/quasi RCTs and observational studies were included. Data extraction and quality assessment were performed by one reviewer and verified by another. Risk of bias was assessed using the Cochrane Risk of Bias 2.0 tool for RCTs and the Joanna Brigg's Institute (JBI) checklists for non-randomized and observational studies. When deemed appropriate, studies were pooled via random-effects models. The overall certainty of the evidence was assessed following GRADE guidance.

RESULTS

Three new papers reporting on existing RCT trial data and 26 observational studies were included. No new RCTs were identified in this update. No study reported results by ethnicity, race, proportion of study population with dense breasts, or socioeconomic status. For breast cancer mortality, RCT data from the prior review reported a significant relative reduction in the risk of breast cancer mortality with screening mammography for a general population of 15% (RR 0.85 95% CI 0.78 to 0.93). In this review update, the breast cancer mortality relative risk reduction based on RCT data remained the same, and absolute effects by age decade over 10 years were 0.27 fewer deaths per 1000 in those aged 40 to 49; 0.50 fewer deaths per 1000 in those aged 50 to 59; 0.65 fewer deaths per 1000 in those aged 60 to 69; and 0.92 fewer deaths per 1000 in those aged 70 to 74. For observational data, the relative mortality risk reduction ranged from 29 to 62%. Absolute effects from breast cancer mortality over 10 years ranged from 0.79 to 0.94 fewer deaths per 1000 in those aged 40 to 49; 1.45 to 1.72 fewer deaths per 1000 in those aged 50 to 59; 1.89 to 2.24 fewer deaths per 1000 in those aged 60 to 69; and 2.68 to 3.17 fewer deaths per 1000 in those aged 70 to 74. For all-cause mortality, RCT data from the prior review reported a non-significant relative reduction in the risk of all-cause mortality of screening mammography for a general population of 1% (RR 0.99, 95% CI 0.98 to 1.00). In this review update, the absolute effects for all-cause mortality over 10 years by age decade were 0.13 fewer deaths per 1000 in those aged 40 to 49; 0.31 fewer deaths per 1000 in those aged 50 to 59; 0.71 fewer deaths per 1000 in those aged 60 to 69; and 1.41 fewer deaths per 1000 in those aged 70 to 74. No observational data were found for all-cause mortality. For overdiagnosis, this review update found the absolute effects for RCT data (range of follow-up between 9 and 15 years) to be 1.95 more invasive and in situ cancers per 1000, or 1 more invasive cancer per 1000, for those aged 40 to 49 and 1.93 more invasive and in situ cancers per 1000, or 1.18 more invasive cancers per 1000, for those aged 50 to 59. A sensitivity analysis removing high risk of bias studies found 1.57 more invasive and in situ cancers, or 0.49 more invasive cancers, per 1000 for those aged 40 to 49 and 3.95 more invasive and in situ cancers per 1000, or 2.81 more invasive cancers per 1000, in those aged 50 to 59. For observational data, one report (follow-up for 13 years) found 0.34 more invasive and in situ cancers per 1000 in those aged 50 to 69. Overall, the GRADE certainty of evidence was assessed as low or very low, suggesting that the evidence is very uncertain about the effect of screening for breast cancer on the outcomes evaluated in this review.

CONCLUSIONS

This systematic review update did not identify any new trials comparing breast cancer screening to no screening. Although 26 new observational studies were identified, the overall quality of evidence remains generally low or very low. Future research initiatives should prioritize studying screening in higher risk populations such as those from different ages, racial or ethnic groups, with dense breasts or family history.

SYSTEMATIC REVIEW REGISTRATION

Protocol available on the Open Science Framework: https://osf.io/xngsu/.

More than a Half Century of Misinformation About Breast Cancer Screening

The following is an overview of the numerous efforts to reduce access for women to breast cancer screening. Misinformation has been promoted over the many years to suggest that screening only works for women aged 50 years and over. In fact, there are no, scientifically derived data, to support the use of the age of 50 years as a threshold for screening. The randomized, controlled trials have proved that screening saves lives for women aged 40 to 74 years (the age of the women who participated).

USPSTF Recommendations and Overdiagnosis

Overdiagnosis is the concept that some cancers detected at screening would never have become clinically apparent during a woman's lifetime in the absence of screening. This could occur if a woman dies of a cause other than breast cancer in the interval between mammographic detection and clinical detection (obligate overdiagnosis) or if a mammographically detected breast cancer fails to progress to clinical presentation. Overdiagnosis cannot be measured directly. Indirect methods of estimating overdiagnosis include use of data from randomized controlled trials (RCTs) designed to evaluate breast cancer mortality, population-based screening studies, or modeling. In each case, estimates of overdiagnosis must consider lead time, breast cancer incidence trends in the absence of screening, and accurate and predictable rates of tumor progression. Failure to do so has led to widely varying estimates of overdiagnosis. The U.S. Preventive Services Task Force (USPSTF) considers overdiagnosis a major harm of mammography screening. Their 2024 report estimated overdiagnosis using summary evaluations of 3 RCTs that did not provide screening to their control groups at the end of the screening period, along with Cancer Intervention and Surveillance Network modeling. However, there are major flaws in their evidence sources and modeling estimates, limiting the USPSTF assessment. The most plausible estimates remain those based on observational studies that suggest overdiagnosis in breast cancer screening is 10% or less and can be attributed primarily to obligate overdiagnosis and nonprogressive ductal carcinoma in situ.

Screening Mammography Utilization in the United States

Breast cancer is the second leading cause of cancer mortality in adult women in the United States. Screening mammography reduces breast cancer mortality between 22% and 48%; however, screening mammography remains underutilized. Screening mammography utilization data are available from insurance claims, electronic medical records, and patient self-report via surveys, and each data source has unique benefits and challenges. Numerous barriers exist that adversely affect the use of screening mammography in the United States. This article will review screening mammography utilization in the United States, explore factors that impact utilization, and briefly discuss strategies to improve utilization.

The Association Between Mammography Screening Frequency and Breast Cancer Treatment and Outcomes: A Retrospective Cohort Study

OBJECTIVE

Guidelines for optimal frequency of screening mammography vary by professional society. Sparse evidence exists on the association between screening frequency and breast cancer treatment options. The main objective was to examine differences in cancer treatment rendered for U.S. women with different numbers of screenings prior to breast cancer diagnosis. Cancer stage at diagnosis and health care cost were assessed in secondary analyses.

METHODS

This IRB-exempt retrospective study used administrative claims data to identify women aged 44 or older with various numbers of mammographic screenings ≥11 months apart, during the four years prior to incident breast cancer diagnosis from January 2010 to December 2018. Outcomes were assessed over the six months following diagnosis. Generalized linear regression models were used to compare women with differing numbers of mammograms, adjusting for patient characteristics.

RESULTS

Claims data review identified 25 492 women who met inclusion criteria. There was a stepwise improvement in each of these screening categories such that women with four screenings, compared to women with only one screening, experienced higher rates of lumpectomy (70% vs 55%) and radiation therapy (48% vs 36%), lower rates of mastectomy (27% vs 34%) and chemotherapy (28% vs 36%), less stage 3 or 4 cancer at diagnosis (15% vs 29%), and lower health care costs within six months postdiagnosis (P < 0.001). Results were similar in a subgroup limited to women aged 44 to 49 at diagnosis.

CONCLUSION

Potential benefits of more frequent screening include less aggressive treatment and lower health care costs among women who develop breast cancer.

Misinformation and Facts about Breast Cancer Screening

Quality medical practice is based on science and evidence. For over a half-century, the efficacy of breast cancer screening has been challenged, particularly for women aged 40-49. As each false claim has been raised, it has been addressed and refuted based on science and evidence. Nevertheless, misinformation continues to be promoted, resulting in confusion for women and their physicians. Early detection has been proven to save lives for women aged 40-74 in randomized controlled trials of mammography screening. Observational studies, failure analyses, and incidence of death studies have provided evidence that there is a major benefit when screening is introduced to the general population. In large part due to screening, there has been an over 40% decline in deaths from breast cancer since 1990. Nevertheless, misinformation about screening continues to be promoted, adding to the confusion. Despite claims to the contrary, a careful reading of the guidelines issued by major groups such as the U.S. Preventive Services Task Force and the American College of Physicians shows that they all agree that most lives are saved by screening starting at the age of 40. There is no scientific support for using the age of 50 as a threshold for screening. All women should be provided with the facts and not false information about breast cancer screening so that they can make "informed decisions" for themselves about whether to participate.

Marrying Story with Science: The Impact of Outdated and Inconsistent Breast Cancer Screening Practices in Canada

Behind the science of breast cancer in Canada, as well as globally, are the stories of thousands of women, their families, and their communities. These include stories from those who have died or those suffering from the realities of stage III and stage IV breast cancer due to late detection, misinformation, and dismissal. The reality for these women is that, whilst grateful for the latest developments in cancer research, much of this knowledge is not reflected in policy and practice. Canadian guidelines do not reflect the recommended screening by experts within the field and inequities in screening practices and practitioner knowledge exist in different areas within Canada. Told through the stories of women with lived experiences of late-stage breast cancer and supported by scientific evidence, this paper explores the impact of outdated breast cancer screening practices on the lives of women. Recent patient advocacy is driving changes, such as notifying women of their breast density in a few jurisdictions in Canada, but we call for the whole medical community to take responsibility and ensure breast screening is optimised to save more lives.

Initial and ten-year treatment patterns among 11,000 breast cancer patients undergoing breast surgery-an analysis of German claims data

BACKGROUND

We aimed to explore the potential of German claims data for describing initial and long-term treatment patterns of breast cancer patients undergoing surgery.

METHODS

Using the German Pharmacoepidemiological Research Database (GePaRD, ~ 20% of the German population) we included patients with invasive breast cancer diagnosed in 2008 undergoing breast surgery and followed them until 2017. We described initial and long-term treatment patterns and deaths. Analyses were stratified by stage (as far as available in claims data), age at diagnosis, and mode of detection (screen-detected vs. interval vs. unscreened cases).

RESULTS

The cohort comprised 10,802 patients. The proportion with neoadjuvant therapy was highest in patients < 50 years (19% vs. ≤ 8% at older ages). The proportion initiating adjuvant chemotherapy within four months after diagnosis decreased with age (< 50 years: 63%, 50-69: 46%, 70-79: 27%, 80 + : 4%). Among women < 69 years, ~ 30% had two breast surgeries in year one (70-79: 21%, 80 + : 14%). Treatment intensity was lower for screen-detected compared to interval or unscreened cases, both in year one (e.g., proportion with mastectomy ~ 50% lower) and within 2-10 years after surgery (proportions with radiotherapy or chemotherapy about one third lower each).

CONCLUSIONS

This study illustrates the potential of routine data to describe breast cancer treatment and provided important insights into differences in initial and long-term treatment by mode of detection and age.

Benefits and harms of breast cancer mammography screening for women at average risk of breast cancer: A systematic review for the European Commission Initiative on Breast Cancer

OBJECTIVES

Mammography screening is generally accepted in women aged 50-69, but the balance between benefits and harms remains controversial in other age groups. This study systematically reviews these effects to inform the European Breast Cancer Guidelines.

METHODS

We searched PubMed, EMBASE and Cochrane Library for randomised clinical trials (RCTs) or systematic reviews of observational studies in the absence of RCTs comparing invitation to mammography screening to no invitation in women at average breast cancer (BC) risk. We extracted data for mortality, BC stage, mastectomy rate, chemotherapy provision, overdiagnosis and false-positive-related adverse effects. We performed a pooled analysis of relative risks, applying an inverse-variance random-effects model for three age groups (<50, 50-69 and 70-74). GRADE (Grading of Recommendations Assessment, Development and Evaluation) was used to assess the certainty of evidence.

RESULTS

We identified 10 RCTs including 616,641 women aged 38-75. Mammography reduced BC mortality in women aged 50-69 (relative risk (RR) 0.77, 95%CI (confidence interval) 0.66-0.90, high certainty) and 70-74 (RR 0.77, 95%CI 0.54-1.09, high certainty), with smaller reductions in under 50s (RR 0.88, 95%CI 0.76-1.02, moderate certainty). Mammography reduced stage IIA+ in women 50-69 (RR 0.80, 95%CI 0.64-1.00, very low certainty) but resulted in an overdiagnosis probability of 23% (95%CI 18-27%) and 17% (95%CI 15-20%) in under 50s and 50-69, respectively (moderate certainty). Mammography was associated with 2.9% increased risk of invasive procedures with benign outcomes (low certainty).

CONCLUSIONS

For women 50-69, high certainty evidence that mammography screening reduces BC mortality risk would support policymakers formulating strong recommendations. In other age groups, where the net balance of effects is less clear, conditional recommendations will be more likely, together with shared decision-making.

Current controversies in breast cancer screening

Multiple large-scale, randomized controlled trials throughout the world have demonstrated screening mammography significantly reduces a woman's risk of dying from breast cancer. Despite the known mortality reduction, the perceived harms of mammography are weighed against the known value. Multiple national guidelines have moved away from recommending all women have annual screening mammograms beginning at age 40. Instead, many now encourage women at average risk for developing breast cancer to engage in shared decision-making with their providers, carefully weighing the perceived harms against the known benefits of mammography. These factors should be incorporated into the decision about when to begin and how often to screen. This paradigm shift has been particularly controversial as it relates to women in the 40-49-year age group, considering their incidence of breast cancer and therefore derived benefit of screening is lower, yet the breast cancers that do occur tend to be more aggressive and often require intensive therapy. Thus, debates ensue over the appropriate age at which to begin screening for breast cancer, how often screening should occur, and when to stop.

Breast cancer screening: Impact on care pathways

Background

Controversy persists concerning screening programs (SPs), related to a potential risk of overdiagnosis or the impact on survival. One of the main questions to be addressed concerns the aggressiveness of the related treatments.

Methods

Using the "Cancer Cohort,” a national‐based cohort (medico‐administrative database), all women between the ages of 50 and 74 years and treated in 2014 for incident breast cancer were compared, according to whether their diagnosis was made following a mammogram performed within the framework of the SP (SP group) or outside it (NSP group).

Results

A total of 23 788 women were identified: 13 530 (57%) in the SP group and 10 258 (43%) in the NSP group. The women in the SP group had a higher rate of in situ or localized invasive breast cancer. They had a higher rate of breast‐conserving surgery (82% vs 70%), and a lower rate of chemotherapy (34% vs 53%). These findings were observed irrespective of the stage. They had a higher rate of pathways involving breast‐conserving surgery followed by radiotherapy. Among women with metastatic cancer, those in the SP group had a lower proportion of liver, lung, brain, and bone metastases, and a higher proportion of lymph node metastases (other than axillary), irrespective of the time to onset of the metastases.

Conclusion

The women in whom cancer was diagnosed following a mammogram performed in the context of the SP had less advanced cancer and less aggressive treatments. This observational study helps illustrate the benefit of the SP in France using a different approach.

Differences in Breast Cancer Characteristics by Mammography Screening Participation or Non-Participation

BACKGROUND

The goal of the German Mammography Screening Program (MSP) is to enable the early detection and less intensive treatment of breast cancer. We compared tumor characteristics and prognostic markers in breast cancers that were detected by screening in the MSP, in the interval after a negative screening, or among non-participants in screening.

METHODS

This retrospective series includes all of the 1531 cases of invasive and in situ breast cancer (DCIS, ductal carcinoma in situ) that were newly diagnosed in two certified breast care centers in Münster in the period 2006-2012 among women in the MSP target population. Complete information on the tumor characteristics, tumor biology, and primary surgical treatment were available for all cases. The mode of cancer detection was determined from the state cancer registry of North Rhine-Westphalia. Due to the retrospective design of this case series, there was no randomized allocation.

RESULTS

The 874 cases of breast cancer among MSP participants (714 detected by screening, 160 in the interval after a negative screen) and the 657 cases among non-participants arose in women of similar age (mean, 60.2 versus 59.3 years). MSP participants with breast cancer had DCIS more commonly than non-participants did (23% versus 13%); invasive carcinomas were smaller (74% versus 55% in the T1 stage), less commonly node-positive (25% versus 31%), less commonly high-grade (19% versus 27%), and less commonly triple-negative (7% versus 12%); MSP participants received neoadjuvant treatment less frequently (2% versus 8%) and more frequently underwent breast-conserving surgery (75% versus 62%). They less commonly had a guideline-based indication for adjuvant chemotherapy (46% versus 52%).

CONCLUSION

MSP participants with invasive breast cancer can generally be treated with less intensive surgical and systemic therapy than non-participants, even if interval cancers are also taken into account. Future studies should also investigate quality of life after a diagnosis of invasive carcinoma in screening participants.

Treatment Intensity Differences After Early-Stage Breast Cancer (ESBC) Diagnosis Depending on Participation in a Screening Program

BACKGROUND

While population mammographic screening identifies early-stage breast cancers (ESBCs; ductal carcinoma in situ [DCIS] and invasive disease stages 1-3A), commentaries suggest that harms from overdiagnosis and overtreatment may outweigh the benefits. Apparent benefits to patients with screen-detected cancers may be due to selection bias from exclusion of interval cancers (ICs). Treatment intensity is rarely discussed, with an assumption that all ESBCs are treated similarly. We hypothesized that women diagnosed while in a screening program would receive less-intense treatment than those never or not recently screened (NRS).

METHODS

This was a retrospective analysis of all women aged 50-69 years managed for ESBC (invasive or DCIS) during the period 2007-2013 within a single service, comparing treatment according to screening status. Data on demographics, detection, pathology, and treatment were derived from hospital, cancer registry, and screening service records.

RESULTS

Overall, 622 patients were active screeners (AS) at diagnosis (569 screen-detected and 53 ICs) and 169 patients were NRS. AS cancers were smaller (17 mm vs. 26 mm, p < 0.0001), less likely to involve nodes (26% vs. 48%, p < 0.0001), and lower grade. For invasive cancer, NRS patients were more likely to be recommended for mastectomies [35% vs. 16%; risk ratio(RR) 2.2, p < 0.0001], axillary dissection (43% vs. 19%; RR 2.3, p < 0.0001), adjuvant chemotherapy (65% vs. 37%; RR 1.7, p < 0.0001), and postmastectomy radiotherapy (58% vs. 39%; RR 1.5, p = 0.04).

CONCLUSION

Participants in population screening diagnosed with ESBC receive substantially less-intense treatment than non-participants. Differences persist when potential overdiagnosis is taken into account; these differences should be factored into debates around mammographic screening.

Surgical options for Chinese patients with early invasive breast cancer: Data from the Hong Kong Breast Cancer Registry

BACKGROUND

Breast conserving surgery (BCS) is preferred for suitable candidates, while mastectomy (MTX) with reconstruction (MTX + R) is considered a better option for patients requiring MTX. In Hong Kong, the rates of BCS and breast reconstruction are relatively low. This paper aims to study the surgical options and their predictors among Hong Kong breast cancer patients.

METHODS

Data is retrieved from the Hong Kong Breast Cancer Registry (HKBCR) from 2007 to 2013. A total of 4519 Stage I-II breast cancer patients who had surgical treatments were included in this retrospective study.

RESULTS

Our multivariate logistic regression shows that people who were younger (age < 40 years: OR, 1.5; 95% CI, 1.1-2.1; p = 0.010), more educated (undergraduate/postgraduate: OR, 2.8; 95% CI, 1.7-4.4; p < 0.0001), never married (OR, 1.5; 95% CI, 1.1-1.9; p = 0.002), had regular mammography screening (OR, 1.5; 95% CI, 1.3-1.8; p < 0.0001), had screen-detected cancers (OR, 1.3; 95% CI, 1.0-1.6; p = 0.031), and who underwent surgery at a private medical service facility (OR, 1.8; 95% CI, 1.6-2.2; p < 0.0001) were more likely to receive BCS. In addition, people who were younger (age < 40 years: OR, 15.9; 95% CI, 6.5-39.2; p < 0.0001), more educated (undergraduate/postgraduate: OR, 26.8; 95% CI, 3.6-201.4; p = 0.001), had regular mammography screening (OR, 1.6; 95% CI, 1.1-2.3; p = 0.008), had screen-detected cancers (OR, 2.1; 95% CI, 1.4-3.3; p = 0.001), and had smaller tumor (≤ 2.0 cm: OR, 0.39; 95% CI, 0.20-0.76; p = 0.005) were more likely to have reconstruction after MTX.

CONCLUSION

Chinese patients have lower BCS and breast reconstruction rate. Besides cultural difference, patient-related factors such as age, education, marital status, mammography screening, the use of private medical facilities, and clinical characteristics including smaller tumor size and peripherally located tumor were significant predictors for type of surgical treatments in Chinese women with early breast cancer.

European Code against Cancer, 4th Edition: Cancer screening

In order to update the previous version of the European Code against Cancer and formulate evidence-based recommendations, a systematic search of the literature was performed according to the methodology agreed by the Code Working Groups. Based on the review, the 4th edition of the European Code against Cancer recommends: "Take part in organized cancer screening programmes for: Bowel cancer (men and women); Breast cancer (women); Cervical cancer (women)." Organized screening programs are preferable because they provide better conditions to ensure that the Guidelines for Quality Assurance in Screening are followed in order to achieve the greatest benefit with the least harm. Screening is recommended only for those cancers where a demonstrated life-saving effect substantially outweighs the potential harm of examining very large numbers of people who may otherwise never have, or suffer from, these cancers, and when an adequate quality of the screening is achieved. EU citizens are recommended to participate in cancer screening each time an invitation from the national or regional screening program is received and after having read the information materials provided and carefully considered the potential benefits and harms of screening. Screening programs in the European Union vary with respect to the age groups invited and to the interval between invitations, depending on each country's cancer burden, local resources, and the type of screening test used For colorectal cancer, most programs in the EU invite men and women starting at the age of 50-60 years, and from then on every 2 years if the screening test is the guaiac-based fecal occult blood test or fecal immunochemical test, or every 10 years or more if the screening test is flexible sigmoidoscopy or total colonoscopy. Most programs continue sending invitations to screening up to the age of 70-75 years. For breast cancer, most programs in the EU invite women starting at the age of 50 years, and not before the age of 40 years, and from then on every 2 years until the age of 70-75 years. For cervical cancer, if cytology (Pap) testing is used for screening, most programs in the EU invite women starting at the age of 25-30 years and from then on every 3 or 5 years. If human papillomavirus testing is used for screening, most women are invited starting at the age of 35 years (usually not before age 30 years) and from then on every 5 years or more. Irrespective of the test used, women continue participating in screening until the age of 60 or 65 years, and continue beyond this age unless the most recent test results are normal.

Stage, treatment and outcomes for patients with breast cancer in British Columbia in 2002: a population-based cohort study

BACKGROUND

There are very few long-term Canadian data on breast cancer outcomes by stage. We described the stage, treatment and outcomes of breast cancer at a population level for patients in British Columbia.

METHODS

This population-based cohort study included almost all patients with incident breast cancer registered in 2002 (about 97.6% registry case completeness). For these patients, information on stage, primary local surgery, radiotherapy, chemotherapy, hormone therapy and survival outcome (based on registry date and cause-of-death data) were available. We calculated Kaplan-Meier curves for breast cancer-specific survival and overall survival by stage and analyzed prognostic and treatment factors with a multivariable Cox model.

RESULTS

The 2927 incident cases of breast cancer identified in 2002 had the following distribution by stage: stage 0 (in situ), 424 (14%); stage I, 1118 (38%); stage II, 938 (32%); stage III, 233 (8%); stage IV, 123 (4%); unknown, 91 (3%). The distribution of patients' ages was < 40 years, 127 (4%); 40-49, 538 (18%); 50-59, 719 (25%); 60-69, 660 (23%); 70-79, 583 (20%); ≥ 80, 300 (10%). Within the first year after diagnosis, radiotherapy was provided to 1649 patients (56%), chemotherapy to 928 (32%) and hormone therapy to 1664 (57%). Ten-year breast cancer-specific survival rates by stage were > 99% for stage 0, 95% for stage I, 81% for stage II, 55% for stage III and 4% for stage IV. Ten-year overall survival rates were 89% for stage 0, 81% for stage I, 68% for stage II, 43% for stage III and 2% for stage IV.

INTERPRETATION

This analysis provides a Canadian benchmark for treatment rates and 10-year outcomes by stage for all incident cases of breast cancer in a single province. Outcomes in British Columbia compared well with published rates for the United States and Europe.

Impact of mammography detection on the course of breast cancer in women aged 40-49 years

PURPOSE

To analyze trends in detection method related to breast cancer stage at diagnosis, treatments, and outcomes over time among 40-49-year-old women.

MATERIALS AND METHODS

i This study was institutional review board approved, with a waiver of informed consent, and HIPAA compliant. A longitudinal prospective cohort study was conducted of women aged 40-49 years who had primary breast cancer, during 1990-2008, and were identified and tracked by a dedicated registry database (n = 1977). Method of detection--patient detected (PtD), physician detected (PhysD), or mammography detected (MamD)--was chart abstracted. Disease-specific survival and relapse-free survival statistics were calculated by using the Kaplan-Meier method for stage I-IV breast cancer.

RESULTS

A significant increase in the percentage of MamD breast cancer over time (28%-58%) and a concurrent decline in patient and physician detected (Pt/PhysD) breast cancer (73%-42%) (Pearson x(2) = 72.72, P < .001) were observed over time from 1990 to 2008, with an overall increase in lower-stage disease detection and a decrease in higher-stage disease. MamD breast cancer patients were more likely to undergo lumpectomy (67% vs 48% of Pt/PhysD breast cancer patients) and less likely to undergo modified radical mastectomy (25% vs 47% of the Pt/PhysD breast cancer patients) (P < .001). Uncorrected for stage, 13% of MamD breast cancer patients underwent surgery and chemotherapy versus 22% of Pt/PhysD breast cancer patients (P < .001), and 31% of MamD breast cancer patients underwent surgery, radiation therapy, and chemotherapy versus 59% of Pt/PhysD breast cancer patients (x(2) = 305.13, P < .001). Analyzing invasive cancers only, 5-year relapse-free survival for MamD breast cancer patients was 92% versus 88% for Pt/PhysD patients (log-rank test, 12.47; P < .001).

CONCLUSION

Increased mammography-detected breast cancer over time coincided with lower-stage disease detection resulting in reduced treatment and lower rates of recurrence, adding factors to consider when evaluating the benefits of mammography screening of women aged 40-49 years.

Comparison of nonbreast cancer incidence, survival and mortality between breast screening program participants and nonparticipants

Comparisons of cancer mortality between users and nonusers of screening are potentially biased because of the effects of self-selection. Previous studies of breast screening have found that individuals likely to participate have lower breast cancer mortality than those unlikely to participate. This study compares the incidence, survival and mortality for all cancer types other than breast between participants and nonparticipants in a service screening mammography program. British Columbian females having their first mammogram between the ages of 40 and 79 and the years 1988 and 2004 were identified as a cohort of "participants". Person-years of follow-up of participants were aggregated by age and year. Nonparticipant person-years were obtained by subtraction from the total female population. Cancer diagnoses other than breast were identified for participants and nonparticipants. Age, calendar year, and income adjusted relative risks of cancer incidence were estimated from generalized additive models with Poisson errors. Hazard ratios were estimated by Cox regression. Observed cancer mortality in participants was compared with expected mortality generated from nonparticipant incidence and survival rates. Incidence rates of cancer showed a mixed relationship with some elevated, some decreased and others similar to nonparticipant rates. Cancer survival was higher among participants for most cancer types, with an overall hazard ratio of 0.76 (0.73-0.79). Observed mortality in participants was less than expected for most cancers, with an overall mortality ratio of 0.60 (0.58-0.62). The general cancer experience of screening program participants is different from that of the general population.