Mammography screening reduces rates of advanced and fatal breast cancers: Results in 549,091 women

BACKGROUND

It is of paramount importance to evaluate the impact of participation in organized mammography service screening independently from changes in breast cancer treatment. This can be done by measuring the incidence of fatal breast cancer, which is based on the date of diagnosis and not on the date of death.

METHODS

Among 549,091 women, covering approximately 30% of the Swedish screening-eligible population, the authors calculated the incidence rates of 2473 breast cancers that were fatal within 10 years after diagnosis and the incidence rates of 9737 advanced breast cancers. Data regarding each breast cancer diagnosis and the cause and date of death of each breast cancer case were gathered from national Swedish registries. Tumor characteristics were collected from regional cancer centers. Aggregated data concerning invitation and participation were provided by Sectra Medical Systems AB. Incidence rates were analyzed using Poisson regression.

RESULTS

Women who participated in mammography screening had a statistically significant 41% reduction in their risk of dying of breast cancer within 10 years (relative risk, 0.59; 95% CI, 0.51-0.68 [P < .001]) and a 25% reduction in the rate of advanced breast cancers (relative risk, 0.75; 95% CI, 0.66-0.84 [P < .001]).

CONCLUSIONS

Substantial reductions in the incidence rate of breast cancers that were fatal within 10 years after diagnosis and in the advanced breast cancer rate were found in this contemporaneous comparison of women participating versus those not participating in screening. These benefits appeared to be independent of recent changes in treatment regimens.

Early detection of breast cancer rectifies inequality of breast cancer outcomes

Objectives

To explain apparent differences among mammography screening services in Sweden using individual data on participation in screening and with breast cancer–specific survival as an outcome.

Methods

We analysed breast cancer survival data from the Swedish Cancer Register on breast cancer cases from nine Swedish counties diagnosed in women eligible for screening. Data were available on 38,278 breast cancers diagnosed and 4312 breast cancer deaths. Survival to death from breast cancer was estimated using the Kaplan–Meier estimate, for all cases in each county, and separately for cases of women participating and not participating in their last invitation to screening. Formal statistical comparisons of survival were made using proportional hazards regression.

Results

All counties showed a reduction in the hazard of breast cancer death with participation in screening, but the reductions for individual counties varied substantially, ranging from 51% (95% confidence interval 46–55%) to 81% (95% confidence interval 74–85%). Survival rates in nonparticipating women ranged from 53% (95% confidence interval 40–65%) to 74% (95% confidence interval 72–77%), while the corresponding survival in women participating in screening varied from 80% (95% confidence interval 77–84%) to 86% (95% confidence interval 83–88%), a considerably narrower range.

Conclusions

Differences among counties in the effect of screening on breast cancer outcomes were mainly due to variation in survival in women not participating in screening. Screening conferred similarly high survival rates in all counties. This indicates that the performance of screening services was similar across counties and that detection and treatment of breast cancer in early-stage reduces inequalities in breast cancer outcome.

The impact of organized mammography service screening on breast carcinoma mortality in seven Swedish counties

BACKGROUND

The evaluation of organized mammographic service screening programs is a major challenge in public health. In particular, there is a need to evaluate the effect of the screening program on the mortality of breast carcinoma, uncontaminated in the screening epoch by mortality from 1) cases diagnosed in the prescreening period and 2) cases diagnosed among unscreened women (i.e., nonattenders) after the initiation of organized screening.

METHODS

In the current study, the authors ascertained breast carcinoma deaths in the prescreening and screening epochs in 7 Swedish counties from tumors diagnosed in these epochs and in the age group 40-69 years in 6 counties and 50-69 years in 1 county. Data regarding deaths were obtained from the Uppsala Regional Oncologic Center in conjunction with the National Cause of Death Register. The total number of women in the eligible age range living in each county was obtained from the annual population data of Statistics Sweden. Detailed screening data were provided by the screening centers in the seven counties, including the number of invited, the number attended, and whether each individual breast carcinoma case was exposed (screen-detected and interval cases combined) or unexposed (not-invited or nonattenders) to mammographic screening. There were 2044 breast carcinoma deaths from 14,092 incident tumors diagnosed in the prescreening and screening epochs, and the total number of person-years was 7.5 million. Data were analyzed using Poisson regression with corrections for self-selection bias and lead-time bias when appropriate.

RESULTS

The mortality reduction for breast carcinoma in all 7 counties combined for women actually exposed to screening compared with the prescreening period was 44% (relative risk [RR] = 0.56; 95% confidence interval [95% CI], 0.50-0.62). When all incident tumors were considered, both those exposed and those unexposed to screening combined, counties with > 10 years of screening were found to demonstrate a significant 32% mortality reduction (RR = 0.68; 95% CI, 0.60-0.77) and counties with < or = 10 years of screening showed a significant 18% reduction in breast carcinoma mortality (RR = 0.82; 95% CI, 0.72-0.94) for the screening epoch compared with the prescreening epoch. Within the screening epoch, after adjustment for self-selection bias, a 39% mortality reduction (RR = 0.61; 95%CI, 0.55-0.68) was observed in association with invitation to screening.

CONCLUSIONS

Organized service screening in 7 Swedish counties, covering approximately 33% of the population of Sweden, resulted in a 40-45% reduction in breast carcinoma mortality among women actually screened. The policy of offering screening is associated with a mortality reduction in breast carcinoma of 30% in the invited population, exposed and unexposed combined. The results of the current study indicate that the majority of the breast carcinoma mortality reduction is indeed due to the screening.

Implementation of service screening with mammography in Sweden: from pilot study to nationwide programme

Establishment of mammography screening in Sweden has progressed logically from pilot study through clinical trials to service screening. Screening with mammography for early detection of breast cancer has been provided by all Sweden's 26 county councils since 1997. It took 23 years from the initial pilot study through clinical trials to the establishment of mammography service screening throughout Sweden. In the screening rounds completed by 1995-96, and provided by all but one county council, 1040000 women participated, corresponding to 81% of those invited. The national average recall rate was 2.2%, and consequently 23000 women were recalled for additional investigations. Eleven county councils invited women aged 40-74, six invited women aged 50-69, the remaining eight invited women between both these age intervals. Mammography outside screening programmes-clinical mammography-is available throughout Sweden. About 100000 women a year were referred for clinical mammography and about 50% of these were either younger or older than those invited for screening. A negative relation between the use of clinical mammography and participation in the screening programmes was noticed.

Management of accidentally found pathological lymph nodes on routine screening mammography

Normal lymph nodes in the anterior part of the axilla are readily seen on routine mammography. It is important, however, to recognize pathological lymph nodes, characterized by increased attenuation, high density, a round or irregular shape and lack of fat in the hilus, as they often indicate significant diseases. We examined the final diagnosis in 22 patients referred for clinical examination from a mammographic screening programme because of pathological lymph nodes without concomitant breast malignancy. Ten of them were found to have a malignant lesion, and one had sarcoidosis. None of the malignancies had been diagnosed before screening. Among women with abnormal but impalpable nodes, only one malignancy was found (in a woman with previous breast cancer), whereas nine of 13 women with palpable nodes had malignancies. Seven malignant lymphomas were discovered, but among all 60 women of the age group in question with newly diagnosed lymphomas in the region, only 13 had pathological axillary nodes. Mammography cannot therefore be used as a screening method for lymphoma. We conclude that mammographically pathological lymph nodes in the axilla should be examined clinically and propose a simple programme for patient management.

Trisomy 8 syndrome. The rib anomaly and some new features in two cases

Two further cases of trisomy 8 syndrome are reported. Both displayed characteristic anomalies of the ribs. An index of variation in rib diameter was constructed, and the value was found to differ from that in normal children. Our first patient, who was examined post mortem, had an atresia of the gallbladder and common mesentary. Patient 2 had muscular hypotonia and atrophy. She also showed an anomaly of the perineum, where the posterior commissure of the vulva was absent and the mucosae of the vulva and anus met at the midline, a defect which has not been described previously as a part of the syndrome. Otherwise, both present patients had abnormalities already known typical for the syndrome. The literature is reviewed, and the features of the trisomy 8 syndrome are divided into three groups - major, minor and inconstant, to facilitate the diagnosis.