Statistical analyses in Swedish randomised trials on mammography screening and in other randomised trials on cancer screening : a systematic review

We compared calculations of relative risks of cancer death in Swedish mammography trials and in other cancer screening trials. Participants: Men and women from 30 to 74 years of age. Setting: Randomised trials on cancer screening. For each trial, we identified the intervention period, when screening was offered to screening groups and not to control groups, and the post-intervention period, when screening (or absence of screening) was the same in screening and control groups. We then examined which cancer deaths had been used for the computation of relative risk of cancer death. Main outcome measures: Relative risk of cancer death. In 17 non-breast screening trials, deaths due to cancers diagnosed during the intervention and post-intervention periods were used for relative risk calculations. In the five Swedish trials, relative risk calculations used deaths due to breast cancers found during intervention periods, but deaths due to breast cancer found at first screening of control groups were added to these groups. After reallocation of the added breast cancer deaths to post-intervention periods of control groups, relative risks of 0.86 (0.76;0.97) were obtained for cancers found during intervention periods and 0.83 (0.71; 0.97) for cancers found during post-intervention periods, indicating constant reduction in the risk of breast cancer death during follow-up, irrespective of screening. Conclusions: The use of unconventional statistical methods in Swedish trials has led to overestimation of risk reduction in breast cancer death attributable to mammography screening. The constant risk reduction observed in screening groups was probably due to the trial design that optimised awareness and medical management of women allocated to screening groups

Maps and atlases of cancer mortality : a review of a useful tool to trigger new questions

In this review we illustrate our view on the epidemiological relevance of geographically mapping cancer mortality. In the first part of this work, after delineating the history of cancer mapping with a view on interpretation of Cancer Mortality Atlases, we briefly illustrate the 'art' of cancer mapping. Later we summarise in a non-mathematical way basic methods of spatial statistics. In the second part of this paper, we employ the 'Atlas of Cancer Mortality in the European Union and the European Economic Area 1993-1997' in order to illustrate spatial aspects of cancer mortality in Europe. In particular, we focus on the cancer related to tobacco and alcohol epidemics and on breast cancer which is of particular interest in cancer mapping. Here we suggest and reiterate two key concepts. The first is that a cancer atlas is not only a visual tool, but it also contain appropriate spatial statistical analyses that quantify the qualitative visual impressions to the readers even though at times revealing fallacy. The second is that a cancer atlas is by no means a book where answers to questions can be found. On the contrary, it ought to be considered as a tool to trigger new questions

Observed and predicted risk of breast cancer death in randomized trials on breast cancer screening

BACKGROUND: The role of breast screening in breast cancer mortality declines is debated. Screening impacts cancer mortality through decreasing the number of advanced cancers with poor diagnosis, while cancer treatment works through decreasing the case-fatality rate. Hence, reductions in cancer death rates thanks to screening should directly reflect reductions in advanced cancer rates. We verified whether in breast screening trials, the observed reductions in the risk of breast cancer death could be predicted from reductions of advanced breast cancer rates. PATIENTS AND METHODS: The Greater New York Health Insurance Plan trial (HIP) is the only breast screening trial that reported stage-specific cancer fatality for the screening and for the control group separately. The Swedish Two-County trial (TCT)) reported size-specific fatalities for cancer patients in both screening and control groups. We computed predicted numbers of breast cancer deaths, from which we calculated predicted relative risks (RR) and (95% confidence intervals). The Age trial in England performed its own calculations of predicted relative risk. RESULTS: The observed and predicted RR of breast cancer death were 0.72 (0.56-0.94) and 0.98 (0.77-1.24) in the HIP trial, and 0.79 (0.78-1.01) and 0.90 (0.80-1.01) in the Age trial. In the TCT, the observed RR was 0.73 (0.62-0.87), while the predicted RR was 0.89 (0.75-1.05) if overdiagnosis was assumed to be negligible and 0.83 (0.70-0.97) if extra cancers were excluded. CONCLUSIONS: In breast screening trials, factors other than screening have contributed to reductions in the risk of breast cancer death most probably by reducing the fatality of advanced cancers in screening groups. These factors were the better management of breast cancer patients and the underreporting of breast cancer as the underlying cause of death. Breast screening trials should publish stage-specific fatalities observed in each group

Enhancing Eye Fundus Images for Diabetic Retinopathy Screening

International audienceMany eye fundus images present strong variations of contrast which can be a limitation to the diagnosis of the retinopathy. Either some lesions are not taken into account or only a limited part of the domain of the image can be read. Graders have to manually adjust the contrast, which is tedious and not easily reproducible. We have developed an automatic system, which standardises the colour contrast across the whole domain of the image. The method is consistent with the physical principles or image formation and ensures that the colour aspect of lesions such as micro-aneurysms or anatomical structures such as veins are similar. It is more powerful than the existing grey level methods. We have tested our approach on several thousand images acquired in good or in harsher conditions. Some were bright while others were dark. Expert graders have checked the enhanced images. Diagnosis becomes more obvious and the grading more comfortable. Another limitation for the diagnosis is that images of the same patient acquired for different examinations cannot be directly superimposed. Indeed, the eye of the patient is never in the exact same position, the image is a projection of a 3D scene into the plane of the sensor, the optics of the camera creates a radial deformation and the colour of the image may have changed. We have developed an automatic method to superimpose eye fundus images acquired in the same position (nasal or macular). It is based on contrast standardisation, matching of salient points and a deformation model taking into account two radial distortions. We have performed tests for 69 patients with pairs of retinal examinations acquired in good conditions at an interval of one year with and without the same camera. A similar test has been performed on 5 patients with 20 pairs acquired in harsher conditions. A minimum of 96% of pairs were correctly superimposed. This is an important step towards the longitudinal analysis of large public health databases

Reported and predicted risk of colorectal cancer (CRC) death in the PLCO trial^*.

<p>Reported and predicted risk of colorectal cancer (CRC) death in the PLCO trial^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0154113#t002fn002" target="_blank">*</a>}.</p

Computations of predicted numbers of breast cancer deaths in the Two-County trial.

<p>Computations of predicted numbers of breast cancer deaths in the Two-County trial.</p