Why mammography screening has not lived up to expectations from the randomised trials.
ABSTRACT We analysed the relation between tumour sizes and stages and the reported effects on breast cancer mortality with and without screening in trials and observational studies. The average tumour sizes in all the trials suggest only a 12% reduction in breast cancer mortality, which agrees with the 10% reported in the most reliable trials. Recent studies of tumour sizes and tumour stages show that screening has not lowered the rate of advanced cancers. In agreement with this, recent observational studies of breast cancer mortality have failed to find an effect of screening. In contrast, screening leads to serious harms in healthy women through overdiagnosis with subsequent overtreatment and false-positive mammograms. We suggest that the rationale for breast screening be urgently reassessed by policy-makers. The observed decline in breast cancer mortality in many countries seems to be caused by improved adjuvant therapy and breast cancer awareness, not screening. We also believe it is more important to reduce the incidence of cancer than to detect it 'early.' Avoiding getting screening mammograms reduces the risk of becoming a breast cancer patient by one-third.
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ABSTRACT: The mammography screening trials have shown varying results. This could be because screening was better in some trials than in others at advancing the time of diagnosis. If so, more cancers would be identified in such trials relative to the control group, and fewer of the cancers would have reached an advanced stage. I performed a systematic review of the mammography screening trials using metaregression. Finding many cancers was not related to the size of the reduction in breast cancer mortality (p = 0.19 after seven and p = 0.73 after 13 years of follow-up). In contrast, finding few cancers in stage II and above predicted a larger reduction in breast cancer mortality (p = 0.04 and p = 0.006). This expected association was also found for node-positive cancers (p = 0.008 and p = 0.04). However, a screening effectiveness of zero (same proportion of node-positive cancers in the screened group as in the control group) predicted a significant 16% reduction in breast cancer mortality after 13 years (95% confidence interval, 9% to 23% reduction). This can only occur if there is bias. Further analyses uncovered bias in both assessment of the cause of death and of the number of cancers in advanced stages. Consequently, the differences in the reported reductions in breast cancer mortality cannot be explained by differences in screening effectiveness. Given that the size of the bias was similar to the estimated screening effect, screening appeared ineffective.Danish medical bulletin 03/2011; 58(3):A4246. · 0.92 Impact Factor
Article: ApoE genotype and Down's syndrome.The Lancet 05/1994; 343(8903):979-80. · 39.06 Impact Factor
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ABSTRACT: A 1999 study found no decrease in breast-cancer mortality in Sweden, where screening has been recommended since 1985. We therefore reviewed the methodological quality of the mammography trials and an influential Swedish meta-analysis, and did a meta-analysis ourselves. We searched the Cochrane Library for trials and asked the investigators for further details. Meta-analyses were done with Review Manager (version 4.0). Baseline imbalances were shown for six of the eight identified trials, and inconsistencies in the number of women randomised were found in four. The two adequately randomised trials found no effect of screening on breast-cancer mortality (pooled relative risk 1.04 [95% CI 0.84-1.27]) or on total mortality (0.99 [0.94-1.05]). The pooled relative risk for breast-cancer mortality for the other trials was 0.75 (0.67-0.83), which was significantly different (p=0.005) from that for the unbiased trials. The Swedish meta-analysis showed a decrease in breast-cancer mortality but also an increase in total mortality (1.06 [1.04-1.08]); this increase disappeared after adjustment for an imbalance in age. Screening for breast cancer with mammography is unjustified. If the Swedish trials are judged to be unbiased, the data show that for every 1000 women screened biennially throughout 12 years, one breast-cancer death is avoided whereas the total number of deaths is increased by six. If the Swedish trials (apart from the Malmö trial) are judged to be biased, there is no reliable evidence that screening decreases breast-cancer mortality.The Lancet 02/2000; 355(9198):129-34. · 39.06 Impact Factor