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Mammography screening questioned

Professor Richard SullivanA study by the Division of Cancer Studies and the International Prevention Research Institute in Lyon, confirms the likelihood of a substantial overestimation of the health benefits of mammography screening.

The findings, published in the online journal PLOS ONE, indicate little difference to the decline in breast cancer mortality rates between countries who had been screening women over 40 for the last 26 years and those who implemented screening programmes over a decade later.

Breast cancer is the most common cancer in women and early diagnosis can save lives. The key is to diagnose it before deadly metastases have spread to lymph-nodes or other organs. To this end, for decades, many countries have strongly recommended regular mammography screenings for women starting between 40 and 50 until they reach 69 to 74. However, results of population studies make it increasingly clear that breast cancer mortality did not decrease more rapidly in countries where mammography screening programmes started around 1990 than in countries where screening programmes were implemented ten to fifteen years later.

The recommendations to attend mammography screening is based on eight trials had estimated that in countries where at least 70% of women 40 to 74 would regularly attend mammography screenings, breast cancer mortality could drop by 20%. Confusingly, the results obtained by the eight trials were very diverse, from 31% mortality reduction in the Two-country trial in Sweden to no reduction in the two Canadian trials. This is more relevant now than ever as recent discussions regarding the possibly insufficient influence of mammography screening programmes on breast cancer mortality have intensified. One hypothesis for the variations is that the randomized trials ‘overestimated’ the ability of mammography screening to reduce the risk of breast cancer death.

The study concluded that the poor effectiveness of mammography screening in populations can be explained by the fact that randomized trials overestimated the capacity of mammography screening to reduce the risk of breast cancer death. Between 20% to 25% of breast cancers found in women could be over-diagnosed, leading to unnecessary, potentially harmful, treatments.

Professor Richard Sullivan (pictured) from the Division of Cancer Studies and co-author of the paper said "The findings of this study are essential for evidence based-policymaking, particularly in emerging economies in their allocation of funds for national screening programmes. Clearly screening programs directed at cervical, head and neck and colorectal should take priority."

Considering the potential over-diagnosis and ensuing over-treatment induced by mammography screening and its ineffective ability to reduce breast cancer mortality in general populations, there is an urgent need to search for efficient methods for the early detection of breast cancer.

Read the full article on the PLOS One website.