The rate of interval cancers is too high

EDITOR—The recent wave of litigation in relation to screening for breast and cervical cancer is consistent with the current “compensation culture” but to some extent reflects a failure of both the public and its legal representatives to appreciate the principles and shortcomings of screening programmes.1

There is an urgent need to educate women and give them accurate information so that informed decision making can occur and any adverse sequelae are better understood. Despite widespread publicity and vehement lobbying by patients' advocacy groups in the United States, surveys have revealed that women have little knowledge or understanding of the basic screening principles: over three quarters believed that the benefit of screening for breast cancer in women in the 40 to 49 year age group had been proved, and almost 40% thought screening was effective in women under 40 years of age, though no published data support such a benefit.2 Concepts of probability and numeracy may be difficult to convey during a clinical consultation even when the patient seems to understand the issues.3

It is perhaps not surprising that the occurrence of interval cancers after a normal screening investigation evokes doubt and confusion, leading women to seek legal and financial recompense. The heterogeneity of breast tumours, with variable mean sojourn times and a range of biological aggressiveness, makes it difficult to estimate the prognostic significance of any delay in diagnosis. However, if a national screening programme is offered to women, certain levels of expectation must be honoured and the screening process rigorously monitored for quality assurance and outcome measures. Data from the NHS breast screening programme indicate that the screening interval is too long: more than 80% of cancers occurring within the screened population in the third year after a screening mammogram are interval cancers.4 Thus almost as …