Re: Why cancer screening has never been shown to “save lives”—and what we can do about it
The authors argued that cancer screening is not useful to reduce overall mortality, although it reduces disease specific mortality, and gave reasons why it does not decrease overall mortality. The way of analyzing the facts targeted in trials are with the purpose of screening specifically is to bring down morbidity and mortality due to a specific disease and not to reduce the overall mortality. For example, cervical cancer screening is to catch up the pre-neoplastic lesions rather than neoplastic lesions for decrease in that cancer related morbidity and mortality which can also be called clinical down staging of that disease in the community. Moreover, it appears rather impractical to weigh it against overall mortality as the proportion of cancer cases is also meager in comparison to deaths due to all causes. The main aim of screening is to detect the cancer lesion early before it grows to an advanced stage for effective treatment. In advanced disease, treatment becomes difficult. In view of the burden to health resources the cost of treatment to advanced stage disease or full blown cancer is much higher as compared to pre-cancer and early cancer. Another advantage is screening tests are supposed to be cheaper and cost effective when applied on a mass scale on specific population to reduce burden of specific disease in a community and along with a proportion of burden of overall disease on health care infrastructure.
Screening for preventable indolent lesions has a potential benefit from available low cost screening tests. These low cost tests can be useful even in a low resource setting. These tests are useful only in case of cancers which have a long pre-invasive stage with a long latent phase as compared to tests for highly malignant tumors with a non-significant pre-invasive stage. However, the harms of over-diagnosis should not be ignored for any screening, for example, in breast and prostate cancer. A proper counselling and adequate referral facility are needed before planning a screening programme.
The authors emphasized the need for large screening trials for reducing mortality infect trials for reducing disease specific mortality can be more beneficial if focused for high risk group, say, for example, oral screening in smokers and tobacco users. Conducting big trials with the objective to record overall reduction in mortality due to a specific disease first and of all cause mortality will cause a huge burden on resources. Quality control of such a big trial can also be a major issue. In conclusion, decrease in mortality due to screening is not a good statistical indicator of reduction in overall mortality but an excellent indicator for disease specific mortality. We agree with the recommendations of authors as use of cancer registries and civil registrations for monitoring overall mortality changes.
Dr Smita Asthana, Scientist D
Dr Satyanarayana Labani, Scientist G
Institute of Cytology &Preventive Oncology (ICMR)
Sec 39 Noida, India
Competing interests: No competing interests