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The holy grail for a screening test is that it discovers more cancers in the screened arm than in the control; that those cancers are of an earlier stage and there is, as a consequence, a stage shift towards lower stage cancers compared with the control group; that the test is acceptable to, basically, healthy individuals with low risks of serious side effects resulting from tests following a positive screen; and that the cost of a life saved, or a quality-adjusted life-year (QALY) is acceptable to the economy of the day.
Published in Thorax there is an end-of-screening report on a Danish CT-based study.1 They entered 4104 men and women, (of which 45% were women, unusually high) aged between 50 and 70 years, a 20 pack-year smoking history; lung function was recorded but was not used as an inclusion criterion. The screened group underwent five annual CTs and the control group nothing, but were seen every year. It was not stated why, or what was done to this latter group. At the end of the study period 69 cancers were found in the screened arm and 24 in the control. There were more early stage (stages I and IIB) cancers found in the screened arm than in the control arm: 48 versus 21. However, the number of advanced stage cases (IIIB and IV, and extensive disease small cell) were similar: 21 versus 16, ie, no stage shift effect. There was also a large preponderance of adenocarcinomas and bronchoalveolar cell tumours, typical of screened populations. Also, of 611 participants followed for 5 years, 1404 non-calcified nodules (NCN) were identified, another enduring problem in CT-based trials. Evaluating all deaths by the end of the study, there were 61 in the screen arm of which 15 were from lung cancer, compared with 42 deaths …