DETERMINATION OF CAUSE OF DEATH AMONG BREAST-CANCER CASES IN THE SWEDISH RANDOMIZED MAMMOGRAPHY SCREENING TRIALS - A COMPARISON BETWEEN OFFICIAL STATISTICS AND VALIDATION BY AN END-POINT COMMITTEE

Between 1976 and 1982, four randomized mammography screening trials st arted in five screening centres in Sweden, involving 282 777 women (15 6 911 invited and 125 866 controls) with the aim to study if invitatio n to screening reduced the breast cancer mortality. An overview of the trials was performed to reduce the confidence intervals for the relat ive risk estimates. All 1296 deaths occurring in women with breast can cer detected after randomization were evaluated by an independent endp oint committee (EPC), consisting of four physicians who reviewed colle cted medical information that was blinded regarding mammography screen ing. If there was disagreement between the EPC members at the initial individual evaluation the final classification was made at concensus m eetings. In only 6.9% (n = 89) of the cases was there disagreement as to whether breast cancer was or was not the underlying cause of death. It was also found that 'breast cancer as underlying cause of death' a nd 'breast cancer as underlying or contributory cause of death' accord ing to Statistics Sweden resulted in relative risk estimates very simi lar to those based on the classification by the EPC. The study thus su pports the use of official health statistics in the evaluation of rand omized breast screening trials in Sweden.