Protocol allocation and exclusion in two Danish randomised trials in ovarian cancer

Abstract

Between September 1981 and November 1984 the Danish Ovarian Cancer Group (DACOVA) performed two randomised trials. One for adjuvant therapy in stages Ib, Ic and II and one for chemotherapy treatment in stages III and IV. One hundred and twenty patients fulfilled criteria for the early stage protocol but only 60% was randomised. Three hundred and sixty-one fulfilled criteria for the advanced stages protocol, 73% was randomised. In early stages 11% were excluded because of unavoidable reasons and 29% because of avoidable reasons. In contrast, in advanced stages 21% were excluded because of unavoidable reasons and only 6% because of avoidable reasons. Allocation to the early stage protocol varied with stage, histologic type, residual tumour, and the presence of ascites. These factors had no influence upon allocation to the advanced stages protocol. The experience from this study is: only essential and simple questions should be examined in multicentre trials. Patient accrual and the difference between randomisation groups are usually overestimated, large scale trials are often required to get statistically significant differences, and the participation of departments only randomising a small and selected part of their patients is questionable.