Are psychological interventions effective and accepted by cancer patients? I. Standards and levels of evidence.

Different standards and levels of evidence for evaluating the effectiveness of psychological interventions for managing distress in cancer patients are presented and discussed. We conclude that the strongest evidence comes from systematic qualitative and quantitative (i.e., meta-analyses) reviews of the relevant literature and that the most appropriate standard of evidence is the "preponderance of evidence" rather than "beyond a reasonable doubt." Results of four selected qualitative and quantitative systematic reviews of the literature are described. The preponderance of evidence furnished by these systematic reviews, particularly that gleaned from meta-analyses, suggests that psychological interventions are effective in managing distress in cancer patients. Although effectiveness may vary as a function of the specific nature of the intervention, overall, effectiveness appears strongest for anxiety-related outcomes and when participants are prescreened for distress. Different standards and indexes for evaluating evidence regarding the acceptability of psychological interventions with cancer patients are presented and discussed. The use of simple study accrual rates as an index of intervention acceptability is deemed inappropriate. We suggest alternative indexes of acceptability and conclude that sufficient information does not exist at the present time to draw the conclusion that contemporary psychological interventions for managing distress in cancer patients are unacceptable.