The impact of a psychosocial support program on survival with breast cancer: the importance of selection bias in program evaluation.
A retrospective follow-up study was conducted to assess the impact of a psychosocial support program on survival with breast cancer. One-hundred and two nonparticipants were individually matched to 34 participants on several prognostic factors, and both groups were followed from date of cancer diagnosis (1971-1980) until December, 1981. Preliminary findings suggest a strong beneficial effect of the program on survival, which is statistically significant. However, this observed effect is due largely to a selection bias caused by the failure to match on the duration of the lag period between cancer diagnosis and program entry. Correcting for this bias in the analysis results in a small, nonsignificant program effect. We are not able to rule out a possible effect, however, because of the relative lack of statistical power and because of a modest, though nonsignificant benefit observed for women who entered the program shortly after diagnosis. Furthermore, the program might have other beneficial effects on the quality of life.
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000401:mortality / Q000523:psychology*; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D008875:Middle Aged; D011379:Prognosis; D011788:Quality of Life; D012189:Retrospective Studies; D012657:Self-Help Groups; D012931:Social Environment; D012944:Social Support