Demographic and medical variables are described in . There were no differences between the randomized treatment and control groups (N = 177 and N = 176, respectively) at baseline on demographic or medical status variables except for stage of disease (Chi-square = 6.32, p = 0.04). Fifteen women had stage 3 disease in the control condition (8.5% from the control condition) compared with six women in the treatment condition (3.4% from the treatment condition)
Summary of demographic and medical characteristics of the sample of women with primary breast cancer
Three hundred and twenty-six women provided follow-up data and were included in the analysis. For women in the treatment condition, the mean slope on the POMS was −0.52 (SD = 1.57) and for women in the education control condition the mean slope was −0.13 (SD = 2.39). An exploratory analysis revealed an extreme outlier in the control condition with a slope of 25.04. This participant completed the baseline and 3-month assessment only, with TMD scores of 50 and 156, respectively. Owing to the high distress she was experiencing, she dropped out of the study. It was decided to exclude this observation from the analysis. Removing the outlier resulted in a mean slope of −0.28 (SD = 1.37) on the POMS for the control condition. shows the number of women, by condition who completed questionnaires at each assessment point and the number who provided at least one follow-up assessment.
POMS scores for each assessment point by condition with outlier removed
We found that there was neither a main effect for treatment in either the model using imputed data (F(1,252) =0.85, p = 0.36) or in the reduced model (F(1,211) = 1.8, p = 0.18), nor an interaction effect for treatment by level of distress in either the model with imputed data (F (18,252) = 0.46, p = 0.50) or reduced model (F (15,211) = 0.52, p = 0.47). Similarly, no effects were found on any of the secondary outcome measures.
When we analyzed the data with the outlier included, we found that there was a statistically significant difference in the mean slope of change in TMD among women who received group therapy compared with those in the control condition for the model with imputed data and the reduced model (F (1,253) =4.7, p = 0.031 and F (1,212) = 6.5, p = 0.001, respectively). There were significant condition by baseline distress effects favoring the women who were highly distressed and in the treatment condition (F (18,253) = 3.9, p = 0.05 and F (15,212) = 4.3, p = 0.04). There were also significant differences across cohorts and condition by cohort interaction, as well as a significant three-way interaction of baseline distress by condition by cohort.
When including the outlier, beneficial effects of treatment were found on the secondary outcomes of HADS anxiety, HADS depression, MAC helpless/hopeless and Yale instrumental support using both the model with imputed data and the reduced model (F (1,253) = 4.5, p = 0.034 and F (1,212) = 3.9, p = 0.049, respectively, for anxiety; F (1,253) = 5.4, p = 0.021 and F (1,212) = 6.3, p = 0.013, respectively, for depression; F (1,253) = 5.2, p = 0.024 and F (1,212) = 5.3, p = 0.022, respectively, for MAC helpless/hopeless; F (1,253) = 5.5, p = 0.020 and F (1,212) = 6.4, p = 0.012, respectively, for instrumental support). Using the reduced model, there was a treatment effect for Yale negative support favoring the treatment condition (F (1,212) =4.1, p = 0.044). Condition by baseline distress interactions were found on HADS anxiety, HADS depression, Yale informational support for both the imputed data model and the reduced model (F (1,253) = 6.0, p= 0.015 and F (1,212) = 5.4, p = 0.021, respectively, for anxiety; F (1,253) = 6.9, p = 0.009 and F (1,212) = 6.3, p = 0.012, respectively, for depression; F (1,253) = 9.4, p = 0.002 and F (1,212) = 8.3, p = 0.004, respectively, for Yale informational support). For both anxiety and depression, the highly distressed women in the treatment condition showed the greatest improvement. The highly distressed in the education group improved the most on informational support.
Spearman’s rho correlation of effect size with number of years experience conducting psychotherapy and whether or not the therapist had a mental health degree were rho = 0.02 (p = 0.96) and rho = 0.15 (p = 0.62), respectively.