Purpose: To identify factors that condition or moderate the impact of a previously described set of interventions on psychological and physical adjustment after diagnosis and treatment for early-stage breast cancer.

Patients and Methods: Younger women (age < 51 years, N = 252) with early-stage breast cancer within 2 months of having completed active nonhormonal adjuvant therapy were randomly assigned to a three-arm clinical trial, consisting of a control arm, an education arm, and a nutrition arm. Primary end points, assessed before random assignment and 4 and 13 months later, included mental functioning, physical functioning, and depressive symptoms. Four types of moderator variables were identified, including two sets reflecting psychosocial resources, specifically personality factors and factors related to the person's social environment, a set reflecting demographic variables, and a set reflecting treatment and disease variables (including comorbidities).

Results: Psychosocial factors were more likely to moderate treatment effects than were demographic and disease-related factors, but the moderating effects of these psychosocial factors were limited to patients receiving the nutrition intervention. Patients with lower psychosocial resources benefited from the nutrition intervention, whereas patients with a greater amount of psychosocial resources did not.

Conclusion: Future trials of this type should stratify by or select for the moderating variables identified here (ie, dispositional pessimism, unmitigated communion, and negative social interaction) to establish more firmly their role in responses to psychosocial interventions. Effort should also be made to collect data to inform the delivery of interventions to those who might benefit the most.