Abstract
Women diagnosed with breast cancer experience an exceptional amount of emotional distress compared to their healthy peers. There is long standing evidence that this degree of emotional distress is positively associated with increased inflammatory signaling and consequently poorer disease outcomes. The purpose of this study was to examine whether reductions in emotional distress over the first-year post-diagnosis in breast cancer patients is associated with better mental health outcomes and less fatigue-related quality of life impairment. Furthermore, this study examined the association between changes in pro-inflammatory cytokines IL-1, IL-6, TNF-a, and S100A8/A9 over the first-year post-diagnosis and changes in depressive symptomatology during the same time period. To build upon previous literature examining the association between inflammatory cytokines and depressive symptomatology at the post-surgical time point (Nahin et al., under review), this study included mediation analyses to determine whether the changes in depressive symptomatology over the first year mediates the corresponding changes in pro-inflammatory cytokines and mental health and fatigue related outcomes 5 years later. An alternative model was also tested to examine changes in depressive symptomatology as a mediator between corresponding changes in pro-inflammatory cytokines and long-term outcomes due to lack of evidence regarding directionality and the likely cyclical nature of the model.
Female breast cancer patients in South Florida (ages 34-64) with Stage 0-III cancers (N=240) were recruited between December 1998 and February 2005 2-10 weeks following breast surgery. Each participant participated in a randomized controlled trial of a stress management intervention. All women were administered the Hamilton Rating Scale for Depression (HAMD) interview and provided blood samples prior to receiving adjuvant chemotherapy or radiation. Women selected for the present study (N=52) had cryopreserved blood available for analysis. Women included did not significantly differ from the parent sample on any study variables (all p’s >.05). Women in the sample used in this study were predominantly non-Hispanic white (75%) followed by Hispanic/other (7.7%) and African American (5.8%).
Changes in pro-inflammatory cytokines (IL-1, IL-6, TNF-a, and S100A8/A9) during the first-year post-diagnosis were not significantly related to corresponding changes in depressive symptomatology (all p’s >.05). Neither changes in pro-inflammatory cytokines nor changes in depressive symptomatology over the first-year post-diagnosis were related to depressive symptomatology, affect, breast cancer specific distress, nor fatigue 5-years later (all p’s >.05). Changes in pro-inflammatory cytokines did not mediate changes in depressive symptomatology during the same period and depressive symptomatology, affect, breast cancer specific distress, nor fatigue 5-years later (all confidence intervals contained zero). Likewise, changes in depressive symptomatology did not mediate changes in pro-inflammatory cytokines during the same time period and depressive symptomatology, affect, breast cancer specific distress, nor fatigue 5-years later.
The results indicate that changes in depressive symptomatology and pro-inflammatory cytokines over the first-year post-diagnosis are not associated with one another and are not predictive of mental health outcomes and quality of life related fatigue interference 5 years into survivorship. Previous research has shown an association between pro-inflammatory cytokines and depressive symptomatology at the post-surgical time point. The lack of association between changes in both may indicate two separate processes that occur over the first year. The small sample size may also have prevented me from being able to detect significant changes.