This study provides the first examination of the relationship between the recently validated IOCv2 and health status and functioning and QOL in a large sample of post-treatment NHL survivors. This analyses extends prior IOC research with mixed [11
] and breast [13
] cancer samples by using a robust set of covariates (demographic, clinical, psychosocial) and employing an NHL sample with good gender, race, and diagnosis (indolent and aggressive NHL) distributions, thereby enhancing generalizability.
Findings from the bivariate analyses indicate statistically significant relationships between QOL-related outcomes and select demographic (race, income, education, marital and employment status, age), clinical (treatment types, comorbidity), and psychosocial (social support, appraisals, and insurance and employment issues related to cancer) characteristics, which is consistent with previous studies of long-term cancer survivors [2
]. However, many of these relationships became non-significant with the introduction of the IOCv2 scores in the multivariate models (Tables -). For example, only age, comorbidity and social support remained independently associated with the mental health status and functioning component summary score (MCS) after the IOCv2 Positive and Negative Impact Summary scores were entered in the hierarchical regression. A possible explanation for older respondents reporting better QOL than the younger respondents is that they are likely to have more experience coping with stressful events and fewer family-related and other demands than younger individuals.
In only one model (FACT-G) did a variable (race) gain significance after accounting for the IOCv2 scores (Positive Impact). It is possible that differences remained between the Caucasian and non-Caucasian cancer survivors that are not accounted for in the set of covariates used in this study and that were evident only after considering the IOCv2 in the hierarchical regression model. Further, it seems that the positive IOC that was statistically significantly related to race was largely operative for QOL among non-Caucasians.
Consistent with Zebrack et al. [11
], our findings indicate that individuals’ perceptions of the positive and negative IOC on various life domains are related to their health status and functioning and QOL. In addition, accounting for IOCv2 scores reduced or diminished associations between demographic, clinical and psychosocial variables and the outcome measures in most instances. Furthermore, our findings indicate that positive IOC was significantly associated with PCS (P<.05; ) after controlling for all other variables, which was the only deviation from the previous study [11
]. Finally, in only one instance did a demographic or clinical variable meet the criteria for minimally important difference [22
] on the SF-36 scales after accounting for all variables; being presently employed added 3 points (P
<.001) to the PCS score ().
Our findings suggest that how individuals perceive the cancer experience may influence or be influenced by their health status and functioning and QOL. As our colleagues [11
] suggest, further research in the area of cognitive and behavioral interventions (e.g., cognitive re-framing) is needed to determine if positive reinterpretation of a negative traumatic event could subsequently lead to improved QOL and decreased distress. Based upon findings reported here and elsewhere [14
], the IOCv2, with strong reliability and validity psychometrics, shows evidence of potential utility for monitoring intervention effects longitudinally.
As is typical for any cross-sectional study, we are unable to establish a cause-effect relationship between the IOCv2 and health status and functioning and QOL. For example, we cannot determine if perceptions of the cancer experience preceded the outcome variables of interest (health status and functioning, QOL), whether subjective QOL-related symptoms adjusted perceptions of how cancer impacted the survivors’ lives, or if both are true. The ability to assess a cohort over time, as would be possible in a longitudinal design, would help determine the direction(s) of causality. As a second limitation, the inclusion of NHL survivors from only two NC cancer centers may limit the generalizability of our results to survivors living in other regions and treated at smaller hospitals. However, our demographic profile closely mirrors that of the national population of NHL survivors [23
], thereby strengthening the generalizability of our analyses. Further, some of the findings may reflect the fact that the IOCv2 and outcome measures assess similar constructs, although psychometric evaluation indicates that while overlapping, the measures have distinct aspects [14
]. Finally, study strengths include a high response rate (74%) and balanced gender ratio.
In closing, our findings suggest that positive and negative perceptions of cancer’s impact on survivors’ lives may influence or be influenced by self-reported physical and mental health and QOL. Longitudinal intervention research is needed to establish evidence of causality related to the IOCv2, which could lead to the development of treatments targeting perceptions of the cancer experience, ultimately to enhance health and QOL in survivors. In addition, results suggest that targeted screening, aimed at survivors who are younger, have comorbidities, and less social support would be beneficial to identify QOL-related issues that might be amenable to intervention.