With nearly three quarters of a million people diagnosed in 2008, colorectal cancer is estimated to be the most common incident cancer in the developed world . In 2008 there were an estimated 3.3 million people living with a diagnosis of colorectal cancer within the previous 5 years . Although there has been a decrease in incidence rates in Australia , as in the United States , the numbers of people diagnosed with colorectal cancer (CRC) each year continue to increase . Despite having one of the highest incidence rates in the world , survival outcomes for Australians diagnosed with colorectal cancer are relatively high compared to other countries . Survival expectations increase the longer they survive, so that CRC cancer patients who have survived seven years after diagnosis can anticipate similar 5-year survival outcomes to the general population . The high prevalence of this disease brings into sharp focus the issue of how colorectal cancer influences long term quality of life.
A recent systematic review of quality of life (QOL) outcomes for long term colorectal cancer survivors concluded that long term QOL overall is good for these patients, but noted that research to date was limited by being largely cross sectional in design . Predictors of poorer outcomes included: younger age, lower income and a smaller social network. A longitudinal study of CRC patients over a ten year period found that CRC survivors reported stable or improved QOL over the first three years from diagnosis, however from three to ten years function declined . Younger age at diagnosis (<60 years) was found to be predictive of poorer QOL across role, social, emotional, and cognitive functioning and on this basis it was concluded that longitudinal development of QOL was dependent upon age at diagnosis. Our team identified that baseline QOL was a strong predictor of QOL five years after treatment, with gender, private health insurance, social support, and threat appraisal influencing various QOL domains . However, by comparison to the previous study  no effect was found for age. Hence, there is still lack of clarity about who is most at risk for poorer long term outcomes.
In this regard, optimism presents as a dispositional trait that influences both psychological and quality of life outcomes after cancer [9–11]. Optimism is defined as the generalized expectancy that more good things than bad will happen in the future . The effect of optimism on outcomes appears to be mediated by threat appraisal , such that more optimistic people form more positive appraisals about the consequences of their cancer, and the likely outcomes, and from this experience less distress compared to people who are more pessimistic. Finally, social support is also an important and well accepted antecedent of both psychological and HR-QOL outcomes , such that the social environment in which a person lives may help (if positive) or hinder (if negative) the adjustment process.
In assessing QOL after cancer, two measurement approaches present: health-related quality of life and life satisfaction. Health-related quality of life (HR-QOL) is a multi-dimensional construct that incorporates, at minimum. the social, psychological and physical aspects of health . On this view, these different aspects of HR-QOL make up layers of well-being that influence a person’s health status and that when disrupted by disease are expressed as decrements in these domains of quality of life. Accordingly, measurement approaches for HR-QOL tend to be domain and symptom-based, matching these layers. Over the past three decades a wealth of research, on a global scale, has emerged seeking to accurately measure HR-QOL, some of which has developed more generic approaches relevant to a person with any illness status , and some if which is tied to a specific disease, such as cancer and the various cancer types .
By contrast, life satisfaction is conceptualized as the outcome of a person’s judgment about the extent to which their current life quality matches their self-imposed life standards . Hence, by contrast to the quite specific measurement approach used in HRQOL, assessment of life satisfaction is more global and relates more to internal individual standards that are likely, at least in part, dispositional. As an example, one person may perceive that if they were unable to function physically in a certain way that their life would be intolerable, whereas another person might view these functions as less crucial. The actual physical changes may be the same, however the judgment of what these changes mean differs, and hence so does the person’s overall life satisfaction.
Our study assessed the five year trajectories of both HR-QOL and life satisfaction in long term colorectal cancer survivors’ adjustment using an analytic approach known as growth mixture modelling . Socio-demographic variables as well as optimism, threat appraisal and social support were included as predictor variables. In this approach we aimed to provide a more complete understanding of the QOL implications of colorectal cancer, both health-related and subjective, over time and more clearly identify what subgroups of patients are at risk for poorer outcomes.