Social vulnerability in patients with advanced cancer in Denmark: implications for access to physical rehabilitation and specialized palliative care

Background
This PhD project is part of Danish Research Centre for Equity in Cancer and was carried out during my employment at REHPA, the Danish Knowledge Centre for Rehabilitation and Palliative care.
Inequality in cancer trajectories have been documented internationallybut also in Denmark, despite our tax-funded healthcare system. Inequalitywithin the area of physical rehabilitation and specialized palliative care issparsely documented and with diverging findings. If inequality should be avoided, the first and fundamental step is to identify the target group. Previous research has focused on single social indicators to explain inequality, whereas more complex measures like social vulnerability remain unexplored. Social vulnerability describes a person’s overall social position relying on several social indicators. No measure of social vulnerability exists on the basis of data from the Danish registers.

Aim
The aim of this PhD project was to develop a register-based social vulnerability index (rSVI) and to evaluate its properties, comprising the stability of the measure throughout the cancer trajectory. Lastly, the rSVI was applied to investigate inequality regarding physical rehabilitation and specialized palliative care. 

Methods
All three studies were register-based using population-based samples of Danish cancer patients. In study I, the rSVI was developed and initially validated in a sample of cancer patients, who died from cancer within five years after the diagnosis. Changes in social vulnerability after a cancer diagnosis using the rSVI as a measure was performed in study II, including both cancer survivors and patients who died from cancer within three years. Lastly, physical rehabilitation and specialized palliative care services were mapped for both cancer survivors and patients who died from cancer within three years. Inequality in this respect were investigated using competing-risk models. 

Results
The rSVI was developed for patients, who died from cancer from three to five years after the diagnosis but was found applicable on patients who died from cancer within three years after the diagnosis. The rSVI identified a unique group of socially vulnerable cancer patients – a group that could not be identified using fewer social indicators and especially not with single social indicators. Associations found in previous research on social vulnerability could largely be reproduced using the rSVI. During the cancer trajectory, the level of social vulnerability measured by the rSVI was predominantly stable. However, patients who were socially vulnerable at diagnosis, decreased at the level of social vulnerability, whereas patients who were non-vulnerable at diagnosis only increased slightly at the level of social vulnerability. Physical rehabilitation was a part of the entire cancer trajectory, whereas specialised palliative care was primarily in the last year of life. The most well-served group were patients, who died from cancer from one to three years after the diagnosis with respect to physical rehabilitation (approx. 30-40%), specialised palliative care teams (approx. 50%), and hospices (approx. 25%). Socially vulnerable patients hadless contact with specialised palliative care, while socially vulnerable cancer survivors had more contact with respect to physical rehabilitation, compared with the non-vulnerable patients.

Conclusion
This PhD project has developed and initially validated a register-based index of social vulnerability and finding the index promising for future research. The level of social vulnerability measure with the rSVI was relatively stable throughout the cancer trajectories, but for some patients the level of social vulnerability changed, and often in a decreasing direction. Thus, considerations of when to capture the level of social vulnerability may be necessary. Physical rehabilitation and specialized palliative care constituted a substantial part of cancer trajectories. The largest disparities were related to disease duration, but in specialized palliative care, socially vulnerable patients were underserved. 

Implications
The rSVI is a tool for identifying socially vulnerable groups. On an overall level, social vulnerability did not change during a cancer trajectory, but some patients may experience deterioration, and thus it is relevant to identify and provide support. In specialized palliative care, the essence of the rSVI may be used to identify and support an under-prioritized group.