Development of an age- and comorbidity- adjusted optimal radiotherapy utilisation rate for lung, rectal, prostate and...

Optimal radiotherapy utilisation (RTU) modelling estimates the proportion of people with cancer who would benefit from radiotherapy. Assessment of comorbidities is an important component of the assessment of suitability for radiotherapy in addition to chronological age and life expectancy. Comorbidities have not been considered in previous optimal RTU models. We aimed to develop an age- and comorbidity- adjusted optimal RTU model for patients with lung, rectal, prostate, and cervical cancer, and compare them to actual RTU rates, with a particular focus on those aged 80+ years, METHODS: New South Wales (NSW) Cancer Registry data (2010-2014) linked to radiotherapy data (2010-2015) and hospitalisation data (2008-2015) were used to determine the number of patients diagnosed with lung, rectal, prostate and cervical cancer. The Cancer Specific C3 'all sites' comorbidity index was calculated from hospital diagnosis data for each patient to determine suitability for radiotherapy. The index was then incorporated into a tumour site-specific decision tree model. The actual RTU was also calculated using the linked datasets.

14,696 patients were diagnosed with non-small cell lung cancer (NSCLC), 1839 with small cell lung cancer (SCLC), 5551 with rectal cancer, 30,935 with prostate cancer and 1216 with cervical cancer in New South Wales from 2010-2014. The proportion of patients aged 80+ years at cancer diagnosis was 25% (3603 patients), 15% (279 patients), 17% (943 patients), 12% (3745 patients), and 7% (88 patients) respectively. The age- and comorbidity- adjusted optimal RTU rates for patients aged 80+ years using the C3 index were 49% (NSCLC), 49% (SCLC), 43% (rectal), 51% (prostate) and 40% (cervical). The corresponding actual RTU rates for patients aged 80+ years were 25%, 32%, 27%, 16%, and 56%.

Even after adjusting for age and comorbidities, the actual radiotherapy utilisation rates were lower than optimal radiotherapy utilisation rates in patients aged 80+ years except for patients with cervical cancer. This warrants further assessment and research into reasons and solutions.