Development of an age- and comorbidity adjusted- optimal radiotherapy utilisation rate for women with breast cancer.

Optimal radiotherapy utilisation (RTU) modelling estimates the proportion of people with cancer who would benefit from radiotherapy. Older adults with cancer may have comorbidities that can impact physiological reserve and affect radiotherapy recommendations. These have not been considered in previous models. We aimed to develop an age- and comorbidity-adjusted optimal RTU model for breast cancer. New South Wales (NSW) Cancer Registry data (2010–2014) linked to radiotherapy data (2010–2015) and hospitalisation data (2008–2015) was used to determine the number of women diagnosed with invasive breast cancer in four pre-specified age groups. The Charlson Comorbidity Index (CCI), Cancer-Specific C3 'all sites' index and the Hospital Frailty Risk Score (HFRS) were derived for each woman from diagnostic codes in hospital records. Women were deemed unfit, and thus unsuitable candidates for radiotherapy, if the comorbidity indices were as follows: CCI ≥2; C3 score ≥ 3; and HFRS ≥5. The proportions of women suitable for radiotherapy in each age group were then incorporated into a breast cancer decision tree model. The actual RTU was also calculated using the linked datasets. 23,601 women were diagnosed with breast cancer in NSW from 2010 to 2014 and 2526 were aged 80+ years. The overall comorbidity adjusted- RTU for women of all ages was 85·9% (CCI), 83·7% (C3) and 81·9% (HFRS). The optimal comorbidity adjusted- RTU for women aged 80+ was 76·1% (CCI), 70·1% (C3) and 61·8% (HFRS). The actual RTU for women aged 80+ years was 24.7%. The vast majority of older Australian women with breast cancer are fit for radiotherapy. The overall optimal RTU is only slightly reduced when adjusted for age and comorbidities and was similar using each of the three indices examined. Our data suggest radiotherapy is markedly underutilised for older women with breast cancer. [ABSTRACT FROM AUTHOR]