Oral Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2021

Estimating the need for radiotherapy in older women with breast cancer (#155)

Penny Mackenzie 1 2 3 , Claire Vajdic 4 , Tracy Comans 5 , Gabriel Gabriel , Meera Agar 6 , Geoff Delaney 7 , Michael Barton
  1. Department of Radiation Oncology, Icon Cancer Care, St Andrews Hospital, Toowoomba, QLD, Australia
  2. CCORE, Ingham Institute for Applied Medical Research, Liverpool Hospital, Sydney, NSW, Australia
  3. UNSW, South Western Sydney Clinical School, Sydney, New South Wales, Australia
  4. Centre for Big Data Research, UNSW, Sydney, NSW, Australia
  5. Centre for Health Services Research, University of QLD, Brisbane, QLD, Australia
  6. Palliative Medicine, University of Technology, Sydney, Sydney, NSW, Australia
  7. UNSW, South Western Sydney Clinical School, Sydney, NSW, Australia

Background:

Decision tree models based on clinical guidelines have been developed to calculate optimal radiotherapy utilisation (RTU) rates for people diagnosed with cancer. The optimal RTU is the proportion of patients with indications for radiotherapy based on a local control or a survival benefit. Although performance status was considered, age was not specifically considered in the models and the optimal RTU for older patients is not known. We developed an age- and comorbidity-adjusted RTU for breast cancer.

Methods and Population:


Linked NSW Cancer Registry, Radiotherapy and Admitted Patient Data Collection data (2009-2014) was used to determine the number of women diagnosed with incident breast cancer in four pre-specified age groups. The Charlson Comorbidity Index CCI (excluding cancer) was derived from diagnostic codes in hospital records 24 months prior to diagnosis. A patient with a CCI ≤ 3 was deemed fit, that is, a suitable candidate for radiotherapy. The proportion of women suitable for radiotherapy in each age group was then incorporated in the Breast Cancer decision tree model to determine the comorbidity-adjusted age-specific RTU. 

Results:


28125 women were diagnosed with breast cancer in NSW from 2009-2014. 13222 were <60 years of age, 7489 were aged 60-69yrs, 4496 were aged 70-79yrs, and 3018 were aged >79yrs. Applying the CCI cut off of >3, only 354 or 7.9% of women aged 70-79yrs, and 425 or 14.1% of women aged >79yrs were deemed unfit for radiotherapy. The overall optimal RTU was 85% following age- and comorbidity-adjustment. The comorbidity-adjusted optimal RTU for the four different age groups were 87%, 85%, 81% and 76% respectively.

Implications:


Comorbidity affects a proportion of breast cancer patients who are fit for radiotherapy but the vast majority of older patients are fit for treatment and should not be excluded from treatment on age alone.