The Canadian Cancer Trials Group (CCTG) Symptom Control 24 protocol (SC.24) was a multicenter randomized controlled phase 2/3 trial conducted in Canada and Australia. Patients with painful spinal metastases were randomized to either 24 Gy/2 stereotactic body radiation therapy (SBRT) or 20 Gy/5 conventional external beam radiation therapy (CRT). The study met its primary endpoint and demonstrated superior complete pain response rates at 3 months following SBRT (35%) versus CRT (14%). SBRT planning and delivery is resource intensive. Given its benefits in SC.24, we performed an economic analysis to determine the incremental cost-effectiveness of SBRT compared with CRT.

The trial recruited 229 patients. Cost-effectiveness was assessed using a Markov model taking into account observed survival, treatments costs, retreatment, and quality of life over the lifetime of the patient. The EORTC-QLU-C10D was used to determine quality of life values. Transition probabilities for outcomes were from available patient data. Health system costs were from the Canadian health care perspective and were based on 2021 Canadian dollars (CAD). The incremental cost-effectiveness ratio (ICER) was expressed as the ratio of incremental cost to quality-adjusted life years (QALY). The impact of parameter uncertainty was investigated using deterministic and probabilistic sensitivity analyses.

The base case for SBRT compared with CRT had an ICER of $9,040CAD per QALY gained. Sensitivity analyses demonstrated that the ICER was most sensitive to variations in the utility assigned to "No local failure" ($5,457CAD to $241,051CAD per QALY), adopting low and high estimates of utility and the cost of the SBRT (ICERs ranging from $7345-$123,361CAD per QALY). It was more robust to variations in assumptions around survival and response rate.

SBRT is associated with higher upfront costs than CRT. The ICER shows that, within the Canadian health care system, SBRT with 2 fractions is likely to be more cost-effective than CRT.