Objective: To determine the cost-effectiveness of several external beam radiation treatment modalities for the treatment of patients with localized prostate cancer. Methods: A lifetime Markov model incorporated the probabilities of experiencing treatment-related long-term toxicity or death. Toxicity probabilities were derived from published sources using meta-analytical techniques. Utilities and costs in the model were obtained from publicly available secondary sources. The model calculated quality-adjusted life expectancy and expected lifetime cost per patient, and derived ratios of incremental cost per quality-adjusted life year (QALY) gained between treatments. Analyses were conducted from both payer and societal perspectives. One-way and probabilistic sensitivity analyses were performed. Results: Compared to intensity-modulated radiation therapy (IMRT) and proton beam therapy (PT), stereotactic body radiation therapy (SBRT) was less costly and resulted in more QALYs. Sensitivity analyses showed that the conclusions in the base-case scenario were robust with respect to variations in toxicity and cost parameters consistent with available evidence. At a threshold of $50,000/QALY, SBRT was cost-effective in 75% and 94% of probabilistic simulations compared to IMRT and PT, respectively, from a payer perspective. From a societal perspective, SBRT was cost-effective in 75% and 96% of simulations compared to IMRT and PT, respectively, at a threshold of $50,000/QALY. In threshold analyses, SBRT was less expensive with better outcomes compared to IMRT at toxicity rates 23% greater than the SBRT base-case rates. Conclusion: Based on the assumption that each treatment modality results in equivalent long-term efficacy, SBRT is a cost-effective strategy resulting in improved quality-adjusted survival compared to IMRT and PT for the treatment of localized prostate cancer.

87 Background: The study assessed the cost-effectiveness of CyberKnife (CK) compared to surgery and radiation therapy for the treatment of prostate cancer (PC) from a third-party and societal perspective. Methods: For patients > 65 yrs with localized PC, a Markov model compared treatment with CK, intensity modulated radiation therapy (IMRT), surgery or proton therapy (PT). Following treatment, patients were at risk of long-term toxicity: genitourinary (GU); gastrointestinal (GI); and sexual dysfunction (SD). Long-term toxicity was defined as adverse events >grade 2 on Radiation Therapy Oncology Group scale occurring at least 12 months following treatment. Markov states included all possible combinations of GI, GU, and SD long-term toxicities, no toxicity, and death. During each year patients remained in the same Markov state or died. Costs and utilities were assigned using published sources. Toxicity probabilities were derived using meta-analytical techniques to pool results from multiple studies. It was assumed that long-term disease control would not differ across treatments. The model projected expected lifetime costs and quality adjusted life years (QALYs) for each treatment and incremental cost-effectiveness of CK vs comparators as cost per QALY gained. Costs from societal perspective included lost productivity. Extensive sensitivity analyses were conducted. Results: Surgery was the least expensive treatment option followed by CK. CK patients had higher expected QALYs (8.11) than other treatment options (7.72- 8.06). From a payer perspective, total lifetime costs were $25,904, $22,295, $38,915, and $58,100 for CK, surgery, IMRT and PT, respectively. Incremental cost per QALY gained for CK versus Surgery was $9,200/QALY. Compared to IMRT and PT, CK was less costly and resulted in higher QALYs (dominance). At a threshold of $50,000/QALY, CK was cost effective in 86%, 79%, and 91% of simulations compared to surgery, IMRT, and PT, respectively. From a societal perspective, CK costs $4,200/QALY compared to surgery and remained dominant vs IMRT and PT. Results were most sensitive to costs of surgery and CK. Conclusions: Initial CK costs are higher than surgery, but CK patients have better quality of life. CK patients have lower lifetime costs and higher QALYs than IMRT and PT patients. [Table: see text]

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