Background: Radiotherapy (RT) for Hodgkin lymphoma leads to the incidental irradiation of organs-at-risk (OAR) which may confer excess risks of second primary cancers as well as cardiovascular disease. Comparative dosimetry studies show that proton beam therapy (PBT) may reduce OAR irradiation compared to conventional photon-RT, but the benefit in terms of risk reduction is highly heterogeneous within cohorts of comparatively planned patients. Furthermore, PBT is likely to be more expensive and treatment capacity is limited. In this study, we aim to inform the use of PBT for intermediate-stage Hodgkin lymphoma (ISHL) in England by modelling the life course and healthcare costs of 606 illustrative patients.
Methods: A microsimulation model simulating the life-time course of ISHL, background mortality, and incidence and mortality of late effects was used to estimate comparative quality-adjusted life years (QALYs) lived and healthcare costs after consolidative PBT or photon-RT, both in deep inspiration breath hold (DIBH). Outcomes were compared for the illustrative patients who covered a spectrum of clinical presentations, varying by two age strata (20y and 40y), sex, smoking status (never, former, and current), and 61 pairs of OAR radiation doses from a comparative planning study. Both undiscounted and discounted (3.5% annually) outcomes were estimated. We performed threshold analysis to calculate the maximum additional cost of PBT over photon-RT that might be considered cost-effective by the UK’s National Institute for Health and Care Excellence (NICE).
Findings: Box plots of the estimated difference in QALYS between PBT and photon-RT by age, sex, smoking status, and discount rate are given in Figure 1. Current smokers benefited the most, averaging 0.583 undiscounted QALYs (range -0.339 to 2.151) and 0.137 discounted QALYs (range -0.059 to 0.620) whereas never smokers benefited the least, averaging 0.071 undiscounted QALYs (range -0.198 to 0.499) and 0.016 discounted QALYs (range -0.030 to 0.085). For the gain in discounted QALYs to be considered cost-effective at NICE’s £30,000/per QALY threshold, PBT would have to cost, at most, £4458 more than photon-RT for current smokers and £598 for never smokers. This is likely far below the cost of PBT over conventional photon-RT.