Abstract
AimsProton therapy is a radiation technique that yields less dose in normal tissues than photon therapy. In the Netherlands, proton therapy is reimbursed if the reduced dose to normal tissues is predicted to translate into a prespecified reduction in toxicity, based on nationally approved validated models. The aim of this paper is to present the development of a national indication protocol for proton therapy (NIPP) for model-based selection of breast cancer patients and to report on first clinical experiences. Materials and methodsA national proton therapy working group for breast cancer (PWG-BC) screened the literature for prognostic models able to estimate the individual risk of specific radiation-induced side-effects. After critical appraisal and selection of suitable models, a NIPP for breast cancer was written and subjected to comments by all stakeholders. The approved NIPP was subsequently introduced to select breast cancer patients who would benefit most from proton therapy. ResultsThe model of Darby et al. (N Engl J Med 2013; 368:987–82) was the only model fulfilling the criteria prespecified by the PWG-BC. The model estimates the relative risk of an acute coronary event (ACE) based on the mean heart dose. The absolute lifetime risk of ACE <80 years was calculated by applying this model to the Dutch absolute incidence of ACE for female and male patients, between 40 and 70 years at breast cancer radiotherapy, with/without cardiovascular risk factors. The NIPP was approved for reimbursement in January 2019. Based on a threshold value of a 2% absolute lower risk on ACE for proton therapy compared with photons, 268 breast cancer patients have been treated in the Netherlands with proton therapy between February 2019 and January 2021. ConclusionThe NIPP includes a model that allows the estimation of the absolute risk on ACE <80 years based on mean heart dose. In the first 2 years, 268 breast cancer patients have been treated with proton therapy in The Netherlands.
Highlights
Proton therapy is a radiation technology that yields less dose to normal tissues without jeopardising the target dose compared with photon therapy
The aim of the current paper is to present the development of the national indication protocol for proton therapy (NIPP) for breast cancer patients, and to report on the first experiences with model-based selection
The proton therapy working group for breast cancer (PWG-Breast Cancer (BC)) considered cardiac injury, such as acute coronary event (ACE), heart failure and valve disorders, radiation pneumonitis and induction of secondary tumours as the most relevant end points, from which they could potentially expect a benefit of proton therapy over photon therapy
Summary
Proton therapy is a radiation technology that yields less dose to normal tissues without jeopardising the target dose compared with photon therapy. Despite the lower dose to the normal tissues, randomised clinical trials (RCT) showing the actual clinical benefit of proton therapy compared with photon therapy are scarce, whereas the costs of proton therapy are around two times higher than with photons [1]. It has been postulated that proton therapy can be cost-effective, if the superior dose distribution translates into a clinically relevant decrease in the risk of radiation-induced side-effects [2]. The risk of a specific sideeffect (i.e. the normal tissue complication probability; NTCP) has to be estimated for both the proton therapy plan and the photon plan, and proton therapy is reimbursed only if the difference (i.e. DNTCP) exceeds a predefined threshold [3].
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