Promise and pitfalls of heavy-particle therapy

Abstract

Proton beam therapy, the most common form of heavy-particle radiation therapy, is not a new invention, but it has gained considerable public attention because of the high cost of installing and operating the rapidly increasing number of treatment centers. This article reviews the physical properties of proton beam therapy and focuses on the up-to-date clinical evidence comparing proton beam therapy with the more standard and widely available radiation therapy treatment alternatives. In a cost-conscious era of health care, the hypothetical benefits of proton beam therapy will have to be supported by demonstrable clinical gains. Proton beam therapy represents, through its scale and its cost, a battleground for the policy debate around managing expensive technology in modern medicine.

Fig 1.

Comparison of relative depth dose distributions of photons versus protons.

Fig 2.

Isodose distribution in the sagittal projection along the spinal column for (A) x-rays, (B) intensity-modulated radiation therapy, and (C) protons.

Fig 3.

Radiotherapy treatment plans for one patient included in the study by Trofimov et al. (A) Seven-field intensity-modulated radiation therapy and (B) three-dimensional conformal proton plan with two opposed lateral fields.

Fig 4.

Dose-volume histograms (DVHs) in the study by Trofimov et al for (A-C) the rectum and (D-F) the bladder. Individual DVH from 10 three-dimensional conformal proton therapy (3D-CPT) and intensity-modulated radiation therapy (IMRT) plans are shown in (A, D) and (C, F), respectively. Plots (B) and (E) show curves obtained by averaging, over the irradiated volume, of the DVH from 10 plans, as well as one-standard-deviation (SD) variability bounds (dashed lines). CGE, cobalt Gray equivalent.