Proton beam therapy

Proton beam therapy (PBT) was first selected for review by the HTA program in 2014.
  • In 2018, the HCA director selected PBT for rereview based on newly available published evidence that could change the original coverage determination.
  • A rereview of proton beam therapy was conducted in 2019.

Status: Decision completed

Policy context

PBT has the potential to be an important therapeutic option for specific cancers given its physical properties. Interest in its use for a variety of clinical applications has grown substantially in recent years. There are 12 operating PBT facilities in the U.S., with the most recent facility opening in Seattle, WA in March 2013. Fifteen additional centers are currently under construction or in development in the U.S.

However, there are significant uncertainties with the use of PBT. Some of these are technical. For example, treatment planning is more complex with protons due to the lack of an exit dose, and may be affected by organ motion, anatomical variation, and other factors. In addition, there are questions regarding how the more targeted treatment delivery with PBT translates into comparative effects on cancer control, toxicity, and health-related quality of life relative to other treatment approaches. These uncertainties have led to variability in coverage policy for PBT among public and private payers. 

In addition, the cost of treatment with PBT is substantially higher than for other EBRT modalities such as IMRT and 3D-CRT. Proton facilities must be able to house large cyclotrons to effectively accelerate protons for treatment delivery, and can cost anywhere from $25 million to over $200 million to construct. In addition, Medicare payments for each PBT session are 4-8 times higher than for other EBRT modalities.

With the recent availability of PBT in Washington, it is timely to assess the evidence on its clinical benefits, potential harms, and costs in comparison to alternative treatment options for a variety of cancers.

Primary criteria ranking

  • Safety = Medium
  • Efficacy = High
  • Cost = High
Documents (all assessments)

Documents (2019 assessment)

Documents (2014 assessment)

Assessment timeline (2019)

  • Draft key questions published: July 3, 2018
  • Public comment period: July 4 to 18, 2018
  • Final key questions published: July 31, 2018
  • Draft report published: March 1, 2019
  • Public comment period: March 2 to April 1, 2019
  • Final report published: April 17, 2019
  • HTCC public meeting: May 17, 2019


It is estimated that nearly 14 million Americans are cancer survivors and that 1.7 million new cases will be diagnosed in 2013. Among the treatment options for cancer, radiation therapy is commonly employed; an estimated 50% of patients receive radiation therapy at some point during the course of their illness.

The use of external beam radiation therapy (EBRT) for the treatment of cancer dates back more than 100 years. Conventional EBRT is comprised of photon (X-ray) beams and is targeted directly at solid tumors to destroy cancerous cells. While photons are an effective means of eliminating malignant cells, these high-energy x-rays also cause damage to normal tissue along the beam path as they enter and exit the body. Toxicities associated with injury to normal tissue include those specific to the anatomic location being treated (e.g., incontinence in patients treated for prostate or gynecological cancers) as well as general effects such as nausea and fatigue. Exposure of normal tissues to radiation also may increase the future risk of secondary malignancies.

To address these concerns, advanced techniques in the application of X-rays to reduce toxicity and more accurately target the cancer have been developed, including intensity-modulated radiation therapy (IMRT), CT-based 3D-conformational radiation therapy (3D-CRT), and stereotactic radiation therapy. An alternate approach to the use of photons is the use of heavy particles such as electrons, neutrons and protons as agents of radiation energy deposition. Of particular interest is proton beam therapy (PBT), as the physical properties of protons permit dose delivery at specific tissue depths. Protons deliver a low dose of energy when entering the body and deposit the bulk of their radiation energy at the end of their range of penetration, a phenomenon known as the "Bragg peak." By focusing delivery of radiation to the target tumor, it is believed that PBT may reduce toxicity associated with normal tissue damage.