Requirements for Development and Expansion of Particle Therapy

Reviewer: Christine Hill-Kayser
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 28, 2010

Presenter: Andrew K. Lee
Presenter Affiliation: The University of Texas M.D. Anderson Cancer Center, Department of Radiation Oncology, Houston, TX


  • Dr. Lee provided a discussion of indications for expansion of particle therapy, with a focus on the United States, as well as ways in which the radiation community may support this growth. He also identified some of the inhibitory factors to further expansion.
  • He pointed out that radiation therapy is used in treatment of approximately 1 million patients per year in the US, but that proton therapy is used for < 1%, despite rapid increase in the number of treatment centers in the past 5 years.
  • At the M.D. Anderson Cancer Center, Dr. Lee and his colleagues have treated about 1900 patients since their center opened in May 2006.
    • They began using spot scanning in 2008, and have now treated over 300 patients with this technique.
    • They have expanded their clinical sites to include lung cancer, lymphoma, and esophageal cancer.
    • At this time, 50% of their patients are treated for prostate cancer, with the remaining 50% divided between pediatrics, central nervous system, and thoracic (including gastroesophageal junction tumors).
  • Dr. Lee points out that as clinical indications are expanded, greater numbers of patients may be referred for proton therapy.

Factors That May Influence Expansion

Dr. Lee identified the following factors that need to be addressed by the radiation oncology community as a whole to allow further expansion of particle therapy:

  • Determination of optimal utilization (the number of centers that are needed)
  • Appropriate scaling of treatment units and facilities
  • Improvement of treatment delivery
  • Improvement in treatment planning
  • Improvement in radiobiologic understanding of particle therapy
  • Improving clinical evidence supporting the use of particle therapy
  • Innovation in more clinical sites
  • Education of patients, colleagues in other specialties, and third-party payers regarding benefits of particle therapy.

Addressing the Identified Needs

Dr. Lee explained that we are well on our way to addressing certain of the needs which he identified, and further away from addressing some others.

  • Determination of optimal utilization (the number of centers that are needed)
    • Dvorak and colleagues recently published an analysis of patients receiving radiotherapy at Brown University, a relatively small but tertiary academic center.
    • The authors demonstrated that 17% of patients treated with conventional radiotherapy would be reasonable candidates for proton radiation based on today's US standards of care.  This number is consistent with those from other facilities making similar predictions (range 13% - 17%).
    • If the numbers from Brown University are extrapolated to the United States in general, these estimates demonstrated a need for between 500 and 800 proton gantries in the US alone.
    • This would translate to an increase of 1 billion dollars per year in Medicare costs (a 15% increase).
    • Dr. Lee points out that if such an expansion were market driven, use could increase much more than predicted.
    • He also notes that even if prostate cancer patients were eliminated, a need for 100 gantries in the US could be demonstrated.
  • Appropriate scaling of treatment units and facilities
    • Dr. Lee notes that new centers may learn from established ones. For example, M.D. Anderson has 3 large gantries, all of which are capable of treating vertex fields. He points out that this need is relatively rare, and that the center could probably have built two smaller gantries and one larger one, improving efficiency in terms of both cost and space.
    • He also described several potential smaller products for delivery of proton radiation that may be available in the future for centers not wishing or able to invest the time and space for several large gantries.
  • Improvement of treatment delivery
    • Dr. Lee explained his view that proton radiotherapy should eventually have all of the tools and techniques associated with it that photon therapy currently does, namely:
      • Image-guidance
      • Gating
      • Continuous multifield treatment
      • Multileaf collimators
  • Improvement in treatment planning
    • Dr. Lee describes that this is an area of constant improvement, but that individual centers remain largely responsible for this.
  • Improvement in radiobiologic understanding of particle therapy
    • Again, he describes this as an unmet need, although continuous work is being done in this area.
  • Improving clinical evidence supporting the use of particle therapy
    • Dr. Lee describes the continued requests from third-party payers and others that further clinical data be provided. He acknowledged that ethical concerns regarding performing randomized trials in every disease site are valid, but still expressed a need for more clinical evidence.
  • Innovation in more clinical sites
    • Dr. Lee referred to expansion in treatment site at M.D. Anderson, but also called for further innovation at his center and throughout the country.
  • Education of patients, colleagues in other specialties, and third-party payers regarding benefits of particle therapy.
    • Dr. Lee pointed out that the biggest impediment for patient enrollment on an NCI P-O1 study at M.D. Anderson comparing intensity modulated radiotherapy to proton radiotherapy in treatment of lung cancer is insurance re-imbursement.  He used this to support his feelings that education of third-party payers needs to both continue and improve.

Impediments to Expansion

Dr. Lee identified the following factors as inhibiting or limiting expansion, despite efforts to address the needs identified above:

  • Expensive
  • Economy
    • Affects referring physicians, patients, and payers
  • Expertise
    • Specialists are required for building centers, planning and delivering treatment, and quality assurance.
  • Effectiveness
    • Again, he points out the need for more clinical data supporting particle therapy.
  • Efficiency
  • Engineering
    • Including hardware and software, both of which are vendor dependent.
  • Equality
    • Including patient access, which may be based on both logistics and insurance.
  • Education
    • Education of patients, payers, and colleagues in our field and others is essential.

Scientific/Clinical Implications

  • Dr. Lee gave a comprehensive overview of some areas that may need to improve in the US for continued expansion of particle therapy.
    • Although areas in which more clinical data is needed may be controversial, Dr. Lee makes the valid point that the questions regarding the need for particle therapy will likely not go away in the absence of further data.
  • As more and more centers are announced and initiated, it will also be worthwhile for us to be mindful, as a field, of expanding in systematic and thoughtful ways that will improve access to patients and allow us to gather data to support this type of treatment.
  • We will also benefit from working together and with our vendors to provide the technology needed to further improve particle therapy, and expand its indications.