Protons 101: Comparative Effectiveness of Proton Chemoradiotherapy to Photon Chemoradiotherapy

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Below is a more technical post on what I think is one of the most powerful studies to come out this year. This study was presented at ASCO this summer and showed that by treating patients with protons rather than with traditional x-rays, patients suffered significantly less side effects. This has broad reaching ramifications due to the scope of the impact. I’d guess that currently about 1/3 of all radiation patients are treated with concurrent chemotherapy and radiotherapy. I currently practice in Oklahoma. This data suggests that essentially 1/3 of patients treated in the neighboring states of Arkansas, Kansas, New Mexico, and Colorado could avoid hospitalization 15% of the time if they had access to proton therapy. I have written a more patient friendly review of this content, but I think it is important to summarize the clinical technical details of a critical trial in a more technical fashion.

BRAIN C. BAUMANN, MD, WASHINGTON UNIVERSITY SCHOOL OF MEDICINE

SUMMARY OF JUNE 1 ASCO 2019 PRESENTATION:

  • 1483 patients: 391 proton, 1092 photon.
  • Primary criteria: concurrent chemotherapy patients
  • Primary Sites: Lung, brain, head and neck, gastrointestinal and gynecologic cancers
  • Patients treated from 2011 to 2016 at University of Pennsylvania
  • Median Age: proton 66, photon 61  (p<0.05 favoring photon)
  • Charlson-Deyo Comorbidity Scores: proton 3.0, photon 2.0 (p<0.05 favoring photon)
  • Baseline EGOG: no difference
  • Primary Study Endpoint: 90 day Severe Toxicity (grade 3 or higher AE’s associated with unplanned hospitalizations).

PRIMARY STUDY ENDPOINT: SEVERE SIDE EFFECTS

  • Proton chemoradiotherapy 11.5%
  • Photon chemoradiotherapy 27.6%
  • Relative risk of 0.31 (p<0.01, 95% ci[0.15,0.66])

Further study endpoints: All in favor of proton therapy.

  • Grade 2 or higher toxicity  – RR 0.78, p<0.01
  • Decline in ECOG PS – RR 0.51, p<0.01
  • Proton delivered less radiation to normal tissue (p<0.05)
  • No difference in DFS or OS.

Dr. Mark Storey MD
OKCProton.com