University of Florida, Jacksonville, FL Is It Safe For Patients With Implanted Cardiac Devices To Undergo Proton Beam Therapy? Rohan Samson, MD, Junaid A. Ahmed, MD, Alice Schroeder, RN, Cynthia Gist, ACNP, Ali Nasur, MD, Naseer Nasser, MD, Robert Kim, MD, David Nabert, MD and Steve Hsu, MD. University of Florida, Jacksonville, FL

Disclosures Nothing to Disclose

Background Proton therapy is a type of particle therapy which uses a beam of protons to irradiate diseased tissue, most often in the treatment of cancer. A cyclotron strips hydrogen atoms, accelerates and directs the resulting protons towards tumors. As protons slow in tissue they deliver the majority of their energy as ionizing radiation. This process may also produce scatter radiation that impacts cardiac devices.

The Cyclotron Through electrolysis, protons are taken from water and injected into the cyclotron (cylindrical structure at center) which accelerates protons to nearly the speed of light. The protons are guided through the beam line at right.

The Beam Line The protons travel through the beam line, guided by electromagnets, into one of four treatment rooms.

The Gantry Proton therapy is delivered while you lie on the treatment table. A gantry rotates to deliver therapy precisely to the tumor site.

Bragg Peak Described by William Bragg over 100 years ago Depth is dependent on the energy of the proton beam This energy can be controlled very precisely

Diseases Treated by Proton Therapy Urological cancers, especially prostate cancer Lung cancer Head and neck cancer Pediatric malignancies Bone and soft tissue sarcomas Cancer of the eye and other disorders such as macular degeneration Brain cancer and cancer of the central nervous system

Proton Beam Statistics As of 2008, 55,000 patients have been treated with proton therapy worldwide In the United States, there are five facilities offering this treatment Locations where PBT is being offered in the US: The Harvard Cyclotron laboratory at Massachusetts General Hospital The Proton Treatment Center at Loma Linda University Medical Center (LLUMC) M.D. Anderson Proton Therapy Center in Houston University of Pennsylvania's proton facility in Philadelphia University of Florida's Proton Therapy Institute in Jacksonville

Effect of Proton Beam on cardiac devices? Current implanted cardiac devices are prone to electromagnetic interference (EMI). There is limited literature in the interaction between cardiac devices and proton beam therapy.

AIM of our study To study the Effects of Proton Beam Therapy on Appropriate Functioning of Implantable Cardiac Pacemakers and Defibrillators

Methods Prospective study Evaluated patients with Pacemakers, Implantable Cardioverter Defibrillators (ICD) undergoing proton beam therapy at our Proton Therapy Institute from 2006 through 2010. Device interrogation done at : Baseline (prior to starting therapy) Immediately post initial therapy Weekly during the entire treatment duration Inferential statistics in the form of univariate tests (T-tests, Chi square) were utilized to compare the group with device resets to the group without device resets on the characteristics collected.

Results Demographics and Clinical Characteristics

Results Percentage of pts with ICDs vs Pacemakers ICD = 12 pts PM = 19 pts Site of Proton beam Therapy Prostate = 27 pts Chest = 2 pts Head/Neck=2 pts

Results Device Manufacturers: Type of ICD implanted: Single Chamber ICD = 1 pt Dual Chamber ICD = 8 pts BiV-ICD = 3 pts Device Manufacturers: Medtronic = 18 pts St Jude = 5 pts BSC = 7 pts ELA = 1 pt

Results – Device Reprogramming

Analysis of Device Reprogramming

Results All resets occurred in ICDs, not Pacemakers: Statistically Significant (p=0.007) There was an increased incidence of resets in patients with higher number of leads: Statistically Significant (p=0.013) No statistically significant differences were noted between patients with device resets and those without device resets when comparing other variables: Site of Therapy Radiation Dose

Conclusions All resets occurred in ICDs, none in Pacemakers Higher incidence of resets in patients with more number of leads. Device resets observed predominantly in Medtronic devices may be a biased observation due to the large number of Medtronic devices implanted in study population (58% overall). Despite small numbers of patients, we are the first to report observations or significant findings of any kind involving device resets in patients receiving Proton beam Therapy. As this category of patients grows over time, it will become important to understand the interactions of Proton Beam Therapy and Cardiac Devices, especially since patients are dependent on the appropriate functioning of their devices, especially ICDs.

Thank you ! Questions ?