Improving Health Through Medical Physics

IROC Houston Report

Jessica Lowenstein | Houston, TX

AAPM Newsletter — Volume 44 No. 4 — July | August 2019

50 Years of Supporting Clinical Trials and the Radiation Oncology Community

This past year the IROC Houston QA Center (formerly the Radiological Physics Center) celebrated its 50-year anniversary supporting NCI multi-institution clinical trials and the radiation oncology community. The RPC/IROC-Houston QA Center was funded and established in September 1968 in collaboration with the AAPM and under the leadership of Dr. Robert Shalek. It has, for the past 50 years, contributed to the development, conduct, and QA of NCI-funded clinical trials and their participating institutions in North America and 52 other countries. There have only been four Directors of this QA Center; Dr. Robert Shalek (1968-1986), Dr. William Hanson (1986-2001), Dr. Geoffrey Ibbott (2001-2010) and currently, Dr. David Followill (2010-present).

The Mission of the RPC/IROC-Houston QA Center has consistently been to 1) assure NCI and clinical trial groups that institutions participating in clinical trials deliver prescribed doses that are comparable and consistent, minimizing dose uncertainty, 2) help participating institutions to make any corrections to their dose determination and delivery processes that might be needed and 3) report findings to the radiation oncology community. All this while maintaining strict confidentiality. The implemented RPC/IROC-Houston QA program, which is the largest in the world, is designed to audit the radiation dose calculation/delivery chain from the NIST traceable reference beam calibration, to the dosimetry parameters used to calculate tumor doses, to the delivery of the treatment. The QA program includes 5 major components: 1) remote TLD/OSLD audit of machine output, 2) on-site dosimetry review visits, 3) credentialing for advanced technologies, 4) review of patient treatment records, and 5) approval and credentialing of proton therapy.

Over the years, key milestones and implementations have included the following:

Year Milestone
1968 First onsite dosimetry visit conducted
1977 TLD program for photon beams
1982 TLD program for electron beams
1986 Conversion to TG21
1995 Laptops first used on site visits
1998 RADs relational database went live
2000 Conversion from TG21 to TG51
2001 Initiated end to end phantom program
2007 TLD program for proton beams
2010 Switched from TLD to OSLD
2010 First proton site visit
2015 Virtual site visit program begins
2018 First work on carbon ions begins

The number of institutions monitored by RPC/IROC-Houston QA Center has increased from 22 in 1968 to 2,214 by the end of 2018. There were over 4,000 therapy machines and 24,600 therapy beams monitored at institutions by 2018. A total of 301,719 beam output checks have been performed since 1968. Within the 17,000 photon, electron and proton beam outputs monitored annually with TLD/OSLD since 2000, 6–22% of the institutions have one or more beams outside the 5% criterion. Dosimetry site visits to institutions have continually resulted in 2–4 recommendations affecting key dosimetry parameters. One in four patient treatment records reviewed require their reported dose data to be corrected by >5%. End-to-end phantom audits currently exceed 700 annually with an average historical failure rate of 10–15%. Twenty-six of thirty-one clinically active proton centers have been approved to participate clinical trials. Since 1972, 342 peer reviewed articles have been published with a little less than 50% of these occurring since 2010.

The RPC/IROC-Houston efforts and findings over the past 50 years suggest that errors continue to manifest in radiotherapy, and that without its independent peer review QA program, many of these errors would go undetected. The clear value of IROC Houston's services over the past five decades in detecting errors and improving the quality of radiotherapy highlight the ongoing and continued need for these programs. Radiation oncology has changed dramatically over the past 50 years and continues to change with new technological advances and new cancer therapies. IROC Houston's services have also and will continue to evolve to address those changes to improve the quality and consistency of radiotherapy, clinical trials, and patient outcomes.

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