RPC Report to the AAPM Therapy Physics Committee Page 15 of 15
Report No. 122
REPORT TO THE AAPM THERAPY PHYSICS COMMITTEE
Report No. 122 July 1, 2005 – October 1, 2005
In lieu of a specific report addressed to the Therapy Physics Committee, the RPC is providing the text for this section from the annual non-competing application (progress report) to the National Cancer Institute (NCI).
RPC Report to the AAPM Therapy Physics Committee Page 15 of 15
Report No. 122
a) Specific Aims
The specific aims of this project have not changed during this reporting period. The primary aim is to assure NCI and the cooperative groups that the participating institutions have adequate staff, equipment, and quality assurance procedures, so that all participants can be expected to deliver radiation treatments that are clinically comparable to other institutions in the cooperative groups. To accomplish this, the RPC monitors external beam and brachytherapy calibrations, evaluates the accuracy of dose calculation algorithms, and determines the adequacy of quality assurance procedures at the participating institutions. Methods include on-site dosimetry reviews, remote monitoring by mailed TLD and anthropomorphic phantoms, and evaluation of benchmark and human patient treatment plans. During recent years, efforts have focused on the credentialing of institutions to participate in specific protocols, and on the development of techniques to monitor advanced technology treatment modalities such as conformal therapy and intensity-modulated radiation therapy (IMRT).
b) Studies and Results
The RPC presently monitors 1,388 megavoltage therapy sites in North America, Europe, and elsewhere in the world, who participate in cooperative group clinical trials funded by the NCI. The cooperative groups monitored include ACOSOG, ACRIN, CALGB, COG, ECOG, GOG, NABTT, NCCTG, NSABP, RTOG and SWOG. We also communicate regularly with the Cancer Trials Support Unit (CTSU) to assure that institutions participating through their programs are properly monitored.
· On-Site Dosimetry Reviews: Since January 1, 2005, RPC physicists have performed on-site dosimetry evaluation at 26 institutions, evaluating 205 beams (a “beam” is a single photon beam or a cadre of electron beams). 26 (100%) of the institutions received at least one recommendation for actions that should improve their quality assurance programs. During the last two years, additional procedures were added to our measurement program, specifically to monitor IMRT.
· TLD: Between October 1, 2003 and September 30 2005, 18,800 beams were monitored with TLD at the monitored institutions. Overall, 2.4% of the irradiated TLD received doses that disagreed with the institution’s stated dose by more than 5%. Institutions currently using the obsolete calibration protocol (TG-21) exhibited a higher discrepancy rate than the institutions that had converted to the new calibration protocol (TG-51). Of institutions using TG-21, 22% had at least one beam with a calibration discrepancy >5% (obvious irradiation errors were excluded from this analysis). At institutions using TG-51, 13% exhibited calibration discrepancies >5%.
· Patient Treatment Review: Since January 1 2005, individual protocol patient treatment records were evaluated for 150 patients treated on GOG, NSABP, NCCTG, and RTOG protocols. Of this, 71 patients were receiving brachytherapy treatments.
· Credentialing Processes: The RPC participates in the credentialing of institutions for protocols involving advanced technologies including brachytherapy, IMRT and stereotactic radiosurgery (SRS). This activity is partially supported by a subcontract from the Advanced Technologies for Clinical Trials grant. For IMRT and SRS, credentialing includes irradiation of an anthropomorphic phantom provided by the RPC that contains anatomic structures and dosimeters. To date, the RPC has issued 163 reports to institutions that irradiated the RPC head and neck IMRT phantom. Of these, 115 indicated that the irradiation complied with the institution’s treatment plan within criteria agreed to by the RPC and the RTOG. 48 irradiations failed to meet these criteria for a first-time failure rate of 32%. The RPC plays the lead role in credentialing institutions for a partial breast irradiation (PBI) trial run jointly by NSABP and RTOG. Credentialing requires completion of facility and knowledge-assessment questionnaires (using web-based forms) and electronic submission of a benchmark treatment plan. To date, 963 applications for credentialing have been received (all or part) and 581 credentials have been issued (3D CRT arm-353; Mammosite arm-178; multicatheter arm-50). The remainder are awaiting submission of required information or replies to questions. Complete applications are processed within 2 business days.
· Low-Energy Brachytherapy Sources: Dr. Ibbott represents the RPC on a subcommittee appointed by the AAPM to address the use of new seeds and the RPC serves as a clearinghouse for information. A number of publications have resulted from this work. An update of the TG-43 dosimetry protocol has been published, and a second update is in preparation.
· TG-51 Calibration Protocol: To date, over 1,044 institutions (approximately 74% of the clinical trial participants) have indicated that they have converted to the new protocol. We continue to receive occasional phone calls concerning implementation of the protocol. The RPC has presented a total of 39 workshops and publications on this protocol (see Publications section).
· Monitoring Conformal and Dynamic Therapies: The RPC now routinely evaluates dynamic wedges, asymmetric jaws, and multileaf collimators during an on-site review. In addition, the RPC continues to develop anthropomorphic phantoms. Part of this effort is carried out under the ATC grant. The RPC recently developed a liver phantom; this phantom incorporates motion to simulate breathing and has been irradiated at two institutions in preparation for RTOG 0438.
· Database: The RPC database continues to greatly facilitate our work. Results of remote measurements, on-site dosimetry reviews, and treatment record reviews are available to RPC staff immediately. We make extensive use of the database to improve our efficiency, generate publications, and provide information via our website to the cooperative groups.
· Webpage: The RPC webpage is again undergoing a major revision. By the end of the year, we expect to introduce a new state of the art webpage. Study groups and CTSU use our website to determine an institution’s participation in the RPC QA programs. In addition, we have implemented online web forms for certain credentialing activities, including RTOG 0413/NSABP B-39.
· AAPM Oversight: The AAPM Therapy Physics Committee continues to be our scientific advisory committee. We report to this committee three times per year, and participate in subcommittees, task group, and working groups. A task group of the TPC performs a one-day in depth evaluation annually.
· Clinical Advisory Committee: A group of 5 radiation oncologists was formed as a clinical advisory committee. The Committee is contacted when questions arise regarding RPC operations.
c) Significance
Radiation therapy continues to move towards highly conformal therapies using high technology modalities. As clinical trials incorporate these technologies, the RPC is developing tools to monitor the quality of these therapies. At the same time, we continue our traditional role, monitoring conventional therapies, which still represent the bulk of treatments in clinical trial studies. The TLD monitoring program and on-site dosimetry reviews have played a key role in achieving consistent dosimetry over the years. Evidence of our contributions to improved dosimetry at participating institutions is demonstrated by the recommendations made by the RPC following a visit.
d) Plans
Plans for this budget period are not significantly changed from those outlined in the application for the current grant cycle.
· On-Site Dosimetry Reviews: Each FTE traveling physicist should review 50 beams.
· Mailed TLD Program: Our criteria for acceptability have not been changed.
· Credentialing: We will continue to work with the groups to focus our efforts appropriately.
· Patient Treatment Review: Except for some studies evaluated by the RTOG QA office, the RPC is the only QA office that focuses on technical evaluation of radiation dose (dosimetry review). The RPC will continue to review some fraction of patients to assess the quality of the data currently being submitted.
· Anthropomorphic Phantoms: Additional phantoms have been purchased during the last year, to meet the demand for credentialing on all existing protocols and newly-developed protocols. The demand for credentialing plus the repair of unanticipated damage from handling and radiation exposure have necessitated an increase in machinist time.
· Liaison with Cooperative Groups, AAPM, etc.: The AAPM Therapy Physics Committee continues as our scientific advisory body. The RPC participated in the development and conduct of a roundtable conference on quality assurance practices in radiation oncology held at the NCI in September 2005. This workshop was in preparation for a larger workshop presently anticipated to be held in the Spring of 2006. The RPC will play a lead role in organizing and conducting this workshop.
· Data Transfer: The RPC, through the ATC subcontract, continues to develop and implement electronic data exchange capabilities. We now use electronic data routinely in the evaluation of phantom irradiations.
· Webpage: We continue to add capabilities to the RPC webpage, and plan in the near future to convert our TLD review mechanism to a fully electronic process. Discussions have been held with the AAPM regarding access to the RPC database for data mining activities.
PARTICIPANT FEE:
Institutions invoiced FY05 1307
No XRT/Canceled/Inactive 87
Invoiced by RDS 10
Institutions paid 1028
PUBLICATIONS AND ABSTRACTS
Publications Accepted/Published (2001-2005):
1. Kirsner, S.M., Prado, K.L., Tailor, R.C., and Bencomo, J.A.: Verification of the accuracy of 3D calculations of breast dose during tangential irradiation: measurements in a breast phantom. J. Applied Clin. Med. Phys., 2 (3), pp. 149-156, 2001.
2. Melia, Sc.M., Michele; Abramson, M.D., David; Albert, M.D., Daniel; Boldt, M.D. Culver; Earle, M.D., John; Hanson, Ph.D., William; Montague, Paul; Moy, Ph.D., Claudia; Schachat, M.D., Andrew; Simpson, M.D., Rand; Straatsma, M.D., Bradley; Vine, M.D., Andrew; and Weingeist, M.D., Ph.D., Thomas: Collaborative Ocular Melanoma Study (COMS) Randomized Trial of I-125 Brachytherapy for Medium Choroidal Melanoma I. Visual Acuity after 3 Years, COMS Report No. 16”, Opthalmology, 108 (2):348-366, 2001.
3. Kim, C-H., Reece, W. D., and Cho, S. H. Computer simulation of radiation exposure in a S/G channel head. Trans. Am. Nucl. Soc., 84:325-326, 2001.
4. Tailor, R., Hanson, W., Calculated absorbed-dose ratios, TG-51/TG-21, for most widely used cylindrical and parallel-plate ion chambers over a range of photon and electron energies, Med. Phys. Vol. 29:1464-1472, 2002.
5. Gifford, K.A., Followill, D.S., Liu, H.H., and Starkschall, G. Verification of the accuracy of a photon dose-calculation algorithm. J. Applied Clin. Med. Phys. 3:26-45, 2002.
6. Villarruel, S., Ibbott, G.S., and Lai-Fook, S.J.: Effect of concentration and hydration on restriction of albumin by lung interstitium. Microvascular Research 63, 27-40, 2002.
7. Cadman, P., Bassalow, R., Sidhu, N.P.S., Ibbott, G., Nelson, A. Dosimetric considerations for validation of a sequential IMRT process with a commercial treatment planning system. Physics in Medicine and Biology Vol. 47, 3001-3010, 2002.
8. Ibbott, G., Beach, M., Maryanski, M. An anthropomorphic head phantom with a BANG® polymer gel insert for dosimetric evaluation of IMRT treatment delivery. Standards and Codes of Practice in Medical Radiation Dosimetry, Proceedings of an International Symposium, Vienna, Vol. 2, pp. 361-368, November 25-28, 2002.
9. Ibbott, G., Nelson, A., Followill, D., Balter, P., Hanson, W. An anthropomorphic head and neck phantom for evaluation of intensity modulated radiation therapy. Standards and Codes of Practice in Medical Radiation Dosimetry, Proceedings of an International Symposium, Vienna, Vol. 2, pp. 209-217, November 25-28, 2002.
10. Izewska, J., Svensson, H., Ibbott, G. Worldwide QA networks for radiotherapy dosimetry. Standards and Codes of Practice in Medical Radiation Dosimetry, Proceedings of an International Symposium, Vienna, Vol. 2, pp. 139-155, November 25-28, 2002.
11. Aguirre J, Tailor R, Ibbott G, Stovall M, Hanson W. TLD as a remote verification of output for radiotherapy beams: 25 years of experience. Standards and Codes of Practice in Medical Radiation Dosimetry, Proceedings of an International Symposium, Vienna, Vol. 2, pp. 191-199, November 25-28, 2002.
12. Tailor R, Hanson W, and Ibbott G, TG-51 Experience from 150 institutions, common errors, and helpful hints, J. Applied Clin. Med. Phys., Vol. 4, pp.102-111, 2003.
13. Urie, M., FitzGerald, T.J., Followill, D., Laurie, F., Marcus, R., Michalski, J. Current calibration, treatment, and treatment planning techniques among institutions participating in the Children’s Oncology Group. Int. J. of Radiat. Oncol., Biol., Phys. 1:245-260, 2003.
14. Followill D.S., Hanson, W.F., Ibbott, G.S., Eglezopoulos, L.R., and Chui, C.S. Differences in electron beam dosimetry using two commercial ionization chambers and the TG-21 protocol: another reason to switch to TG-51. J. Applied Clin. Med. Phys. 4: 124-131, 2003.
15. Nag, S., Quivey, J.M., Earle, J.D., Followill, D.S., Fontanesi, J., and Finger, P. The American Brachytherapy Society Recommendations for Brachytherapy of Uveal Melanomas, Int. J. of Radiat. Oncol., Biol., Phys. 56:544-555, 2003.
16. Krintz, A.L., Hanson, W.F., Ibbott, G.I. and Followill, D.S., A Reanalysis of the Collaborative Ocular Melanoma Study Medium Tumor Trial Eye Plaque Dosimetry, Int. J. of Radiat. Oncol., Biol., Phys. 56:889-898, 2003.
17. Followill, D.S., Stovall, M.S., Kry, S.F., and Ibbott, G.S., Neutron source strength measurements for Varian, Siemens, Elekta, and General Electric linear accelerators. J. Applied Clin. Med. Phys. 4:189-194, 2003.
18. Diener-West, M., Albert, D. M., Frazier Byrne, SI, Davidorf, F. H. Followill, D. S., Green, R.L., Hawkins, B.S., Kaiser, P.K., Robertson, D.M., and Straatsma, B.R., Comparison of Clinical, Echographic and Histopathologic Measurements from Eyes with Medium-Sized Choroidal Melanoma: in the Collaborative Ocular Melanoma Study. COMS Report No. 21, The Collaborative Ocular Melanoma Study Group, Archives of Ophthalmology 121: 2003.
19. Tailor, R.C., Followill, D.S., Hernandez, N., Ibbott, G.S., and Hanson, W.F., “Predictability of electron cone ratios with respect to linac make and model,” J. Applied Clin. Med. Phys., Vol. 4 (2), pp. 172-178, 2003.
20. Cho, S.H. and Ibbott, G.S., “Reference photon dosimetry data: A preliminary study of in-air off-axis factor, percentage depth dose, and output factor of the Siemens Primus linear accelerator”, J. Applied Clin. Med. Phys. 4 (4): 300-306, 2003.
21. Cho S, Reece W, Kim C. Validity of two simple rescaling methods for electron/beta dose point kernels in heterogeneous source-target geometry. Radiation Physics and Chemistry 69:265-72, 2004.
22. Rivard M, Coursey B, DeWerd L, Hanson W, Huq M, Ibbott G, Mitch M, Nath R, Williamson J. Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations. Med. Phys. 31:633-74, 2004.