State of dose prescription and compliance to international standard (ICRU-83) in intensity modulated radiation therapy among academic institutions

Purpose: The purpose of this study was to evaluate dose prescription and recording compliance to international standard (International Commission on Radiation Units & Measurements [ICRU]-83) in patients treated with intensity modulated radiation therapy (IMRT) among academic institutions. Methods and materials: Ten institutions participated in this study to collect IMRT data to evaluate compliance to ICRU-83. Under institutional review board clearance, data from 5094 patients-including treatment site, technique, planner, physician, prescribed dose, target volume, monitor units, planning system, and dose calculation algorithm-were collected anonymously. The dose-volume histogram of each patient, as well as dose points, doses delivered to 100% (D100), 98% (D98), 95% (D95), 50% (D50), and 2%(D-2), of sites was collected and sent to a central location for analysis. Homogeneity index (HI) as a measure of the steepness of target and is a measure of the shape of the dose-volume histogram was calculated for every patient and analyzed. Results: In general, ICRU recommendations for naming the target, reporting dose prescription, and achieving desired levels of dose to target were relatively poor. The nomenclature for the target in the dose prescription had large variations, having every permutation of name and number contrary to ICRU recommendations. There was statistically significant variability in D95, D50, and HI among institutions, tumor site, and technique with P values b.01. Nearly 95% of patients had D50 higher than 100%(103.5 +/- 6.9) of prescribed dose and varied among institutions. On the other hand, D95 was close to 100% (97.1 +/- 9.4) of prescribed dose. Liver and lung sites had a higher D50 compared with other sites. Pelvic sites had a lower variability indicated by HI (0.13 +/- 1.21). Variability in D50 is 101.2 +/- 8.5, 103.4 +/- 6.8, 103.4 +/- 8.2, and 109.5 +/- 11.5 for IMRT, tomotherapy, volume modulated arc therapy, and stereotactic body radiation therapy with IMRT, respectively. Conclusions: Nearly 95% of patient treatments deviated from the ICRU-83 recommended D50 prescription dose delivery. This variability is significant (P b.01) in terms of treatment site, technique, and institution. To reduce dosimetric and associated radiation outcome variability, dose prescription in every clinical trial should be unified with international guidelines. (C) 2016 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.