A Survey of the ITC Volumetric Treatment Planning Data Archive Supporting RTOG Advanced Technology Clinical Trials

Abstract

Purpose: Survey of volumetric treatment planning (TP) data, linked to outcomes, collected by the Image-guided Therapy QA Center (ITC) in 15 years of facilitating QA review for RTOG multi-institutional advanced technology (AT) clinical trials. Materials & Methods: The ITC as part of the Advanced Technology QA Consortium (ATC) collects volumetric TP data sets linked to outcomes for RTOG Advanced Technology clinical trials. CT images, target-volume/organ-at-risk contours, and 3D dose distributions exported from commercial TP systems are submitted to the ITC using either DICOM or RTOG Data Exchange format. ITC staff evaluates dataset integrity and completeness, and requests re-submission as needed. DoseVolume Histograms (DVHs) for required volumes are recalculated from submitted contours and dose distributions. RTOG dosimetrists and study chairs review contours and dose distributions for protocol compliance using ITC’s web-based Remote Review Tool (RRT). Clinical outcomes are reported to RTOG headquarters using protocol-specific forms. Results: The ITC has collected over 5000 complete TP data sets quantifying the relationship between image-based anatomy and planned doses. Disease sites treated in the 10 closed protocols (1800 cases) include prostate, lung, brain, head/neck, and breast. An additional 13 active protocols (>3500 cases) also include liver, cervix, and anus. A sample of data sets available for analysis is listed below. (Doses (Gy) and % volumes are the minimum/maximum/average values.) Prostate (3DCRT, N=984; PTV D98: 52.2/81.6/75.0, bladder Dmean: 4.9, 75.9, 37.7, rectum Dmean: 12.9, 72.5, 42.7, femoral heads Dmean: 1.8, 49.5, 32.4), HeadN PTV D98: 58.0/73.4/67.6, spinal cord D2: 32.8/44.8/39.6, parotid Dmean: 21.2/50.3/32.4, larynx Dmean: 3.9/57.7/32.9), Lung (3DCRT, N=158; PTV D98: 50.3/98.2/77.4, spinal cord D2: 0.1/60.1/26.0, esophagus Dmean: 0/63.8/15.9, heart Dmean: 0/45.3/10.5, liver Dmean: 0/19.3/1.2, brachial plexus Dmean: 0/57.7/4.6, lung V20: 5.3/46.6 /21.2 %,). The ITC has provided access to these TP protocol data sets for secondary analysis by: (1) export of entire TP data sets as RTOG data exchange files and (2) online data analysis using the RRT. External investigators have used these data for dose escalation trials in prostate (RTOG 9406) and lung cancer (RTOG 9311) and obtained two NIH R01 grants focused on the development of normal tissue complication probability (NTCP) models. Also, online access to RTOG 9406 TP data has been used to analyze erectile dysfunction following 3DCRT for prostate cancer. Using the contour editing feature in the RRT, penile bulb structures, not originally contoured for RTOG 9406, were delineated on these datasets. New DVHs were computed from the stored 3D dose distributions and compared with reported clinical outcomes (impotence). Such an analysis would have required an entirely new study if the volumetric TP data had not been archived in the ITC database. Conclusion: The ITC archive of volumetric images and dosimetry for RTOG Advanced Technology Clinical Trials is a rich resource for developing and testing models of tissue response to ionizing radiation. The value of this archive continues to grow with the incorporation of new data sets from new anatomical sites, and new imaging modalities. Supported by NIH U24 grant CA81647 and U10 grant CA21661