Quality assurance methods for the first Radiation Therapy Oncology Group permanent prostate implant protocol

To report the quality assurance methodology used by the Radiation Therapy Oncology Group in the first cooperative group, multi-institution Phase II trial of transrectal ultrasound guided permanent radioactive implantation of the prostate for definitive treatment of localized adenocarcinoma of the prostate.

Participating institutions were credentialed to participate in this protocol, Radiation Therapy Oncology Group 98-05. International Commission on Radiation Units and Measurements (ICRU) Report 58 was used as the basis for definition of terms. The AAPM's dosimetric prerequisites for low energy interstitial brachytherapy sources were adopted. A nondigital approach to central review was used. The implant dosimetry was recalculated based upon centrally reviewed target volumes by both a radiation oncologist and a diagnostic radiologist.

There are differences in the definition of the postimplant prostate between the participating institution, the central review radiation oncologist, and the central review diagnostic radiologist. Thus, there are differences in dose/volume parameters. Six of the 95 patients reviewed did not meet the per protocol criteria based upon information supplied by the participating institution. This increased to 18 cases when using the postimplant target volume defined by the central oncologist and to 23 cases when defined by the radiologist.

This work indicated that there is a need for a central review process of dose-volume analysis within the cooperative group setting. It is indicated that a digital approach to centralized review, which has now been developed, would result in a higher quality and easier review.