Int. J. Radiation Oncology Biol. Phys.. Vol. 34, No. 3. pp. 555-564. 1996 Copyright 0 1996 Elsevier Science Inc. Printed in the USA. All rights reserved 0360-3016/96 $15.00 + 40 ELSEVIER 0360-3016(95)02103-S l Clinical Original Contribution CONVENTIONAL VS. CONFORMAL RADIOTHERAPY FOR PROSTATE CANCER: PRELIMINARY RESULTS OF DOSIMETRY AND ACUTE TOXICITY ALAN POLLACK, M.D., PH.D.,* GUNAR K. ZAGARS, M.D.,* GEORGE STARKSCHALL, PH.D.+ CONSTANCE H. CHILDMSS, B.S., C.M.D., R.T.(R)(T),t SUSAN KOPPLIN, R.N., B.S.N.,* ARTHUR L. BOYER, PH.D.+ AND ISAAC I. ROSEN, PH.D.+ Departments of *Radiotherapy and Radiation ‘Physics, The University of Texas M. D. Anderson Cancer Center. 15 15 Holcombe Boulevard, Houston, TX Purpose: To compare conformat radiotherapy using three dimensional treatment planning (3D-CRT) to conventional radiotherapy (Convert-RT) for patients with Stages T2-T4 adenocarcinoma of the prostate. Methods and Materials: A Phase III randomized study was activated in May 1993, to compare treatment toxicity and patient outcome after 78 Gy in 39 fractions using 3D-CRT to that after 70 Gy in 35 fractions using Convert-RT. The first 46 Gy were administered using the same nonconform field arrangement (four- field) in both arms. The boost was given nonconformalty usiug four fields in the Conven-RT arm and conformally using six fields in the 3D-CRT arm. The dose was specifkd to the isocenter. The hrst 60 patients, 29 in the 3D-CRT arm and 31 in the Conven-RT arm, are the subject of this pretimtnary analysis. Results: The two treatment arms were tirst compared in terms of dosimetry by dose-volume histogram anafys~s. Using a subgroup of patients in the 3D-CRT arm (n = U), both Conven-RT and 3D-CRT plans were generated and the dose-volume histogram data compared. The mean volumes treated to doses above 60 Gy for the bladder and rectmn were 28 and 36% for the 3D-CRT plans, and 43 and 38% for the Conven-RT plans, respectively @ < 0.05 for the bladder volumes). The mean clinicat target volume (prostate and seminal vesicles) treated to 95% of the prescribed dose was 97.5% for the 3D-CRT arm, and 95.6% for the Convert-RT arm (p < 0.05). There were no signiticant differences in the acute reactions between the two arms, with the majority experiencing Grade 2 or less toxicity (92%). Moreover, no relationship was seen between acute toxicity and the volume of bladder and rectum receiving in excess of 60 Gy for those in the 3D-CRT arm. There was also no difference between the groups in terms of early biochemical response. Prostate-specific antigen levels at 3 and 6 months after completion of radiotherapy were similar in the two treatment arms. There was only one biochemical failure in the study population at the time of the analysis. Conclusions: Comparison of the Conven-RT and 3D-CRT treatment plans revealed that signiticantty less bladder was in the high dose volume iu the 3D-CRT plans, white the volume of rectum receiving doses over 60 Gy was equivalent. There were no differences between the two treatment arms in terms of acute toxicity or early biochemical response. Longer follow-up is needed to determine the impact of 3D-CRT on long-term patient outcome and late reactions. Conformal radiotherapy, Dosimetry, Acute toxicity, Prostate specific antigen. INTRODUCTION Conformal radiotherapy using three dimensional treat- ment planning (3D-CRT) allows for more precise delivery of treatment, and hence, the potential for sparing more of the surrounding normal tissues from the higher doses, as compared to conventional radiotherapy (Conven-RT). Although the feasibility of dose escalation is being ad- dressed (9, 15), to our knowledge no direct comparisons of 3D-CRT and Conven-RT in the setting of a randomized trial have been made. We initiated such a trial in May 1993 with the goal of accruing 150 patients per treatment arm over a 3-year period. As of this writing, over 100 patients have been entered and treated. A preliminary Reprint requests to: Alan Pollack, M.D., Ph.D., Department of Radiotherapy (Box 97), M. D. Anderson Cancer Center, 1515 man Services, and an American Cancer Society Career Develop- ment Award (A.P.). The authors thank Ms. Joan Day, Adminis- Holcombe Boulevard, Houston, TX 77030. trative Assistant, for typing tbe manuscript, and tbe residents Acknowledgements-This work was supported in part by GrantsCA 06294, CA 43840, and CA 16672awarded by tbe in tbe Department of Radiotherapy for their supportive role in National CancerInstitute, U.S. Department of Health and Hu- the implementation of the protocol. Acceptedfor publication21 August 1995. 555