PHYSICS CONTRIBUTION DOSIMETRIC COMPARISON OF BONE MARROW-SPARING INTENSITY- MODULATED RADIOTHERAPY VERSUS CONVENTIONAL TECHNIQUES FOR TREATMENT OF CERVICAL CANCER LOREN K. MELL, M.D.,* HANIFI TIRYAKI,PH.D., y KANG-HYUN AHN,PH.D., z ARNO J. MUNDT, M.D.,* JOHN C. ROESKE,PH.D., x AND BULENT AYDOGAN,PH.D. { * Department of Radiation Oncology, University of California San Diego, School of Medicine, La Jolla, CA; y Department of Radiation and Cellular Oncology, University of Illinois at Chicago, Chicago, IL; z Department of Radiation Oncology, Stanford University, Palo Alto, CA; x Department of Radiation Oncology, Loyola University Medical Center, Maywood, IL; { Department of Radiation and Cellular Oncology, University of Chicago Pritzker School of Medicine, Chicago, IL Purpose: To compare bone marrow-sparing intensity-modulated pelvic radiotherapy (BMS-IMRT) with conven- tional (four-field box and anteroposterior–posteroanterior [AP–PA]) techniques in the treatment of cervical cancer. Methods and Materials: The data from 7 cervical cancer patients treated with concurrent chemotherapy and IMRTwithout BMS were analyzed and compared with data using four-field box and AP–PA techniques. All plans were normalized to cover the planning target volume with the 99% isodose line. The clinical target volume con- sisted of the pelvic and presacral lymph nodes, uterus and cervix, upper vagina, and parametrial tissue. Normal tissues included bowel, bladder, and pelvic bone marrow (PBM), which comprised the lumbosacral spine and ilium and the ischium, pubis, and proximal femora (lower pelvis bone marrow). Dose–volume histograms for the plan- ning target volume and normal tissues were compared for BMS-IMRT vs. four-field box and AP–PA plans. Results: BMS-IMRT was superior to the four-field box technique in reducing the dose to the PBM, small bowel, rectum, and bladder. Compared with AP–PA plans, BMS-IMRT reduced the PBM volume receiving a dose >16.4 Gy. BMS-IMRT reduced the volume of ilium, lower pelvis bone marrow, and bowel receiving a dose >27.7, >18.7, and >21.1 Gy, respectively, but increased dose below these thresholds compared with the AP–PA plans. BMS-IMRT reduced the volume of lumbosacral spine bone marrow, rectum, small bowel, and bladder at all dose levels in all 7 patients. Conclusion: BMS-IMRT reduced irradiation of PBM compared with the four-field box technique. Compared with the AP–PA technique, BMS-IMRTreduced lumbosacral spine bone marrow irradiation and reduced the volume of PBM irradiated to high doses. Therefore BMS-IMRT might reduce acute hematologic toxicity compared with con- ventional techniques. Ó 2008 Elsevier Inc. Bone marrow, Bone marrow-sparing, Intensity-modulated radiotherapy, IMRT, Cervical cancer. INTRODUCTION Concurrent chemotherapy with external beam radiotherapy is the standard treatment of bulky and locally advanced cervical cancer (1–3). The use of concomitant chemotherapy, how- ever, frequently causes acute hematologic toxicity (HT) (1, 3, 4). Previous studies have associated the volume of pelvic (PBM) and lumbosacral bone marrow (LSBM) receiving 10 and 20 Gy with the development of acute HT in patients undergoing concurrent chemotherapy and intensity-modu- lated radiotherapy (IMRT) (5, 6). Therefore, reducing the volume of BM receiving low-dose RT might prevent HT. Intensity-modulated RT reduces the dose to normal tissues for whole pelvic RT (7–10). However, the ability of IMRT to reduce the PBM dose, particularly low-dose radiation, com- pared with conventional forward planning techniques has not been fully investigated. Quantifying the expected dosi- metric benefits of BM-sparing (BMS) IMRT (BMS-IMRT) plans compared with conventional plans is an important pre- cursor to prospective clinical testing of this novel treatment approach. The purpose of this study was, therefore, to ascer- tain the dosimetric benefits of BMS-IMRT compared with anteroposterior–posteroanterior (AP–PA) and four-field box techniques in the treatment of patients with cervical cancer. Reprint requests to: Bulent Aydogan, Ph.D., Department of Radia- tion and Cellular Oncology, University of Chicago Hospitals, 5758 S. Maryland Ave., MC 9006, Chicago, IL 60637. Tel: (312) 413- 7965; Fax: (312) 413-3068; E-mail: baydogan@radonc.uchicago.edu Conflict of interest: none. Received Jan 10, 2008, and in revised form April 11, 2008. Accepted for publication April 14, 2008. 1504 Int. J. Radiation Oncology Biol. Phys., Vol. 71, No. 5, pp. 1504–1510, 2008 Copyright Ó 2008 Elsevier Inc. Printed in the USA. All rights reserved 0360-3016/08/$–see front matter doi:10.1016/j.ijrobp.2008.04.046