Intensity Modulated Radiation Therapy for Retroperitoneal Sarcoma:A Case for Dose Escalation and Organ at Risk Toxicity Reduction

[摘要] Purpose:Radiation therapy for retroperitoneal sarcoma remains challenging because of proximity to surrounding organs atrisk (OAR). We report the use of intensity modulated radiation therapy (IMRT) in the treatment of retroperitoneal sarcomasto minimize dose to OAR while concurrently optimizing tumor dose coverage.Patients and methods:From January 2000 to October 2002, 10 patients (average age 56 years) with retroperitoneal sarcomaand one with inguinal sarcoma were treated with radiation at Emory University. Prescription dose to the planning treatmentvolume (PTV) was commonly 50.4 at 1.8 Gy/fraction. CT simulation was used in each patient, three patients were treatedwith 3D-conformal treatment (3D-CRT), and the remaining eight received multi-leaf collimator-based (MLC) IMRT.IMRT treatment fields ranged from eight to 11 and average volume treated was 3498 cc. Optimal 3D-CRT plans weregenerated and compared with IMRT with respect to tumor coverage and OAR dose toxicity. Dose volume histograms werecompared for both the 3D-CRT and IMRT plans.Results:Mean dose to small bowel decreased from 36 Gy with 3D-CRT to 27 Gy using IMRT, and tumor coverage (V95)increased from 95.3% with 3D-CRT to 98.6% using IMRT. Maximum and minimum doses delivered to the PTV weresignificantly increased by 6 and 22%, respectively (P= 0.011,P= 0.055). Volume of small bowel receiving > 30Gy wassignificantly decreased from 63.5 to 43.1% with IMRT compared with conventional treatment (P= 0.043). Seven patientsdeveloped grade 2 nausea, three developed grade 2 diarrhea, one had grade 2 skin toxicity, and one patient developed grade3 liver toxicity (RTOG toxicity scale). No other delayed toxicities related to radiation were observed. At a median follow-upof 58 weeks, there were no local recurrences and only one patient developed disease progression with distant metastasis inthe liver.Conclusions:IMRT for retroperitoneal sarcoma allowed enhanced tumor coverage and better sparing of dose tocritical normal structuressuch as small bowel, liver, and kidney.Escalation of dose has a positive impact on local control for retroperitoneal sarcoma;IMRT may be an effective method to achieve this goal. We are evaluating preoperative dose escalation to 59.4 Gy.

[学科分类] 肿瘤学