A Phase II Study of Intensity Modulated Radiation Therapy (IMRT) to the Pelvic for Post-operative Patients with Endometrial Carcinoma (RTOG 0418)

Article Outline

• Purpose/Objective(s)
• Materials/Methods
• Results
• Conclusions
• Copyright

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Purpose/Objective(s) 

To determine the transportability of pelvic IMRT for patients with endometrial carcinoma to a multi-institutional setting with a secondary endpoint to test the hypothesis that there is a reduction in short-term bowel injury compared to standard treatments.

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Materials/Methods 

Patients with stage I-IIIC adenocarcinoma of the endometrium judged to require pelvic radiation therapy alone were eligible. Guidelines for target definition and delineation, dose prescription, and dose/volume constraints for the targets and critical structures were detailed in the study protocol as well as an adjoining web-based atlas. The doses to the nodal PTV (planning treatment volume) and vaginal PTV were 50.4 Gy in 28 fractions. Chemotherapy was not allowed. Central quality assurance (Q/A) was performed for all participating centers and all patient treatment plans. Adverse events (AEs) were assessed using the CTCAE v. 3.0. The primary endpoint of this study is the reproducibility of the radiation technique. If <5 of 42 treatments are scored as deviation unacceptable, the treatment will be determined to be reproducible and considered for further study. A secondary endpoint was the reduction grade ≥2 short-term (within 90 days) bowel AEs [defined as the following: diarrhea, enteritis, fistula, ileus:GI, incontinence:anal, necrosis:GI, obstruction:GI, perforation:GI, proctitis and stricture/stenosis (including anastomotic):GI].

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Results 

58 patients were accrued by 25 institutions and 42 were eligible for analysis. Stages: 4% stage IB G2-3, 43% stage IC G1-3, 12% stage IIA, 33% IIB and 7% IIIC. For the PTV nodal, 29 (69%) were per protocol, 12 (29%) were minor variation and 1 (2%) had major variation. All cases of the vaginal PTV were within protocol or minor variation. Only 1 patient had an overall unacceptable deviation score. For the contouring of nodal CTV (clinical tumor volume), there were more variations. Forty three percent were contoured per protocol, 53% had minor variations, including 10 patients who had sacral nodes treated without cervix involvement. More variations were noted in the contouring of normal tissue especially small bowel. Of the 42 patients, 11 patients (28%) developed grade 2 or higher bowel toxicity.

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Conclusions 

Pelvic IMRT is feasible across multiple institutions using a detailed protocol and centralized Q/A, with most having some minor protocol variation in contouring PTV and normal tissues. Potential relationships between minor and major protocol variation and possible clinical outcome will be discussed.

Supported by RTOG U10 CA21661, CCOP U10 CA37422, and Stat U10 CA32115 grants from the NCI.