2818 - Comparative Dosimetric Analysis of Adjuvant Post-Op Pelvic IMRT Using Standard Volumes vs. EMBRACE Low-Risk Pelvic Volume for Patients with Stage I Cervical Cancer Meeting Sedlis Criteria
Presenter(s)
C. Padilla1, A. R. Santos2, N. Nair2, L. Portelance3, A. H. Wolfson3, A. Rivera3, R. Bui3, S. Han4, and I. M. Reis5; 1Universidad del Norte, Barranquilla, Colombia, 2Division of Gynecologic Oncology, University of Miami/Sylvester Comprehensive Cancer Center, Miami, FL, 3Department of Radiation Oncology, University of Miami/Sylvester Comprehensive Cancer Center, Miami, FL, 4Biostatistics and Bioinformatics Shared Resources, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL, 5Department of Public Health Sciences and Sylvester Biostatistics/Bioinformatics Shared Resources (BBSR), University of Miami, Sylvester Comprehensive Cancer Center, Miami, FL
Purpose/Objective(s): Adjuvant pelvic radiation decreases the risk of pelvic recurrence for patients with FIGO Stage I A/B1-2 cervical cancer who undergo surgery and are found to have a combination of lymphovascular invasion, deep cervical involvement, tumor = to 5 cm (Sedlis criteria). In this clinical situation, the nodal treatment volume includes the internal, external, pre-sacral (S1-3) and common iliac nodes (CIN) extending superiorly to the bifurcation of the aorta leading to a large volume of bowel loops being irradiated and a significant risk of acute and long-term gastrointestinal (GI) toxicity. EMBRACE I analysis suggests that it might be safe to exclude the CIN for low-risk cervical cancer patients (no parametrial or nodal involvement). We performed a dosimetric analysis of standard versus EMBRACE low-risk treatment volume for a cohort of patients who were found to meet Sedlis criteria following radical hysterectomy for cervical cancer in our institution with the hypothesis that the bowel and bone marrow sparing would be significant.
Materials/Methods: Using an IRB-approved cervical cancer databank, we identified 18 patients who received adjuvant pelvic radiation based on the presence of Sedlis criteria. The planning CT scans were retrieved. The following structures were contoured: bowel bag, rectum, bladder, bone marrow, CTV nodal standard, CTV nodal EMBRACE (excluding CIN), vaginal vault, ITV, PTV 45 standard, PTV 45 modified., Two IMRT treatment plans were generated for each patient. The difference between treatment plans were assessed using paired t-tests and Wilcoxon signed-rank one-sample tests for the following outcomes: bowel bag volume (cc) receiving 15, 30, 40 and 45 Gy and the % of bone marrow receiving 10 and 20 Gy.
Results: Mean bowel bag volume (cc) receiving V15 was significantly lower for the EMBRACE plans compared to standard plans V15 (761 versus 1326 cc), V30 (355 versus 515 cc), V40 (205 versus 277 cc) and V45 (152 versus 210 cc) (p<0.0001 for all dose levels). Bone marrow V10 and V20 also reached a statistically significant difference in favor of the EMBRACE volume (V10: mean 85% versus 73% and V20 mean 69% versus 59%) (P<0.0001).
Conclusion: Our results show statistically significant differences in the bowel volume receiving 15, 30, 40 and 45 Gy when comparing EMBRACE low risk to standard pelvic field. This analysis suggests that EMBRACE volumes could reduce short- and long-term GI radiation toxicity and potentially improve the quality of life of the patients. Bone marrow sparing was also statistically significant and is of particular interest in an era of broadened systemic therapy options for recurrent cervical cancer. Based on our results, we conclude that this concept of using the EMBRACE volumes to treat cervical cancer patients who meet Sedlis criteria merits evaluation in a prospective trial.