Gynecological Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_15_3466 - Hematological Toxicity in Cervix Cancer Patients Treated with Extended Field with IMRT or VMAT and Feasibility in Achieving Bone Marrow Planning Constraints

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Hematological Toxicity in Cervix Cancer Patients Treated with Extended Field with IMRT or VMAT and Feasibility in Achieving Bone Marrow Planning Constraints
J. Jutzy1, M. Degnan1, R. Arya2, P. Peters1, E. W. Daily1, A. R. Howard3, A. R. R. McCall4, C. H. Son1, and Y. Hasan1; 1University of Chicago, Chicago, IL, 2Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL, 3UIC Radiation Oncology, Chicago, IL, 4UCMC Cancer Center at Silver Cross, New Lenox, IL

Purpose/Objective(s): In patients with locally advanced cervix cancer, extended field radiotherapy (EFRT) is often utilized to provide coverage of the para-aortic nodes. This results in a large portion of the bone marrow (BM) being included within the radiation field. We evaluated hematologic toxicity in cervix cancer patients treated with EFRT concurrent chemoradiotherapy during an institutional transition from IMRT to VMAT and to compare feasibility in achieving BM dose constraint metrics with comparison plans generated for a subset of patients.

Materials/Methods: From 2007-2017, 34 patients with Stage IB1-IVA cervix cancer treated with EFRT (45 Gy/1.8 Gy) with a simultaneously-integrated boost (SIB) to gross nodal disease (55 Gy /2.2 Gy) and concurrent chemotherapy (C) using IMRT or VMAT were identified . With IRB approval, each patient’s chart was reviewed and evaluated for hematologic toxicity, C dose reduction, and treatment duration. For 7 selected patients, IMRT and VMAT plans were generated to directly compare feasibility of meeting BM constraints. EFRT clinical target volumes (CTVs) were contoured to the renal veins with a 7 mm uniform expansion to create a planning target volume (PTV). The BM was defined as the bones of the pelvis, sacrum and lumbar spine to the top of the PTV. Using these target volumes, an IMRT plan with 7 angles and a 2-arc VMAT plan were created for each of the 7 patients. The target planning goal was to cover the PTV by ≥ 95% of the prescribed dose. Dose constraints included V10 < 90%, V20 < 75% and V40 < 37% for BM; V35 <33%, V50 < 10cc and max <56 Gy for bowel; V40 < 50% and max < 49.5 Gy for bladder; V35 < 10% for femora; and V18 < 30% for kidney. Chi-square, student’s t-test and two-sided Wilcoxon’s test were used for statistical analysis (p<0.05 was considered to be significant).

Results: Of the 34 patients identified, 25 were treated using IMRT and 9 using VMAT. All but two patients received SIB. All BM planning parameters (V10, V20, V40) were achieved in 4 of 7 VMAT plans, 6 of 11 IMRT plans; 2 of 9 VMAT and 13 of 25 IMRT plans were planned without BM constraints. A significant difference was seen in acute Grade 3-4 hematologic toxicity (IMRT 60.0% vs VMAT 33.3%, p=0.001), but not in C dose reduction (29.4% vs 11.1%, p=0.38), or treatment length (54 days vs 55 days, p=0.62). In plans generated for dosimetric comparison with equivalent PTV45 and PTV55 coverage, VMAT plans had significantly decreased BM V20 (73.6% vs 77.5%, p=0.02) and V40 (23.7% vs 28.1%, p=0.03). No significant differences were seen in the BM V10.

Conclusion: In this analysis, we found that VMAT techniques provided plans with improved BM sparing (V20 and V40 parameters). In treated patients, those planned with VMAT had lower rates of severe (grade 3-4) hematologic toxicity compared to those treated with IMRT.

Author Disclosure: J. Jutzy: Employee; Rush University. Deferred faculty appointment; Loma Linda University Medical Center. M. Degnan: None. R. Arya: None. E.W. Daily: None. A.R. Howard: None. C.H. Son: None. Y. Hasan: Employee; Northwestern University.

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