(P081) SBRT Boost as a Substitute for Brachytherapy in the Definitive Treatment of Gynecologic Malignancies With Radiotherapy

OncologyOncology Vol 29 No 4_Suppl_1
Volume 29
Issue 4_Suppl_1

With respect to local control and toxicity, SBRT may be a reasonable method of boosting patients who cannot safely undergo brachytherapy boosts for locally advanced gynecologic malignancies.

Neilayan Sen, MD, Jessica Zhou, MD, Ryan Jozwiak, Yixiang Liao, PhD, Krystyna Kiel, MD; Rush University Medical Center

PURPOSE: Delivery of high doses of radiation within a prescribed period of time is associated with local control when treating primary or recurrent gynecologic cancers. Occasionally, patients can not undergo a brachytherapy boost. We report our experience with alternative stereotactic body radiation treatment (SBRT) boost.

MATERIALS AND METHODS: From 2012 to 2014, a total of 8 patients with locally advanced squamous cell carcinoma of the cervix (2 patients) and recurrent endometrial cancer in the vaginal cuff (6 patients) received an SBRT boost after pelvic external beam (EB) radiotherapy (range: 45–50 Gy). One patient received SBRT after EB and 2 high-dose-rate (HDR) brachytherapy fractions. Patients either refused brachytherapy or were high-risk (by medical comorbidities) for brachytherapy. Patients were immobilized using a CIVCO body frame (CIVCO Medical Solutions, Coralville, IA) with abdominal compression. Vaginal and fiducial markers were used to localize tumor at simulation and treatment. Doses typically used for brachytherapy were prescribed to D90 of the planning target volume (PTV) (0–5-mm expansion on clinical target volume [CTV] excluding the rectum when not involved by the tumor). Dose was limited by organ-at-risk tolerances. The Eclipse planning system (Varian, Palo Alto, CA) was used to generate RapidArc plans with 6-MV photons. Treatment was delivered using a True Beam STx linear accelerator (Varian, Palo Alto, CA). Daily cone-beam computed tomographies (CTs) were performed using the rectum, bladder, visible tumor, and markers for image guidance, and ExacTrac (BrainLab, Germany) was used to ensure precision of delivery. Tumor status and toxicities were recorded at regular follow-up intervals; toxicity was graded according to Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0).

RESULTS: Dose/fractionation schemes were 7 Gy × 2 for one patient (after two HDR brachytherapy fractions), 6 Gy × 5 for six patients, and 5.8 Gy × 5 for one patient. Cumulative equalized total dose in 2 Gy/fraction (EQD2Gy) to D90 of the target volume ranged from 74.6 Gy to 84.3 Gy (mean 81.3 Gy). Mean D2cc rectum and bladder doses were 66.3 Gy (range: 59.4–75.8 Gy) and 77.3 Gy (range: 69.6–83.6 Gy), respectively. Mean overlap between the rectum as contoured on daily cone-beam CTs and the PTV was 0.29 cc (range: 0.00–1.42 cc). There were no local recurrences at a mean follow-up of 14.5 months. One patient developed distant metastases at 7 months. One patient developed grade 3 vaginal fibrosis. No grade 4 toxicities were observed.

CONCLUSIONS: With respect to local control and toxicity, SBRT may be a reasonable method of boosting patients who cannot safely undergo brachytherapy boosts for locally advanced gynecologic malignancies.

Proceedings of the 97th Annual Meeting of the American Radium Society- americanradiumsociety.org

Articles in this issue

(P005) Ultrasensitive PSA Identifies Patients With Organ-Confined Prostate Cancer Requiring Postop Radiotherapy
(P001) Disparities in the Local Management of Breast Cancer in the United States According to Health Insurance Status
(P002) Predictors of CNS Disease in Metastatic Melanoma: Desmoplastic Subtype Associated With Higher Risk
(P003) Identification of Somatic Mutations Using Fine Needle Aspiration: Correlation With Clinical Outcomes in Patients With Locally Advanced Pancreatic Cancer
(P004) A Retrospective Study to Assess Disparities in the Utilization of Intensity-Modulated Radiotherapy (IMRT) and Proton Therapy (PT) in the Treatment of Prostate Cancer (PCa)
(S001) Tumor Control and Toxicity Outcomes for Head and Neck Cancer Patients Re-Treated With Intensity-Modulated Radiation Therapy (IMRT)-A Fifteen-Year Experience
(S003) Weekly IGRT Volumetric Response Analysis as a Predictive Tool for Locoregional Control in Head and Neck Cancer Radiotherapy 
(S004) Combination of Radiotherapy and Cetuximab for Aggressive, High-Risk Cutaneous Squamous Cell Cancer of the Head and Neck: A Propensity Score Analysis
(S005) Radiotherapy for Carcinoma of the Hypopharynx Over Five Decades: Experience at a Single Institution
(S002) Prognostic Value of Intraradiation Treatment FDG-PET Parameters in Locally Advanced Oropharyngeal Cancer
(P006) The Role of Sequential Imaging in Cervical Cancer Management
(P008) Pretreatment FDG Uptake of Nontarget Lung Tissue Correlates With Symptomatic Pneumonitis Following Stereotactic Ablative Radiotherapy (SABR)
(P009) Monte Carlo Dosimetry Evaluation of Lung Stereotactic Body Radiosurgery
(P010) Stereotactic Body Radiotherapy for Treatment of Adrenal Gland Metastasis: Toxicity, Outcomes, and Patterns of Failure
(P011) Stereotactic Radiosurgery and BRAF Inhibitor Therapy for Melanoma Brain Metastases Is Associated With Increased Risk for Radiation Necrosis
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