D. Erler

Role of stereotactic body radiotherapy for symptom control in head and neck cancer patients

PurposeOur aim was to determine the efficacy and quality of life outcomes of head and neck (HN) stereotactic body radiotherapy (SBRT) in a palliative population with significant proportions of de novo HN tumors not amenable to surgery or protracted course of curative radiotherapy (RT).MethodsA retrospective review of a prospective database identified 21 patients with 24 sites that were treated. Patients were treated with intensity modulated RT (IMRT), usually 7–9 static fields with a 2–3-mm margin from gross tumor volume to planning target volume only with no microscopic margin added. Electronic patient records and treatment plans were reviewed. Basic demographic information was collected. The EORTC QLQ-H&N35 questionnaire was the tool used to collect QOL data both pre- and on-treatment fraction 5. Univariate analysis was performed for predictors of local control (LC) and prognostic factors for overall survival (OS).ResultsA total of 21 patients had 24 sites that were treated. The median age was 87 (range 25–103) and median KPS was 70. The most common histology was squamous cell carcinoma (SCC) 19/24 (79xa0%), basal cell carcinoma (BCC) 3/24 (16xa0%), and melanoma (4xa0%). The median maximal diameter was 3.7xa0cm (range 1–10xa0cm). The most commonly treated site was lymph nodes in the neck 13/24 (54xa0%), skin 8/24 (33xa0%), 4/24 (16xa0%) other HN mucosal primary sites. Of the 24 lesions, 17 (71xa0%) were de novo, without prior treatment and 7/24 (29xa0%) were recurrent. The most commonly used dose/fraction (fx) was 40xa0Gy/5 (fx) (range 35/5fx−48/6fx). Of the 24 lesions, 6 (25xa0%) had complete response, 16/24 (67xa0%) had partial response, and 2/24 (8xa0%) had no response. Control was defined as no further progression after treatment. For the entire cohort, LC at 3, 6, and 9xa0months were 66, 50, and 33xa0%, respectively. In the de novo group, 2/16 (12.5xa0%) had local failures with the LC rate of 94, 94, and 87xa0% at 3xa0months, 6xa0months, and 1xa0year, respectively. In the recurrent group, 4/8 (50xa0%) had failure with LC rates of 87. 5, 62.5, and 50xa0% at 3xa0months, 6xa0months, and 1xa0year, respectively. Of the 21 patients, 10 died during follow up, with the OS rate at 3xa0months, 6xa0months, and 1xa0year of 90, 70, and 60xa0%, respectively. Being defined “de novo” showed a trend toward statistical significance pu2009=u20090.046 for local failure. Overall survival did not show significant difference between de novo and recurrent with a p value of 0.267. No significant prognostic variables for OS were found. Pre-treatment QOL scores for the entire cohort were 53/130 versus 38/130 (lower scores indicating better QOL) scores with a trend toward statistical significance pu2009=u20090.05.ConclusionsSBRT is efficacious with improved quality of life within this elderly frail population in the treatment of de novo and recurrent tumors of the head and neck with promising quality of life scores.

Tumor Response After Stereotactic Body Radiation Therapy to Nonspine Bone Metastases: An Evaluation of Response Criteria

PURPOSEnTo evaluate the applicability of the Response Evaluation Criteria in Solid Tumors (RECIST 1.1) and University of Texas MD Anderson (MDA) Cancer Center criteria in the setting of stereotactic body radiation therapy (SBRT) to nonspine bone metastases.nnnMETHODSnPatients who were treated with SBRT to nonspine bone metastases were identified by retrospective chart review. An independent musculoskeletal radiologist evaluated response to treatment using computed tomography (CT) scans.nnnRESULTSnThirty-three patients were treated to 42 nonspine bone metastases. The most common primary cancer cites were renal cell carcinoma (RCC) (33.3%), lung (24.2%), and prostate (18.2%). Bone metastases were either mainly lytic (57.1%), mainly sclerotic (28.6%), or mixed (14.3%). When lytic and sclerotic lesions were evaluated according to RECIST 1.1, local control (LC) was 83%, 85%, 88%, and 80% for those with CT imaging between months 1 to 3, 4 to 6, 7 to 9, and 10 to 12, respectively. When evaluated by the MDA criteria by density, LC within each time period was slightly greater. Overall LC decreased considerably when evaluated by MDA in terms of size.nnnCONCLUSIONSnConsensus definitions of response are required as they have implications on clinical trials and disease management. Without consistent response criteria, outcomes from clinical trials cannot be compared and treatment efficacy remains undetermined.

4DCT Simulation With Synchronized Contrast Injection in Liver SBRT Patients

Background/Purpose: Delivering stereotactic body radiotherapy for liver metastases remains a challenge because of respiratory motion and poor visibility without intravenous contrast. The purpose of this article is to describe a novel and simple computed tomography (CT) simulation process of integrating timed intravenous contrast that could overcome the uncertainty of target delineation. Methods and Results: The simulation involves two 4-dimensional CT (4DCT) scans. The first scan only encompasses the immediate region of the tumor and surrounding tissue, which reduces the 4DCT scan time so that it can be optimally timed with intravenous contrast injection. The second 4DCT scan covers a larger volume and is used as the primary CT data set for dose calculation, as well as patient setup verification on the treatment unit. The combination of the two 4DCT scans allows us to optimally visualize liver metastases over all phases of the breathing cycle while simultaneously acquiring a long enough 4DCT data set that is suitable for planning and patient setup verification. Conclusion: This simulation technique allows for a better target definition when treating liver metastases, without being invasive.

Poster — Thur Eve — 16: 4DCT simulation with synchronized contrast injection of liver SBRT patients

Stereotactic body radiation therapy (SBRT) has recently emerged as a valid option for treating liver metastases. SBRT delivers highly conformai dose over a small number of fractions. As such it is particularly sensitive to the accuracy of target volume delineation by the radiation oncologist. However, contouring liver metastases remains challenging for the following reasons. First, the liver usually undergoes significant motion due to respiration. Second, liver metastases are often nearly indistinguishable from the surrounding tissue when using computed tomography (CT) for imaging making it difficult to identify and delineate them. Both problems can be overcome by using four dimensional CT (4DCT) synchronized with intravenous contrast injection. We describe a novel CT simulation process which involves two 4DCT scans. The first scan captures the tumor and immediately surrounding tissue which in turn reduces the 4DCT scan time so that it can be optimally timed with intravenous contrast injection. The second 4DCT scan covers a larger volume and is used as the primary CT dataset for dose calculation, as well as patient setup verification on the treatment unit. The combination of two 4DCT scans, short and long, allows visualization of the liver metastases over all phases of breathing cycle while simultaneously acquiring long enough 4DCT dataset suitable for planning and patient setup verification.

Computed Tomography Evaluation of Density Following Stereotactic Body Radiation Therapy of Nonspine Bone Metastases.

Introduction: Stereotactic body radiation therapy allows for the precise delivery of high-dose radiation to disease sites and is becoming increasingly used to treat nonspine bone metastases. Previous studies have shown that remineralization of lytic bone metastases follows after conventional radiotherapy. The objective of this study was to investigate changes in bone density in nonspine bone metastases following stereotactic body radiation therapy. Methods: A retrospective review was conducted for all patients treated with stereotactic body radiation therapy to nonspine bone metastases between May 2011 and April 2014. A minimum of 1 pretreatment and 1 posttreatment computed tomography scan was required. An independent musculoskeletal radiologist contoured the lesions on the most representative computed tomography slices. Density was measured in Hounsfield units and analyzed using pretreatment and posttreatment ratios. Results: Forty sites were treated (55% lytic, 30% sclerotic, and 15% mixed). The median follow-up duration was 7 months. Lytic osseous metastases from renal cell carcinoma progressed during initial follow-up imaging and then returned to baseline. Of 9 lytic lesions not from renal cell carcinoma, 6 showed an immediate increase in density and 2 remained stable. Six of 7 sclerotic lesions from prostate cancer showed decreased density throughout all follow-ups. Conclusion: Stereotactic body radiation therapy is efficacious in the remineralization of lytic and demineralization of sclerotic nonspine bone metastases.

Implementation of a volumetric modulated arc therapy treatment planning solution for kidney and adrenal stereotactic body radiation therapy

To develop a volumetric modulated arc therapy (VMAT) treatment planning solution in the treatment of primary renal cell carcinoma and oligometastatic adrenal lesions with stereotactic body radiation therapy. Single-arc VMAT plans (n = 5) were compared with clinically delivered step-and-shoot intensity-modulated radiotherapy (IMRT) with planning target volume coverage normalized between techniques. Target volume conformity, organ-at-risk (OAR) dose, treatment time, and monitor units were compared. A VMAT planning solution, created from a combination of arc settings and optimization constraints, auto-generated treatment plans in a single optimization. The treatment planning solution was evaluated on 15 consecutive patients receiving kidney and adrenal stereotactic body radiation therapy. Treatment time was reduced from 13.0 ± 2.6 to 4.0 ± 0.9 minutes for IMRT and VMAT, respectively. The VMAT planning solution generated treatment plans with increased target homogeneity, improved 95% conformity index, and a reduced maximum point dose to nearby OARs but with increased intermediate dose to distant OARs. The conformity of the 95% isodose improved from 1.32 ± 0.39 to 1.12 ± 0.05 for IMRT and VMAT treatment plans, respectively. Evaluation of the planning solution showed clinically acceptable dose distributions for 13 of 15 cases with tight conformity of the prescription isodose to the planning target volume of 1.07 ± 0.04, delivering minimal dose to OARs. The introduction of a stereotactic body radiation therapy VMAT treatment planning solution improves the efficiency of planning and delivery time, producing treatment plans of comparable or superior quality to IMRT in the case of primary renal cell carcinoma and oligometastatic adrenal lesions.

Impact of Magnetic Resonance Imaging on Gross Tumor Volume Delineation in Non-spine Bony Metastasis Treated With Stereotactic Body Radiation Therapy

PURPOSEnThis study investigates the inter-observer variability of contouring non-spine bone metastases using the planning CT alone vs. the addition of MRI T1 and T2 imaging sequences.nnnMETHODS AND MATERIALSn10 cases of non-spine bone metastases treated with SBRT at our institution were selected. The gross tumor volume (GTV) for each case was delineated by six SBRT radiation oncologists (RO) and one diagnostic radiologist (DR) on the treatment planning CT. After a minimum of three months, each case was re-contoured on the CT fused with a MRI T1 sequence followed by a MRI T2 sequence. STAPLE consensus contours were created from the RO volumes and inter-observer variability was measured using both κ agreement and the Dice coefficient (DSC).nnnRESULTSnIn total, 180 RO contours were analyzed within three datasets (CT, CT + MRI T1 and CT + MRI T1 + MRI T2). The mean GTV was 16.95 cm3 (range, 0.12-269.6 cm3). The RO κ agreement was 0.6129 based on CT alone, and significantly increased to 0.7045 in the CT + MRI T1 (P = .042) dataset and 0.7017 in the CT + MRI T1 + MRI T2 dataset (P = .048). The mean DSC in the CT alone dataset was 0.7047, and significantly increased to 0.7628 in the CT + MRI T1 dataset (P < .001) and 0.7544 in the CT + MRI T1 + MRI T2 dataset (P = .001). There were no statistical differences in RO κ agreement (P = .948) or mean DSC (P = .573) when comparing the CT + MRI T1 and CT + MRI T1 + MRI T2 datasets. The DSC agreement between DR and RO volumes was lowest (0.6887) in the CT alone dataset and significantly increased to 0.7398 in the CT + MRI T1 dataset (P = .003) and 0.7342 in the CT + MRI T1 + MRI T2 dataset (P = .008).nnnCONCLUSIONSnThe fusion of MRI T1 images to CT significantly reduced inter-observer variability amongst ROs in delineating non-spine bone metastases, and improved agreement between GTVs delineated by the RO to the DR.

SU-E-T-488: Treatment of a Unique CNS Patient with Tomotherapy

Purpose: We describe a whole spinal cord, cauda equine, and brainstem radiation treatment using an in‐house developed tomotherapy approach for a unique patient diagnosed with an extramedullary spinal melanocytoma with leptomeningeal seeding, treated with 48.6 Gy in 28 fractions. Methods and Materials: Given that the prescribed dose is within the range of tolerance to the spinal cord, tomotherapy was chosen to take advantage of the superior dose uniformity achievable with this technology and ability to deliver modulated radiotherapy in a single treatment to a long volume. The patient was treated supine and immobilized with a thermoplastic mask for the head and shoulders and a long Vac‐Lok bag for the body. The CTV consisted of the entire spinal cord, thecal sac to the level of S2 and brainstem. A 1 cm margin was applied to create the PTV. Jaws, pitch and the modulation factor were set to 5 cm, 0.43 and 2.5, respectively. Before each treatment, the treated volume was imaged for setup verification using the integrated megavoltage CT (MVCT). Weekly the patient was also imaged post‐ treatment to confirm setup stability. Results: The patient is finishing treatment at the time of abstract submission. A highly conformal dose distribution was created with doses to the organs at risk within their tolerance limits. The beam on time was 17 minutes. Patient setup proved to be trouble‐free and reproducible. The total patient‐on‐the‐bed time was approximately one hour. The 1 cm PTV margin was adequate according to pre‐ and post‐treatment MVCT image analysis. Conclusions: Tomotherapy is a safe and effective tool for treating long CNS volumes to high dose. It allows avoiding junctions and sparing healthy CNStissue and other organs at risk. A relatively simple immobilization technique used for this patient proved to be stable and reproducible with a 1 cm PTV margin.