I. Bacchus

Thyroid V50 Highly Predictive of Hypothyroidism in Head-and-Neck Cancer Patients Treated With Intensity-modulated Radiotherapy (IMRT).

Objectives: Radiation-induced hypothyroidism affects a significant number of patients with head-and-neck squamous cell cancer (HNSCC). We examined detailed dosimetric and clinical parameters to better determine the risk of hypothyroidism in euthyroid HNSCC patients treated with intensity-modulated radiation therapy (IMRT). Materials and Methods: From 2006 to 2010, 75 clinically euthyroid patients with HNSCC were treated with sequential IMRT. The cohort included 59 men and 16 females with a median age of 55 years (range, 30 to 89 y) who were treated to a median dose of 70 Gy (range, 60 to 75 Gy) with concurrent chemotherapy in nearly all (95%) cases. Detailed thyroid dosimetric parameters including maximum dose, mean dose, and other parameters (eg, V50—percent volume receiving at least 50 Gy) were obtained. Freedom from hypothyroidism was evaluated using the Kaplan-Meier method. Univariate and multivariate analyses were conducted using Cox regression. Results: After a median follow-up period of 50 months, 25 patients (33%) became hypothyroid. On univariate analysis, thyroid V50 was highly correlated with developing hypothyroidism (P=0.035). Other dosimetric paramaters including mean thyroid dose (P=0.11) and maximum thyroid dose (P=0.39) did not reach statistical significance. On multivariate analysis incorporating patient, tumor, and treatment variables, V50 remained highly statistically significant (P=0.037). Regardless of other factors, for V50>60%, the odds ratio of developing hypothyroidism was 6.76 (P=0.002). Conclusions: In HNSCC patients treated with IMRT, thyroid V50 highly predicts the risk of developing hypothyroidism. V50>60% puts patients at a significantly higher risk of becoming hypothyroid. This can be a useful dose constraint to consider during treatment planning.

Development of a standardized method for contouring the larynx and its substructures

ObjectivesLimiting radiation dose to the larynx can diminish effects of laryngeal dysfunction. However, no clear guidelines exist for defining the larynx and its substructures consistently on cross-sectional imaging. This study presents computed tomography (CT)- and magnetic resonance imaging (MRI)-based guidelines for contouring laryngeal organs-at-risk (OARs).Materials and MethodsStandardized guidelines for delineating laryngeal OARs were devised and used to delineate on CT and MRI for head-and-neck cancer patients. Volumetric comparisons were performed to evaluate consistency and reproducibility of guideline-based contours.ResultsFor the initial 5 patients the mean CT and MRI based larynx volume did not differ significantly between imaging modalities; 34.39 ± 9.85 vs. 35.01 ± 9.47 (p = .09). There was no statistical difference between the CT based mean laryngeal volume in the subsequent 44 patients compared to the initial 5 patients outlined on CT and the MRI scan (p = 0.53 and 0.62). The OAR volume for laryngeal substructures were not statistically different among patients or between imaging modalities. Once established, the guidelines were easy to follow.ConclusionThe guidelines developed provide a precise method for delineating laryngeal OARs. These guidelines need to be validated and clinical significance of outlining laryngeal substructures and dose-volume constraints should be investigated before routine implementation in clinic practice.

Whole-Field Sequential Intensity-Modulated Radiotherapy for Local-Regional Advanced Head-and-Neck Squamous Cell Carcinoma.

Purpose:There is little published data on the technique and results of whole-field (WF) sequential intensity–modulated radiotherapy (S-IMRT) for patients with head-and-neck squamous cell carcinoma (HNSCC). We report the treatment outcomes, adverse events (AEs), and dosimetric parameters in local-regional advanced (LRA) HNSCC patients treated with the WF S-IMRT technique. Methods:The IRB approved this retrospective study. Patients received WF S-IMRT with or without concomitant chemotherapy. Three separate IMRT plans corresponding to 3 planning target volumes were generated. This study reports patient and tumor characteristics, treatment-induced acute AEs based on CTCAE version 3.0, chronic AEs according to RTOG scale and treatment outcomes, local-regional control (LRC), distant metastases (DM), relapse-free survival (RFS), and overall survival (OS). Results:Between January 2003 and December 2010, 103 patients with LRA HNSCC were treated either definitively or postoperatively with WF S-IMRT, with (99 patients) or without (4 patients) concurrent chemotherapy. The median age was 55 years (range, 30 to 89 y). The median cumulative target dose was 70 Gy (range, 60 to 75 Gy). At a median follow-up of 40 months (range, 4 to 95 mo), the 2- and 5-year rates of OS were 94% and 77%, RFS were 90% and 84%, LRC were 97% and 93%, and DM were 9% and 11%, respectively. Grade 3 acute AEs included mucositis (68%), dysphagia (35%), weight loss (19.6%), and xerostomia (7.8%). Chronic worst grade 3 AEs included xerostomia (21.9%), weight loss (12.8%), and dysphagia (12.5%). Chronic grade 3 AEs at last follow-up included weight loss (6.25%), dysphagia (6.2%), and xerostomia (6.2%). No patient had an acute or chronic grade 4 AE, brachial plexopathy, or spinal cord injury. Conclusions:WF S-IMRT results in excellent tumor control and an acceptable toxicity profile in LRA HNSCC patients treated with this technique.

Brain metastases management paradigm shift: A case report and review of the literature

Brain metastases are the most common intracranial tumors in adults, accounting for over half of all lesions. Whole-brain radiation therapy (WBRT) has been a cornerstone in the management of brain metastases for decades. Recently, stereotactic radiosurgery (SRS) has been considered as a definitive or postoperative approach instead of WBRT, to minimize the risk of cognitive impairment that may be associated with WBRT. This is the case report of a 74-year-old female patient who was diagnosed with lung cancer in November, 2002, and histopathologically confirmed brain metastases in January, 2005. The patient received 5 treatments with Gamma Knife SRS for recurring brain metastases between 2005 and 2014. The patient remains highly functional, with stable intracranial disease at 10 years since first developing brain metastases, and with stable lung disease. Therefore, Gamma Knife SRS is a safe and effective treatment modality for patients with recurrent intracranial metastases, with durable local control and minimal cognitive impairment.

SU‐E‐T‐72: A Retrospective Correlation Analysis On Dose‐Volume Control Points and Treatment Outcomes

Purpose: To quantify correlation between dose-volume control points and treatment outcomes. Specifically, two outcomes are analyzed: occurrence of radiation induced dysphagia and target complications. The results inform the treatment planning process when competing dose-volume criteria requires relaxations. Methods: 32 patients, treated with whole-field sequential intensity modulated radiation therapy during 2009–2010 period, are considered for this study. Acute dysphagia that is categorized into 3 grades is observed on all patients. 3 patients are observed in grade 1, 17 patients in grade 2, and 12 patients in grade 3. Ordinal logistic regression is employed to establish correlations between grades of dysphagia and dose to cervico-thoracic esophagus. Particularly, minimum (Dmin), mean (Dmean), and maximum (Dmax) dose control points are analyzed. Additionally, target complication, which includes local-regional recurrence and/or distant metastasis, is observed on 4 patients. Binary logistic regression is used to quantify correlation between target complication and four dose control points. Namely, ICRU recommended dose control points, D2, D50, D95, and D98 are analyzed. Results: For correlation with dysphagia, Dmin on cervico-thoracic esophagus is statistically significant (p-value = 0.005). Additionally, Dmean on cervico-thoracic esophagus is also significant in association with dysphagia (p-value = 0.012). However, no correlation was observed between Dmax and dysphagia (p-value = 0.263). For target complications, D50 on the target is a statistically significant dose control point (p-value = 0.032). No correlations were observed between treatment complications and D2 (p-value = 0.866), D95 (p-value = 0.750), and D98 (p-value = 0.710) on the target. Conclusion: Significant correlations are observed between radiation induced dysphagia and Dmean (and Dmin) to cervico-thoracic esophagus. Additionally, correlation between target complications and median dose to target (D50) is observed. Quantification of these correlations can inform treatment planners when any competing objectives requires relaxation of target D50 or Dmean (or Dmin) to cervico-thoracic esophagus.

SU‐E‐T‐570: Improvement to the Histogram Analysis in Radiation Therapy (HART): An Open Source Software System for the Multi‐Dimensional Dose‐ Volume Histogram Analysis in Digital Image Communication in Medicine ‐ Radiation Therapy (DICOM‐RT) Treatment Plans

PURPOSE Histogram Analysis in Radiation Therapy (HART) is an efficient and accurate dose-volume histogram (DVH) computational tool in radiotherapy research. Several applications of the program have been presented previously (J Appl Clin Med Phys 11(1): 3013, 2010; Med Phys 38(6), p.3678, 2011) for the Radiation Therapy Oncology Group (RTOG) users. The program has been further developed to incorporate various types of DVH analysis features to support the research using DICOM-RT plans. The main objective of this work was to present the improvement and compatibility of the program for the DICOM-RT plans. METHODS AND MATERIALS MATLAB based codes were primarily designed to read and write a simpler HART format from the standard DICOM-RT data objects exported from the Xio treatment planning system (CMS Inc., St. Louis, MO). This format employed an optimal polynomial fitting technique to interpolate the co-ordinates of the contours in the regions-of-interest. The format was efficient for the (a) precise extraction of the cumulative DVH (cDVH) and spatial DVH (sDVH; x-,y-, and z-DVHs respectively) data- statistics, (b) universal-plan indices evaluation, (c) biological modeling based outcome analyses (BMOA), (d) radiobiological dose-response modeling, and (e) physical parameterization modules. The fundamental DVH statistics were validated using the DVH statistics extracted from the Computational Environment for Radiotherapy Research program. RESULTS HART offers various types of DVH computational functionalities, several plan evaluation and radiobiological outcome analysis modules in a user- friendly software package for the RTOG and DICOM-RT planners. The cDVH and BMOA modules were found to be the most applicable features for the global researchers. CONCLUSIONS HART is a novel and universal multi-dimensional DVH analysis tool for the radiation therapy research. We further expect to develop HART for the space-time DVH analysis and proton therapy applications. The software is available online (http://www2.uic.edu/∼apyaku1) for the radiotherapy research. This work was partially supported by NIH-NIDCD grant.