V. Sathiaseelan

Contouring Guidelines for the Axillary Lymph Nodes for the Delivery of Radiation Therapy in Breast Cancer: Evaluation of the RTOG Breast Cancer Atlas.

PURPOSE The purpose of this study was to identify the axillary lymph nodes on pretreatment diagnostic computed tomography (CT) of the chest to determine their position relative to the anatomic axillary borders as defined by the Radiation Therapy Oncology Group (RTOG) breast cancer atlas for radiation therapy planning. METHODS AND MATERIALS Pretreatment diagnostic CT chest scans available for 30 breast cancer patients with clinically involved lymph nodes were fused with simulation CT. Contouring of axillary levels I, II, and III according to the RTOG guidelines was performed. Measurements were made from the area of distal tumor to the anatomic borders in 6 dimensions for each level. RESULTS Of the 30 patients, 100%, 93%, and 37% had clinical involvement of levels I, II, and III, respectively. The mean number of lymph nodes dissected was 13.6. The mean size of the largest lymph node was 2.4 cm. Extracapsular extension was seen in 23% of patients. In 97% of patients, an aspect of the involved lymph node lay outside of the anatomic border of a level. In 80% and 83% of patients, tumor extension was seen outside the cranial (1.78 ± 1.0 cm; range, 0.28-3.58 cm) and anterior (1.27 ± 0.92 cm; range, 0.24-3.58 cm) borders of level I, respectively. In 80% of patients, tumor extension was seen outside the caudal border of level II (1.36 ± 1.0 cm, range, 0.27-3.86 cm), and 0% to 33% of patients had tumor extension outside the remaining borders of all levels. CONCLUSIONS To cover 95% of lymph nodes at the cranial and anterior borders of level I, an additional clinical target volume margin of 3.78 cm and 3.11 cm, respectively, is necessary. The RTOG guidelines may be insufficient for coverage of axillary disease in patients with clinical nodal involvement who are undergoing neoadjuvant chemotherapy, incomplete axillary dissection, or treatment with intensity modulated radiation therapy. In patients with pretreatment diagnostic CT chest scans, fusion with simulation CT should be considered for tumor delineation.

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.

Hyperthermia and radiation therapy for locally advanced or recurrent breast cancer.

INTRODUCTION This study aims to report the outcome and toxicity of combined hyperthermia (HT) and radiation therapy (RT) in treatment of locally advanced or loco-regionally recurrent breast cancer. PATIENTS AND METHODS Patients treated with HT and RT from January 1991 to December 2007 were reviewed. RT doses for previously irradiated patients were > 40 Gy and for RT naïve patients > 60 Gy, at 1.8-2 Gy/day. HT was planned for 2 sessions/week, immediately after RT, for a minimum of 20 min and for > 4 sessions. Superficial or interstitial applicators were used with temperature measured by superficial or interstitial thermistors based on target thickness. HT treatment was assessed by thermal equivalent dose (TED), > 42.5 °C and > 43 °C. Endpoints included treatment response, lack of local progression (local control), and survival. RESULTS 127 patients received HT and RT to 167 sites. These included the intact breast (24.4%), chest wall/skin (67.7%), and breast/chest wall and nodes (7.9%). At a median follow-up of 13 months (mean 30 ± 38), improved overall survival was significantly associated with increasing RT dose (p < 0.0001), median TED 42.5 °C ≥ 200 min (p = 0.003), and local control (p = 0.0002). Local control at last follow-up was seen in 55.1% of patients. Complete response was significantly associated with median TED 42.5 °C ≥ 200 min (p = 0.002) and median TED 43 °C ≥ 100 min (p = 0.03). CONCLUSION HT and RT are effective for locally advanced or recurrent breast cancer in patients that have been historically difficult to treat by RT alone. Over 50% of patients achieved control of locoregional disease. Overall survival was improved with local control.

Simultaneous localized 915 MHz external and interstitial microwave hyperthermia to heat tumors greater than 3 cm in depth

A technique for heating superficial lesions extending to a depth greater than 3 cm using 915 MHz electromagnetic energy is described. It is well established that with external microwave applicators operating at 915 MHz, it is only possible to heat adequately up to a maximum depth of 3 cm. However, it is demonstrated that by implanting additional layers of interstitial microwave antennas (1.5 cm spacing) at required depths greater than 3 cm, and by simultaneously exciting these applicators as well as an external applicator, it is possible to extend the depth of heating at this frequency. A large neck node was successfully heated when this combined technique was used. The details of the method and the equipment used are described. Specific Absorption Rate (SAR) values and temperature distributions obtained during the four treatments delivered to the patient are also presented. This technique can be used in situations where it is not possible to perform extensive interstitial implantation, and in institutions where hyperthermia equipment for heating deeper lesions is not available.

Gamma Knife Stereotactic Radiosurgery for Grade 2 Meningiomas

Purpose This study aims to report long‐term clinical outcomes after Gamma Knife radiosurgery (GKRS) for intracranial grade 2 meningiomas. Methods In this Institutional Review Board approved study, we reviewed records of all patients with grade 2 meningiomas treated with GKRS between 1998 and 2014. Results A total of 97 postoperative histopathologically confirmed grade 2 meningiomas in 75 patients were treated and are included in this study. After a mean follow‐up of 41 months, 28 meningiomas had local recurrence (29.79%). Median time to local recurrence was 89 months (mean: 69, range: 47‐168). The 3‐ and 5‐year actuarial local control (LC) rates were 68.9 and 55.7%, respectively. The 3‐ and 5‐year overall survival rates were 88.6 and 81.1%, respectively. There was a trend toward worse LC with tumors treated with radiation doses ≤ 13 versus > 13 Gy. There was no radiation necrosis or second malignant tumors noted in our series. Conclusion This report, one of the largest GKRS series for grade 2 meningiomas, demonstrates that GKRS is a safe and effective treatment modality for patients with grade 2 meningiomas with durable tumor control and minimal toxicity. Adjuvant GKRS could be considered as a reasonable treatment approach for patients with grade 2 meningiomas.

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.

SU-F-T-08: Brachytherapy Film Dosimetry in a Water Phantom for a Ring and Tandem HDR Applicator

PURPOSE The feasibility of dose measurement using new generation EBT3 film was explored in a water phantom for a ring and tandem HDR applicator for measurements tracking mucosal dose during cervical brachytherapy. METHODS An experimental fixture was assembled to position the applicator in a water phantom. Prior to measurement, calibration curves for EBT3 film in water and in solidwater were verified. EBT3 film was placed at different known locations around the applicator in the water tank. A CT scan of the phantom with applicator was performed using clinical protocol. A typical cervical cancer treatment plan was then generated by Oncentra brachytherapy planning system. A dose of 500 cGy was prescribed to point A (2 cm, 2 cm). Locations measured by film included the outer surface of the ring, measurement point A_m (2.2 cm, 2.2 cm), and profiles extending from point A_m parallel to the tandem. Three independent measurements were conducted. The doses recorded by film were carefully analyzed and compared with values calculated by the treatment planning system. RESULTS Assessment of the EBT3 films indicate that the dose at point A matches the values predicted by the planning system. Dose to the point A_m was 411.5 cGy, and the outer circumferential surface dose of the ring was between 500 and 1150 cGy. It was found that from the point A_m, the dose drops 60% within 4.5 cm on the line parallel to the tandem. The measurement doses agree with the treatment planning system. CONCLUSION Use of EBT3 film is feasible for in-water measurements for brachytherapy. A carefully machined apparatus will likely improve measurement accuracy. In a typical plan, our study found that the ring surface dose can be 2.5 times larger than the point A prescription dose. EBT3 film can be used to monitor mucosal dose in brachytherapy treatments.

SU-F-T-75: Dosimetry Considerations in the Use of Hanging-Eye Block for Lesions of the Conjunctiva

PURPOSE Superficial lesions in the conjunctiva are frequently treated with en face electrons, using a hanging block to spare dose to the lens of the eye. Dose to the tumor and lens depend on the design and setup of the block and supporting apparatus. We performed in phantom measurements in order to characterize the dose sparing effects of the block as well as the under-dosing effect under the supporting apparatus for 6 MeV treatment. METHODS The commercial hanging block studied uses a 1.2 cm diameter tungsten cylinder supported by a 3 mm diameter acrylic rod. Point dose measurements under the hanging block, under an unblocked part of the field, and under the acrylic rod were performed using MOSFET detectors. In addition, EBT3 film was used for both PDD and profile measurements at a depth in phantom of 3 mm for both 105 and 103 cm SSD. RESULTS MOSFET measurements reported a dose reduction of 95% under the tungsten block when using an SSD of 103 cm, and 86% when using an SSD of 105 cm at a depth in phantom of 3 mm. Film measurements showed that the area under the acrylic rod may be under-dosed by as much as 30% when using 103 SSD. MOSFET measurements confirmed that when using an SSD of 103 cm, the area under the acrylic rod is under-dosed by up to 30% at 3mm depth, compared to the unblocked part of the field. CONCLUSION The effectiveness of the commercial hanging block apparatus depends on setup, with 95% lens sparing possible with an SSD of 103 cm. This short SSD is necessary for sharp penumbra. At this SSD, substantial under-dosing under the acrylic support rod is possible. This must be mitigated with either feathering, or using an alternative method of support for the tungsten block.

Low-Dose-Rate Brachytherapy Boosting Concurrent Chemoradiation as a Definitive Treatment Modality for Cervical Cancer: Long-term Clinical Results of Outcomes and Associated Toxicity.

Purpose:To review and report the long-term treatment-induced adverse events (AEs) and outcomes of concomitant chemoradiotherapy boosted by low-dose-rate (LDR) conventional brachytherapy (BT) planning in patients with locoregionally advanced cervical cancer. Patients and Methods:After obtaining institutional review board approval, we reviewed the records of patients with stage IB1 to IVA, intact cervical cancer who were treated at our institution between 1983 and 2009. Eligible patients underwent definitive radiotherapy with external-beam radiation concomitant with cisplatin-based chemotherapy and boosted by LDR BT. Patient, tumor, and treatment characteristics; treatment-induced AEs, namely, gastrointestinal and genitourinary toxicities, as well as treatment outcomes; locoregional control (LRC), distant control (DC), progression-free survival (PFS), and overall survival (OS) were reviewed and reported. Results:The study included 129 eligible cervical cancer patients; the median age was 46 years (mean, 47±11 y; range, 28 to 81 y), consisting of stages I, II, III, and IV (29.5%, 48.1%, 17.8%, and 4.6%, respectively). The median follow-up was 37 months (mean, 58±59 mo; range, 3 to 275 mo). The 3-year OS, PFS, LRC, and DC were 75.9%, 71.6%, 84.7%, and 80.2%, respectively. The 5-year OS, PFS, LRC, and DC were 70.7%, 68.7%, 84.7%, and 78.3%, respectively. The 10-year OS, PFS, LRC, and DC were 68.7%, 62.3%, 82.5%, and 73.2%, respectively. Gastrointestinal and genitourinary grade 3 and 4 acute AEs were reported in 3.9% and 0%, and chronic grade 3 and 4 AEs were reported in 20.9% and 12.4% of all patients, respectively. Conclusions:Definitive chemoradiotherapy followed by conventional LDR BT boost is effective, feasible, and tolerable treatment modality for cervical cancer. A comparison with MRI image-guided BT shows comparable treatment outcomes with superior OS in favor of LDR BT but inferior LC with a relatively worse toxicity profile.

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.