Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer: A Retrospective, Single-Center Study of 55 Patients.

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) is an effective treatment for patients with early-stage non-small cell lung cancer (NSCLC) who are not surgical candidates or who refuse surgical management. In this study, we report on our clinical outcomes and toxicity in the treatment of early-stage NSCLC with SBRT. METHODS AND MATERIALS: Fifty-five patients with 59 T1-2N0M0 NSCLC lesions were treated at our institution between December 2009 and August 2014. The majority of the patients [38 (69%)] were treated with 50 Gy in 5 fractions, 7 patients (13%) with 48 Gy in 4 fractions, 8 patients (14%) with 60 Gy in 3 fractions, 1 patient (2%) with 62.5 Gy in 10 fractions, and 1 patient (2%) with 54 Gy in 3 fractions. Tumor response was evaluated using RECIST 1.1, and toxicity was graded using the CTCAE (Common Terminology Criteria for Adverse Events) version 3.0. The primary endpoints of this retrospective review included rates of overall survival, disease-free and progression-free survival, local failure, regional failure, and distant failure. A secondary endpoint included radiation-related toxicities. RESULTS: The median follow-up was 23.8 months (range 1.1-57.6). The 3-year local control, progression-free survival, and overall survival rates were 91, 55, and 71%, respectively. The median age at diagnosis was 67.9 years (range 51.4-87.1). There were a total of 54 T1N0 tumors (92%) and 5 T2N0 lesions (8%). Adenocarcinoma was the most common pathology, comprising 54% of the lesions. A total of 16 of the patients (29%) failed. Among these, 5 local (9%), 14 regional (25%), and 4 distant failures (7%) were observed. On follow-up, one patient had grade 2 and another had grade 5 pneumonitis. Three patients experienced grade 2 chest wall tenderness. Two patients had grade 1 rib fractures, one of which could not be discerned from radiation-induced toxicity versus a traumatic fall. CONCLUSION: The University of Mississippi Medical Center SBRT experience has shown that SBRT provides satisfactory local control and overall survival rates with minimal toxicity in early-stage NSCLC patients.

Potential Clinical Significance of Overall Targeting Accuracy and Motion Management in the Treatment of Tumors That Move With Respiration: Lessons Learnt From a Quarter Century of Stereotactic Body Radiotherapy From Dose Response Models.

OBJECTIVE: To determine the long-term normal tissue complication probability with stereotactic body radiation therapy (SBRT) treatments for targets that move with respiration and its relation with the type of respiratory motion management (tracking vs. compression or gating). METHODS: A PubMed search was performed for identifying literature regarding dose, volume, fractionation, and toxicity (grade 3 or higher) for SBRT treatments for tumors which move with respiration. From the identified papers logistic or probit dose-response models were fitted to the data using the maximum-likelihood technique and confidence intervals were based on the profile-likelihood method in the dose-volume histogram (DVH) Evaluator. RESULTS: Pooled logistic and probit models for grade 3 or higher toxicity for aorta, chest wall, duodenum, and small bowel suggest a significant difference when live motion tracking was used for targeting tumors with move with respiration which was on the average 10 times lower, in the high dose range. CONCLUSION: Live respiratory motion management appears to have a better toxicity outcome when treating targets which move with respiration with very steep peripheral dose gradients. This analysis is however limited by sparsity of rigorous data due to poor reporting in the literature.

Hypofractionation Radiotherapy vs. Conventional Fractionation for Breast Cancer: A Comparative Review of Toxicity.

The use of postoperative radiation therapy after breast-conserving surgery was longstanding standard practice. The treatment protocol used a standard fractionation of 50 Gy in 25 fractions plus a boost. Recently, the hypofractionation approach has gained support based on Canadian and English studies that claimed equal tumor control and similar toxicity to the standard protocol. We conducted a review of the literature of hypofractionation studies and compared the reported toxicity with the general literature. We placed special emphasis on breast fibrosis after hypofractionation versus standard fractionation. We found a striking difference in the breast toxicity reported by the hypofractionation literature regarding breast fibrosis as compared to standard fractionation. Breast fibrosis should be explored further via additional studies and discussed with potential breast-conserving surgery patients.

Modeling treatment couches in the Pinnacle treatment planning system: Especially important for arc therapy.

This study is to demonstrate the importance and a method of properly modeling the treatment couch for dose calculation in patient treatment using arc therapy. The 2 treatment couch tops-Aktina AK550 and Elekta iBEAM evo-of Elekta LINACs were scanned using Philips Brilliance Big Bore CT Simulator. Various parts of the couch tops were contoured, and their densities were measured and recorded on the Pinnacle treatment planning system (TPS) using the established computed tomography density table. These contours were saved as organ models to be placed beneath the patient during planning. Relative attenuation measurements were performed following procedures outlined by TG-176 as well as absolute dose comparison of static fields of 10 × 10 cm(2) that were delivered through the couch tops with that calculated in the TPS with the couch models. A total of 10 random arc therapy treatment plans (5 volumetric-modulated arc therapy [VMAT] and 5 stereotactic body radiation therapy [SBRT]), using 24 beams, were selected for this study. All selected plans were calculated with and without couch modeling. Each beam was evaluated using the Delta(4) dosimetry system (Delta(4)). The Student t-test was used to determine statistical significance. Independent reviews were exploited as per the Imaging and Radiation Oncology Core head and neck credentialing phantom. The selected plans were calculated on the actual patient anatomies with and without couch modeling to determine potential clinical effects. Large relative beam attenuations were noted dependent on which part of the couch top beams were passing through. Substantial improvements were also noted for static fields both calculated with the TPS and delivered physically when the couch models were included in the calculation. A statistically significant increase in agreement was noted for dose difference, distance to agreement, and γ-analysis with the Delta(4) on VMAT and SBRT plans. A credentialing review showed improvement in treatment delivery after couch modeling with both thermoluminescent dosimeter doses and film analysis. Furthermore, analysis of treatment plans with and without using the couch model showed a statistically significant reduction in planning target volume coverage and increase in skin dose. In conclusion, ignoring the treatment couch, a common practice when generating a patient treatment plan, can overestimate the dose delivered especially for arc therapy. This work shows that explicitly modeling the couch during planning can meaningfully improve the agreement between calculated and measured dose distributions. Because of this project, we have implemented the couch models clinically across all treatment plans.

Examination under anesthetic for occult pelvic ring instability.

OBJECTIVE: To describe the technique and results of stress examination with fluoroscopy under anesthesia (EUA) to determine stability and the need for operative stabilization of traumatic pelvic ring injuries. DESIGN: Retrospective chart and radiographic review. SETTING: Level I trauma center. SUBJECTS: Skeletally mature patients with traumatic incomplete posterior pelvic ring injuries. METHODS: Patients were consented for EUA if preoperative radiographs and computed tomographic scanning of the pelvis demonstrated an incomplete injury to the posterior pelvic ring (Orthopaedic Trauma Association [OTA] 61-B type injuries). Patients with nondisplaced anterior compression fractures of the sacral ala without internal rotation or a fracture line exiting the posterior cortex were excluded from this analysis. Similarly, skeletally immature patients or those with complete instability of the pelvic ring (OTA 61-C type injuries) were excluded. All patients meeting inclusion criteria were taken to the operating room, anesthetized, and placed in the supine position for stress examination (EUA) of the pelvic ring using intraoperative dynamic fluoroscopy. Examination consisted of a resting static film followed by internal rotation, external rotation, and push-pull maneuvers of both lower extremities. Each of these maneuvers was performed using the anteroposterior, inlet, and outlet projections, providing a total of 15 distinct images for each patient's examination. The preoperative classification of the pelvic ring injury was then accepted or redefined based on the amount of rotational and translational instability in the axial, coronal, and sagittal planes. The decision to proceed with anterior and/or posterior operative reduction and stabilization was subsequently based on the degree of pelvic ring instability noted during the EUA. RESULTS: A total of sixty-eight patients underwent an EUA of their pelvis by the senior author. Fifty males and 18 females with an average age of 35 years comprised the study group. In all, 37 anteroposterior compression (APC or OTA 61-B1) injuries and 31 lateral compression (LC or OTA 61-B2) injuries were evaluated. Of the 14 pelvic ring injuries initially classified as an APC-1, seven (50%) were deemed stable and treated nonsurgically, whereas seven (50%) were felt to have sufficient instability (an occult APC-2) to warrant treatment with anterior fixation based on EUA. Of the 23 injuries initially classified as an APC-2, all but one required surgical fixation: 13 (57%) were treated with anterior fixation alone (APC-2a), whereas nine (39%) were treated with anterior fixation and supplemental iliosacral screw placement (APC-2b) based on the degree of instability noted during the EUA. Of the 20 injuries initially classified as an LC-1, 13 (65%) were stable and treated nonsurgically (LC-1a), whereas seven (35%) were treated with anterior and/or posterior stabilization (LC-1b) based on the degree of instability noted during the EUA. CONCLUSIONS: The reported incidence of poor functional outcomes associated with pelvic fracture may be attributable, in part, to inadequate treatment of misdiagnosed injuries and chronic instability and/or malunion. Performing an examination under anesthesia with dynamic stress fluoroscopy as described in this series revealed occult instability in 50% of presumed APC-1 injuries, 39% of APC-2 injuries, and 37% of LC-1 injuries. We propose a modification to the Young-Burgess Classification system to reflect the dynamic component of pelvic ring instability disclosed on EUA as follows: APC-2a for those injuries requiring anterior only fixation, APC-2b for those injuries that may require treatment with anterior and posterior fixation, LC-1a for those injuries that are stable and do not require internal fixation, and LC-1b for those lateral compression injuries that may require treatment with internal fixation. We conclude that pelvic EUA merits further analysis as an important diagnostic tool that may provide additional information regarding instability of the pelvic ring.