Tumor treating fields suppress tumor cell growth and neurologic decline in models of spinal metastases.

Spinal metastases can result in severe neurologic compromise and decreased overall survival. Despite treatment advances, local disease progression is frequent, highlighting the need for novel therapies. Tumor treating fields (TTFields) impair tumor cell replication and are influenced by properties of surrounding tissue. We hypothesized that bone's dielectric properties will enhance TTFields-mediated suppression of tumor growth in spinal metastasis models. Computational modeling of TTFields intensity was performed following surgical resection of a spinal metastasis and demonstrated enhanced TTFields intensity within the resected vertebral body. Additionally, luciferase-tagged human KRIB osteosarcoma and A549 lung adenocarcinoma cell lines were cultured in demineralized bone grafts and exposed to TTFields. Following TTFields exposure, the bioluminescence imaging (BLI) signal decreased to 10%-80% of baseline, while control cultures displayed a 4.48- to 9.36-fold increase in signal. Lastly, TTFields were applied in an orthotopic murine model of spinal metastasis. After 21 days of treatment, control mice demonstrated a 5-fold increase in BLI signal compared with TTFields-treated mice. TTFields similarly prevented tumor invasion into the spinal canal and development of neurologic symptoms. Our data suggest that TTFields can be leveraged as a local therapy within minimally conductive bone of spinal metastases. This provides the groundwork for future studies investigating TTFields for patients with treatment-refractory spinal metastases.

Practical Strategies in Reconstruction of Soft-Tissue Sarcoma.

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Discuss the natural history and pathophysiology of sarcoma. 2. Summarize the most up-to-date multidisciplinary management of soft-tissue sarcoma. 3. Provide a synopsis of reconstructive modalities based on anatomical location. 4. Highlight some novel strategies for treatment of lymphedema and phantom limb pain that are common sequelae following treatment and resection of soft-tissue sarcomas. SUMMARY: The management of soft-tissue sarcoma presents unique challenges to the reconstructive surgeon. The optimal management mandates a multidisciplinary approach; however, reconstruction must take into account the extent of the resection and exposed vital structures, but often occurs in the setting of adjuvant treatments including chemotherapy and radiation therapy. Reconstruction is based on the extent of the defect and the location of the primary tumor. As such, an evidence-based, algorithmic approach following the reconstructive ladder is warranted to minimize the risks of complications and maximize success, which varies from head and neck to torso to breast to extremity sarcomas. Aside from reconstruction of the defect, advances in the surgical treatment of lymphedema and neuropathic pain resulting from treatment and extirpation of soft-tissue sarcoma are critical to maintain function and patients' quality of life.

Illustrated instructions for mechanical quality assurance of a medical linear accelerator.

PURPOSE: The purpose of this study was to develop and test a set of illustrated instructions for effective training for mechanical quality assurance (QA) of medical linear accelerators (linac). METHODS: Illustrated instructions were created for mechanical QA and underwent several steps of review, testing, and refinement. Eleven testers with no recent QA experience were then recruited from our radiotherapy department (one student, two computational scientists, and eight dosimetrists). This group was selected because they have experience of radiation therapy but no preconceived ideas about how to do QA. The following parameters were progressively decalibrated on a Varian C-series linac: Group A = gantry angle, ceiling laser position, X1 jaw position, couch longitudinal position, physical graticule position (five testers); Group B = Group A + wall laser position, couch lateral and vertical position, collimator angle (three testers); Group C = Group B + couch angle, wall laser angle, and optical distance indicator (three testers). Testers were taught how to use the linac and then used the instructions to try to identify these errors. An experienced physicist observed each session, giving support on machine operation as necessary. RESULTS: Testers were able to follow the instructions. They determined gantry, collimator, and couch angle errors within 0.4°, 0.3°, and 0.9° of the actual changed values, respectively. Laser positions were determined within 1 mm and jaw positions within 2 mm. Couch position errors were determined within 2 mm and 3 mm for lateral/longitudinal and vertical errors, respectively. Accessory-positioning errors were determined within 1 mm. Optical distance indicator errors were determined within 2 mm when comparing with distance sticks and 6 mm when using blocks, indicating that distance sticks should be the preferred approach for inexperienced staff. CONCLUSIONS: Inexperienced users were able to follow these instructions and catch errors within the criteria suggested by AAPM TG-142 for linacs used for intensity-modulated radiation therapy. These instructions are, therefore, suitable for QA training.