The Stanford Volumetric Modulated Arc Therapy Total Body Irradiation Technique.

PURPOSE: In this article, we describe the technical aspects of the Stanford volumetric modulated arc therapy (VMAT) total body irradiation (TBI) technique, compare it with other VMAT-TBI techniques, and share our initial experience. METHODS AND MATERIALS: From September 2019 to August 2021, 35 patients were treated with VMAT-TBI at our institution. Treatment planning was performed using in-house developed automated planning scripts. Organ sparing depended on the regimen: myeloablative (lungs, kidneys, and lenses) and nonmyeloablative with benign disease (lungs, kidneys, lenses, gonads, brain, and thyroid). Quality assurance was performed using electronic portal imaging device portal dosimetry and Mobius3D. Robustness was evaluated for the first 10 patients by performing local and global isocenter shifts of 5 mm. Treatment was delivered using image-guided radiation therapy for every isocenter and every fraction. In vivo measurements were performed on the match line between the VMAT and anterior-posterior/posterior-anterior fields and on the testes for the first fraction. RESULTS: The lungs, lungs - 1 cm, and kidneys Dmean were consistently spared to 57.6% ± 4.4%, 40.7% ± 5.5%, and 70.0% ± 9.9% of the prescription dose, respectively. Gonadal sparing (Dmean = 0.69 ± 0.13 Gy) was performed for all patients with benign disease. The average planning target volume (PTV) maximum dose to 1 cubic centimeter (D1cc) was 120.7% ± 6.4% for all patients. The average Gamma passing rate for the VMAT plans was 98.1% ± 1.6% (criterion of 3%/2 mm). Minimal differences were observed between Mobius3D- and Eclipse AAA-calculated PTV Dmean (0.0% ± 0.3%) and lungs Dmean (-2.5% ± 1.2%). Robustness evaluation showed that the PTV Dmax and lungs Dmean were insensitive to small positioning deviations between the VMAT isocenters (1.1% ± 2.4% and 1.2% ± 1.0%, respectively). The average match-line dose measurement indicated patient setup was reproducible (96.1% ± 4.5% relative to prescription dose). Treatment time, including patient setup and beam-on, was 47.5 ± 9.5 min. CONCLUSIONS: The Stanford VMAT-TBI technique, from simulation to treatment delivery, was presented and compared with other VMAT-TBI techniques. Together with publicly shared autoplanning scripts, our technique may provide the gateway for wider adaptation of this technology and the possibility of multi-institutional studies in the cooperative group setting.

Unusually large pedal schwannoma.

We present a rare case of an unusually large schwannoma of the posterior tibial nerve that extended through the tarsal tunnel into the forefoot. Radiographic, computerized tomographic and magnetic resonance images supported the diagnosis, and the diagnosis was confirmed by pathological analysis. We found this schwannoma to be unique because of the combination of its location and extensive involvement of the foot.

Carcinomas of ovary and lung with clear cell features: can immunohistochemistry help in differential diagnosis?

Metastatic lung carcinomas with clear cell morphology can be confused with primary ovarian clear cell carcinomas. We performed immunohistochemical stains in 14 cases of non-small cell lung carcinomas with clear cell features and 14 cases of ovarian clear cell carcinomas using a panel of markers, including thyroid transcription factor 1 (TTF-1), carcinoembryonic antigen (CEA), Wilms tumor gene 1, octamer-binding transcription factor 4 (OCT-4), cancer antigen 125 (CA-125), estrogen receptor, and progesterone receptor. Among non-small cell lung carcinomas with clear cell features, 87.5% of adenocarcinomas (or 50% overall frequency in lung carcinomas) were positive for TTF-1, whereas none of the ovarian clear cell carcinomas were positive (P = 0.002). All 14 ovarian clear cell carcinomas stained for CA-125 as compared with 1 non-small cell lung carcinoma (P < 0.001). On the other hand, 85% of non-small cell lung carcinomas stained for CEA, whereas none of the ovarian clear cell carcinomas did (P < 0.001). Interestingly, 4 ovarian clear cell carcinomas (28%) showed positive staining for the germ cell marker OCT-4. Either lung or ovarian carcinomas stained for Wilms tumor gene 1, estrogen receptor, or progesterone receptor very infrequently; and the difference between the 2 groups was not statistically significant. Our results suggest that an immunohistochemical panel consisting of TTF-1, CEA, CA-125, and OCT-4 is helpful in distinguishing most pulmonary and ovarian carcinomas with clear cell features.