Comparative analysis for renal stereotactic body radiotherapy using Cyberknife, VMAT and proton therapy based treatment planning.

PURPOSE: We conducted this dosimetric analysis to evaluate the feasibility of a multi-center stereotactic body radiation therapy (SBRT) trial for renal cell carcinoma (RCC) using different SBRT platforms. MATERIALS/METHODS: The computed tomography (CT) simulation images of 10 patients with unilateral RCC previously treated on a Phase 1 trial at Institution 1 were anonymized and shared with Institution 2 after IRB approval. Treatment planning was generated through five different platforms aiming a total dose of 48 Gy in three fractions. These platforms included: Cyberknife and volumetric modulated arc therapy (VMAT) at institution 1, and Cyberknife, VMAT, and pencil beam scanning (PBS) Proton Therapy at institution 2. Dose constraints were based on the Phase 1 approved trial. RESULTS: Compared to Cyberknife, VMAT and PBS plans provided overall an equivalent or superior coverage to the target volume, while limiting dose to the remaining kidney, contralateral kidney, liver, spinal cord, and bowel. CONCLUSION: This dosimetric study supports the feasibility of a multi-center trial for renal SBRT using PBS, VMAT and Cyberknife.

Proton Beam Therapy in the Treatment of Periorbital Malignancies.

PURPOSE: Periorbital tumor location presents a significant challenge with 3-dimensional conformal radiation therapy or intensity modulated radiation therapy due to high tumor dose needed in the setting of close proximity to orbital structures with lower tolerance. Proton beam therapy (PBT) is felt to be an effective modality in such cases due to its sharp dose gradient. MATERIALS AND METHODS: We reviewed our institutional PBT registry and identified 17 patients with tumor epicenters within 2 cm of the eye and optic apparatus treated with passive scatter PBT with comparison volumetric arc therapy plans available. Maximum and mean doses to organs at risk of interest, including optic nerves, optic chiasm, lens, eye ball, pituitary, cochlea, lacrimal gland, and surrounding brain, were compared using the paired Wilcoxon signed rank test. Overall survival was determined using the Kaplan-Meier method. RESULTS: Median age was 67. Median follow-up was 19.7 months. Fourteen patients underwent upfront resection and received postoperative radiation and 3 received definitive radiation. One patient received elective neck radiation, 2 underwent reirradiation, and 3 had concurrent chemotherapy. There was a statistically significant reduction in mean dose to the optic nerves and chiasm, brain, pituitary gland, lacrimal glands, and cochlea as well as in the maximum dose to the optic nerves and chiasm, pituitary gland, lacrimal glands, and cochlea with PBT. The 18-month cumulative incidence of local failure was 19.1% and 1-year overall survival was 80.9%. CONCLUSION: Proton beam therapy resulted in significant dose reductions to several periorbital and optic structures compared with volumetric arc therapy. Proton beam therapy appears to be the optimal radiation modality in such cases to minimize risk of toxicity to periorbital organs at risk.

Reirradiation for Recurrent Scalp Angiosarcoma: Dosimetric Advantage of PBT over VMAT and EBT.

PURPOSE: Reirradiation in the scalp area can be challenging given the proximity to organs at risk (OARs), such as the eye and brain. Our aim is to evaluate the dosimetric differences of volumetric modulated arc therapy (VMAT) and electron beam therapy (EBT) compared with 3-dimensional proton beam therapy (PBT). PATIENTS AND METHODS: We evaluated a patient with recurrent angiosarcoma of the left temporal scalp after prior surgical resections and radiation therapy to 60 Gy in 30 fractions who needed reirradiation. We generated VMAT, EBT, and PBT plans using the Pinnacle Treatment Planning System (TPS). Both VMAT and EBT plans used a skin bolus, whereas no bolus was used for the proton plan. Doses to the OARs, including cochlea, eyes, lens, lacrimal glands, optic nerves, optic chiasm, pituitary gland, and underlying brain, were compared. RESULTS: The reirradiation treatment dose was 60 Gy(RBE). Target volume coverage was comparable in all plans. Compared with VMAT and EBT, the PBT plan showed reductions in mean and maximum doses to all OARs. Without the use of protons, several OARs would have exceeded dose tolerance utilizing VMAT or electrons. Dose reduction of up to 100% was achieved for central and contralateral OARs. CONCLUSION: Compared with VMAT and EBT, PBT resulted in dose reductions to all OARs, while maintaining excellent target coverage. PBT showed a significant advantage in treating superficially located skin cancers, such as angiosarcoma, without the need for a bolus. PBT can be considered in the upfront treatment and certainly in the reirradiation setting.

Evaluating radiotherapy treatment delay using Failure Mode and Effects Analysis (FMEA).

PURPOSE: This study identified and evaluated the factors that are responsible for delay in the clinical workflow of radiation therapy, starting from the CT simulation (CT-Sim) to the first fraction of treatment delivery using the Failure Mode and Effects Analysis (FMEA) methodology. MATERIALS AND METHODS: A total of 1106 patient cases were retrospectively analyzed using FMEA methodology. For each failure mode (FM), the following factors were rated and discussed by the group: occurrence (O), severity (S), detectability (D), and methods of improvement or mitigation. In addition, two new factors, namely social effect (SE) and economic effect (EE), were introduced to evaluate the impact of FM on the department or hospital. Risk priority number (RPN) and the product of RPN, SE, and EE (i.e. RPNSE-EE) were calculated for each FM. RESULTS: Average delay caused by identified FM was 8 days while 76% of the FMs resulted in delay of less than 5 days. The RPN of all the FMs ranged from 4 to 60 with an average value of 18. "Tumor volume, prescription and objective" had the highest average RPN of 23. The majority of FMs with high RPN were identified in "CT-Sim" (RPN: 21.5 ±â€¯11.1; RPNSE-EE: 97.0 ±â€¯46.4) and "treatment planning" (RPN: 20.1 ±â€¯8.1, RPNSE-EE: 152.9 ±â€¯76.5) stages. CONCLUSION: The FMEA enabled identification of the factors that caused delay in the pre-treatment process of radiation therapy. "CT-Sim" and "treatment planning" stages had more FMs with high RPN values which have higher priority for future improvement. Two new factors, SE and EE, were introduced and appeared to be valuable in evaluating the impact of FMs on radiation oncology department or hospital in general.

Comparison of helical tomotherapy versus conventional radiation to deliver craniospinal radiation.

The purpose of this study was to investigate whether helical tomotherapy would better dose-limit growing vertebral ring apophyses during craniospinal radiation as compared to conventional techniques. Four pediatric patients with M0 medulloblastoma received tomotherapy craniospinal radiation (23.4 Gy, 1.8 Gy/fx) by continuous helical delivery of 6 MV photons. Weekly blood counts were monitored. For comparison, conventional craniospinal radiation plans were generated. To assist in tomotherapy planning, a cross-sectional growth study of 52 children and young adults was completed to evaluate spine growth and maturation. Vertebral ring apophyses first fused along the posterolateral body-pedicle synostosis, proceeding circumferentially toward the anterior vertebral body such that the cervical and lumbar vertebrae fused early and mid-thoracic vertebrae fused late. For the four pediatric patients, tomotherapy resulted between 2% and 14% vertebral volume exceeding 23 Gy. Conventional craniospinal radiation predicted between 33% and 44% exceeding 23 Gy. Cumulative body radiation doses exceeding 4 Gy were between 50% and 57% for tomotherapy and between 25% and 37% for conventional craniospinal radiation. Tomotherapy radiation reduced neutrophil, platelet, and erythrocyte hemoglobin levels during treatment. Tomotherapy provides improved dose avoidance to growing vertebrae as compared to conventional craniospinal radiation. However, the long-term effects of tomotherapy dose avoidance on spine growth and large volume low dose radiation in children are not yet known.

Tomotherapy for prostate adenocarcinoma: a report on acute toxicity.

BACKGROUND AND PURPOSE: To analyze the impact of Tomotherapy (TOMO) intensity modulated radiotherapy (IMRT) on acute gastrointestinal (GI) and genitourinary (GU) toxicity in prostate cancer. MATERIALS AND METHODS: The records of 55 consecutively treated TOMO patients were reviewed. Additionally a well-matched group of 43 patients treated with LINAC-based step and shoot IMRT (LINAC) was identified. Acute toxicity was scored according to Radiation Therapy Oncology Group acute toxicity criterion. RESULTS: The grade 2-3 acute GU toxicity rates for the TOMO vs. LINAC groups were 51% vs. 28% (p=0.001). Acute grade 2 GI toxicity was 25% vs. 40% (p=0.024), with no grade 3 GI toxicity in either group. In univariate analysis, androgen deprivation, prostate volume, pre-treatment urinary toxicity, and prostate dose homogeneity correlated with acute GI and GU toxicity. With multivariate analysis use of Tomotherapy, median bladder dose and bladder dose homogeneity remained significantly correlated with GU toxicity. CONCLUSIONS: Acute GI toxicity for prostate cancer is improved with Tomotherapy at a cost of increased acute GU toxicity possibly due to differences in bladder and prostate dose distribution.

Comparison of Ray Tracing and Monte Carlo Calculation Algorithms for Thoracic Spine Lesions Treated With CyberKnife-Based Stereotactic Body Radiation Therapy.

Stereotactic body radiation therapy (SBRT) is an emerging technology for the treatment of spinal metastases, although the dosimetric impact of the calculation method on spinal dose distribution is unknown. This study attempts to determine whether CyberKnife (CK)-based SBRT using a Ray Tracing (RyTc) algorithm is comparable dosimetrically to that of Monte Carlo (MC) for thoracic spinal lesions. Our institutional CK-based SBRT database for thoracic spinal lesions was queried and a cohort was generated. Patients were planned using RyTc and MC algorithms using the same beam angles and monitor units. Dose-volume histograms of the planning target volume (PTV), spinal cord, esophagus, and skin were generated, and dosimetric parameters were compared. There were 37 patients in the cohort. The average percentage volume of PTV covered by the prescribed dose with RyTc and MC algorithms was 91.1% and 80.4%, respectively (P < .001). The difference in average maximum spinal cord dose between RyTc and MC plans was significant (1126 vs 1084 cGy, P = .004), with the MC dose ranging from 18.7% below to 13.8% above the corresponding RyTc dose. A small reduction in maximum skin dose was also noted (P = .017), although no difference was seen in maximum esophageal dose (P = .15). Only PTVs smaller than 27 cm(3) were found to correlate with large (>10%) changes in dose to 90% of the volume (P = .014), while no correlates with the average percentage volume of PTV covered by the prescribed dose were demonstrated. For thoracic spinal CK-based SBRT, RyTc computation may overestimate the MC calculated average percentage volume of PTV covered by the prescribed dose and have unpredictable effects on doses to organs at risk, particularly the spinal cord. In this setting, use of RyTc optimization should be limited and always verified with MC.

Hematological toxicity after robotic stereotactic body radiosurgery for treatment of metastatic gynecologic malignancies.

PURPOSE: To evaluate hematological toxicity after robotic stereotactic body radiosurgery (SBRT) for treatment of women with metastatic abdominopelvic gynecologic malignancies. METHODS AND MATERIALS: A total of 61 women with stage IV gynecologic malignancies treated with abdominopelvic SBRT were analyzed after ablative radiation (2400 cGy/3 divided consecutive daily doses) delivered by a robotic-armed Cyberknife SBRT system. Abdominopelvic bone marrow was identified using computed tomography-guided contouring. Fatigue and hematologic toxicities were graded by retrospective assignment of common toxicity criteria for adverse events (version 4.0). Bone marrow volume receiving 1000 cGy (V10) was tested for association with post-therapy (median 32 days [25%-75% quartile, 28-45 days]) white- or red-cell counts, hemoglobin levels, and platelet counts as marrow toxicity surrogates. RESULTS: In all, 61 women undergoing abdominopelvic SBRT had a median bone marrow V10 of 2% (25%-75% quartile: 0%-8%). Fifty-seven (93%) of 61 women had received at least 1 pre-SBRT marrow-taxing chemotherapy regimen for metastatic disease. Bone marrow V10 did not associate with hematological adverse events. In all, 15 grade 2 (25%) and 2 grade 3 (3%) fatigue symptoms were self-reported among the 61 women within the first 10 days post-therapy, with fatigue resolved spontaneously in all 17 women by 30 days post-therapy. Neutropenia was not observed. Three (5%) women had a grade 1 drop in hemoglobin level to <10.0 g/dL. Single grade 1, 2, and 3 thrombocytopenias were documented in 3 women. CONCLUSIONS: Abdominopelvic SBRT provided ablative radiation dose to cancer targets without increased bone marrow toxicity. Abdominopelvic SBRT for metastatic gynecologic malignancies warrants further study.

18FDG-PET/CT Definition of Clinical Target Volume for Robotic Stereotactic Body Radiosurgery Treatment of Metastatic Gynecologic Malignancies.

The objective of the current article was to evaluate 2-[18F]fluoro-2-deoxy-D-glucose 18F-FDG) as measured by positron emission tomography for delineation of abdominopelvic gross tumor volumes (GTV) for stereotactic body radiosurgery treatment (SBRT) of metastatic gynecologic cancers. A retrospective review of SBRT was conducted in 27 women with stage IV gynecologic cancers recurring in para-aortic lymph nodes. Robotic SBRT involved 2400 cGy in 3 consecutive 800 cGy daily fractions prescribed to a 3.0 mm expanded planning tumor volume (PTV) defined by both CT-based and 18F-FDG-based GTVs. In this study, 18F-FDG-based GTVs led to significantly larger PTVs in all 27 women, than if they had been based on CT GTVs alone (P < 0.001). Enlarged PTVs may have resulted from the breathing-induced target motion during the time of 18F-FDG image acquisition smearing 18F-FDG signal over a greater anatomic dimension. Ultimately, SBRT-target local control, based on the RECIST 1.1 criteria, was 96% (26 of 27), and associated with minor reversible toxicity. The use of 18F-FDG to define SBRT target volumes warrants further interrogation in SBRT clinical trials.