Development of a video image-based QA system for the positional accuracy of dynamic tumor tracking irradiation in the Vero4DRT system.

PURPOSE: To develop and evaluate a new video image-based QA system, including in-house software, that can display a tracking state visually and quantify the positional accuracy of dynamic tumor tracking irradiation in the Vero4DRT system. METHODS: Sixteen trajectories in six patients with pulmonary cancer were obtained with the ExacTrac in the Vero4DRT system. Motion data in the cranio-caudal direction (Y direction) were used as the input for a programmable motion table (Quasar). A target phantom was placed on the motion table, which was placed on the 2D ionization chamber array (MatriXX). Then, the 4D modeling procedure was performed on the target phantom during a reproduction of the patient's tumor motion. A substitute target with the patient's tumor motion was irradiated with 6-MV x-rays under the surrogate infrared system. The 2D dose images obtained from the MatriXX (33 frames/s; 40 s) were exported to in-house video-image analyzing software. The absolute differences in the Y direction between the center of the exposed target and the center of the exposed field were calculated. Positional errors were observed. The authors' QA results were compared to 4D modeling function errors and gimbal motion errors obtained from log analyses in the ExacTrac to verify the accuracy of their QA system. The patients' tumor motions were evaluated in the wave forms, and the peak-to-peak distances were also measured to verify their reproducibility. RESULTS: Thirteen of sixteen trajectories (81.3%) were successfully reproduced with Quasar. The peak-to-peak distances ranged from 2.7 to 29.0 mm. Three trajectories (18.7%) were not successfully reproduced due to the limited motions of the Quasar. Thus, 13 of 16 trajectories were summarized. The mean number of video images used for analysis was 1156. The positional errors (absolute mean difference + 2 standard deviation) ranged from 0.54 to 1.55 mm. The error values differed by less than 1 mm from 4D modeling function errors and gimbal motion errors in the ExacTrac log analyses (n = 13). CONCLUSIONS: The newly developed video image-based QA system, including in-house software, can analyze more than a thousand images (33 frames/s). Positional errors are approximately equivalent to those in ExacTrac log analyses. This system is useful for the visual illustration of the progress of the tracking state and for the quantification of positional accuracy during dynamic tumor tracking irradiation in the Vero4DRT system.

[A case report of successful treatment for rectosigmoid cancer with peritoneal dissemination after neoadjuvant chemoradiotherapy with XELOX and bevacizumab].

A 60-year-old woman underwent emergency operation for ileus due to rectosigmoid cancer. Intraoperative cytology and peritoneal dissemination were positive. After performing sigmoid colostomy, she underwent neoadjuvant radiation therapy (40 Gy)and eight courses of a XELOX and bevacizumab regimen. FDG-PET did not indicate FDG accumulation after chemoradiotherapy, thus, we performed low anterior resection. Peritoneal dissemination and washing cytology were negative in the second operation. Neoadjuvant chemoradiotherapy with XELOX and bevacizumab were useful for down staging in patients with advanced colorectal cancer.

Complete response of liver metastasis of gastric cancer treated by s-1 chemoradiotherapy: a case report.

This paper presents a case of suspected liver metastasis of gastric cancer and a virtual complete response to S-1 chemoradiotherapy. A 69-year-old man underwent distal gastrectomy for gastric cancer in 2008. Multiple liver metastases occurred in 2009. He underwent 15 courses of S-1 therapy and radiation therapy (37.5 Gy). Abdominal computed tomography showed virtual complete disappearance of liver metastasis after chemoradiotherapy. Hence, this case was interpreted as a complete response. No sign of recurrence was noted 18 months after complete response was confirmed. S-1 chemoradiotherapy is likely to be effective in treating patients with liver metastases of gastric cancer.

Complete Response of Isolated Para-aortic Lymph Node Recurrence from Rectosigmoid Cancer Treated by Chemoradiation Therapy with Capecitabine/Oxaliplatin plus Bevacizumab: A Case Report.

Para-aortic lymph node recurrence is a rare type of metastasis from colorectal cancer, and no treatment has yet been established. Here, we report on a case of isolated para-aortic lymph node metastasis from rectosigmoid cancer that showed complete response to chemoradiation therapy with capecitabine/oxaliplatin plus bevacizumab. A 58-year-old woman underwent high anterior resection for rectosigmoid cancer in 2009. Para-aortic lymph node recurrence occurred in 2011. She underwent radiation therapy (50 Gy) and 8 courses of capecitabine/oxaliplatin plus bevacizumab. Abdominal computed tomography and positron emission tomography with 18-fluorodeoxyglucose did not reveal any para-aortic lymph node recurrence after chemoradiation therapy. Hence, this case was interpreted as a complete response. No recurrence was noted 6 months after the complete response. Chemoradiation therapy with capecitabine/oxaliplatin plus bevacizumab is likely to be effective in treating patients with para-aortic lymph node recurrence.

[A case report of pathologically complete response of locally advanced rectal cancer after neoadjuvant chemoradiotherapy with XELOX and bevacizumab].

A 70-year-old man was admitted to our hospital for constipation. A clinical examination showed locally advanced rectal cancer with possible invasion to the prostate gland and pelvic wall. After performing colostomy, he underwent neoadjuvant radiation therapy (40 Gy) and six courses of a XELOX and bevacizumab regimen. A subsequent examination demonstrated significant reduction of the tumor, so we performed super low anterior resection and colo-anal anastomosis. Pathological examination revealed no residual cancer cells and showed pathological CR. Neoadjuvant chemoradiotherapy with XELOX and bevacizumab were useful for down staging and function-preserving surgery in patients with locally advanced rectal cancer.

Effect of respiratory trace shape on optimal treatment margin.

PURPOSE: To evaluate the effect of target trajectory shape on the optimal treatment margin. METHODS: Intensity-modulated radiation therapy and volumetric modulated arc therapy plans were created for three spherical targets (3, 5, and 7 cm diameter) simulated in exhalation phases, each with margins of 2, 4, 6, 8, and 10 mm to account for motion. The plans were delivered to a stationary 2D ion chamber array, and dose movies were obtained of the delivered doses. The dose movie frames were then displaced to simulate different respiratory traces. Five traces were used: sin2, sin4 sin6, and two patient traces. The optimal margin was defined as the margin for which the dose delivered to 95% of the target was closest to that obtained with no margin or motion. The equivalent uniform dose was also investigated as an alternative cost function. RESULTS: The optimal margin was always smaller than the peak-to-peak motion. When the respiratory trace spent less time in the inhale phases, the optimal margin was consistently smaller than when more time was spent in the inhale phases. The target size and treatment modality also affected the optimal margin. CONCLUSIONS: The necessary margin for targets that spend less time in the exhale phase (sin6) is 2-4 mm smaller than for targets that spend equal time in the inhale and exhale phases (sin).

Use of a realistic breathing lung phantom to evaluate dose delivery errors.

PURPOSE: To compare the effect of respiration-induced motion on delivered dose (the interplay effect) for different treatment techniques under realistic clinical conditions. METHODS: A flexible resin tumor model was created using rapid prototyping techniques based on a computed tomography (CT) image of an actual tumor. Twenty micro-MOSFETs were inserted into the tumor model and the tumor model was inserted into an anthropomorphic breathing phantom. Phantom motion was programed using the motion trajectory of an actual patient. A four-dimensional CT image was obtained and several treatment plans were created using different treatment techniques and planning systems: Conformal (Eclipse), step-and-shoot intensity-modulated radiation therapy (IMRT) (Pinnacle), step-and-shoot IMRT (XiO), dynamic IMRT (Eclipse), complex dynamic IMRT (Eclipse), hybrid IMRT [60% conformal, 40% dynamic IMRT (Eclipse)], volume-modulated are therapy (VMAT) [single-arc (Eclipse)], VMAT [double-arc (Eclipse)], and complex VMAT (Eclipse). The complex plans were created by artificially pushing the optimizer to give complex multileaf collimator sequences. Each IMRT field was irradiated five times and each VMAT field was irradiated ten times, with each irradiation starting at a random point in the respiratory cycle. The effect of fractionation was calculated by randomly summing the measured doses. The maximum deviation for each measurement point per fraction and the probability that 95% of the model tumor had dose deviations less than 2% and 5% were calculated as a function of the number of fractions. Tumor control probabilities for each treatment plan were calculated and compared. RESULTS: After five fractions, measured dose deviations were less than 2% for more than 95% of measurement points within the tumor model for all plans, except the complex dynamic IMRT, step-and-shoot IMRT (XiO), complex VMAT, and single-arc VMAT plans. Reducing the dose rate of the complex IMRT plans from 600 to 200 MU/min reduced the dose deviations to less than 2%. Dose deviations were less than 5% after five fractions for all plans, except the complex single-arc VMAT plan. CONCLUSIONS: Rapid prototyping techniques can be used to create realistic tumor models. For most treatment techniques, the dose deviations averaged out after several fractions. Treatments with unusually complicated multileaf collimator sequences had larger dose deviations. For IMRT treatments, dose deviations can be reduced by reducing the dose rate. For VMAT treatments, using two arcs instead of one is effective for reducing dose deviations.