Prospective study on stereotactic body radiotherapy for small pancreatic neuroendocrine tumors: tolerance and effectiveness analysis.

INTRODUCTION: Surgery is the standard treatment for pancreatic neuroendocrine tumors (pNETs), obtaining favorable results but associating high morbidity and mortality rates. This study assesses stereotactic body radiation therapy (SBRT) as a radical approach for small (< 2 cm) nonfunctioning pNETs. MATERIALS AND METHODS: From January 2017 to June 2023, 20 patients with small pNETs underwent SBRT in an IRB-approved study. Endpoints included local control, tolerance, progression-free survival, and overall survival (OS). Diagnostic assessments comprised endoscopy, CT scans, OctreScan or PET-Dotatoc, abdominal MRI, and histological confirmatory samples. RESULTS: In a 30-month follow-up of 20 patients (median age 55.5 years), SBRT was well-tolerated with no grade > 2 toxicity. 40% showed morphological response, 55% remained stable. Metabolically, 50% achieved significant improvement. With a median OS of 41.5 months, all patients were alive without local or distant progression or need for surgical resection. CONCLUSION: SBRT is a feasible and well-tolerated approach for small neuroendocrine pancreatic tumors, demonstrating effective local control. Further investigations are vital for validation and extension of these findings.

Image-guided radiation therapy (IGRT) in prostate cancer in México, survey of SOMERA (Sociedad Mexicana de Radioterapeutas/Mexican Society of Radiation Oncologists) with recommendations on its implementation and process.

Background: Prostate cancer is one of the main tumors worldwide, its treatment is multidisciplinary, includes radiotherapy in all stages: curative, radical, adjuvant, salvage and palliative. Technological advances in planning systems, image acquisition and treatment equipment have allowed the delivery of higher doses limiting toxicity in healthy tissues, distributing radiation optimally and ensuring reproducibility of conditions. Image-guided radiotherapy (IGRT) is not standard in guidelines, only recommended with heterogeneity in its own process. Materials and methods: A survey was conducted to members of the Mexican Society of Radiation Oncologists (SOMERA), to know the current status and make recommendations about its implementation and use, taking into account existing resources. Results: Responses of 541 patients were evaluated, 85% belonged to the intermediate-high risk group, 65% received adjuvant or salvage radiotherapy (RT), 80% received intensity-modulated radiation therapy (IMRT) using doses up to 80 Gy/2 Gy. Cone beam computed tomography (CBCT) was performed on 506 (93.5%), (100% IMRT) and 90% at a periodicity of 3-5/week. 3D treatment with 42% portal images 1/week. Online correction strategies (36% changes before treatment), following a diet and bladder and rectal control. Evidence and recommendations are reviewed. Conclusions: IGRT should be performed in patients with prostate cancer. In Mexico, despite limitations in the distribution of human and technological resources, it is routinely applied. More information is still needed on clinical evidence of its benefits and the process should be implemented according to infrastructure, following institutional guidelines, recommending to report the initial experience that helps to standardize national conduct.

Surface-guided radiation therapy for breast cancer: more precise positioning.

INTRODUCTION: Hypofractionated radiation therapy for breast cancer requires highly precise delivery through the use of image-guided radiotherapy (IGRT). Surface-guided radiation therapy (SGRT) is being increasingly used for patient positioning in breast radiotherapy. We aimed to assess the role of SGRT for verification of breast radiotherapy and the tumour bed. MATERIALS AND METHODS: Prospective study of 252 patients with early stage breast cancer. A total of 1170 determinations of daily positioning were performed. Breast surface positioning was determined with SGRT (AlignRT) and correlated with the surgical clips in the tumour bed, verified by IGRT (ExacTrac). RESULTS: SGRT improved surface matching by a mean of 5.3 points compared to conventional skin markers (98.0 vs. 92.7), a statistically significant difference (p < 0.01, Wilcoxon Test). For surface matching values > 95%, ≥ 3 clips coincided in 99.7% of the determinations and all markers coincided in 92.5%. For surface matching rates > 90%, the location of ≥ 3 clips coincided in 99.55% of determinations. CONCLUSIONS: SGRT improves patient positioning accuracy compared to skin markers. Optimal breast SGRT can accurately verify the localisation of the tumour bed, ensuring matching with ≥ 3 surgical clips. SGRT can eliminate unwanted radiation from IGRT verification systems.

Frameless Image-Guided Radiosurgery for Multiple Brain Metastasis Using VMAT: A Review and an Institutional Experience.

We undertook a structured review of stereotactic radiosurgery (SRS) using linear particle accelerator (linac) equipment, focusing on volumetric modulated arc therapy (VMAT) technology, and frameless image-guided radiotherapy (IGRT), for the treatment of brain metastases. We analyzed the role of linac SRS and its clinical applications, exploring stereotactic localization. Historically, there was a shift from fixed frames to frameless approaches, moving toward less invasive treatments. Thus, we reviewed the concepts of VMAT for multiple-target applications, comparing its dosimetric and technical features to those of other available techniques. We evaluated relevant technical issues and discussed the planning parameters that have gained worldwide acceptance to date. Thus, we reviewed the current literature on the clinical aspects of SRS, especially its main indications and how the advantages of VMAT may achieve clinical benefits in such scenarios. Finally, we reported our institutional results on IGRT-VMAT for SRS treatments for patients with multiple brain metastases.

Problems and solutions in IGRT for cervical cancer.

The contribution of Image-guided Radiotherapy (IGRT) to modern radiotherapy is undeniable, being the way to bring into daily practice the dosimetric benefits of Intensity-Modulated Radiotherapy (IMRT). Organ and target motion is constant and unpredictable at the pelvis, thus posing a challenge to the safe execution of IMRT. There are potential benefits of IMRT in the radical treatment of cervical cancer patients, both in terms of dose escalation and decrease of toxicity. But it is essential to find IGRT solutions to control the aspects that can lead to geographic miss targeting or organs at risk (OAR) overdose. This review seeks to describe the problems and possible solutions in the clinical implementation of IMRT/IGRT protocols to treat intact cervical cancer patients.

Analysis of translational errors in frame-based and frameless cranial radiosurgery using an anthropomorphic phantom.

OBJECTIVE: To evaluate three-dimensional translational setup errors and residual errors in image-guided radiosurgery, comparing frameless and frame-based techniques, using an anthropomorphic phantom. MATERIALS AND METHODS: We initially used specific phantoms for the calibration and quality control of the image-guided system. For the hidden target test, we used an Alderson Radiation Therapy (ART)-210 anthropomorphic head phantom, into which we inserted four 5mm metal balls to simulate target treatment volumes. Computed tomography images were the taken with the head phantom properly positioned for frameless and frame-based radiosurgery. RESULTS: For the frameless technique, the mean error magnitude was 0.22 ± 0.04 mm for setup errors and 0.14 ± 0.02 mm for residual errors, the combined uncertainty being 0.28 mm and 0.16 mm, respectively. For the frame-based technique, the mean error magnitude was 0.73 ± 0.14 mm for setup errors and 0.31 ± 0.04 mm for residual errors, the combined uncertainty being 1.15 mm and 0.63 mm, respectively. CONCLUSION: The mean values, standard deviations, and combined uncertainties showed no evidence of a significant differences between the two techniques when the head phantom ART-210 was used.

OBJETIVO: Comparar os erros de posicionamento e erros residuais translacionais tridimensionais de uma radiocirurgia guiada por imagem, frame versus frameless, com uso de um objeto simulador antropomórfico. MATERIAIS E MÉTODOS: Para a calibração e qualidade do sistema de imagem foram utilizados objetos simuladores específicos. Para o teste hidden target foi utilizado o crânio do objeto simulador antropomórfico Alderson Radiation Therapy (ART)-210, dentro do qual foram inseridas quatro esferas metálicas de 5 mm de diâmetro como volumes alvos de tratamento. Imagens tomográficas foram realizadas com o ART-210 devidamente posicionado para ambos os métodos de imobilização. RESULTADOS: Para o método frameless, a média foi 0,22 ± 0,04 mm para os erros setup e 0,14 ± 0,02 mm para os erros residuais, apresentando uma incerteza combinada de 0,28 mm e 0,16 mm, respectivamente. Para o método frame, a média foi 0,73 ± 0,14 mm para os erros setup e 0,31 ± 0,04 mm para os erros residuais, apresentando uma incerteza combinada de 1,15 mm e 0,63 mm, respectivamente. CONCLUSÃO: Com base nas médias, desvios-padrão e incertezas combinadas, os resultados mostraram não haver evidências de diferença significativa entre as técnicas em questão quando utilizado um objeto simulador antropomórfico craniano ART-210.

Analysis of translational errors in frame-based and frameless cranial radiosurgery using an anthropomorphic phantom / Análise dos erros de posicionamento translacionais em radiocirurgia craniana frame e frameless com uso de objeto simulador antropomórfico

Abstract Objective: To evaluate three-dimensional translational setup errors and residual errors in image-guided radiosurgery, comparing frameless and frame-based techniques, using an anthropomorphic phantom. Materials and Methods: We initially used specific phantoms for the calibration and quality control of the image-guided system. For the hidden target test, we used an Alderson Radiation Therapy (ART)-210 anthropomorphic head phantom, into which we inserted four 5mm metal balls to simulate target treatment volumes. Computed tomography images were the taken with the head phantom properly positioned for frameless and frame-based radiosurgery. Results: For the frameless technique, the mean error magnitude was 0.22 ± 0.04 mm for setup errors and 0.14 ± 0.02 mm for residual errors, the combined uncertainty being 0.28 mm and 0.16 mm, respectively. For the frame-based technique, the mean error magnitude was 0.73 ± 0.14 mm for setup errors and 0.31 ± 0.04 mm for residual errors, the combined uncertainty being 1.15 mm and 0.63 mm, respectively. Conclusion: The mean values, standard deviations, and combined uncertainties showed no evidence of a significant differences between the two techniques when the head phantom ART-210 was used.

Resumo Objetivo: Comparar os erros de posicionamento e erros residuais translacionais tridimensionais de uma radiocirurgia guiada por imagem, frame versus frameless, com uso de um objeto simulador antropomórfico. Materiais e Métodos: Para a calibração e qualidade do sistema de imagem foram utilizados objetos simuladores específicos. Para o teste hidden target foi utilizado o crânio do objeto simulador antropomórfico Alderson Radiation Therapy (ART)-210, dentro do qual foram inseridas quatro esferas metálicas de 5 mm de diâmetro como volumes alvos de tratamento. Imagens tomográficas foram realizadas com o ART-210 devidamente posicionado para ambos os métodos de imobilização. Resultados: Para o método frameless, a média foi 0,22 ± 0,04 mm para os erros setup e 0,14 ± 0,02 mm para os erros residuais, apresentando uma incerteza combinada de 0,28 mm e 0,16 mm, respectivamente. Para o método frame, a média foi 0,73 ± 0,14 mm para os erros setup e 0,31 ± 0,04 mm para os erros residuais, apresentando uma incerteza combinada de 1,15 mm e 0,63 mm, respectivamente. Conclusão: Com base nas médias, desvios-padrão e incertezas combinadas, os resultados mostraram não haver evidências de diferença significativa entre as técnicas em questão quando utilizado um objeto simulador antropomórfico craniano ART-210.

Displacements of fiducial markers in patients with prostate cancer treated with image guided radiotherapy: A single-institution descriptive study.

AIM: To describe daily displacements when using fiducial markers as surrogates for the target volume in patients with prostate cancer treated with IGRT. BACKGROUND: The higher grade of conformity achieved with the use of modern radiation technologies in prostate cancer can increase the risk of geographical miss; therefore, an associated protocol of IGRT is recommended. MATERIALS AND METHODS: A single-institution, retrospective, consecutive study was designed. 128 prostate cancer patients treated with daily on-line IGRT based on 2D kV orthogonal images were included. Daily displacement of the fiducial markers was considered as the difference between the position of the patient when using skin tattoos and the position after being relocated using fiducial markers. Measures of central tendency and dispersion were used to describe fiducial displacements. RESULTS: The implant itself took a mean time of 15 min. We did not detect any complications derived from the implant. 4296 sets of orthogonal images were identified, 128 sets of images corresponding to treatment initiation were excluded; 91 (2.1%) sets of images were excluded from the analysis after having identified that these images contained extreme outlier values. If IGRT had not been performed 25%, 10% or 5% of the treatments would have had displacements superior to 4, 7 or 9 mm respectively in any axis. CONCLUSIONS: Image guidance is required when using highly conformal techniques; otherwise, at least 10% of daily treatments could have significant displacements. IGRT based on fiducial markers, with 2D kV orthogonal images is a convenient and fast method for performing image guidance.