Organ-sparing techniques and dose-volume constrains used in breast cancer radiation therapy - Results from European and Latin American surveys.

Background: Advances in local and systemic therapies have improved the outcomes of patients with breast cancer (BC), leading to a possible increased risk for postoperative radiation therapy (RT) late adverse events. The most adequate technologies and dose constraints for organs at risk (OAR) in BC RT have yet to be defined. Methods: An online survey was distributed to radiation oncologists (ROs) practicing in Europe and Latin America including the Caribbean (LAC) through personal contacts, RO and BC professional groups' networks. Demographic data and clinical practice information were collected. Results:  The study included 585 responses from ROs practicing in 57 different countries. The most frequently contoured OAR by European and LAC participants were the whole heart (96.6 % and 97.7 %), the ipsilateral (84.3 % and 90.8 %), and contralateral lung (71.3 % and 77.4 %), whole lung (69.8 % and 72.9 %), and the contralateral breast (66.4 % and. 83.2 %). ESTRO guidelines were preferred in Europe (33.3 %) and the RTOG contouring guideline was the most popular in LAC (62.2 %), while some participants used both recommendations (13.2 % and 19.2 %). IMRT (68.6 % and 59.1 %) and VMAT (65.6 % and 60.2 %) were the preferred modalities used in heart sparing strategies, followed by deep inspiration breath-hold (DIBH) (54.8 % and 37.4 %) and partial breast irradiation (PBI) (41.6 % and 24.6 %). Only a small percentage of all ROs reported the dose-volume constraints for OAR used in routine clinical practice. A mean heart dose (Heart-Dmean) between 4 and 5 Gy was the most frequently reported parameter (17.2 % and 39.3 %). Conclusion:  The delineation approaches and sparing techniques for OAR in BC RT vary between ROs worldwide. The low response rate to the dose constraints subset of queries reflects the uncertainty surrounding this topic and supports the need for detailed consensus recommendations in the clinical practice.

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.

Evaluation of a composite Gel-Alanine phantom on an end-to-end test to treat multiple brain metastases by a single isocenter VMAT technique.

PURPOSE: This work aims to evaluate the application of a cylindrical phantom made of dosimetric gel containing alanine pellets distributed inside the gel volume during an end-to-end test of a single isocenter VMAT for simultaneous treatment of multiple brain metastases. The evaluation is based on the comparison of the results obtained with the composite phantom with the treatment planning system (TPS) dose distribution validated by using the clinical conventional quality control with point and planar dose measurements. METHODS: A cylindrical MAGIC-f gel phantom containing alanine dosimeters (composite phantom) was used to design the VMAT plan in the treatment planning system (TPS). The alanine dosimeters were pellets with radius of 2.5 mm and height of 3 mm, and played the role of brain metastasis inside the gel cylinder, which simulated the cerebral tissue. Five of the alanine dosimeters were selected to simulate five lesions; five planning target volumes (PTVs) were created including the dosimeters and irradiated with different doses. Conventional quality assurance (QA) was performed on the TPS plan and on the composite phantom; a phantom containing only gel (Gel 1 phantom) was also irradiated. One day after irradiation, magnetic resonance images were acquired for both phantoms on a 3T scanner. An electron spin resonance spectrometer was used to evaluate alanine doses. Calibration curves were constructed for the alanine and the gel dosimeters. All the gel only measurement was repeated (Gel 2 phantom) in order to confirm the previous gel measurement. RESULTS: The VMAT treatment plan was approved by the conventional QA. The doses measured by alanine dosimeters on the composite gel phantom agreed to the TPS on average within 3.3%. The alanine dose for each lesion was used to calibrate the gel dosimeter measurements of the concerned PTV. Both gel dose volume histograms (DVH) achieved for each PTV were in agreement with the expected TPS DVH, except for a small discrepancy observed for the Gel 2 curve of PTV1 and the Gel 1 curve of PTV5. In a 3D gamma analyses performed for each PTV volume independently, comparing both the gels' measurements to the TPS and using 3%/3 mm, 5%/2 mm, and 7%/2 mm, more than 90% of the points were approved for all the PTVs, except for the PTV5 comparison in the Gel 1 measurement and for the PTV2 comparison in the Gel 2 measurement. A 3D gamma analysis was also applied for each PTV independently, to compare both gel measurements in order to evaluate the consistence of repeated gel measurements of the same plan, and more than 94.5% of the points were approved. CONCLUSIONS: The composite Gel-Alanine phantom can be used for the end-to-end test of a single isocenter VMAT for simultaneous treatment of multiple brain metastases. The use of the alanine as the lesion cores for the treatment planning provided the precise dose measurements inside each lesion and allowed the conversion of the gel R2 values based on an accurate dose measurement inside the target.

Spine radiosurgery for the local treatment of spine metastases: Intensity-modulated radiotherapy, image guidance, clinical aspects and future directions.

Many cancer patients will develop spinal metastases. Local control is important for preventing neurologic compromise and to relieve pain. Stereotactic body radiotherapy or spinal radiosurgery is a new radiation therapy technique for spinal metastasis that can deliver a high dose of radiation to a tumor while minimizing the radiation delivered to healthy, neighboring tissues. This treatment is based on intensity-modulated radiotherapy, image guidance and rigid immobilization. Spinal radiosurgery is an increasingly utilized treatment method that improves local control and pain relief after delivering ablative doses of radiation. Here, we present a review highlighting the use of spinal radiosurgery for the treatment of metastatic tumors of the spine. The data used in the review were collected from both published studies and ongoing trials. We found that spinal radiosurgery is safe and provides excellent tumor control (up to 94% local control) and pain relief (up to 96%), independent of histology. Extensive data regarding clinical outcomes are available; however, this information has primarily been generated from retrospective and nonrandomized prospective series. Currently, two randomized trials are enrolling patients to study clinical applications of fractionation schedules spinal Radiosurgery. Additionally, a phase I clinical trial is being conducted to assess the safety of concurrent stereotactic body radiotherapy and ipilimumab for spinal metastases. Clinical trials to refine clinical indications and dose fractionation are ongoing. The concomitant use of targeted agents may produce better outcomes in the future.

Spine radiosurgery for the local treatment of spine metastases: Intensity-modulated radiotherapy, image guidance, clinical aspects and future directions

Many cancer patients will develop spinal metastases. Local control is important for preventing neurologic compromise and to relieve pain. Stereotactic body radiotherapy or spinal radiosurgery is a new radiation therapy technique for spinal metastasis that can deliver a high dose of radiation to a tumor while minimizing the radiation delivered to healthy, neighboring tissues. This treatment is based on intensity-modulated radiotherapy, image guidance and rigid immobilization. Spinal radiosurgery is an increasingly utilized treatment method that improves local control and pain relief after delivering ablative doses of radiation. Here, we present a review highlighting the use of spinal radiosurgery for the treatment of metastatic tumors of the spine. The data used in the review were collected from both published studies and ongoing trials. We found that spinal radiosurgery is safe and provides excellent tumor control (up to 94% local control) and pain relief (up to 96%), independent of histology. Extensive data regarding clinical outcomes are available; however, this information has primarily been generated from retrospective and nonrandomized prospective series. Currently, two randomized trials are enrolling patients to study clinical applications of fractionation schedules spinal Radiosurgery. Additionally, a phase I clinical trial is being conducted to assess the safety of concurrent stereotactic body radiotherapy and ipilimumab for spinal metastases. Clinical trials to refine clinical indications and dose fractionation are ongoing. The concomitant use of targeted agents may produce better outcomes in the future.

Role of intra- or periprostatic calcifications in image-guided radiotherapy for prostate cancer.

PURPOSE: Image-guided radiotherapy (IGRT) allows more precise localization of the prostate, thus minimizing errors resulting from organ motion and set-up during treatment of prostate cancer. Using megavoltage cone-beam computed tomography (MVCBCT), references such as bones, the prostate itself or implanted fiducial markers can be used as surrogates to correct patient positioning immediately before each treatment fraction. However, the use of fiducials requires an invasive procedure and may increase costs. We aimed to assess whether intra- or periprostatic calcifications (IPC) could be used as natural fiducials. METHODS AND MATERIALS: Data on patients treated with IGRT for prostate cancer with clearly visible IPC and implanted fiducials in both planning CT and MVCBCT images were reviewed. IPC were classified as central when inside the prostate and peripheral when within the planning target volume. Daily deviations in lateral, longitudinal, and vertical directions from baseline positioning using fiducials and using IPC were compared. RESULTS: A total of 287 MVCBCT images were obtained and analyzed from 10 patients. The mean ± standard deviation daily deviation (mm) in the lateral, longitudinal, and vertical coordinates were 0.55 ± 3.11, 0.58 ± 3.45, and -0.54 ± 4.03, respectively, for fiducials, and 0.72 ± 3.22, 0.63 ± 3.58, and -0.69 ± 4.26, for IPC. The p values for comparisons (fiducials vs. IPC) were 0.003, 0.653, and 0.078 for lateral, longitudinal, and vertical coordinates, respectively. When cases with central IPC were analyzed (n = 7), no significant difference was found in such comparisons. Central IPC and fiducials exhibited a similar pattern of displacement during treatment, with equal values for daily displacements in the three directions for more than 90% of measurements. CONCLUSIONS: Our data suggest that centrally located IPC may be used as natural fiducials for treatment positioning during IGRT for prostate cancer, with potential reductions in the risks and costs associated with fiducial implantation.

Educação a Distância (EaD) em Física Médica / Distance education within medical physics / Educación a Distancia (EaD) en Física Médica

A formação inicial e continuada de profissionais de física médica possui características peculiares por ser uma área interdisciplinar, de evolução tecnológica constante. Em países como o Brasil, existem barreiras como: pequeno número de profissionais, geograficamente mal distribuídos, baixos recursos financeiros, e poucas opções em termos de acesso à informação, dificultando a incorporação e disseminação de novas técnicas que impactam na qualidade do atendimento em saúde. Esta revisão da literatura se propôs a avaliar o papel da EaD na educação de físicos médicos, retratando sua aplicabilidade mediante a identificação de experiências relevantes. Os trabalhos mostram que a EaD tem características interessantes para a área, tais como alta efetividade pedagógica e eficiência econômica, possibilitando o uso massivo de recursos multimídia, com grande abrangência geográfica e de forma gerenciável. Portanto tem potencial para superar as barreiras e suprir carências da área.

Pre-service and in-service education relating to medical physics have peculiar characteristics since this is an interdisciplinary field with constant technological evolution. In countries like Brazil, several barriers exist, such as small numbers of professionals who are geographically poorly distributed, low financial resources and few options for information access, thereby hindering and delaying the incorporation and dissemination of new techniques that could have an impact on healthcare quality. This literature review evaluated the role of distance education within medical physics, and portrayed its applicability through identifying relevant experiences. Studies have shown that distance education within this field presents interesting characteristics, such as high pedagogical effectiveness and economic efficiency, which enables massive use of multimedia resources with wide geographical coverage, in a manageable way. Therefore, distance education has potential to overcome the barriers and meet the needs.

La formación y la educación continua de profesionales en física médica tiene características únicas, es un campo interdisciplinario, donde la tecnología está en evolución constante. Países como Brasil, tienen barreras como: número reducido de profesionales, geográficamente distribuidos de forma desigual, escasos recursos financieros y pocas opciones en términos de acceso a información, dificultando la incorporación y difusión de nuevas técnicas que afectan la calidad de atención en salud. Esta revisión de literatura evalúa el papel de EaD en la educación de físicos médicos, retratando su aplicabilidad mediante identificación de experiencias relevantes. Artículos muestran que EaD tiene características interesantes para la física médica, como alta eficacia pedagógica y eficiencia económica, permitiendo uso masivo de recursos mediáticos, con amplia cobertura geográfica y de forma manejable. Por lo tanto, la herramienta tiene potencial para superar los obstáculos y satisfacer las necesidades del área.