Intensity-modulated radiation therapy for orbital lymphoma

Purpose: Orbital manifestations of non-Hodgkin\u27s lymphoma (NHL) are rare and accounts for only 1% of all cases of NHL. There have been no reports of treating orbital lymphoma using intensity-modulated radiotherapy (IMRT). Materials and methods: Four patients were treated at our institution for orbital lymphoma using IMRT. Radiotherapy (RT) plans using wedged pair fields were developed for comparison. Clinical results using IMRT are presented and a dosimetric analysis between IMRT and RT was performed. Results: All patients had a complete response based on their physical examinations and post-IMRT imaging. Symptoms that had been present at initial presentation resolved in all patients during the course of the treatment. All four patients experienced only grade 1 dry eye syndrome and keratitis. The average dose to the contralateral orbit, lacrimal gland, and lens were all significantly reduced (P \u3c 0.01) in IMRT patients as compared to the RT patients. IMRT reduced the V5 and V10 for the contralateral lens, orbit, and lacrimal gland and the optic chiasm (P \u3c 0.05). Conclusion: IMRT is feasible when treating orbital lymphoma and reduces dose to critical structures while providing excellent dose coverage of target volumes. IMRT offers patients with orbital lymphoma excellent clinical outcomes, similar to conventional RT, with no increased toxicity. © 2008 Japan Radiological Society

A Novel Method of Island Blocking in Whole Abdominal Radiotherapy Using a Modified Electronic Tissue Compensation Technique

Traditionally, large fields requiring island blocking used external beam radiation therapy (EBRT) with Cerrobend blocks to limit dose to the critical structures. It is laborious to construct blocks and use them on a daily basis. We present a novel technique for island blocking using a modified electronic tissue compensation (MECOMP) technique. Five patients treated at our institution were selected for this study. The study compared two planning techniques: a novel MECOMP and a conventional EBRT technique. Conventional fields were defined using anterior-posterior and posterior-anterior (PA) fields. The kidneys were contoured and an aperture cut-out block was fitted to the OAR with a 1-cm margin (OARCTV) and placed in the PA field. A dynamic multileaf collimation (DMLC) plan with ECOMP was developed using identical beam and blocking strategy; this tissue compensation-based fluence map was modified to deliver a zero dose to the CTVOAR from the PA field. There were no significant differences in the mean, maximum, and minimum doses to the right or left kidney between the two methods. The mean, maximum, and minimum doses to the peritoneal cavity were also not significantly different. The number of monitor units (MUs) required was increased using the MECOMP (273 vs. 1152, p \u3c 0.01). The MECOMP is effectively able to deliver DMLC-based radiotherapy, even with island blocks present. This novel use of MECOMP for whole abdominal radiotherapy should substantially reduce the labor, daily treatment time, and treatment-related errors through the elimination of cerrobend blocks. © 2010 American Association of Medical Dosimetrists

Improvement in dose homogeneity with electronic tissue compensation over IMRT and conventional RT in whole brain radiotherapy

Background and purpose: To perform a dosimetric analysis of whole brain radiotherapy using electronic tissue compensation (ECOMP) with dynamic multileaf collimation (dMLC) and its comparisons with inverse-planned intensity modulated radiation therapy (IMRT) with optimization constraints and conventional whole brain radiotherapy (WBRT). Materials and methods: Ten patients (6 adult, 4 pediatric) who were treated at our institution were selected for this study. WBRT fields were defined using opposed lateral fields directed at the intracranial contents and MLC leaves were used to block the critical normal structures. A two-field inverse-planned IMRT plan was then developed using sliding window technique and two optimization constraints. Finally, a dMLC plan with electronic tissue compensation (ECOMP) was developed using identical beam and collimator angles and blocking strategy; the fluence map was generated based on tissue compensation and no additional constraints were given for optimization purposes. This tissue compensation based fluence map was applied to deliver a homogenous dose to the intracranial contents. Radiation dose was identically prescribed to the isocenter (30.0 Gy in 10 fractions) for all the cases. A dosimetric comparison was then performed for each method in our patient population. Results: ECOMP significantly reduced the mean maximum dose (Dmax) to the intracranial contents as compared to both WBRT (103.9% vs. 112.4%, p \u3c 0.0001) and IMRT (106.1%, p = 0.02). ECOMP also reduced the intracranial volume receiving greater than 103% of the prescribed dose (2.6% vs. 54.9%, p \u3c 0.0001) and the intracranial volume receiving greater than 105% of the prescribed dose (0% vs. 26%, p \u3c 0.0001) as compared to WBRT; there was no statistical difference in these two parameters between ECOMP and IMRT. The mean number of monitor units was increased, however, using both ECOMP and IMRT as compared to WBRT (870 and 860 vs. 318, p \u3c 0.0001). Conclusions: Dynamic multileaf collimation with electronic tissue compensation (ECOMP) leads to improved dose homogeneity with less \u27hot spots\u27 as compared to conventional and inverse-planned intensity modulated whole brain radiotherapy. At our institution, ECOMP is being used in all pediatric patients or select adult patients with a long life expectancy requiring cranial radiotherapy. © 2008 Elsevier Ireland Ltd. All rights reserved

Optimization of couch translational corrections to compensate for rotational and deformable target deviations in image guided radiotherapy

The utilization of image-guided radiotherapy (IGRT) technologies helps correct temporal and spatial deviations of the target volume relative to planned radiation beams. With the aid of these IGRT technologies, it becomes possible to better identify the target volume before and even during radiation treatment. However, since components of the detected deviations may be translational, rotational, and deformable, the question remains whether simple treatment-couch translational movement can be optimized to compensate for these complicated deviations. Deviation of the target volume and changes in patient body shape from that acquired for treatment planning may further add to the variations from planned dose distribution. In this study, an optimization strategy is developed to investigate these issues. The optimization process involved the use of the hill climbing algorithm, the detected target volume and patient body shape, and the dose distribution based on acquired images at treatment. During the process, the planned dose distribution was iteratively adjusted to reflect the changes of depth and distance as the translational treatment couch movement was being optimized. The optimal treatment couch movement was considered achieved when the highest fraction of the detected target volume was covered by prescription dose. This optimization strategy was evaluated on clinical prostate cancer cases. For each of the cases, cone beam computed tomography (CBCT) images were acquired right after fiducial marker-based kilovolt orthogonal imaging verification and setup adjustment. Based on the CBCT images, the clinical target volume at the treatment was delineated and the translational treatment-couch movements were optimized with the developed strategy. The resultant dose coverage was compared to that without the optimization. The results showed that with the present strategy, rotational and deformable target deviations can be further compensated with translational couch correction. © 2008 American Association of Physicists in Medicine

Lumpectomy closure technique does not affect dosimetry in patients undergoing external-beam-based accelerated partial breast irradiation

Background: During the breast lumpectomy procedure, surgeons traditionally elect to use either a superficial or full-thickness closure when sealing the wound depending on surgeon preference as well as desired outcomes. The purpose of this study was to examine dosimetric endpoints in patients with superficial versus full-thickness closures with accelerated partial breast irradiation (APBI). Methods: Patients who underwent breast conservation surgery followed by 3D conformal external-beam APBI were identified (n = 45) and were separated according to the type of cavity closure performed: superficial and full thickness. Data gathered from the retrospective review of patient charts was analyzed according to criteria in the NSABP B-39 protocol in order to quantify the amount of radiation delivered to organs at risk. The patient seroma cavity was further given a cavity visualization score to assess the impact of wound closure on treatment planning. Results: There was no significant difference in the mean CVS score for the 2 groups. There were no statistical differences in all dosimetric endpoints compared for the 2 types of closure, and both groups met NSABP B-39 guidelines for the ipsilateral breast, heart, and ipsilateral lung dosimetry. Conclusions: We found no significant difference in dosimetric outcomes in either the superficial or deep closure treatment groups. Breast surgeons should not alter their preferred closure strategy in anticipation of 3D-CRT APBI. © 2012 Society of Surgical Oncology

Risk of leptomeningeal carcinomatosis in patients with brain metastases treated with stereotactic radiosurgery

© 2017, Springer Science+Business Media, LLC, part of Springer Nature. There is limited available literature examining factors that predispose patients to the development of LMC after stereotactic radiosurgery (SRS) for brain metastases. We sought to evaluate risk factors that may predispose patients to LMC after SRS treatment in this case–control study of patients with brain metastases who underwent single-fraction SRS between 2011 and 2016. Demographic and clinical information were collected retrospectively for 19 LMC cases and 30 controls out of 413 screened patients with brain metastases. Risk factors of interest were evaluated by univariate and multivariate logistic regression analyses and overall survival rates were evaluated by Kaplan–Meier survival analysis. About 5% of patients with brain metastases treated with SRS developed LMC. Patients with LMC (median 154 days, 95% CI 33–203 days) demonstrated a poorer overall survival than matched controls (median 417 days, 95% CI 121–512 days, p = 0.002). The most common primary tumor histologies that lead to the development of LMC were non-small cell lung cancer (36.8%), breast cancer (26.3%), and melanoma (21.1%). No association was found between the risk of LMC and the location of the brain lesion or total volume of brain metastases. Prior surgical resection of brain metastases before SRS was associated with a 6.5 times higher odds (95% CI 1.45–29.35, p = 0.01) of developing LMC post-radiosurgery compared to those with no prior resections of brain metastases. Additionally, adjuvant WBRT may help to reduce the risk of LMC and can be considered in decision-making for patients who have had brain metastasectomy