Dosimetric comparison of pencil beam and Monte Carlo algorithms in conformal lung radiotherapy.

PURPOSE: In this study, lung radiotherapy target volumes as well as critical organs such as the lungs, spinal cord, esophagus, and heart doses calculated using pencil beam (PB) and Monte Carlo (MC) algorithm-based treatment planning systems (TPSs) were compared. The main aim was the evaluation of calculated dose differences between the PB and MC algorithms in a highly heterogeneous medium. METHODS: A total of 6 MV photon energy conformal treatment plans were created for a RANDO lung phantom using one PB algorithm-based Precise Plan Release 2.16 TPS and one MC algorithm-based Monaco TPS. Thermoluminescence dosimeters (TLDs) were placed into appropriate slices within the RANDO phantom and then irradiated with an Elekta-Synergy® Linear Accelerator for dose verification. Doses were calculated for the V5, V10, V20, and mean lung doses (MLDs) in bilateral lungs and D50, D98, D2, and mean doses in the target volume (planning target volume, PTV). RESULTS: The minimum, maximum, and mean doses of the target volumes and critical organs in two treatment plans were compared using dose volume histograms (DVHs). The mean dose difference between the PB and MC algorithms for the PTV was 0.3%, whereas the differences in V5, V10, V20, and MLD were 12.5%, 15.8%, 14.4%, and 9.1%, respectively. The differences in PTV coverage between the two algorithms were 0.9%, 2.7% and 0.7% for D50, D98 and D2, respectively. CONCLUSIONS: A comparison of the dose data acquired in this study reveals that the MC algorithm calculations are closer to the 60 Gy prescribed dose for PTV, while the difference between the PB and MC algorithms was found to be non-significant. Because of the major difference arising from the dose calculation techniques by TPS that was observed in the MLD with significant medium heterogeneity, we recommend the use of the MC algorithm in such heterogeneous sites.

Adaptive radiation therapy (art) for patients with limited-stage small cell lung cancer (LS-SCLC): A dosimetric evaluation.

Background: Adaptive radiation therapy (ART) refers to redesigning of radiation therapy (RT) treatment plans with respect to dynamic changes in tumor size and location throughout the treatment course. In this study, we performed a comparative volumetric and dosimetric analysis to investigate the impact of ART for patients with limited-stage small cell lung cancer (LS-SCLC). Methods: Twenty-four patients with LS-SCLC receiving ART and concomitant chemotherapy were included in the study. ART was performed by replanning of patients based on a mid-treatment computed tomography (CT)-simulation which was routinely scheduled for all patients 20-25 days after the initial CT-simulation. While the first 15 RT fractions were planned using the initial CT-simulation images, the latter 15 RT fractions were planned using the mid-treatment CT-simulation images acquired 20-25 days after the initial CT-simulation. In order to document the impact of ART, target and critical organ dose-volume parameters acquired from this adaptive radiation treatment planning (RTP) were compared with the RTP based solely on the initial CT-simulation to deliver the whole RT dose of 60 Gy. Results: Statistically significant reduction was detected in gross tumor volume (GTV) and planning target volume (PTV) during the conventionally fractionated RT course along with statistically significant reduction in critical organ doses with incorporation of ART. Conclusion: One-third of the patients in our study who were otherwise ineligible for curative intent RT due to violation of critical organ dose constraints could be treated with full dose irradiation by use of ART. Our results suggest significant benefit of ART for patients with LS-SCLC.

Optimal timing of thoracic irradiation for limited stage small cell lung cancer: Current evidence and future prospects.

Lung cancer is a global health concern as the leading cause of cancer related mortality worldwide. Small cell lung cancer (SCLC) poses a formidable challenge to the treating physicians with the worst prognosis among all lung cancers. However, limited stage SCLC (LS-SCLC) has a relatively better outcome with multimodality management. Efforts have been focused on optimal integration of treatment modalities to achieve an improved therapeutic ratio for patients with LS-SCLC. While chemotherapy and thoracic radiation therapy (TRT) are primary components of initial management for LS-SCLC, there is no consensus on optimal timing of TRT. Within this context, we herein provide a concise overview of current evidence and future prospects regarding the optimal timing of thoracic irradiation for LS-SCLC in light of the literature.

Concise review of radiosurgery for contemporary management of pilocytic astrocytomas in children and adults.

Pilocytic astrocytoma (PA) may be seen in both adults and children as a distinct histologic and biologic subset of low-grade glioma. Surgery is the principal treatment for the management of PAs; however, selected patients may benefit from irradiation particularly in the setting of inoperability, incomplete resection, or recurrent disease. While conventionally fractionated radiation therapy has been traditionally utilized for radiotherapeutic management, stereotactic irradiation strategies have been introduced more recently to improve the toxicity profile of radiation delivery without compromising tumor control. PAs may be suitable for radiosurgical management due to their typical appearance as well circumscribed lesions. Focused and precise targeting of these well-defined lesions under stereotactic immobilization and image guidance may offer great potential for achieving an improved therapeutic ratio by virtue of radiosurgical techniques. Given the high conformality along with steep dose gradients around the target volume allowing for reduced normal tissue exposure, radiosurgery may be considered a viable modality of radiotherapeutic management. Another advantage of radiosurgery may be the completion of therapy in a usually shorter overall treatment time, which may be particularly well suited for children with requirement of anesthesia during irradiation. Several studies have addressed the utility of radiosurgery particularly as an adjuvant or salvage treatment modality for PA. Nevertheless, despite the growing body of evidence supporting the use of radiosurgery, there is need for a high level of evidence to dictate treatment decisions and establish its optimal role in the management of PA. Herein, we provide a concise review of radiosurgery for PA in light of the literature.

Evaluation of breathing-adapted radiation therapy for right-sided early stage breast cancer patients.

BACKGROUND: Adverse effects of breast irradiation have been an important concern given the increased survival of early stage breast cancer (ESBC) patients with more effective treatments. However, there is paucity of data on the utility of Active Breathing Control (ABC) technique for right-sided ESBC patients. In this study, we assessed the incorporation of ABC into adjuvant Radiation Therapy (RT) of right-sided ESBC patients and report our dosimetric results. METHODS: Thirty-six patients receiving whole breast irradiation followed by a sequential tumor bed boost were included in the study. All patients received field-in-field intensity modulated radiation therapy with incorporation of active breathing control-moderate deep inspiration breath-hold (ABC-mDIBH) after breast conserving surgery. Dose-volume parameters in both plans with and without ABC-mDIBH were compared using Mann-Whitney U test. RESULTS: Mean lung dose decreased from 7 Gy to 5.2 Gy (26% reduction) for the total lung (p < 0.001) and from 12.6 to 9.4 Gy (25% reduction) for the ipsilateral lung (p < 0.001). Mean dose decreased from 4.6 Gy to 1.7 Gy (58% reduction) for liver (p < 0.001) and 1.7 Gy to 1.4 Gy (16% reduction) for the heart (p < 0.001). CONCLUSION: Our study revealed that incorporation of ABC-mDIBH into adjuvant RT of right-sided ESBC patients results in significantly improved critical organ sparing.

Concise review of stereotactic irradiation for pediatric glial neoplasms: Current concepts and future directions.

Brain tumors, which are among the most common solid tumors in childhood, remain a leading cause of cancer-related mortality in pediatric population. Gliomas, which may be broadly categorized as low grade glioma and high grade glioma, account for the majority of brain tumors in children. Expectant management, surgery, radiation therapy (RT), chemotherapy, targeted therapy or combinations of these modalities may be used for management of pediatric gliomas. Several patient, tumor and treatment-related characteristics including age, lesion size, grade, location, phenotypic and genotypic features, symptomatology, predicted outcomes and toxicity profile of available therapeutic options should be considered in decision making for optimal treatment. Management of pediatric gliomas poses a formidable challenge to the physicians due to concerns about treatment induced toxicity. Adverse effects of therapy may include neurological deficits, hemiparesis, dysphagia, ataxia, spasticity, endocrine sequelae, neurocognitive and communication impairment, deterioration in quality of life, adverse socioeconomic consequences, and secondary cancers. Nevertheless, improved understanding of molecular pathology and technological advancements may pave the way for progress in management of pediatric glial neoplasms. Multidisciplinary management with close collaboration of disciplines including pediatric oncology, surgery, and radiation oncology is warranted to achieve optimal therapeutic outcomes. In the context of RT, stereotactic irradiation is a viable treatment modality for several central nervous system disorders and brain tumors. Considering the importance of minimizing adverse effects of irradiation, radiosurgery has attracted great attention for clinical applications in both adults and children. Radiosurgical applications offer great potential for improving the toxicity profile of radiation delivery by focused and precise targeting of well-defined tumors under stereotactic immobilization and image guidance. Herein, we provide a concise review of stereotactic irradiation for pediatric glial neoplasms in light of the literature.

Adaptive radiation therapy of breast cancer by repeated imaging during irradiation.

Breast cancer is the most frequent cancer among females and also a leading cause of cancer related mortality worldwide. A multimodality treatment approach may be utilized for optimal management of patients with combinations of surgery, radiation therapy (RT) and systemic treatment. RT composes an integral part of breast conserving treatment, and is typically used after breast conserving surgery to improve local control. Recent years have witnessed significant improvements in the discipline of radiation oncology which allow for more focused and precise treatment delivery. Adaptive radiation therapy (ART) is among the most important RT techniques which may be utilized for redesigning of treatment plans to account for dynamic changes in tumor size and anatomy during the course of irradiation. In the context of breast cancer, ART may serve as an excellent tool for patients receiving breast irradiation followed by a sequential boost to the tumor bed. Primary benefits of ART include more precise boost localization and potential for improved normal tissue sparing with adapted boost target volumes particularly in the setting of seroma reduction during the course of irradiation. Herein, we provide a concise review of ART for breast cancer in light of the literature.

Breathing adapted radiation therapy for leukemia relapse in the breast: A case report.

BACKGROUND: Infiltration of the breast by leukemic cells is uncommon but may manifest as an oncological emergency requiring prompt management. Extramedullary relapse of T-cell acute lymphoblastic leukemia (T-ALL) within the breast is exceedingly rare and there is paucity of data in the literature regarding this entity. No consensus exists on management of isolated extramedullary breast relapses of T-ALL. Herein, we report a case of isolated extramedullary breast relapse of T-ALL treated with breathing adapted radiation therapy (BART) using the active breathing control (ABC) system. CASE SUMMARY: The patient was a 33-year-old female with diagnosis of T-ALL. She received intensive systemic chemotherapy that resulted in complete remission of her disease, and then underwent allogeneic hematopoietic stem cell transplantation. After a 15 mo period without symptoms and signs of progression, the patient presented with palpable masses in both breasts. She complained from severe pain and swelling of the breasts. Imaging workup showed bilateral breast lesions, and diagnosis of breast infiltration by leukemic cells was confirmed after immunohistopathological evaluation. The patient suffering from severe pain, discomfort, and swelling of both breasts due to leukemic infiltration was referred to the Radiation Oncology Department for symptomatic palliation. Whole breast irradiation was delivered to both breasts of the patient with BART using the ABC system. The patient had complete resolution of her symptoms after treatment with BART. CONCLUSION: BART with the ABC system resulted in complete resolution of the patient's symptoms due to leukemic infiltration of both breasts with T-ALL. This contemporary treatment technique should be preferred for radiotherapeutic management of patients with leukemic infiltration of the breasts to achieve effective symptomatic palliation.

Evaluation of hypofractionated stereotactic radiotherapy (HFSRT) to the resection cavity after surgical resection of brain metastases: A single center experience.

INTRODUCTON: Adjuvant radiotherapy after surgical resection is used for the treatment of patients with brain metastasis. In this study, we assessed the use of adjuvant hypofractionated stereotactic radiotherapy (HFSRT) to the resection cavity for the management of patients with brain metastasis. MATERIALS AND METHODS: A total of 28 patients undergoing surgical resection for their brain metastasis were treated using HFSRT to the resection cavity. A total HFSRT dose of 25-30 Gray (Gy) was delivered in 5 consecutive daily fractions. Patients were retrospectively assessed for toxicity, local control, and survival outcomes. Kaplan-Meier method and log-rank test were used for statistical analysis. RESULTS: Median planning target volume (PTV) was 27.2 cc (range: 6-76.1 cc). At a median follow-up time of 11 months (range: 2-21 months.), 1-year local control rate was 85.7%, and 1-year distant failure rate was 57.1% (16 patients). Median overall survival was 15 months from HFSRT. Higher recursive partitioning analysis class (P = 0.01) and the presence of extracranial metastases (P = 0.02) were associated with decreased overall survival on statistical analysis. There was no radiation necrosis observed during follow-up. CONCLUSION: HFSRT to the resection cavity offers a safe and effective adjuvant treatment for patients undergoing surgical resection of brain metastasis. With comparable local control rates, HFSRT may serve as a viable alternative to whole brain irradiation.

Utility of Molecular Imaging with 2-Deoxy-2-[Fluorine-18] Fluoro-DGlucose Positron Emission Tomography (18F-FDG PET) for Small Cell Lung Cancer (SCLC): A Radiation Oncology Perspective.

BACKGROUND AND OBJECTIVE: Although accounting for a relatively small proportion of all lung cancers, small cell lung cancer (SCLC) remains to be a global health concern with grim prognosis. Radiotherapy (RT) plays a central role in SCLC management either as a curative or palliative therapeutic strategy. There has been considerable progress in RT of SCLC, thanks to improved imaging techniques leading to accurate target localization for precise delivery of RT. Positron emission tomography (PET) is increasingly used in oncology practice as a non-invasive molecular imaging modality. METHODS: Herein, we review the utility of molecular imaging with 2-deoxy-2-[fluorine-18] fluoro-Dglucose PET (18F-FDG PET) for SCLC from a radiation oncology perspective. RESULTS: There has been extensive research on the utility of PET for SCLC in terms of improved staging, restaging, treatment designation, patient selection for curative/palliative intent, target localization, response assessment, detection of residual/recurrent disease, and prediction of treatment outcomes. CONCLUSION: PET provides useful functional information as a non-invasive molecular imaging modality and may be exploited to improve the management of patients with SCLC. Incorporation of PET/CT in staging of patients with SCLC may aid in optimal treatment allocation for an improved therapeutic ratio. From a radiation oncology perspective, combination of functional and anatomical data provided by integrated PET/CT improves discrimination between atelectasis and tumor, and assists in the designation of RT portals with its high accuracy to detect intrathoracic tumor and nodal disease. Utility of molecular imaging for SCLC should be further investigated in prospective randomized trials to acquire a higher level of evidence for future potential applications of PET.

Evaluation of adaptive radiotherapy (ART) by use of replanning the tumor bed boost with repeated computed tomography (CT) simulation after whole breast irradiation (WBI) for breast cancer patients having clinically evident seroma.

PURPOSE: The aim of this study is to evaluate adaptive radiotherapy (ART) by use of replanning the tumor bed boost with repeated computed tomography (CT) simulation after whole breast irradiation (WBI) for breast cancer patients having clinically evident seroma. MATERIALS AND METHODS: Forty-eight patients with clinically evident seroma at the time of planning CT simulation for WBI were included. Two RT treatment plannings were generated for each patient based on the initial CT simulation and tumor bed boost CT simulation to assess seroma and boost target volume (BTV) changes during WBI. Also, dosimetric impact of ART was analyzed by comparative evaluation of critical organ doses in both RT treatment plannings. RESULTS: Median time interval between the two CT simulations was 35 days. Statistically significant reduction was detected in seroma volume and BTV during the conventionally fractionated WBI course along with statistically significant reduction in critical organ doses with ART (p < 0.0001). CONCLUSION: Our data suggest significant benefit of ART by use of replanning the tumor bed boost with repeated CT simulation after WBI for patients with clinically evident seroma.

Hypofractionated stereotactic radiotherapy (HFSRT) for who grade I anterior clinoid meningiomas (ACM).

PURPOSE: While microsurgical resection plays a central role in the management of ACMs, extensive surgery may be associated with substantial morbidity particularly for tumors in intimate association with critical structures. In this study, we evaluated the use of HFSRT in the management of ACM. MATERIALS AND METHODS: A total of 22 patients with ACM were treated using HFSRT. Frameless image guided volumetric modulated arc therapy (VMAT) was performed with a 6 MV linear accelerator (LINAC). The total dose was 25 Gy delivered in five fractions over five consecutive treatment days. Local control (LC) and progression free survival (PFS) rates were calculated using the Kaplan-Meier method. Common Terminology Criteria for Adverse Events, version 4.0 was used in toxicity grading. RESULTS: Out of the total 22 patients, outcomes of 19 patients with at least 36 months of periodic follow-up were assessed. Median patient age was 40 years old (range 24-77 years old). Median follow-up time was 53 months (range 36-63 months). LC and PFS rates were 100 and 89.4 % at 1 and 3 years, respectively. Only two patients (10.5 %) experienced clinical deterioration during the follow-up period. CONCLUSION: LINAC-based HFSRT offers high rates of LC and PFS for patients with ACMs.