Outcomes of Sterotactic Body Radiotherapy (SBRT) for pelvic lymph node recurrences after adjuvant or primary radiotherapy for prostate cancer.

BACKGROUND: There is a paucity of data on the management of recurrent lymph nodes after primary or adjuvant radiotherapy (RT) for prostate cancer (PCa). In this study, we report our tertiary cancer center experience with stereotactic body radiotherapy (SBRT) for the management of pelvic lymph node recurrences after adjuvant or primary RT for PCa. MATERIALS AND METHODS: Patients who underwent SBRT for pelvic lymph node metastases from PCa between 2013 and 2019 were retrospectively assessed for local control (LC), androgen deprivation treatment-free survival (ADT-FS), and toxicity outcomes. The primary endpoint was LC and ADT-FS. The secondary endpoint was late treatment toxicity. RESULTS: Twenty-two lesions of 18 patients receiving SBRT for pelvic lymph node recurrences for PCa between February 2013 and March 2019 were evaluated. At a median follow-up duration of 29.5 months (range: 9-54 months), LC was 95.5% vs. 90.2% at 1 and 2 years, respectively. Ten patients received palliative ADT following SBRT after a median period of 14.5 months (range: 6-31 months). ADT-FS was 72.2% and 54.3% at 1 and 2 years, respectively. Comparative analysis of biologically effective dose (BED) values revealed that higher BED10 values were associated with higher ADT-FS (P = 0.008). ADT-FS was 55.6% and 88.9% for BED10 <50 Gy and for BED10 >50 Gy, respectively (P = 0.008). Assessment of late toxicity outcomes revealed that the most common toxicity was urinary toxicity and fatigue; however, no patient had ≥ grade 3 toxicity. CONCLUSION: Our tertiary cancer center experience confirms the safety and efficacy of SBRT for the management of pelvic lymph node recurrences from PCa.

The novel universal conformity index and unconformity index algorithms for radiotherapy treatment plans.

The purpose of the study is that introduce novel universal Conformity Index (CI) and Unconformity Index (UCIs) Algorithms that can be used for all radiotherapy treatment planning methods. The applicability of existing CIs has been reviewed and analyzed for each radiotherapy plan dose distribution. Novel CI and UCIs have been derived in this study to complement the calculation deficiencies. The novel CI evaluation software has been developed using these algorithms with Eclipse Scripting Application Programing Interface (ESAPI). Also, this software has been tested at clinically case. There are deficiencies in existing CI formulas. Some of currently used CIs only consider the irradiated healthy tissue volume, whereas others solely consider the irradiated tumor volume. The existing CIs can't reveal the cause of unconformity and calculate the unconformity magnitude. In the current study, CI evaluation software were successfully run integrated with TPS. Novel CI and UCIs algorithms introduced in the current study overcome all calculation deficiencies of existing CIs. Results have showed that the novel CI yielding correct results when cold spots has occurred in the tumor volume (TV) and/or healthy tissues has been irradiated was completely compatible with the accepted definitions of the conformity index. Also, it is universally applicable. Besides, cause and magnitude of unconformity in plans can accurately be revealed with the novel UCI algorithms. Thus, what to be done to increase the conformity is well addressed. Novel CI and UCIs can effectively be used as optimization tool to create the best radiotherapy dose distribution.

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.

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.

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.

Dosimetric evaluation of the effect of dental restorative materials in head and neck radiotherapy.

Background: The aim of our study is to assess the dose enhancement from scattered radiation due to dental restorative materials used for occlusal and mesio-occlusal-distal (MOD) cavity filling during simulated head and neck radiotherapy. Methods: We have studied the dose enhancement ratio (DER) of conventional amalgam, high-copper amalgam, and resin composite dental restorative materials at cadaver mandible teeth using 2 therapeutic photon energies of 1.25 MeV (Co-60 gamma ray) and 6 MV (Linac X-ray) for irradiation. Results: DER values at buccal position for Co-60 and 6 MV X-ray were 1.250 ± 0.013 and 1.151 ± 0.012, respectively. For dental cavity fillings, DER values for 6 MV X-ray were 1.065 ± 0.021, 1.100 ± 0.014, and 1.162 ± 0.016 for resin composite filling, low-copper amalgam filling, and high-copper amalgam filling, respectively. Our results revealed that DER regarding irradiation energy was minimum for 6 MV X-rays. With respect to dental restorative filling material, DER was minimum for resin composite filling. Regarding the cavity type, our results with standard deviation (SD) calculations revealed that DER was slightly but not significantly different for both Co-60 gamma ray (1.25 MeV) and 6 MV X-ray energies for both occlusal and MOD cavities. Conclusion: Our dosimetric results for a single beam geometry suggest that, among the three types of filling, resin composite filling is an ideal restorative filling material with minimal morbidity-inducing radiation dose enhancement that may result in increased osteoradionecrosis and secondary caries risk. There is a need for further dosimetric studies with actual clinical beam arrangements.

Single-center outcomes of image-guided radiotherapy in the management of vertebral hemangioma with daily kilovoltage cone-beam computerized tomography.

BACKGROUND: Vertebral hemangiomas are defined as benign proliferation of blood vessels. Vertebral hemangiomas are generally found incidentally by computerized tomography or magnetic resonance imaging; however, they may also cause pain and quality-of-life impairment in some circumstances with reference to their location and association with the spinal cord. In this study, we assessed the utility of image-guided radiation therapy (IGRT) in the management of patients with painful vertebral hemangioma. MATERIALS AND METHODS: Patients receiving IGRT for the management of painful vertebral hemangioma were evaluated. The total dose was 24 Gy delivered in 12 daily fractions. The verbal numeric scale (VNS) was used for the assessment of pain relief. The median follow-up duration was 13 months (range: 6-24 months). RESULTS: Median preradiotherapy VNS score was 8 (range: 6-10) and median postradiotherapy VNS score was 1 (range: 0-2) for the total 135 patients treated with IGRT at our department for painful vertebral hemangioma. Reduction in VNS scores after IGRT was statistically significant (P < 0.05). CONCLUSION: Our single-center study revealed that IGRT resulted in substantial relief of pain from vertebral hemangioma. Randomized prospective multicenter trials are needed to shed light on the optimal management of patients suffering from pain due to vertebral hemangioma.

Evaluation of patient organ doses from kilovoltage cone-beam CT imaging in radiation therapy.

BACKGROUND: Currently, CBCT system is an indispensable component of radiation therapy units. Because of that, it is important in treatment planning and diagnosis. CBCT is also an crucial tool for patient positioning and verification in image-guided radiation therapy (IGRT). Therefore, it is critical to investigate the patient organ doses arising from CBCT imaging. The purpose of this study is to evaluate patient organ doses and effective dose to patients from three different protocols of Elekta Synergy XVI system for kV CBCT imaging examinations in image guided radiation therapy. MATERIALS AND METHODS: Organ dose measurements were done with thermoluminescent dosimeters in Alderson RA NDO male phantom for head & neck (H&N), chest and pelvis protocols of the Elekta Synergy XVI kV CBCT system. From the measured organ dose, effective dose to patients were calculated according to the International Commission on Radiological Protection 103 report recommendations. RESULTS: For H&N, chest and pelvis scans, the organ doses were in the range of 0.03-3.43 mGy, 6.04-22.94 mGy and 2.5-25.28 mGy, respectively. The calculated effective doses were 0.25 mSv, 5.56 mSv and 4.72 mSv, respectively. CONCLUSION: The obtained results were consistent with the most published studies in the literature. Although the doses to patient organs from the kV CBCT system were relatively low when compared with the prescribed treatment dose, the amount of delivered dose should be monitored and recorded carefully in order to avoid secondary cancer risk, especially in pediatric examinations.

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.

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.

Comparative Evaluation of Topical Corticosteroid and Moisturizer in the Prevention of Radiodermatitis in Breast Cancer Radiotherapy.

BACKGROUND: Radiodermatitis is a frequent side effect of breast cancer radiotherapy (RT). Treating radiation oncologist should know the prevention and treatment of every grade of radiodermatitis. AIMS: The aim of this study was to compare the topical corticosteroid and moisturizer usage in breast cancer RT. MATERIALS AND METHODS: Fifty patients with early-stage breast cancer undergoing breast-conserving surgery referred to our department for adjuvant RT between October 2009 and October 2016 were compared with regard to topical steroid or moisturizer usage. Patients were followed up weekly after the start of treatment. RESULTS: Mean age was 46 years. Twenty-four patients had stage 1 breast cancer and 26 patients had stage 2 disease. KPS (Karnofsky performance score) was 100 for all patients. Five patients (20.8%) had grade 2 and seven (29.1%) patients had grade 1 acute radiodermatitis in the first group. Eleven (42.3%) patients had grade 2 and 12 (46.1%) patients had grade 1 acute radiodermatitis in the second group. Thirteen (54.1%) patients in the first group had no acute radiodermatitis and three (11.5%) patients in the second group had no acute radiodermatitis. No patient in either group experienced grade 3 radiodermatitis. CONCLUSIONS: Daily use of topical betamethasone for breast cancer RT improves dermal sparing, reduces acute radiodermatitis, and may be recommended for patients receiving RT to the breast.

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.

Fractionated stereotactic radiosurgery for locally recurrent brain metastases after failed stereotactic radiosurgery.

AIMS AND BACKGROUND: There is scant data on the utility of repeated radiosurgery for management of locally recurrent brain metastases after upfront stereotactic radiosurgery (SRS). Most studies have used single-fraction SRS for repeated radiosurgery, and the use of fractionated stereotactic radiosurgery (f-SRS) in this setting has been poorly addressed. In this study, we assessed the utility of f-SRS for the management of locally recurrent brain metastases after failed upfront single-fraction SRS and report our single-center experience. METHODS AND STUDY DESIGN: A total of 30 patients receiving f-SRS for locally recurrent brain metastases after upfront single-fraction SRS at our department between September 2011 and September 2017 were retrospectively evaluated for local control (LC), toxicity, and overall survival outcomes. RESULTS: Median age and Karnofsky performance status were 57 (range: 38-78 years) and 80 (range: 70-100) at repeated radiosurgery (SRS2). The median time interval between the two radiosurgery applications was 13.5 months (range: 3.7-49 months). LC after SRS2 was 83.3%. Radionecrosis developed in 4 of the 30 lesions after SRS2, and total rate of radionecrosis was 13.3%. Statistical analysis revealed that the volume of planning target volume (PTV) at SRS2 was significantly associated with radionecrosis (P = 0.014). The volume of PTV was >13 cm3 at SRS2 in all patients with radionecrosis. CONCLUSION: A repeated course of radiosurgery in the form of f-SRS may be a viable therapeutic option for the management of locally recurrent brain metastases after failed upfront SRS with high LC rates and an acceptable toxicity profile despite the need for further supporting evidence.

A Concise Review of Pelvic Radiation Therapy (RT) for Rectal Cancer with Synchronous Liver Metastases.

BACKGROUND AND OBJECTIVE: Colorectal cancer is a major health concern as a very common cancer and a leading cause of cancer-related mortality worldwide. The liver is a very common site of metastatic spread for colorectal cancers, and, while nearly half of the patients develop metastases during the course of their disease, synchronous liver metastases are detected in 15% to 25% of cases. There is no standardized treatment in this setting and no consensus exists on optimal sequencing of multimodality management for rectal cancer with synchronous liver metastases. METHODS: Herein, we review the use of pelvic radiation therapy (RT) as part of potentially curative or palliative management of rectal cancer with synchronous liver metastases. RESULTS: There is accumulating evidence on the utility of pelvic RT for facilitating subsequent surgery, improving local tumor control, and achieving palliation of symptoms in patients with stage IV rectal cancer. Introduction of superior imaging capabilities and contemporary RT approaches such as Intensity Modulated Radiation Therapy (IMRT) and Image Guided Radiation Therapy (IGRT) offer improved precision and toxicity profile of radiation delivery in the modern era. CONCLUSION: Even in the setting of stage IV rectal cancer with synchronous liver metastases, there may be potential for extended survival and cure by aggressive management of primary tumor and metastases in selected patients. Despite lack of consensus on sequencing of treatment modalities, pelvic RT may serve as a critical component of multidisciplinary management. Resectability of primary rectal tumor and liver metastases, patient preferences, comorbidities, symptomatology, and logistical issues should be thoroughly considered in decision making for optimal management of patients.

Investigating the effect of dental implant materials with different densities on radiotherapy dose distribution using Monte-Carlo simulation and pencil beam convolution algorithm.

OBJECTIVES: The aim of this study was to investigate the effect of dental implant materials with different physical densities on dose distribution for head and neck cancer radiotherapy planning. METHODS: Titanium (Ti), Titanium alloy (Ti-6Al-4V), Zirconia (Y-TZP), Zirconium oxide (ZrO2), Alumina (Al2O3) and polyetheretherketone (PEEK) dental implant materials were used for determination of implant material effect on dose distribution. Dental implant effect was investigated by using pencil beam convolution (PBC) algorithm of Eclipse treatment planning systems (TPS) and Monte Carlo (MC) simulation technique. 6 MV photon beam of the Varian 2300 C/D linear accelerator was simulated by EGSnrc-based BEAMnrc MC code system. RESULTS: Reasonable consistency was determined for percentage depth dose (PDD) curves between MC simulation and water phantom measurements at 6.4 MeV initial electron energy. The consistency between modelled linear accelerator PDD curve calculations and water-phantom PDD measurements were compatible within 1 % range. The dose increase in front of the dental implant calculated by MC simulation is in the range of 0.4-20.2%. We found by MC and PBC calculations that the differences in dose increase in front of the dental implant materials is in the range of 0.1-17.2% and is dependent on the physical density of the dental implant. CONCLUSIONS: Dose increase for Zirconia was noted to be maximum while PEEK implant dose increase was minimum among the whole dental implant materials studied. This study revealed that the Eclipse TPS PBC algorithm could not accurately estimate the backscatter radiation from dental implant materials.

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.

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.

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.