Use Of Linear Accelerator Research Articles

PO18: An Efficient and Reproducible Autoradiography Technique for HDR-Gynecological Applicators Commissioning

<h3>Purpose</h3> High Dose Rate (HDR) brachytherapy commissioning of Elekta's gynecological (Gyn) applicator sets include a large inventory of CT/MR compatible plastic, applicator tubes of varying shapes and sizes. This often present a challenge to the efficiency of source autoradiography - an essential test to determine and verify final dwell position of the HDR source and its positioning/stepping accuracy. We present a technique of acquiring radiograph-autoradiograph combinations of HDR-Gyn applicators that allows testing of several applicators simultaneously, in a rigid and reproducible set-up. <h3>Materials Methods</h3> Elekta provides x-ray catheter (marker) sets as a required accessory to verify source positioning inside Gyn applicators. Once the markers are calibrated & Final Marker Position (FMP) characterized, using Elekta's Source Position Check Ruler & CT-scans, the technique of radiograph-autoradiograph superposition is recommended for determination of final dwell position (FDP) & verification of source positioning accuracy. To ensure a rigid & reproducible set-up, template trays to hold multiple applicator tubes & Gafochromic EBT3 film for recording multiple radiographs in unison were built using Styrofoam. Channels were carved in styrofoam creating tight narrow groves fitting applicators in place. Applicators were taped with tips laid flat & flush with the film secured to styrofoam base independently. Primary advantage of using styrofoam is that it offers no backscatter to radiography as well as gamma photons from the Ir-192 source. Additionally, it is readily available and easy to work with. Each tray held 4-6 applicators with markers allowing a simultaneous radiograph acquisition, &∼ 5 cm lateral spacing enabled independent images. Truebeam^TM Linear accelerator was used for radiography. Multiple pre-prepared template trays with applicators were exposed at a source-to-film-distance of 100 cm with 400 monitor units using 2.5 MV imaging beam. This technique provided best visualization of the plastic applicator & marker on a gafochromic EBT3 film. Once the multiple-applicator-radiograph is acquired, templates were transported to adjacent HDR suite, set on a rigid couch, markers carefully removed & transfer tube connected for acquisition of autoradiograph coincident with recently acquired radiograph, using Flexitron afterloader. For Ir-192 source's autoradiograph, a 10-15 seconds dwell time is adequate to darken film with marker visualization reasonably intact for analysis. Pre-prepared templates and availability of personnel allowed simultaneous use of linear accelerator & afterloader, for radiograph & autoradiograph acquisition, adding further efficiency. Source positioning & stepping accuracy was verified by coincidence of center of darkening at the exposed dwell-position & center of visualized markers, on a viewbox illuminator. <h3>Results</h3> Using techniques and workflow developed, 60 CT/MR compatible HDR-Gyn plastic applicators were commissioned. Autoradiography-radiography superposition with x-ray markers enabled verification of Elekta specified distances between the outer tip of the IU/ovoid tubes, inner tip & the final dwell position, & HDR source positioning & stepping accuracy within 1 mm. Figure 1-A shows Styrofoam templates with multiple channels for affixing applicators over EBT3 Gafochromic film for radiography, 1-B is HDR room setup for autoradiography and 1-C shows images of multiple different applicator tubes depicting the radiograph-autoradiograph overlay with marker visualization and HDR source positioning. <h3>Conclusion</h3> We present an efficient autoradiography technique for commissioning of a large inventory HDR-Gyn plastic applicators using a linear accelerator & HDR afterloader.

Detection of rotational errors in single-isocenter multiple-target radiosurgery: Is a routine off-axis Winston-Lutz test necessary?

PurposeRecently the use of linear accelerator (linac)‐based stereotactic radiosurgery (SRS) has increased, including single‐isocenter multiple‐target SRS. The workload of medical physicists has grown as a result and so has the necessity of maximizing the efficiency of quality assurance (QA). This study aimed to determine if measurement‐based patient‐specific QA with a high‐spatial‐resolution dosimeter is sensitive to rotational errors, potentially reducing the need for routine off‐axis Winston–Lutz (WL) testing.MethodsThe impact of rotational errors along gantry, couch, and collimator axes on dose coverage of the gross tumor volume (GTV) and planning target volume (PTV) was determined with a 1‐mm GTV/PTV expansion margin. Two techniques, the off‐axis WL test using the StereoPHAN MultiMet‐WL Cube (Sun Nuclear Corporation, Melbourne, Florida, USA) and patient‐specific QA using the SRS MapCHECK (Sun Nuclear Corporation, Melbourne, Florida, USA), were assessed on their ability to detect introduced errors before target coverage was compromised. These findings were also considered in the context of routine machine QA of rotational axis calibrations.ResultsRotational errors significantly impacted PTV dose coverage, especially in the couch angle. GTV dose coverage remained unaffected except for with large couch angle errors (≥1.5°). The off‐axis WL test was shown to be sensitive to rotational errors with results consistently exceeding tolerance levels when or before coverage fell below departmentally accepted limits. Although patient‐specific QA using the SRS MapCHECK was previously validated for SRS, this study showed inconsistency in detection of rotational errors.ConclusionsIt is recommended that off‐axis WL testing be conducted regularly to supplement routine monthly machine QA, as it is sensitive to errors that patient‐specific QA may not detect. This frequency should be determined by individual departments, with consideration of GTV–PTV margins used, limitations on target off‐axis distances, and routine mechanical QA results for particular linacs.

Late Sequelae of Radiotherapy—The Effect of Technical and Conceptual Innovations in Radiation Oncology.

Approximately half of all patients with tumors need radiotherapy. Long-term survivors may suffer from late sequelae of the treatment. The existing radiotherapeutic techniques are being refined so that radiation can be applied more precisely, with the goal of limiting the radiation exposure of normal tissue and reducing late sequelae. This review is based on the findings of a selective search in PubMed for publications on late sequelae of conventional percutaneous radiotherapy, January 2000 to May 2020. Late sequelae affecting the central nervous system, lungs, and heart and the development of second tumors are presented, and radiobiological mechanisms and the relevant technical and conceptual considerations are discussed. The current standard of treatment involves the use of linear accelerators, intensity-modulated radiotherapy (IMRT), image-guided and respiratory-gated radiotherapy, and the integration of positron emission tomography combined with computed tomography (PET-CT) in radiation treatment planning. Cardiotoxicity has been reduced with regard to the risk of coronary heart disease after radiotherapy for Hodgkin's lymphoma (hazard ratio [HR] 0.44 [0.23; 0.85]). It was also found that the rate of radiation- induced pneumonitis dropped from 7.9% with conformal treatment to 3.5% with IMRT in a phase III lung cancer trial. It is hoped that neurocognitive functional impairment will be reduced by hippocampal avoidance in modern treatment planning: an initial phase III trial yielded a hazard ratio of 0.74 [0.58; 0.94]. It is estimated that 8% of second solid tumors in adults are induced by radiotherapy (3 additional tumors per 1000 patients at 10 years). Special challenges for research in this field arise from the long latency of radiation sequelae and the need for largescale, well-documented patient collectives in order to discern dose-effect relationships, and take account of cofactors, when the overall number of events is small. It is hoped that further technical and conceptual advances will be made in the areas of adaptive radiotherapy, proton and heavy-ion therapy, and personalized therapy.

Use of a Linear Accelerator for Conducting In Vitro Radiobiology Experiments.

Radiation therapy remains one of the cornerstones of cancer management. For most cancers, it is the most effective, nonsurgical therapy to debulk tumors. Here, we describe a method to irradiate cancer cells with a linear accelerator. The advancement of linear accelerator technology has improved the precision and efficiency of radiation therapy. The biological effects of a wide range of radiation doses and dose rates continue to be an intense area of investigation. Use of linear accelerators can facilitate these studies using clinically relevant doses and dose rates.

PCN113 - Economic Evaluation of the Use of Linear Accelerator of Electrons for Intraoperative Radiotherapy in the Treatment of Rectal Cancer in Mexico

PCN113 - Economic Evaluation of the Use of Linear Accelerator of Electrons for Intraoperative Radiotherapy in the Treatment of Rectal Cancer in Mexico

THE ALGORITHM FOR DETERMINING TIMING OF RADIOTHERAPY SESSION COMPONENTS FOR DIFFERENT METHODS OF ONCOLOGY PATIENTS IRRADIATION AT THE STAGE OF RADIOTHERAPY PLANNING

One of the main factors affecting the efficiency of oncology patients radiation therapy are time parameters (the amount of time that a patient spends in the therapy room) of the patient exposure session, because the patient treatment position depends on them, and thus the accuracy of delivery of the prescribed dose distribution too. The objective of this work was to define components that influence on the treatment session and to develop an algorithm that allows to determine the duration of the patient treatment sessions with the use of different methods of radiotherapy and tumor localization. In order to determine radiation therapy session components, that cause the dominant influence on the session timing, the authors carried out a retrospective analysis of each fraction of the total sample of cancer patients treatment plans with most often irradiated with the use of linear accelerators in the NCCB localizations of tumors (more than 5200 fractions). The appropriate algorithms were designed to assess the results of the analysis of time parameters of radiation therapy oncology patient session during its pre-radiation preparation. It allowed to take into account the individual characteristics of radiation treatment for each irradiation techniques that are the most useful in clinical practice of NCCB radiotherapy department.The components of radiation therapy sessions that caused dominant influence on session characteristics using methods of three-dimensional conformal radiation therapy (3D CRT), intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) were identified. The characteristics of the linear accelerator and the irradiation plan that influenced the duration of these components (number of radiation fields, dose affecting devices placement, treatment table rotation, treatment field irradiation duration, verification of patient positioning, treatment parameters initialization) were defined. Average exposure time is established for each of the examined methods of radiotherapy and localizations of tumor (from 4 to 8 min for 3D CRT, from 4 to 8 min for IMRT for 3 to 4 min for VMAT).

방사선치료기기 정도관리를 위한 광도전체 센서 제작 및 평가

최근 다엽콜리메이터를 부착한 선형가속기를 이용한 방사선수술의 빈도가 점차 높아지고 있다. 이러한 정교한 방사선 수술은 소조사면 내에 고선량의 방사선이 집중적으로 조사되기 때문에 체계적이고 정확한 정도관리가 필수적이다. 본 연구는 PIB(Particle in Binder) 방식 중 침전법을 이용하여 <TEX>$400{\mu}m$</TEX> 두께의 요오드화납(<TEX>$PbI_2$</TEX>)과 요오드화수은(<TEX>$HgI_2$</TEX>) 광도전체 센서 시편를 제작하였다. 제작된 시편의 전기적 특성은 암전류, 출력전류, 응답특성 및 선형성을 평가하였다. 평가 결과, <TEX>$HgI_2$</TEX> 가 우수한 신호발생량과 선형성을 보였다. 끝으로, 두께에 따른 <TEX>$HgI_2$</TEX> 센서의 신호반응 특성 결과, <TEX>$400{\mu}m$</TEX> 두께에서 신호발생효율이 가장 높았고, <TEX>${\pm}2.5%$</TEX> 이내의 우수한 재현성을 보였다. Recently, a use of linear accelerator with a multi-leaf collimator(MLC) for radiation therapy is increasing. The importance of quality assurance (QA) for the linear accelerator is emphasized as the side effects of the inaccurate delivery of the radiation beam has been increased according to the high dose irradiation technique. In this study, The <TEX>$HgI_2$</TEX> and <TEX>$PbI_2$</TEX> photoconductor layer samples of <TEX>$400{\mu}m$</TEX> thickness were fabricated using sedimentation method among particle-in-binder technology. From the fabricated samples, the electrical properties(dark current, output current, response properties and linearity) were investigated. From the experimental results, <TEX>$HgI_2$</TEX> has good charge signal generation and linearity. Finally, from the signal response results about various thickness of <TEX>$HgI_2$</TEX> sensor, the signal creation efficiency of <TEX>$400{\mu}m$</TEX> thickness of <TEX>$HgI_2$</TEX> sensor has the highest value and the excellent reproducibility below <TEX>${\pm}2.5%$</TEX>.

Surface dose variations in 6 and 10 MV flattened and flattening filter-free (FFF) photon beams.

As the use of linear accelerators operating in flattening filter‐free (FFF) modes becomes more widespread, it is important to have an understanding of the surface doses delivered to patients with these beams. Flattening filter removal alters the beam quality and relative contributions of low‐energy X‐rays and contamination electrons in the beam. Having dosimetric data to describe the surface dose and buildup regions under a range of conditions for FFF beams is important if clinical decisions are to be made. An Elekta Synergy linac with standard MLCi head has been commissioned to run at 6 MV and 10 MV running with the flattening filter in or out. In this linac the 6 MV FFF beam has been energy‐matched to the clinical beam on the central axis (D10). The 10 MV beam energy has not been adjusted. The flattening filter in both cases is replaced by a thin (2 mm) stainless steel plate. A thin window parallel plate chamber has been used to measure a comprehensive set of surface dose data in these beams for variations in field size and SSD, and for the presence of attenuators (wedge, shadow tray, and treatment couch). Surface doses are generally higher in FFF beams for small field sizes and lower for large field sizes with a crossover at 10×10 cm2 at 6 MV and 25×25 cm2 at 10 MV. This trend is also seen in the presence of the wedge, shadow tray, and treatment couch. Only small differences (<0.5%) are seen between the beams on varying SSD. At both 6 and 10 MV the filter‐free beams show far less variation with field size than conventional beams. By removing the flattening filter, a source of contamination electrons is exchanged for a source of low‐energy photons (as these are no longer attenuated). In practice these two components almost balance out. No significant effects on surface dose are expected by the introduction of FFF delivery.PACS number(s): 87.53.Bn, 87.55.ne, 87.56.bd

The use of linear accelerator with RapidArc option for the purposes of stereotactic radiotherapy for lung cancer

In this introductory lecture of the Symposium, essential knowledge concerning biological mechanisms of post highradiation dose will be present. Emerging evidence suggests that distinct mechanisms of cell death, likely including a major contribution from vascular epithelial cell apoptosis (devascularizing effect), might play an important role in the success of SBRT in controlling tumors. Also “5Rs” of conventional fractionated RT will be discussed in aspect of SBRT, including new pathways of tumor clonogen repopulation, i.e. “phoenix rising”, as well as constructing SBRT cell survival curve attempts. However, studies taken toward maximizing this effect should also be designed with the cautionary awareness that tissue regenerative processes might also be triggered as a result.

Linear Accelerator Stereotactic Radiosurgery for Trigeminal Neuralgia

Background: Stereotactic radiosurgery is accepted as an alternative for patients with refractory trigeminal neuralgia, but existing evidence is fundamentally based on the Gamma Knife, which is a specific device for intracranial neurosurgery, available in few facilities. Over the last decade it has been shown that the use of linear accelerators can achieve similar diagnostic accuracy and equivalent dose distribution. Objectives: To assess the effectiveness and safety of linear-accelerator stereotactic radiosurgery for the treatment of patients with refractory trigeminal neuralgia. Methods: We carried out a systematic search of the literature in the main electronic databases (PubMed, Embase, ISI Web of Knowledge, Cochrane, Biomed Central, IBECS, IME, CRD) and reviewed grey literature. All original studies on the subject published in Spanish, French, English, and Portuguese were eligible for inclusion. The selection and critical assessment was carried out by 2 independent reviewers based on pre-defined criteria. In view of the impossibility of carrying out a pooled analysis, data were analyzed in a qualitative way. Results: Eleven case series were included. In these, satisfactory pain relief (BIN I-IIIb or reduction in pain ≥ 50) was achieved in 75% to 95.7% of the patients treated. The mean time to relief from pain ranged from 8.5 days to 3.8 months. The percentage of patients who presented with recurrences after one year of follow-up ranged from 5% to 28.8%. Facial swelling or hypoesthesia, mostly of a mild-moderate grade appeared in 7.5% – 51.9% of the patients. Complete anaesthesia dolorosa was registered in only study (5.3%). Cases of hearing loss (2.5%), brainstem edema (5.8%), and neurotrophic keratoplasty (3.5%) were also isolated. Conclusions: The results suggest that stereotactic radiosurgery with linear accelerators could constitute an effective and safe therapeutic alternative for drug-resistant trigeminal neuralgia. However, existing studies leave important doubts as to optimal treatment doses or the therapeutic target, long-term recurrence, and do not help identify which subgroups of patients could most benefit from this technique. Limitations: Paucity of literature and clear lack of clarification for clinical utilization of this technique. Key words: Radiosurgery, trigeminal neuralgia, functional radiosurgery, radiation therapy of benign diseases, stereotactic radiotherapy

Evaluation of Linear Accelerator (Linac)-Based Stereotactic Radiosurgery (Srs) for The Treatment of Craniopharyngiomas

Although benign histologically, craniopharyngiomas may display clinically malignant behavior with a strong propensity for recurrence. Contemporary therapeutic approaches for craniopharyngiomas include stereotactic irradiation in the form of Stereotactic Radiosurgery (SRS) or Fractionated Stereotactic Radiation Therapy (FSRT) as part of multimodality treatment particularly when complete surgical removal is not feasible. In this study, we evaluate the use of Linear Accelerator (LINAC)-based SRS in the multidisciplinary management of patients with craniopharyngiomas. Between July 1998 and July 2013, 20 patients (11 male, 9 female) with residual or recurrent craniopharyngiomas were treated using LINAC-based SRS at Department of Radiation Oncology, Gulhane Military Medical Academy. Median age was 37 (9-69) years. Median tumor volume was 1.1 (0.9-6.9) cc. Median dose was 13 Gy (range: 10-16 Gy) prescribed to the 80%-95% isodose line encompassing the target volume. Median follow-up time was 47 (7-93) months. Overall local control rate was 88% at 1 year, 79% at 3 years and 66% at 5 years. Three and 5-year progression free survival rates were 95% and 91% whereras 3 and 5-year overall survival rates were 94% and 88%, respectively. Our study supports the usage of LINAC-based SRS as a safe and effective management strategy for patients with recurrent or residual craniopharyngiomas.

Evaluation of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) for cerebral cavernous malformations: a 15-year single-center experience

BACKGROUND AND OBJECTIVESSurgery is the principal treatment for safely accessible hemorrhagic and symptomatic cavernous malformations. Nevertheless, the role of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) in the management of high-risk, symptomatic cavernoma lesions warrants further refinement. In this study, we evaluate the use of LINAC-based SRS for cerebral cavernous malformations (CMs) and report our 15-year single-center experience.DESIGN AND SETTINGSA retrospective study from the Department of Radiation Oncology and the Department of Neurosurgery at Gulhane Military Medical Academy and Medical Faculty, Ankara from April 1998 to June 2013.PATIENTS AND METHODSFifty-two patients (22 females and 30 males) with cerebral CM referred to our department underwent high-precision single-dose SRS using a LINAC with 6-MV photons. All patients had at least 1 bleeding episode prior to radiosurgery along with related symptoms. Median dose prescribed to the 85% to 95% isodose line encompassing the target volume was 15 Gy (range, 10–20).RESULTSOut of the total 52 patients, follow-up data were available for 47 patients (90.4%). Median age was 35 years (range, 19–63). Median follow-up time was 5.17 years (range, 0.08–9.5) after SRS. Three hemorrhages were identified in the post-SRS period. Statistically significant decrease was observed in the annual hemorrhage rate after radiosurgical treatment (pre-SRS 39% vs post-SRS 1.21, P<.0001). Overall, there were no radiosurgery-related complications resulting in mortality.CONCLUSIONLINAC-based SRS may be considered as a treatment option for high-risk, symptomatic cerebral CM of selected patients with prior bleeding from lesions located at surgically inaccessible or eloquent brain areas.

Prostate Cancer and the Hypofractionation Hypothesis

Prostate Cancer and the Hypofractionation Hypothesis

Trigeminal Rhizotomy Performed with Modern Image-guided Linac: Case Report

Introduction: There are substantive articles published within the last ten years describing the use of linear accelerator (Linac) based treatment of trigeminal neuralgia (TN). In this paper, we report a single case of a patient with classic TN successfully treated by radiosurgical rhizotomy using a modern image-guided linear accelerator with a high-definition multileaf collimator and an optically guided targeting system. The measurement of absolute dose prior to treatment greatly facilitated our confidence with radiosurgical lesioning. Materials and Methods: This 54-year-old patient had a six-year history of lancinating pain involving the lower third of the right face which dramatically intensified in December of 2012, shortly after beginning Vincristine. A treatment plan was generated using a nine-field dynamic arc technique. A target volume was placed at 2-3 mm from the root entry zone measuring 6 x 3 x 3 mm. The PTV dose was prescribed to 60 Gy to the 80% isodose line. Initial verification of absolute dose using Gafchromic film resulted in an increase of the planned MU’s by 7.5%. Remeasurement improved the absolute dose to within ±2 % of the calculated dose. Results: The patient was evaluated two weeks and three months following treatment. Her trigeminal pain was 80% resolved after two weeks and 100% at the three-month evaluation. She required none of her chronic pre-treatment medications and demonstrated no clinically detected sensory deficits. Conclusions: Linear accelerator-based radiosurgery utilizing intrafraction motion management and image guidance offers an acceptable alternative for the radiation treatment of trigeminal neuralgia patients if absolute doses are measured prior to treatment.

Preliminary Monte Carlo simulations of linear accelerators in Time-of-Flight Compton Scatter imaging for cargo security

The economic impact of illicit trade is in the trillions of dollars per year, with a proportion of this trade concealed within cargo containers. The interdiction of this trade relies upon efficient and effective external screening of cargo containers, typically using x rays. The present work introduces a technique of x-ray screening that aims to increase the efficiency and effectiveness of x-ray screening. Traditional X-ray screening of cargo containers is performed using high-energy (MV) transmission imaging or low-energy (kV) Compton scatter imaging to provide two-dimensional images. Two-dimensional images can contain complex, overlapping objects and require significant experience and time to interpret. Time-of-Flight information can be used in conjunction with Compton scatter imaging to provide information about the depth of each Compton scatter interaction, leading to three-dimensional images, reducing false positives and image analysis time. The expected Time-of-Flight from photons scattered back from a set of objects is well defined when the photons are produced with a delta-type (infinitely narrow) pulse duration, however, commercially available linear accelerators used for cargo screening typically have pulse widths of the order of 1 μs. In the present work, the possible use of linear accelerators for Time-of-Flight Compton scatter imaging is investigated using a mixture of analytic and Monte Carlo methods. Ideal data are obtained by convolving a number of wide x-ray pulses (up to 5 μs) with the expected Time-of-Flight from a set of objects using a delta-type pulse. Monte Carlo simulations, using Geant4, have been performed to generate x-ray spectra produced by a linear accelerator. The spectra are then used as the input for detailed Monte Carlo simulations of the Time-of-Flight of photons produced by a single linear accelerator pulse scattering back from a set of objects. Both ideal and Monte Carlo data suggest that Time-of-Flight information can be recovered from a wide linear accelerator pulse, provided that the leading and falling edge of the pulse are sharp. In addition, it has been found that using a linear accelerator leads to double the amount of Time-of-Flight information as both the leading and falling edge are utilised (unlike for a delta-type pulse).

Evaluation of stereotactic body radiotherapy (sbrt) boost in the management of endometrial cancer

The purpose of this study is to evaluate the use of linear accelerator (LINAC)-based stereotactic body radiotherapy (SBRT) boost with multileaf collimator technique after pelvic radiotherapy (RT) in patients with endometrial cancer. Consecutive patients with endometrial cancer treated using LINAC-based SBRT boost after pelvic RT were enrolled in the study. All patients had undergone surgery including total abdominal hysterectomy and bilateral salpingo-oophorectomy ± pelvic/paraortic lymphadenectomy before RT. Prescribed external pelvic RT dose was 45 Gray (Gy) in 1.8 Gy daily fractions. All patients were treated with SBRT boost after pelvic RT. The prescribed SBRT boost dose to the upper two thirds of the vagina including the vaginal vault was 18 Gy delivered in 3 fractions with 1-week intervals. Gastrointestinal and genitourinary toxicity was assessed using the Common Terminology Criteria for Adverse Events version 3 (CTCAE v3).Between April 2010 and May 2011, 18 patients with stage I-III endometrial cancer were treated with LINAC-based SBRT boost after pelvic RT. At a median follow-up of 24 (8-26) months with magnetic resonance imaging (MRI) and gynecological examination, local control rate of the study group was 100 % with negligible acute and late toxicity.LINAC-based SBRT boost to the vaginal cuff is a feasible gynecological cancer treatment modality with excellent local control and minimal toxicity that may replace traditional brachytherapy boost in the management of endometrial cancer.

Continuous Decline in Second Malignancy Occurrence in Patients with Hodgkin Lymphoma; Analysis of 1670 Patients Over the Past 5 Decades

Abstract▪2694▪This icon denotes a clinically relevant abstract INTRODUCTION:The treatment of Hodgkin's lymphoma has radically changed over time. The current treatment can achieve a high cure rate with less long-term side effects. We undertook this retrospective study from a single institution to determine how the rate of second malignancy (SM) has changed with the change in therapy and over the past five decades. METHODS:1670 patients diagnosed with Hodgkin's lymphoma between 1956 and 2009, were the subjects of this study. Characteristics examined included: age, gender, stage, B symptoms, bulk of the disease, type of chemotherapy, radiation (dose and field), type of radiation, relapse occurrence, treatment for relapse, type and date of occurrence of SM, status at last follow up.We looked at the relation between patient's characteristics, type of treatment, and time frame in which the treatment was delivered and the risk of developing SM.Pearson’s χ2 was used to analyze the difference in characteristics. Hazard ratios were calculated using logistic regression analysis for potential risk factors. Multivariate analysis was performed to determine the unique contribution of all significant variables in univariate analysis. RESULTS:Second malignancy was significantly associated with time frame at diagnosis, type of chemotherapy delivered, radiation type, dose, and field used.Out of 1670 patients 225 developed SM, 157 solid and 68 hematologic. Compared to patients treated after 1995, patients treated before 1985 had a statistically significant higher risk of developing SM (HR=6.2); same for those treated between 1985 and 1995 (HR=3.9), P< 0.0001. Patients who received MOPP therapy had a statistically higher risk of SM (HR=4.6) compared to patients treated with ABVD chemotherapy. Use of Cobalt radiation had a HR= 2.3 for developing SM (P<0.0001) compared to the use of linear accelerator. Radiation dose of > 36 Gy (HR=1.5; p=NS) the use of mantle field radiation in females (HR=2.9; p=0.004), and the use of subtotal nodal radiation (HR=1.9;p=0.03) were associated with a higher risk. Patients who developed cardiac disease had also a higher risk for SM (HR=3.2;p<0.0001).Risk for death was statistically associated with male gender (HR =0.7 for female; P<0.0001), Age > 60 (HR=8.8; P<0.0001), stage (HR advanced =3.5; P<0.0001), B symptoms (HR=1.5; p=0.001), use of Cobalt (HR=4.3; p<0.0001), subtotal nodal radiation (HR=3.9; P<0.0001) with females having a higher risk for death compared to males (HR= 8 for females versus 2.6 for males), MOPP chemotherapy (HR=3.9;p<0.0001), relapse (HR=7.0; p<0.0001), and occurrence of second malignancy (HR=3.9 for hematological, and 2.4 for solid; P<0.0001 for both). The risk of death decreased significantly comparing patients treated before 1970 (used as a reference) to those treated between 1971–1985, 1986–1995, and 1996–2009 with a HR of 0.6, 0.1, and 0.1 respectively (p< 0.0001). Multivariate analysis showed that the two most important predictors for occurrence of SM are the time frame at diagnosis and relapse (HR 4.2; P=0.0008 and 4.5; p<00001,respectively). CONCLUSION:Our data suggest that the improvement in HL cure rate using less toxic frontline regimens, and the use of modern radiation therapy techniques of smaller fields is associated with a continuous decrease in the rate of SM Disclosures:No relevant conflicts of interest to declare.

TU-SAM-BRB-03: CE - Therapy SAMs

External beam three‐dimensional conformai accelerated partial breast irradiation (APBI) provides a non‐invasive approach for a select group of patients for delivering hypo‐fractionated breast radiation therapy to the area most at‐risk for breast cancer recurrence. Use of linear accelerator generated radiation beams yields more homogeneous coverage of the target volume than afforded by any HDR approach. However, more tissue must be treated to account for uncertainties in cavity location and margins for patient setup. There are several external beam treatment techniques used clinically today: 3D‐CRT (as described by NSABP B39/RTOG 0413 protocol), the MGH method and the NYU prone system. This lecture will provide a rationale for external beam APBI, discuss the various planning techniques and present clinical results. Learning Objectives: 1. Gain basic knowledge of external beam APBI. 2. Review the planning techniques popular today. 3. Learn the challenges and limiting factors of 3D‐CRT APBI.

The Radiosurgical Treatment of Arteriovenous Malformations: Obliteration, Morbidities, and Performance Status

This study examined the single-center treatment outcomes of arteriovenous malformations (AVMs) of the brain using stereotactic radiosurgery, with regard to obliteration, predictive factors, morbidities, and patient performance status. 127 patients were treated between 1990 and 2008 by use of linear accelerator or Gamma Knife. Their median age was 37 years, the median AVM volume was 7.3 cc (range, 0.014-113.13 cc), and the median follow-up duration was 42 months (range, 6-209 months). Forty-two percent of patients presented with intracranial hemorrhage, 31% received embolization, and 8% underwent prior resection. Thirty-one percent of patients received more than one round of radiosurgery. 64% of patients had complete obliteration confirmed by magnetic resonance imaging or angiography. Positive predictors of obliteration included pretreatment hemorrhage (p = 0.042), smaller AVM volume (odds ratio = 1.25; 95% CI, 1.03-1.52), and larger marginal dose (odds ratio = 0.292; 95% CI, 0.100-0.820), whereas embolization (p < 0.001) was a negative predictor . The annual risk of hemorrhage after radiosurgery was 2.2%, and the risk of death as a result of hemorrhage was 0.6-1.3%. Eleven percent of patients reported new or worsened neurologic symptoms. Radiosurgery was effective in treating AVM-related headaches (p < 0.001) but did not improve the performance status of patients. Stereotactic radiosurgery is an effective tool in the treatment of AVMs and amelioration of AVM-related headaches, but it did not affect the patients' performance status. Factors affecting obliteration include prior hemorrhage, marginal dose, prior embolization, and AVM volume. Risk of hemorrhage persists in the latency period after radiosurgery, and it remains finite even after complete obliteration.

Thirty year celebration of journal publications on radiation oncology medical physics

The Australasian Physical & Engineering Sciences in Medicine Journal (APESM) is an avenue for the profession to report scientific work in medicine; provide a facility for the publication of current work, new research and new techniques developed or reviewed; report on professional news from elsewhere and; publish the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) policies and protocols. The journal is a vital instrument within the ACPSEM organisation with a worldwide circulation. This review of APESM on medical physics in radiation oncology is meant to be a progress summary of work in that specialty. Even so, it has become a lengthy appraisal due to the many years involved. In considering publications related to medical physics in radiation oncology, this review has shown the progression of the College journal to an international journal. There is an increase in the number of papers contributed from Asia and other countries world wide for this discipline. Growth in the number of contributions should continue to rise. In order to provide some appreciation of where the present medical physics activity arose from, this article commences its discussion in 1959 and progresses towards the present, describing along the way, from radiation oncology papers published in APESM, the use of linear accelerators, brachytherapy, the medical physics workforce, the formation of the ACPSEM, and the more modern developments in radiotherapy such as 3-D treatment planning and IMRT.