Adequate Radiation Research Articles

Feasibility of concurrent chemoradiotherapy with high-dose cisplatin after induction TPF chemotherapy in head and neck cancer: a critical review of the literature and the experience of the European Institute of Oncology.

Many concerns are related to the idea that the acute toxicity of induction chemotherapy (IC) performed with TPF (docetaxel, cisplatin, 5-fluorouracil) could reduce the ability to deliver the subsequent standard concurrent chemoradiotherapy (CRT) in head and neck cancer patients. We performed a critical review of the literature on the toxicity profile of the standard CRT administered after the IC with TPF. A total of 13 papers (including 950 patients) were selected. Results showed that most patients were treated with an adequate radiation total dose although a significant proportion of them (from 15 to 30%) completed the planned treatment with a delay of more than 5days. A minority of patients were able to be treated with three cycles of concurrent cisplatin, but only few papers reported how many of patients reached the cumulative total dose of almost 200mg/m2 cisplatin. The rate of deaths due to treatment-related toxicity varied from 0 to 9% (median and mean 2%). Two prospective trials stopped patient enrollment due to acute treatment-related toxicity and because a low number of patients were able to undergo the planned full schedule of cisplatin during the CRT, respectively. Retrospective analysis of 45 patients treated at our institute showed that this schedule was feasible with manageable side effects. In conclusion, the literature data did not provide homogeneous information on the feasibility of the standard CRT after induction TPF. A more uniform data collection of treatment-related toxicity will be helpful in better selecting the patients who might adequately tolerate this multimodality strategy.

Patterns of failure and clinical outcomes of definitive radiotherapy for cervical esophageal cancer

PurposeBecause of the scarcity of cervical esophageal cancer (CEC), data for this disease entity is limited. We aim to evaluate the outcomes, prognostic factors and failure patterns of CEC treated by contemporary radiotherapy (RT).MethodsWe retrospectively analyzed 86 CEC patients consecutively treated between 2007 and 2015 by definitive RT with or without concurrent chemotherapy. RT was mainly delivered with Intensity Modulated Irradiation Therapy (IMRT) or Volumetric-Modulated Arc Therapy (VMAT). Statistical analyses were performed on survival, prognostic factors and failure patterns.ResultsThe median follow-up time was 19.4 months. The 3-year overall survival (OS), local regional failure free survival (LRFFS), distant metastatic free survival (DMFS), and progression free survival (PFS) were 53.6%, 57.9%, 81.5% and 41.5%, respectively. Independent predictors for poorer OS were N stage, hoarseness and recurrent laryngeal nerve lymph node (RLN) involvement, and predictors for LRFFS were N stage and EQD2 (equivalent dose in 2 Gy fraction) to gross tumor volume (GTV), with ≥ 66Gy achieving local control of 94.7%. Patients receiving elective nodal irradiation (ENI) had better nodal regional control than those receiving involved field irradiation (IFI). 31 (36%) patients had treatment failure and 15 (17.4%), 8 (9.3%) and 14 (16.2%) patients had local, regional, and distant failure, respectively. 86.7% (13/15) local failures were within GTV, and supraclavicular region (62.5%, 5/8) was the most common regional failure site. No severe toxicities were observed.ConclusionsOur results seem to indicate that good locoregional control might be achieved for CEC with adequate radiation dose and treatment planning approaches.

SENTINEL LYMPH NODE BIOPSY IN EARLY BREAST CANCER: THE EXPERIENCE OF THE N.N. PETROV RESEARCH INSTITUTE OF ONCOLOGY

The aim of the study was to evaluate a 3-year distant treatment outcomes of patients with early breast cancer who had undergone sentinel lymph node biopsy. Methods. A total of 681 patients with early cT1-2N0M0 breast cancer treated in the N.N. Petrov research institute of oncology form 2012 till 2016 were retrospectively enrolled in the study. Radioisotopes were used to identify sentinel nodes. In case a macrometastatic lesion was found (>2mm) ALND was performed. Subsequent adequate systemic treatment and radiotherapy were administered in accordance with the pTNM status, biologic subtype and age. Results. A 3-year overall survival equaled 99.3% (SE 0.4%), recurrence-free survival was 99.2% (SE 0.4%). Survival of patients without nodal involvement reached 100%, whereas for patients with metastatic nodes it was 97.4% (SE 1.8%). The threshold for the number of the affected nodes significantly influencing survival equaled 1 (р=0,0187). Overall survival of patients with 0 to 1 positive lymph nodes was 99.7% (SE 0.3%), with more than 1 node involved - 95.7% (SE 0.3%) (р=0,00444). Conclusion. Overall 3-year survival of patients with early breast cancer approaches 100%. Sentinel lymph node biopsy allows avoiding unnecessary and traumatizing axillary dissection and improves the quality of life.

Radiation Transport Calculation of the UGXR Collimators for the Jules Horowitz Reactor (JHR)

Jules Horowitz Reactor (JHR), a major infrastructure of European interest in the fission domain, will be built and operated in the framework of an international cooperation, including the development and qualification of materials and nuclear fuel used in nuclear industry. For this purpose UGXR Collimators, two multi slit gamma and X-ray collimation mechatronic systems, will be installed at the JHR pool and at the Irradiated Components Storage pool. Expected amounts of radiation produced by the spent fuel and X-ray accelerator implies diverse aspects need to be verified to ensure adequate radiological zoning and personnel radiation protection. A computational methodology was devised to validate the Collimators design by means of coupling different engineering codes. In summary, several assessments were performed by means of MCNP5v1.60 to fulfil all the radiological requirements in Nominal scenario (TEDE < 25µSv/h) and in Maintenance scenario (TEDE < 2mSv/h) among others, detailing the methodology, hypotheses and assumptions employed.

Need for Competency-Based Radiation Oncology Education in Developing Countries

Although not a new concept in itself, competency-based education has set the trend for the globally accepted standard norm for education and training of medical professionals including postgraduate education in radiation oncology. Societal needs demand from radiation oncologists that they be not only competent in the knowledge and skills relevant to their specific discipline, but that they also display competencies such as professionalism, scholarship, health advocacy, management/leadership, collaboration and communication. The realities of developing countries, in particular low and middle income countries (LMICs) set different priorities than in high income countries. A large proportion of cancer patients do not have access to adequate radiotherapy services. Resource constraints determine limitations in equipment, accessories, and dosimetry. Lower than standard staffing levels and limited quality education and training also contribute to substandard care and clinical outcomes. In this environment, the addition and assessment of competency-based elements to training programmes can be challenging. On the other hand, it is precisely in these countries, where competencies such as the ones listed above are highly needed in the radiation oncology profession. Implementation of competency-based medical education in the education of radiation oncologists in LMICs is both a need and a challenge. The available frameworks and competencies, despite being very relevant to the realities faced by radiation oncologists in LMICs, will still need to be adapted in order to ensure effective implementation at the national/regional level. Radiation oncologists need to employ effective change-management strategies to ensure that the changes which are introduced can remain sustainable within the context of national healthcare, education and political systems.

Influence of tumor location on the intensity-modulated radiation therapy plan of helical tomotherapy

Given the design of the Helical TomoTherapy device, the patient's central axis is routinely aligned with the machine's rotational axis to prevent the patient's body from colliding with the machine walls. However, for treatment of tumors located away from the patient's central axis, this position may not be optimal as the adequate radiation dose may not reach the affected site. Our study aimed to investigate the influence of tumor location on dose quality and delivery efficiency of tomotherapy plans. A phantom and 15 patients were selected for this study. Two plans, A and B, were implemented for each case. In plan A, the patient's central axis was aligned with the machine's rotational axis, whereas in plan B, the center of the planning target volume (PTV) was aligned with the machine's rotational axis. Both plans were optimized with the same planning parameters, and the dose quality of the plans was evaluated using dosimetrics. The delivery efficiency was determined from delivery time and monitor units (MUs). A paired t-test or nonparametric Wilcoxon signed-rank test was performed for statistical comparison. In the phantom study, the median delivery times were 358 and 336 seconds for plans A and B, respectively, and this difference was significant (p = 0.005). In the patient study, the median delivery times were 348 and 317 seconds for plans A and B, respectively, and this difference was also significant (p = 0.001). The dose qualities of both plans for each patient were nearly identical. No significant differences were found in the conformal index, heterogeneity index, and mean dose delivered to normal tissue between the plans. Both phantom and patient studies showed that for normal-sized patients, the delivery time reduced as the distance between the PTV and the patient's central axis increased when the PTV center was aligned with the machine axis. In conclusion, aligning the PTV center with the machine's rotational axis by shifting the patient during tomotherapy reduces the delivery time without compromising the dose quality of intensity-modulated radiation therapy.

Influence of Microwave Heating and Thermal Auxiliary on Decomposition of Siderite

In the present study, microwave radiation was used to decrease power inputs and roasting duration time for thermal decomposition of Deveci, Hekimhan siderite ore. The siderite was not enough to absorb adequate microwave radiation to start the decomposition or roasting reaction. Therefore, sucrose as a thermal auxiliary was added to the raw siderite ore before microwave irradiation. The effect of amount of sucrose (10 to 30% by weight) against the duration of heating and roasting temperature of the thermal decomposition of siderite was investigated in the present study. On the contrary of the literature, the experimental results showed that the siderite was decomposed in 3 minutes with addition of 30 wt% sucrose and transformed to Fe3O4. The temperature, the weight loss and the magnetic susceptibility of the roasted final product were recorded as 1100 °C, 32.14 wt.% and 15410.03*10-8 m3/kg., respectively.

Meta-analysis of the side-effect profiles of modern radiation therapies for patients with prostate cancer

One of the most relevant focus of recent developments in radiotherapy technology was the adequate irradiation of prostate cancer. The aim of this study was to analyse the safety of normo- and hypofractionated and high dose intensity-modulated radiotherapy. Toxicities were identified through literature review and evidence was synthetized with meta-analytical methods. The use of high dose intensity-modulated radiotherapy resulted in no difference in severe genitourinary (acute p = 0.9; late p = 0.95) and moderate or severe gastrointestinal (acute: N/A; late: p = 0.08) toxicities compared to 3D conformal radiation therapy. The risk ratio of moderate acute (RR = 1.39, 95% CI: 1.09-1.78; p = 0.008) and late genitourinary toxicities (RR = 1.48, 95% CI: 1.26-1.75; p<0,00001) was higher. There was no difference in hypo- and normofractionated intensity-modulated radiotherapy regarding severe genitourinary (acute: N/A; late: p = 0.73) and moderate or severe gastrointestinal (acute: p = 0.73; late: p = 0.55) toxicities, the risk of late moderate genitourinary toxicities was higher when using hypofractionation scheme (RR = 1.39, 95% CI: 1.00-1.94; p = 0.05). The use of normo- and hypofractionated and high dose intensity-modulated radiotherapy proved to be safe. However the higher risk of moderate genitourinary adverse events require an extensive clinical risk estimation.

Distribution of prostate nodes: a PET/CT-derived anatomic atlas of prostate cancer patients before and after surgical treatment.

BackgroundIn order to define adequate radiation portals in nodal positive prostate cancer a detailed knowledge of the anatomic lymph-node distribution is mandatory. We therefore systematically analyzed the localization of Choline PET/CT positive lymph nodes and compared it to the RTOG recommendation of pelvic CTV, as well as to previous work, the SPECT sentinel lymph node atlas.MethodsThirty-two patients being mostly high risk patients with a PSA of 12.5 ng/ml (median) received PET/CT before any treatment. Eighty-seven patients received PET/CT for staging due to biochemical failure with a median PSA of 3.12 ng/ml. Each single PET-positive lymph node was manually contoured in a “virtual” patient dataset to achieve a 3-D visualization, resulting in an atlas of the cumulative PET positive lymph node distribution. Further the PET-positive lymph node location in each patient was assessed with regard to the existence of a potential geographic miss (i.e. PET-positive lymph nodes that would not have been treated adequately by the RTOG consensus on CTV definition of pelvic lymph nodes).ResultsSeventy-eight and 209 PET positive lymph nodes were detected in patients with no prior treatment and in postoperative patients, respectively. The most common sites of PET positive lymph nodes in patients with no prior treatment were external iliac (32.1 %), followed by common iliac (23.1 %) and para-aortic (19.2 %). In postoperative patients the most common sites of PET positive lymph nodes were common iliac (24.9 %), followed by external iliac (23.0 %) and para-aortic (20.1 %). In patients with no prior treatment there were 34 (43.6 %) and in postoperative patients there were 77 (36.8 %) of all detected lymph nodes that would not have been treated adequately using the RTOG CTV. We compared the distribution of lymph nodes gained by Choline PET/CT to the preexisting SPECT sentinel lymph node atlas and saw an overall good congruence.ConclusionsCholine PET/CT and SPECT sentinel lymph node atlas are comparable to each other. More than one-third of the PET positive lymph nodes in patients with no prior treatment and in postoperative patients would not have been treated adequately using the RTOG CTV. To reduce geographical miss, image based definition of an individual target volume is necessary.

Low-dose brachytherapy strategies to treat uveal melanoma: is less more?

The Collaborative Ocular Melanoma Study (COMS) has established equivalency of globe salvaging brachytherapy compared with enucleation in terms of survival for medium-sized choroidal melanoma. The radiation dose protocol followed by the COMS was 85 Gray to a prescription point of the tumor apex or 5 mm inner sclera; whichever was greater. While the COMS realized appropriate local and distant tumor control rates, ocular morbidity due to radiation complications remains a significant clinical challenge. Recent studies challenge the COMS radiation dose paradigm by demonstrating similar tumor control by utilizing lower radiation doses that are associated with reduced radiation toxicity. Improved operative techniques including intraoperative ultrasound can aid to obtain adequate radiation delivery to the tumor by ensuring optimal plaque position. Adjuvant transpupillary thermotherapy, intravitreal anti-VEGF and posterior sub-Tenon steroids may further enhance outcome by providing additional tumor control and/or facilitating visual recovery.

Quantification of intra-fraction motion in breast radiotherapy using supine magnetic resonance imaging

In early-stage breast-cancer patients, accelerated partial-breast irradiation techniques (APBI) and hypofractionation are increasingly implemented after breast-conserving surgery (BCS). For a safe and effective radiation therapy (RT), the influence of intra-fraction motion during dose delivery becomes more important as associated fraction durations increase and targets become smaller. Current image-guidance techniques are insufficient to characterize local target movement in high temporal and spatial resolution for extended durations. Magnetic resonance imaging (MRI) can provide high soft-tissue contrast, allow fast imaging, and acquire images during longer periods. The goal of this study was to quantify intra-fraction motion using MRI scans from 21 breast-cancer patients, before and after BCS, in supine RT position, on two time scales. High-temporal 2-dimensional (2D) MRI scans (cine-MRI), acquired every 0.3 s during 2 min, and three 3D MRI scans, acquired over 20 min, were performed. The tumor (bed) and whole breast were delineated on 3D scans and delineations were transferred to the cine-MRI series. Consecutive scans were rigidly registered and delineations were transformed accordingly. Motion in sub-second time-scale (derived from cine-MRI) was generally regular and limited to a median of 2 mm. Infrequently, large deviations were observed, induced by deep inspiration, but these were temporary. Movement on multi-minute scale (derived from 3D MRI) varied more, although medians were restricted to 2.2 mm or lower. Large whole-body displacements (up to 14 mm over 19 min) were sparsely observed. The impact of motion on standard RT techniques is likely small. However, in novel hypofractionated APBI techniques, whole-body shifts may affect adequate RT delivery, given the increasing fraction durations and smaller targets. Motion management may thus be required. For this, on-line MRI guidance could be provided by a hybrid MRI/RT modality, such as the University Medical Center Utrecht MRI linear accelerator.

An Implantable Planar Dipole Antenna for Wireless MedRadio-Band Biotelemetry Devices

A novel implantable planar dipole antenna for operation in the Medical Device Radiocommunications Services band (401-406 MHz) is proposed. A basic skin-implantable antenna model is initially developed, and then a prototype is fabricated. The dipole antenna exhibits an extremely thin profile and a very small aperture size; antenna physical volume is approximately 18.1 mm 3 . Effective size reduction is achieved by optimally canceling its inherent high capacitance through L-shaped reactive loading sections within the antenna structure. As demonstrated, the applied design methodology facilitates planar antenna miniaturization with adequate radiation response (gain, radiation pattern shape, and specific absorption rate). A liquid skin medium is employed to experimentally validate the antenna. Measured and simulated results are in good agreement.

Cognitive evoked potentials P300 after radiation exposure

The study was aimed at evaluating features of brain information processes and cognitive functioning in the remote period after irradiation due to the Chornobyl accident by using cognitive evoked potentials P300. The study included 128 people, 112 male Chornobyl clean up workers in 1986-1987 with the records of radiation doses available in Clinical and Epidemiological Registry (CER) of State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine» (NRCRM) (study group) and 16 unexposed persons due to the Chornobyl disaster (control group). At the time of the survey the average age of clean up workers (M ± SD) was (57.3 ± 5.9) years, range 44-65 years, and of unex posed persons was (57.3 ± 6.5) years, range 44-65 years. Radiation doses were within the range 0.0002-1.23 Gy, with the arithmetic mean dose (M ± SD) of (0.2 ± 0.2) Gy and the geometric mean dose of 0.1 Gy. The radiocerebral effect in the projection of the left posterior superior temporal gyrus (Wernicke's area) proportionally to the radiation dose with the possible threshold of 0.05 Gy of total irradiation was revealed, with increasing radiation dose cognitive component P300 amplitude reduces and its latency period (LP) increases, espe cially at doses > 0.3-0.5 Gy. At doses > 0.5 Gy the functional relationship with the radiation dose for LP P300 increase in the projection of Wernicke's area (r = 0.9; p = 0.027) has been found. The neurophysiological features detected are fully consistent with hypotheses both on radiosensitiv ity of human central nervous system and accelerated aging of the brain under the influence of small doses of ioniz ing radiation, and have questioned the feasibility of long term manned space flights (including Mars) until the development of adequate radiation hygiene standardization for space crews and invention of means for radiation protection of space flights. Further dynamic clinical and neurophysiological monitoring of individuals exposed to ionizing radiation is necessary. To identify the neurophysiological biological markers of ionizing radiation further international researches with adequate dosimetry support are needed.

Global Pattern of Nasopharyngeal Cancer: Correlation of Outcome With Access to Radiation Therapy

This study aimed to estimate the treatment outcome of nasopharyngeal cancer (NPC) across the world and its correlation with access to radiation therapy (RT). The age-standardized mortality (ASM) and age-standardized incidence (ASI) rates of NPC from GLOBOCAN (2012) were summarized, and [1-(ASM/ASI)] was computed to give the proxy relative survival (RS). Data from the International Atomic Energy Agency (IAEA) and the World Bank were used to assess the availability of RT in surrogate terms: the number of RT equipment units and radiation oncologists per million population. A total of 112 countries with complete valid data were analyzed, and the proxy RS varied widely from 0% to 83% (median, 50%). Countries were categorized into Good, Median, and Poor outcome groups on the basis of their proxy RS (<45%, 45%-55%, and >55%). Eighty percent of new cases occurred in the Poor outcome group. Univariable linear regression showed a significant correlation between outcome and the availability of RT: proxy RS increased at 3.4% (P<.001) and 1.5% (P=.001) per unit increase in RT equipment and oncologist per million population, respectively. The median number of RT equipment units per million population increased significantly from 0.5 in the Poor, to 1.5 in the Median, to 4.6 in the Good outcome groups, and the corresponding number of oncologists increased from 1.1 to 3.3 to 7.1 (P<.001). Nasopharyngeal cancer is a highly treatable disease, but the outcome varies widely across the world. The current study shows a significant correlation between survival and access to RT based on available surrogate indicators. However, the possible reasons for poor outcome are likely to be multifactorial and complex. Concerted international efforts are needed not only to address the fundamental requirement for adequate RT access but also to obtain more comprehensive and accurate data for research to improve cancer outcome.

An Evaluation of the Organ Dose Received by Cardiologists Arising From Angiography Examinations in Educational Hospital in Rasht.

Interventional procedures, cine acquisitions and operation of fluoroscopic equipment in high-dose fluoroscopic modes, involve long fluoroscopic times which can lead to high staff doses. Also, Coronary angiography (CA) procedures require the cardiologist and assisting personnel to remain close to the patient, which is the main source of scattered radiation. Thus, radiation exposure is a significant concern for radiation workers and it is important to measure the radiation doses received by personnel and evaluate the parameters concerning total radiation burden. In this research, we investigated radiation doses to 10 cardiologists performing 120 CA procedures. Using thermo luminescent dosimeters doses to the wrists, thyroid and eyes per procedure were measured. Based on the measured dose values, maximum doses to the Left wrist, Right wrist, thyroid and eyes of cardiologist were measured 241.45 µSv, 203.17 µSv, 78.21 µSv and 44.58 µSv, respectively. The results of this study indicate that distance from the source, use of protective equipment’s, procedure complexity, equipment performance, and cardiologist experience are the principal exposure-determining variables. It can be conclude that if adequate radiation protection approaches have been implemented, occupational dose levels to cardiologists would be within the regulated acceptable dose limits.

Dual band printed patch antenna on ceramic–polytetrafluoroethylene composite material substrate for GPS and WLAN applications

In this paper, a design concept of modified rectangular shape slotted patch antenna with microstrip feed is proposed for GPS and WLAN applications. The proposed simple planar design of the planar antenna is composed of partially extended radiating surface which is loaded with L-shape slot and two wide square slots. The optimized design of the antenna has overall dimension of $$40 \times 40\; \mathrm{mm}^{2}$$40?40mm2 and is fabricated on 1.905 mm thick high dielectric substrate $$(\varepsilon _{r} = 10.2)$$(?r=10.2) of high frequency copper laminated ceramic composite substrate. The antenna design, simulation and parametric analysis have been performed on finite element method based full-wave 3D electromagnetic field simulation software. The experimental results show that the fabricated antenna has achieved impedance bandwidths (S11 $$\le -10$$≤-10 dB) of around 780 MHz (1.13---1.91?GHz) at resonant frequency of 1.48?GHz and 1220?MHz (4.83---6.05?GHz) at resonant frequency of 5.61?GHz respectively. The gain of the fabricated antenna gives maximum value of 3.42 and 4.37?dBi for lower and upper frequency band of operations respectively. The proposed antenna shows almost consistent radiation patterns with adequate radiation efficiency over the frequency bands which make the antenna appropriate for providing services in both L1/L2 GPS and 5.2/5.8?GHz WLAN bands.

Repeat Gamma-Knife Radiosurgery for Refractory or Recurrent Trigeminal Neuralgia with Consideration About the Optimal Second Dose

To investigate adequate radiation doses for repeat Gamma Knife radiosurgery (GKS) for trigeminal neuralgia in our series and meta-analysis. Fourteen patients treated by ipsilateral repeat GKS for trigeminal neuralgia were included. Median age of patients was 65 years (range, 28-78), the median target dose, 140-180). Patients were followed a median of 10.8 months (range, 1-151) after the second gamma-knife surgery. Brainstem dose analysis and vote-counting meta-analysis of 19 studies were performed. After the second gamma-knife radiosurgeries, pain was relieved effectively in 12 patients (86%; Barrow Neurological Institute Pain Intensity Score I-III). Post-gamma-knife radiosurgery trigeminal nerve deficits were mild in 5 patients. No serious anesthesia dolorosa was occurred. The second GKS radiation dose ≤ 60 Gy was significantly associated with worse pain control outcome (P = 0.018 in our series, permutation analysis of variance, and P = 0.009 in the meta-analysis, 2-tailed Fisher's exact test). Cumulative dose ≤ 140-150 Gy was significantly associated with poor pain control outcome (P = 0.033 in our series and P = 0.013 in the meta-analysis, 2-tailed Fisher's exact test). A cumulative brainstem edge dose >12 Gy tended to be associated with trigeminal nerve deficit (P = 0.077). Our study suggests that the second GKS dose is a potentially important factor.

Evaluation of lunar regolith geopolymer binder as a radioactive shielding material for space exploration applications

Future manned missions to the moon will require the ability to build structures using the moon’s natural resources. The geopolymer binder described in this paper (Lunamer) is a construction material that consists of up to 98% lunar regolith, drastically reducing the amount of material that must be carried from Earth in the event of lunar construction. This material could be used to fabricate structural panels and interlocking blocks that have radiation shielding and thermal insulation characteristics. These panels and blocks could be used to construct living quarters and storage facilities on the lunar surface, or as shielding panels to be installed on crafts launched from the moon surface to deep-space destinations. Lunamer specimens were manufactured in the laboratory and compressive strength results of up to 16MPa when cast with conventional methods and 37MPa when cast using uniaxial pressing were obtained. Simulation results have shown that the mechanical and chemical properties of Lunamer allow for adequate radiation shielding for a crew inside the lunar living quarters without additional requirements.

SU‐E‐T‐560: Monte Carlo Simulation of the Neutron Radiation Field Around a Medical 18 MV Linac

Purpose:Today the majority of radiation therapy treatments are performed at medical electron linear accelerators (linacs). The accelerated electrons are used for the generation of bremsstrahlung photons. The use of higher electron respectively photon energies has some advantages over lower energies such as the longer dose build‐up. However photons with energies higher than ∼7 MeV can additionally to the interaction with bound electrons undergo inelastic reactions with nuclei. These photonuclear reactions lead to the emission of fast neutrons which contaminate the primary photon field. The neutrons might penetrate through the collimators and deliver out‐of‐field dose to the patient. Furthermore the materials inside the linac head as well as the air inside the treatment room get activated which might deliver dose to the medical employees even when the linac is not in operation. A detailed knowledge of these effects is essential for adequate radiation protection of the employees and an optimal patient treatment.Methods:It is a common method to study the radiation fields of such linacs by means of Monte Carlo simulations. For the investigation of the effects caused by photonuclear reactions a typical linac in high energy mode (Varian Clinac 18 MV‐X) as well as the surrounding bunker were modelled and simulated using the Monte Carlo code FLUKA which includes extensive nuclear reaction and neutron transport models additional to electron‐photon transport as well as capabilities for a detailed study of effective dose distributions and activation yields.Results:Neutron spectra as well as neutron effective dose distributions within the bunker were obtained, reaching up to some mSv/Gy in the patient's plane. The results are normalized per Gy in the depth dose maximum at 10×10 cm2 field size. Therefore an absolute interpretation is possible.Conclusion:The obtained data gives a better understanding of the photonuclear reaction caused effects.

Abstract P1-02-03: The effect on short–term progression free survival of the detection of ≥4 FDG-avid nodes or occult N3–disease in breast cancer patients with PET/CT

Abstract Aim: The risk for locoregional recurrence (LRR), after neoadjuvant chemotherapy (NAC), is based on staging before NAC as well as the final pathology after NAC. Especially the number of tumour–positive axillary nodes, which is also an important selection factor for postoperative radiotherapy, is not adequately assessed by ultrasound before NAC or axillary lymph node dissection after NAC. PET/CT has a high positive predictive value for the detection of lymph node metastases. Newly found lymph node metastasis on PET/CT incentivized us to change the radiotherapy plan for patients with primary breast cancer scheduled for NAC in our institute. Koolen et al. reported an upstaging of 23% stage II–III breast cancer patients to the radiotherapy requiring high–risk group (≥4 FDG–avid axillary nodes or detection of occult N3–disease) due to new lymph node metastasis detected with FDG PET/CT imaging. In this study, we report the effect of this upstaging with PET/CT short–term progression free survival (PFS). Materials and methods: Between 2007 and 2011 a total of 278 breast cancer patients (mean age 48.9y, range 19–75y), with a tumour of at least 3 cm and without metastases, received a baseline PET/CT for staging purposes and subsequent response monitoring to NAC. The group was divided in three groups: a low– (T2N0), intermediate– (T0–2N1 and T3N0) and a high–risk group (T0–3N2–3, T3N1 and T4). We classified LRR, distant metastases and death as an "event"; including all patients in the PFS analysis of the first 3 years. Results: With a median follow–up (FU) of 37 months and the upstaging as depicted in table 1 Upstaging of breast cancer risk-group after PET/CTTotal group before PET/CTChanged After PET/CTComplete after PET/CT (FU-events)Low-risk: N=47N=5Low-risk (2) N= 42Intermediate-risk: N=144N=38Intermediate-risk N= 106 (14)High-risk: N=87xHigh-risk N= 130 (27)Total: N=278Total: N= 43Total N= 278Table 1: The group was divided in three groups: a low- (T2N0), intermediate- (T0-2N1 and T3N0) and a high-risk group (T0-3N2-3, T3N1 and T4). The table shows the upstaging of breast cancer patients from low- and intermediate- to the high-risk group, and thus, after PET/CT, requiring radiotherapy. : The patients not upstaged by PET/CT showed no difference in PFS between the high–risk, intermediate–risk and low–risk groups (Logrank p=0.18). Due to the migration of the 43 patients from the low– and intermediate group to the high–risk group, based on PET/CT findings, the PFS differed significantly between the risk–groups (Logrank p=0.04). No difference in loco–regional recurrence was seen between the low–risk and the high–risk group (P=0.18). Conclusion: After upstaging with PET/CT, into the high–risk group requiring radiotherapy, a significant difference is seen between the three risk–groups. PET/CT restaging may more adequately predict progression free survival. The detection occult lymphatic metastasis with PET/CT leads to upstaging in clinically unsuspected patients with primary breast cancer, enabling adequate radiotherapy treatment. Citation Format: Suzana C Teixeira, Bas B Koolen, Paula HM Elkhuizen, Vincent van der Noort, Marie-Jeanne Vrancken-Peeters, Marcel P Stokkel, Emiel J Th Rutgers, Renato A Valdés-Olmos. The effect on short–term progression free survival of the detection of ≥4 FDG-avid nodes or occult N3–disease in breast cancer patients with PET/CT [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-02-03.