S.H. Jeon

Air–electron stream interactions during magnetic resonance IGRT

PurposeTo investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI).Materials and methodsIn all, 20xa0patients who received APBI with axa0magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5u2009Gy in 10xa0fractions of 3.85u2009Gy and delivered with axa0tri-cobalt system (the ViewRay system). For each patient, primary plans were delivered for the first five fractions and modified plans with different gantry angles from those of the primary plan (in-treatment plans) were delivered for the remaining five fractions to reduce the skin dose. Axa01u2009cm thick bolus was placed in front of the patient’s jaw, ipsilateral shoulder, and arm to shield them from the electron stream. Radiochromic EBT3xa0films were attached to the front (towards the breast) and back (towards the head) of the bolus during treatment. Correlations between the measured values and the tumor locations, treatment times, and tumor sizes were investigated.ResultsFor axa0single fraction delivery, the average areas of the measured isodoses of 14% (0.54u2009Gy), 12% (0.46u2009Gy), and 10% (0.39u2009Gy) at the front of the boluses were as large as 3, 10.4, and 21.4u2009cm2, respectively, whereas no significant dose could be measured at the back of the boluses. Statistically significant but weak correlations were observed between the measured values and the treatment times.ConclusionDuring radiotherapy for breast cancer with an MR-IGRT system, the patient must be shielded from electron streams in the air generated by the interaction of the magnetic field with the beams of the three-cobalt treatment unit to avoid unwanted irradiation of the skin outside the treatment field.ZusammenfassungZielsetzungBeim Einsatz eines Magnetresonanztomographie(MRT)-geführten Bestrahlungsgeräts kann durch die Wechselwirkung von Magnetfeld und Strahlenquelle unerwünscht ein Elektronenstrahl außerhalb der Therapiefelder entstehen. In dieser Studie wurde für akzelerierte Teilbrustbestrahlungen (APBI) diese Strahlung abgeschirmt und näher untersucht.Arbeitsmittel und VerfahrenFür diese Studie wurden prospektiv 20xa0Patientinnen ausgewählt, die eine APBI mit einer MRT-geführten Strahlentherapie (MR-IGRT) erhielten. Die Bestrahlung erfolgte mit einem Tri-Kobalt-System, das mit einem Magnetresonanztomographen kombiniert war (ViewRay). Es wurden jeweils 10xa0Fraktionen mit einer Einzeldosis von 3,85u2009Gy und der resultierenden Gesamtdosis von 38,5u2009Gy appliziert. Zur Reduktion der Hautdosis wurden pro Patientin 2xa0unterschiedliche Therapiepläne für jeweils 5xa0Fraktionen mit unterschiedlichen Tragarmwinkeln eingesetzt. Zur Abschirmung des unerwünschten Elektronenstrahls außerhalb der Strahlenfelder wurde ein 1u2009cm starker Bolus vor dem Kiefer sowie vor der ipsilateralen Schulter und dem Arm der Patientin positioniert. Vor dem Bolusmaterial (Richtung Brust) und hinter dem Bolusmaterial (Richtung Kopf) wurden EBT3-Radiochromröntgenfilme befestigt, um die ein- und austretende Dosis zu messen. Die Abhängigkeiten der Messwerte von der Lokalisation des bestrahlten Tumors, der Bestrahlungszeit und der Tumorgröße wurden untersucht.ErgebnisseFür jeweils eine Strahlenfraktion wurden auf den Röntgenfilmen vor dem Bolusmaterial (Richtung Brust) die von den einzelnen Isodosen eingeschlossenen Flächen vermessen: die 14u2009%-Isodosis (0,54u2009Gy) umschloss im Mittel eine Fläche von 3,6u2009cm2, die 12u2009%-Isodosis (0,46u2009Gy) im Mittel 10,4u2009cm2 und die 10u2009%-Isodosis (0,39u2009Gy) im Mittel 21,4u2009cm2. Die Röntgenfilme hinter dem Bolusmaterial zeigten hingegen keine signifikante Dosisbelastung an. Statistisch signifikante, aber nur geringe Korrelationen wurden zwischen der Dosisbelastung und den Behandlungszeiten beobachtet.SchlussfolgerungWerden Brustkrebspatientinnen mit einem MRT-geführten Tri-Kobalt-Bestrahlungsgerät behandelt, kann durch eine Wechselwirkung von Strahlenquelle und Magnetresonanztomograph ein Elektronenstrahl außerhalb der Therapiefelder unerwünscht entstehen. Dieser muss zur Schonung der Haut berücksichtigt und abgeschirmt werden.

Prediction of Pseudoprogression versus Progression using Machine Learning Algorithm in Glioblastoma

We aimed to investigate the feasibility of machine learning (ML) algorithm to distinguish pseudoprogression (PsPD) from progression (PD) in patients with glioblastoma (GBM). We recruited the patients diagnosed as primary GBM who received gross total resection (GTR) and concurrent chemoradiotherapy in two institutions from April 2010 to April 2017 and presented suspicious contrast-enhanced lesion on brain magnetic resonance imaging (MRI) during follow-up. Patients from two institutions were allocated to training (Nu2009=u200959) and testing (Nu2009=u200919) datasets, respectively. We developed a convolutional neural network combined with a long short-term memory ML structure. MRI data, which was 9 axial post-contrast T1-weighted images in our study, and clinical features were incorporated (Model 1). In the testing set, the trained Model 1 resulted in AUC of 0.83, AUPRC of 0.87, and F1-score of 0.74 using optimal threshold. The performance was superior to that of Model 2 (CNN-LSTM model with MRI data alone) and Model 3 (random forest model with clinical feature alone). The developed algorithm involving MRI data and clinical features could help making decision during follow-up of patients with GBM treated with GTR and concurrent CCRT.

Efficacy of adjuvant radiotherapy in the intracranial hemangiopericytoma

We retrospectively evaluated an efficacy of adjuvant radiotherapy (RT) in the intracranial hemangiopericytoma (HPC) and analyzed prognostic factors influencing treatment outcomes. Among 49 patients diagnosed as localized intracranial HPC between 1995 and 2016, 31 patients received adjuvant RT after surgery; 26 with fractionated RT and 5 with stereotactic radiosurgery using Gamma Knife. After gross total resection (GTR) (nu2009=u200932) and subtotal resection (STR) (nu2009=u200917), histopathological grade was confirmed to be grade II (nu2009=u20099) or grade III (nu2009=u200940). The median follow-up period was 50xa0months (range 3–216xa0months). The local recurrence was defined as intracranial relapse within 15xa0mm and regional recurrence as beyond 15xa0mm from the margin of surgical bed. The 10-year overall survival (OS) and progression-free survival (PFS) were 69.9 and 34.4%, respectively. The 10-year local, regional, and distant failure-free rates were 56.6, 88.2, and 73.3%, respectively. Local tumor control was better with GTR followed by RT than GTR alone (pu2009=u20090.056), while there was no difference in OS. Local tumor control and OS after STR plus RT were equivalent to those after GTR alone. There were no differences in distant metastasis-free survival (DMFS) among GTR plus RT, GTR alone, and STR plus RT. Tumor volume >u200940xa0cm3 was associated with poor PFS (pu2009=u20090.024). The local tumor recurrence was reduced by adjuvant RT after surgery. But OS or DMFS was not improved with adjuvant RT. PFS was better in the tumor with small volume at diagnosis.

Effects of trastuzumab on locoregional recurrence in human epidermal growth factor receptor 2-overexpressing breast cancer patients treated with chemotherapy and radiotherapy

PurposeIn the present study, the ability of adjuvant trastuzumab to reduce locoregional recurrence in patients with human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer receiving adjuvant chemotherapy and radiotherapy (RT) was investigated.Materials and methodsWe retrospectively included 520 patients with HER2-overexpressing breast cancer who received surgery followed by adjuvant RT and cytotoxic chemotherapy from 2003 to 2011. Adjuvant trastuzumab was administered to 286 patients. Propensity score matching was conducted to compare trastuzumab-treated and non-treated cohorts.ResultsMedian follow-up duration was 7.1xa0years (range 1.1–14.1xa0years). Propensity score matching yielded 171 matched pairs of patients with no significantly different clinical factors. An improved 7-year locoregional control (LRC) rate was observed in the trastuzumab-treated cohort compared with the non-treated cohort (95.6% vs. 89.9%, pu2009=u20090.014). Based on multivariate analysis, hormone receptor negativity (hazard ratio [HR]u2009=u20095.348, pu2009=u20090.007), positive lymph node ratiou2009>u20090.25 (HRu2009=u20092.549, pu2009=u20090.040), and lack of adjuvant trastuzumab (HRu2009=u20093.401, pu2009=u20090.017) were identified as significant risk factors for poor LRC. Adjuvant trastuzumab significantly reduced the locoregional recurrence rate in patients with one or two risk factors (7-year LRCu2009=u200995.0% vs. 84.2%, pu2009=u20090.007); however, the benefit of adjuvant trastuzumab was non-significant in patients with no risk factors (7-year LRCu2009=u200995.8% vs. 97.9%, pu2009=u20090.75).ConclusionsAdjuvant trastuzumab improved LRC in patients with HER2-overexpressing breast cancer receiving adjuvant RT and cytotoxic chemotherapy, especially in hormone receptor-negative, HER2-enriched subtype, and high positive lymph node ratio breast cancer.