A. Compagnucci

Accelerated Partial Breast Irradiation With IMRT: New Technical Approach and Interim Analysis of Acute Toxicity in a Phase III Randomized Clinical Trial

PURPOSE To evaluate with a randomized clinical trial the possibility of treating the index quadrant with external intensity-modulated radiotherapy (IMRT) in a selected group of patients with early-stage breast cancer and to analyze the acute toxicity. METHODS AND MATERIALS From September 2005, a randomized Phase III clinical trial has been conducted to compare conventional (tangential field) fractionated whole breast treatment (Arm A) with accelerated partial breast irradiation plus intensity-modulated radiotherapy (Arm B). For intensity-modulated radiotherapy, the clinical target volume was drawn with a uniform 1-cm margin around the surgical clips in three dimensions. The ipsilateral and contralateral breast, ipsilateral and contralateral lung, heart, and spinal cord were contoured as organs at risk. All the regions of interest were contoured according to the International Commission on Radiation Units and Measurements reports 50 and 62 recommendations. RESULTS In September 2008, 259 patients were randomized and treated. The mean clinical target volume in Arm B was 44 cm(3) and the mean planning target volume was 123 cm(3). The mean value of the ratio between the planning target volume and the ipsilateral breast volume was 21%. The rate of Grade 1 and Grade 2 acute skin toxicity was 22% and 19% in Arm A (Radiation Therapy Oncology Group scale), respectively. The tolerance in Arm B was excellent with only 5% Grade 1 and 0.8% Grade 2 acute skin toxicity. The planning constraints were fully satisfied in most patients. In a very few cases, this was not possible because of very unfavorable anatomy. Quality assurance procedures were performed according to our internal quality assurance protocol, with excellent results. CONCLUSION In the present preliminary analysis, we have demonstrated that accelerated partial breast irradiation is feasible, with very low acute toxicity.

Gamma Knife Radiosurgery in the management of single and multiple brain metastases.

OBJECTIVES To evaluate the efficacy and safety of Gamma Knife Radiosurgery (GKRS) in the treatment of single and multiple brain metastases. PATIENTS AND METHODS From October 2012 to June 2014 106 patients were treated with Radiosurgery (RS) for brain metastases at University of Florence. 77 out of 106 patients had a radiological follow up and their data were analyzed. The target was defined as the enhancing lesion. The prescription dose was defined depending on tumor volume and tumor location. Each patient performed an MRI one month after GKRS for the first three months and every 3 months thereafter. Overall survival was calculated from the day of RS until death. Local recurrence (LR) was defined as radiologic growth of the irradiated lesion, while distant brain recurrence (DBR) was the evidence of brain lesion outside the previous irradiated field. Both the LR and DBR were calculated from the RS till the day of radiological evidence of relapse. The correlations within patient and disease characteristics and the outcomes of survival and disease control were analyzed. RESULTS Mean follow up was 7.2 ± 4.8 months (range: 2.4-22.8 months). At the time of analysis 21 patients (27.3%) were dead. The overall survival (OS) at 1 year was 74%. On univariate Cox Regression analysis female gender (p=0.043, HR: 0.391, 95% CI: 0.157-0.972) and age >65 years (p=0.003 HR: 4.623, 95% CI: 1.687-12.663) were predictive for survival. On multivariate analysis, age older than 65 years (p=0.005HR: 4.254, 95% CI: 1.544-11.721) was confirmed as associated with worsened overall survival. 19 patients (24.7%) had recurrence in the radiosurgery field. The median time to local failure was 4.8 ± 2.0 months (range: 1.8-9.4 months) from GKRS. On Cox Regression univariate analysis, the only factor associated with higher risk of local failure was a number of treated lesions more than 4 (p=0.015, HR: 3.813, 95% CI: 1.298-11.202), no significant parameters were found at the multivariate analysis. The median time to develop distant brain failure was 6 ± 4.32 months (range: 1.08-21.6 months). Median distant brain control was 74% at 1 year. None of the factors analyzed was statistically significant for the distant brain relapse. The radiosurgery treatment was well tolerated. One patient treated for seven metastases developed seizures 8h after GKRS, he was treated with steroids and anticonvulsants. One patient had radiologic evidence of radionecrosis without any neurological symptoms. CONCLUSIONS In well-performing patients with stable systemic disease radiosurgery can be performed as an exclusive treatment for brain metastases. Younger patients could have a greater benefit from the RS, on the other hand our finding confirm no correlation between the survival outcome and the number of lesions treated.

γTools: A modular multifunction phantom for quality assurance in GammaKnife treatments

PURPOSE We present the γTools, a new phantom designed to assess geometric and dosimetric accuracy in Gamma Knife treatments, together with first tests and results of applications. METHODS The phantom is composed of two modules: the imaging module, a regular grid of 1660 control points to evaluate image distortions and image registration result and the dosimetry module for delivered dose distribution measurements. The phantom is accompanied by a MatLab routine for image distortions quantification. Dose measurement are performed with Gafchromic films fixed between two inserts and placed in various positions and orientations inside the dosimetry module thus covering a volume comparable to the full volume of a head. RESULTS Tests performed to assess the accuracy and precision of the imaging module demonstrated sub-millimetric values. As an example of possible applications, the phantom was employed to measure image distortions of two MRI scanners and to perform dosimetric studies of single shots delivered to homogeneous and heterogeneous materials. Due to the phantom material, the measured absolute dose do not correspond to the planned dose; doses comparisons are thus carried out between normalized dose distributions. Finally, an end-to-end test was carried out in the treatment of a neuroma-like target which resulted in a 100% gamma passing rate (2% local, 2 mm) and a distance between the real target perimeter and the prescription isodose centroids of about 1 mm. CONCLUSIONS The tests demonstrate that the proposed phantom is suitable to assess both the geometrical and relative dosimetric accuracy of Gamma Knife radiosurgery treatments.

EP-1665: Scalp-Sparing focal radiotherapy for gliomas using VMAT or Helical Tomotherapy: a feasibility study

Purpose or Objective: Both transient and permanent alopecia have a huge psychological impact on patient’s quality of life. Sparing the scalp during focal cranial RT for gliomas is a challenging issue during the treatment planning process due to the fact that the scalp is often strictly adjacent to the cortical or subcortical target. In addition, clear constraints for this structure to be used during the inverse planning are not available in literature, most of them being very strict. We report our preliminary experience with scalp sparing technique for patients with high grade gliomas.

EP-1514: γTools: a new multipurpose phantom for end-to-end tests in Gamma Knife SRS treatments

ESTRO 35 2016 _____________________________________________________________________________________________________ At 5 minutes after irradiation, the line profiles on the R2 map across the penumbra region showed the fall-off of the radiation field in both dosimeters while the penumbra region on the right field edge appeared steeper compared to the slope of the penumbra region on the left. The R2 color maps indicated a narrower transition from outside to fully inside the radiation field on the right compared to the transition on the left. 20 hours after irradiation the polymerization of the gel was presumably completed. The overall signal was both higher on the R2 gray scale maps and more pronounced on the R2 color maps. The line profiles across the penumbra regions exhibited a similar trend for both field edges compared to the profiles at 5 minutes post-irradiation. Over the time frame tested, the dosimeter appears stable.

Reproducibility and sensitivity of IQM: A real-time monitoring device for complex radiotherapy treatments

Global and local intra and interfraction detector repeatability results demonstrate the optimal detector performances SENSITIVITY IN DETECTING SMALL DELIVERY ERRORS was checked by inducing 7 types of ERRORS in the IMRT clinical plans for Head & Neck, prostate and the index quadrant by modifying the number of delivered MU (between 1 and 3 per beam) and by introducing deviations in linac leaf positions mimicking an MLC bank error as closing and opening one or both banks.

In-vivo and pre-treatment quality assurance software validation and verification

The aim of this study is to test the accuracy of the dose calculation algorithm available in DosimetryCheck (DC, MathResolution®), a patient QA software for both pretreatment QA and in vivo dose verification, that uses the EPID measured fluence of the treatment fields to reconstruct the dose distribution in the CT planning model of the patient.

SU-E-T-506: Intercomparison Study On Small Field Output Factor Measurements

Purpose In radiotherapy, uncertainties due to small field measurements (SFM) introduce systematic errors to the treatment process and the development of new dosimeters for quality assurance programs is a challenge. In this work we analyze the behavior of seven detectors measuring output factors of 6MV photon beam. Methods The dosimeters employed are: a single cristal diamond detector (SCCD) developed at the University of Rome Tor Vergata, a silicon diode developed within the project MAESTRO, a IBA Razor silicon diode, A1SL and A26 Exradin ion chambers, an EBT3 Gafchromic film and the Exradin W1 Scintillator.Diamond sensitive volume is a cylinder 2.2mm in diameter and 1μm thick. MAESTRO diode is 2×2mm2 active area. Razor sensitive volume is a cylinder 0.6 mm in diameter and 0.02 mm thick. A16 and A1Sl have a collecting volume of 0,015cc and 0,053cc. The W1 is an optical fiber with an active volume of 0.002cc. All measurements were performed in a water phantom, with detector positioned at the isocenter (SSD=90cm, d=10cm), MAESTRO diode being sandwiched in solid water to obtain an equivalent experimental setup. Results These measurements are challenging due to the absence of charged particle equilibrium conditions, detector size and positioning problems. They are in good agreement among each other, especially GAF, Razor, W1 and SCDD. Maximum deviations reported are related to the field 0.8×0.8cm2 for MAESTRO and chambers data with respect to EBT3: around 15% (A1SLvsEBT3), 16% (MAESTROvsEBT3). Razor and W1 show a deviation around 3% with respect to SCDD. Conclusion In this work measurements made with a variety of detectors are compared. These study show the possibility to choose different detectors for SFM and that smaller ion chambers are still not competitive with solid state detectors. Silicon, diamond and optical fiber dosimeters show a similar behavior with minor discrepancies for the smallest field.