Phantom study of stereotactic radioablation for ventricular tachycardia (STRA-MI-VT) using Cyberknife Synchrony Respiratory Tracking System with a single fiducial marker.

PURPOSE: Within the STRA-MI-VT phase Ib/II trial (NCT04066517), the aim of this phantom study was to explore the feasibility of Cyberknife treatments on cardiac lesions by tracking as a single marker the lead tip of an implantable cardioverter defibrillator. The residual displacement of the lesion during the tracking was studied, planning margins were found and the dosimetric accuracy of the treatment was checked. MATERIALS AND METHODS: A lead was inserted into a phantom (EasyCube phantom, Sun Nuclear Co, USA) and then placed on the translating ExacTrac Gating System (BrainLAB AG, Germany). The phantom was rotated, a virtual lesion was identified and its displacement during the tracking was studied. Two plans were compared, calculated on the unrotated volume and on the envelope of the unrotated and the rotated volumes. The plans were delivered using the Cyberknife System (Accuray Inc, USA) and their dosimetric accuracy verified by gamma analysis with gafchromic films. RESULTS: The residual margin increases enhancing the distance between the lead and the lesion. It is 4 mm for distance 0 cm and 5 mm for distance 5 cm. The coverage is reduced by 3.8% (interquartile range 2.5%-4.7%) when the dose is prescribed on the unrotated volume. All treatment plans are accurate and 3% 3 mm gamma analysis results are greater than 94%. CONCLUSIONS: Results showed that tracking with a single marker is feasible considering adequate residual planning margins. The volumes could be further reduced by using additional markers, for example by placing them on the patient's skin.

STRA-MI-VT (STereotactic RadioAblation by Multimodal Imaging for Ventricular Tachycardia): rationale and design of an Italian experimental prospective study.

BACKGROUND: Ventricular tachycardia (VT) is a life-threatening condition, which usually implies the need of an implantable cardioverter defibrillator in combination with antiarrhythmic drugs and catheter ablation. Stereotactic body radiotherapy (SBRT) represents a common form of therapy in oncology, which has emerged as a well-tolerated and promising alternative option for the treatment of refractory VT in patients with structural heart disease. OBJECTIVE: In the STRA-MI-VT trial, we will investigate as primary endpoints safety and efficacy of SBRT for the treatment of recurrent VT in patients not eligible for catheter ablation. Secondary aim will be to evaluate SBRT effects on global mortality, changes in heart function, and in the quality of life during follow-up. METHODS: This is a spontaneous, prospective, experimental (phase Ib/II), open-label study (NCT04066517); 15 patients with structural heart disease and intractable VT will be enrolled within a 2-year period. Advanced multimodal cardiac imaging preceding chest CT-simulation will serve to elaborate the treatment plan on different linear accelerators with target and organs-at-risk definition. SBRT will consist in a single radioablation session of 25 Gy. Follow-up will last up to 12 months. CONCLUSIONS: We test the hypothesis that SBRT reduces the VT burden in a safe and effective way, leading to an improvement in quality of life and survival. If the results will be favorable, radioablation will turn into a potential alternative option for selected patients with an indication to VT ablation, based on the opportunity to treat ventricular arrhythmogenic substrates in a convenient and less-invasive manner.

Lung optimized treatment with CyberKnife® in inoperable lung cancer patients: feasibility analysis of a mono-institutional 115 patient series.

CyberKnife® Lung Optimized Treatment (LOT) allows the treatment of lung cancer without invasive fiducial implantation. The aim of this retrospective analysis was to evaluate the feasibility, toxicity and clinical outcome. One hundred fifteen patients (124 lesions) were treated with CyberKnife® using LOT. The median age was 72.6 years (range 31.8-90.3). From 124 treated lesions, 52 were with histopathological confirmation (41 primitive pulmonary cancers, 8 pulmonary metastases) and 72 as untyped tumors. For 5 patients (6 lesions) treatment was an in-field re-irradiation. Concomitant therapy was administered in 7 patients. Zero-View tracking was applied in 69 patients, 1-View in 33 patients, 2-View in 22 patients. The median total dose was 45 Gy (range 18-54), median dose/fraction was 15 Gy (range 4-18) with a median prescription isodose of 80% (range 68-85). The median planning target volume (PTV) was 25 cm3 (range 3-195). The median follow-up was 20 months (range 7-47). Thirty-seven patients (32%) were alive with no evidence of disease, 39 patients (34%) were alive with clinically evident disease, and 38 patients (33%) died of the disease. The 1- and 2-year overall survival (OS) rate was 83% and 61%. The median time to progression was 19 months (95% confidence interval: 11-19 months), 1- and 2-year progression-free survival (PFS) rates were 62% and 41%, respectively. Smaller PTV was significantly associated with better OS, PFS and in-field PFS in univariate and multivariate analyses. Acute toxicity was observed in 36 patients (41%). Late toxicity was registered in 25 patients (29%). G3 late toxicity was observed in one patient (1.1%). Our data suggest that fiducial less-stereotactic body radiation therapy (SBRT) is a feasible, well-tolerated and potentially effective treatment with high compliance in the setting of inoperable patients due to concomitant disease or previous treatments.

Stereotactic radiation therapy in oligometastatic colorectal cancer: outcome of 102 patients and 150 lesions.

To evaluate the local control (LC), progression free survival (PFS), out-field PFS, overall survival (OS), toxicity and failure predictors of SRT in a series of various sites oligometastatic CRC patients. Patients with oligometastatic CRC disease were analyzed retrospectively. The SRT prescribed dose was dependent on the lesion volume and its location. 102 consecutive oligometastatic CRC patients (150 lesions) were included. They underwent SRT between 2012 and 2015. Median prescription dose was 45 Gy (median dose/fraction was 15 Gy/3 fractions biological equivalent dose (BED10) 112.5 Gy). Median follow-up was 11.4 months. No patients experienced G3 and G4 toxicity. No progression was found in 82% (radiological response at 3 months) and 85% (best radiological response) out of 150 evaluable lesions. At 1 and 2 years: LC was 70% and 55%; OS was 90% and 90%; PFS was 37% and 27%; out-field PFS was 37% and 23% respectively. Progressive disease was correlated with BED10 (better LC when BED10 was ≥ 75 Gy (p < 0.0001)). In multivariate analysis, LC was higher in lesions with a Plpnning target volume (PTV) volume < 42 cm3 and BED10 ≥ 75 Gy. Patients with Karnofsky performance status < 90 showed higher out-field progression. SRT is an effective treatment for patients with oligometastases from CRC. Its low treatment-associated morbidity and acceptable LC make of SRT an option not only in selected cases. Further studies should be focused to clarify which patient subgroup will benefit most from this treatment modality and to define the optimal dose to improve LC while maintaining low toxicity profile.

Recurrent oligometastatic transitional cell bladder carcinoma: is there room for radiotherapy?

This paper presents a retrospective report on radiotherapy (RT) in the oligometastastic recurrence of bladder cancer. Thirteen patients treated for low-volume metastatic transitional cell urinary bladder carcinoma (TCC) were reviewed, with the primary endpoint to evaluate the safety and efficacy of RT, proposed as an alternative to systemic treatment and/or to defer commencement of systemic therapy. The inclusion criteria were: patients who received RT without other local/systemic therapy for oligometastatic TCC with lymph node, bone and lung lesions or local recurrence. Previous systemic therapy and surgery on the primary tumor were allowed in this tumor response, and toxicity evaluation and progression free-survival was also assessed. Thirteen patients with 21 lesions were treated with stereotactic body radiotherapy (SBRT) or conformal 3D radiotherapy (3D-CRT) between 2012 and 2017. All participants were discussed by a multidisciplinary urological board. The median age at RT was 68 years (range 50-80), the median Karnofsky performance status (KPS) was 90 (range 80-90) and the median interval between TCC diagnosis and commencement of RT on oligometastasis was 23 months (range 8-105). The median treatment dose was 25 Gy (range 20-36 Gy) given over a median of 5 fractions (range 3-10 fractions) with a median follow-up of 25 months (range 3-43 months). Imaging assessment was available for 20 lesions. The radiological progression of disease was registered in 9 patients at the median of 4.2 months from radiotherapy (range 1.9-18.8 months). This identified in-field and out-field progression in 6 patients and only out-field progression in the remaining 3. At last contact, 3 patients were alive with no evidence of disease, 3 had evidence of disease, 6 died of cancer-related disease and one died from another cause. No severe acute and late toxicity was observed. The literature contains no consistent data on TCC oligometastatic setting, but radiotherapy on lymph node, bone and/or lung oligo-recurrence from TCC offers durable disease control in a small number of patients with a very low toxicity profile. Further studies are required to establish the radiotherapy role in oligometastatic recurrent bladder cancer.

Case series on multiple prostate re-irradiation for locally recurrent prostate cancer: something ventured, something gained.

The aim is to present the technical feasibility and efficacy of multiple re-irradiation (re-EBRT) for local recurrence of prostate cancer (PCa) using retrospective analysis of an updated series of patients who received ablative re-EBRT with stereotactic image-guided technique for isolated local recurrence of PCa. Eight patients received three RT courses (2 re-RTs); of those 2 received 4 RT courses (3 re-RTs). Local relapse in the prostate was assessed by multiparametric magnetic resonance and/ or choline positron emission tomography. Before treatment planning, all patients had been evaluated for late toxicity from previous RT according to RTOG/EORTC. Biochemical control was assessed according to Phoenix definition. Mean age at the third RT course was 68 (standard deviation, SD: 7.2); all patients had a good performance status. At diagnosis, four cases were classified as high risk PCa, three as intermediate and one as low per NCCN 2017. Biochemical progression free interval after first and second RT-course were 74 (IQR: 59.3-133.6) months and 33 (IQR: 20.8-53.1) months, respectively. Biochemical and radiological response was registered in all patients. At present, seven out of eight patients are disease free. Overall toxicity profile was good; no severe acute or late genitourinary or gastrointestinal events were recorded. Multiple RT courses with high precision technology and image guidance can be proposed as a possible salvage therapy for locally recurrent, low-burden PCa recurrence in adequately selected patients. Deeper understanding of radiobiological effects of hypofractionation and larger series of patients are warranted to fully evaluate the applicability of multiple RT courses in the setting of locally recurrent PCa.

Genital marginal failures after intensity-modulated radiation therapy (IMRT) in squamous cell anal cancer: no higher risk with IMRT when compared to 3DCRT.

Intensity-modulated radiotherapy (IMRT) is considered the preferred option in squamous cell canal cancer (SCAC), delivering high doses to tumor volumes while minimizing dose to surrounding normal tissues. IMRT has steep dose gradients, but the technique is more demanding as deep understanding of target structures is required. To evaluate genital marginal failure in a cohort of patients with non-metastatic SCAC treated either with IMRT or 3DCRT and concurrent chemotherapy, 117 patients with SCAC were evaluated: 64 and 53 patients were treated with IMRT and 3DCRT techniques, respectively. All patients underwent clinical and radiological examination during their follow-up. Tumor response was evaluated with response evaluation criteria in solid tumors v1.1 guideline on regular basis. All patients' data were analyzed, and patients with marginal failure were identified. Concomitant chemotherapy was administered in 97 and 77.4% of patients in the IMRT and 3DCRT groups, respectively. In the IMRT group, the median follow-up was 25 months (range 6-78). Progressive disease was registered in 15.6% of patients; infield recurrence, distant recurrence and both infield recurrence and distant recurrence were identified in 5, 4 and 1 patient, respectively. Two out of 64 patients (3.1%) had marginal failures, localized at vagina/recto-vaginal septum and left perineal region. In the 3DCRT group, the median follow-up was 71.3 months (range 6-194 months). Two out of 53 patients (3.8%) had marginal failures, localized at recto-vaginal septum and perigenital structures. The rate of marginal failures was comparable in IMRT and 3DCRT groups (χ2 test p = 0.85). In this series, the use of IMRT for the treatment of SCAC did not increase the rate of marginal failures offering improved dose conformity to the target. Dose constraints should be applied with caution-particularly in females with involvement of the vagina or the vaginal septum.

Validation of a pretreatment delivery quality assurance method for the CyberKnife Synchrony system.

PURPOSE: To evaluate the geometric and dosimetric accuracies of the CyberKnife Synchrony respiratory tracking system (RTS) and to validate a method for pretreatment patient-specific delivery quality assurance (DQA). METHODS: An EasyCube phantom was mounted on the ExacTrac gating phantom, which can move along the superior-inferior (SI) axis of a patient to simulate a moving target. The authors compared dynamic and static measurements. For each case, a Gafchromic EBT3 film was positioned between two slabs of the EasyCube, while a PinPoint ionization chamber was placed in the appropriate space. There were three steps to their evaluation: (1) the field size, the penumbra, and the symmetry of six secondary collimators were measured along the two main orthogonal axes. Dynamic measurements with deliberately simulated errors were also taken. (2) The delivered dose distributions (from step 1) were compared with the planned ones, using the gamma analysis method. The local gamma passing rates were evaluated using three acceptance criteria: 3% local dose difference (LDD)/3 mm, 2%LDD/2 mm, and 3%LDD/1 mm. (3) The DQA plans for six clinical patients were irradiated in different dynamic conditions, to give a total of 19 cases. The measured and planned dose distributions were evaluated with the same gamma-index criteria used in step 2 and the measured chamber doses were compared with the planned mean doses in the sensitive volume of the chamber. RESULTS: (1) A very slight enlargement of the field size and of the penumbra was observed in the SI direction (on average <1 mm), in line with the overall average CyberKnife system error for tracking treatments. (2) Comparison between the planned and the correctly delivered dose distributions confirmed the dosimetric accuracy of the RTS for simple plans. The multicriteria gamma analysis was able to detect the simulated errors, proving the robustness of their method of analysis. (3) All of the DQA clinical plans passed the tests, both in static and dynamic conditions. No statistically significant differences were found between static and dynamic cases, confirming the high degree of accuracy of the Synchrony RTS. CONCLUSIONS: The presented methods and measurements verified the mechanical and dosimetric accuracy of the Synchrony RTS. Their method confirms the fact that the RTS, if used properly, is able to treat a moving target with great precision. By combining PinPoint ion chamber, EBT3 films, and gamma evaluation of dose distributions, their DQA method robustly validated the effectiveness of CyberKnife and Synchrony system.

Planning study to compare dynamic and rapid arc techniques for postprostatectomy radiotherapy of prostate cancer.

PURPOSE: To compare our standard technique for postprostatectomy radiotherapy of prostate cancer, i.e. using two lateral conformal dynamic arcs with volumetric-modulated arc therapy (VMAT) performed with the RapidArc(®) (Varian Medical Systems, Palo Alto, CA, USA). The plans were referred to as DA and RA, respectively. MATERIALS AND METHODS: The treatment plans of 44 patients receiving adjuvant/salvage radiotherapy in the first months of 2010 were compared. In all cases, the prescribed total dose was 66-68.2 Gy (2.2 Gy per fraction). Both DA and RA plans were optimized in terms of dose coverage and constraints. RESULTS: Small differences between the techniques were observed for planning target volume (PTV) dose distribution, whereas significant differences in sparing of organs at risk (OARs) were recorded (p < 0.0001). The OAR values (median; 95 % confidence interval, CI) were: rectum: D30 % = 60.7 Gy (59.40-62.04 Gy) and 48.2 Gy (46.40-52.72 Gy), D60 % = 34.1 Gy (28.50-38.92 Gy) and 27.7 Gy (21.80-31.51 Gy); bladder: D30 % = 57.3 Gy (45.83-64.53 Gy) and 46.4 Gy (33.23-61.48 Gy), D50 % = 16.4 Gy (11.89-42.38 Gy) and 17.2 Gy (10.97-27.90 Gy), for DA and RA, respectively. Treatment times were very similar, whereas the monitor units (MU) were 550 ± 29 versus 277 ± 3 for RA and DA, respectively. CONCLUSION: Dose-volume histograms (DVHs) show improvements in OAR sparing with RA. However, the RA technique is associated with almost double the number of MUs compared to DA. Regarding the PTV, DA is slightly superior in terms of D2 % and dose homogeneity. On the whole, the results suggest that RA be the favorable technique.

Prostate positioning using cone-beam computer tomography based on manual soft-tissue registration: interobserver agreement between radiation oncologists and therapists.

PURPOSE: To check the interobserver agreement between radiation oncologists and therapists (RTT) using an on- and off-line cone-beam computer tomography (CBCT) protocol for setup verification in the radiotherapy of prostate cancer. MATERIALS AND METHODS: The CBCT data from six prostate cancer patients treated with hypofractionated intensity-modulated radiotherapy (IMRT) were independently reviewed off-line by four observers (one radiation oncologist, one junior and two senior RTTs) and benchmarked with on-line CBCT positioning performed by a radiation oncologist immediately prior to treatment. CBCT positioning was based on manual soft-tissue registration. Agreement between observers was evaluated using weighted Cohen's kappa statistics. RESULTS: In total, 152 CBCT-based prostate positioning procedures were reviewed by each observer. The mean (± standard deviation) of the differences between off- and on-line CBCT-simCT registration translations along the three directions (antero-posterior, latero-lateral and cranio-caudal) and rotation around the antero-posterior axis were -0.7 (3.6) mm, 1.9 (2.7) mm, 0.9 (3.6) mm and -1.8 (5.0) degrees, respectively. Satisfactory interobserver agreement was found, being substantial (weighted kappa >0.6) in 10 of 16 comparisons and moderate (0.41-0.60) in the remaining six comparisons. CONCLUSIONS: CBCT interpretation performed by RTTs is comparable to that of radiation oncologists. Our study might be helpful in the quality assurance of radiotherapy and the optimization of competencies. Further investigation should include larger sample sizes, a greater number of observers and validated methodology in order to assess interobserver variability and its impact on high-precision prostate cancer IGRT. In the future, it should enable the wider implementation of complex and evolving radiotherapy technologies.

A survey of 14 computed tomography scanners in Greece and 32 scanners in Italy. Examination frequencies, dose reference values, effective doses and doses to organs.

A survey of examination frequencies, dose reference values, effective doses and doses to organs involving 14 scanners from Greece and 32 scanners from Italy was carried out for the years 1999 and 2000. Examination frequencies per scanner and per year were found to be 3590 for Greece and 4520 for Italy. For the types of examinations considered, CDTI(W) and DLP measurements were taken. Also scan lengths used for the same types of examinations were monitored. For the same types of examinations effective doses were calculated by two methods, and it was found that their mean values ranged from 13.1 mSv for thoracic spine to 1.6 mSv for the brain examinations. From the data of the 14 Greek laboratories, doses to organs were calculated and it was found that the thyroid receives 50.2 +/- 19.8 mGy during a cervical spine examination while the gonads receive 17.8 +/- 6.9 mGy during a routine pelvis examination.