Stereotatic Radiosurgery Research Articles

RBIO-05. THE IMPACT OF STEREOTATIC RADIOSURGERY (SRS) FOR THE RESIDUAL LESIONS OF PINEAL NON-GERMINOMATOUS GERM CELL TUMORS (NGGCTS) FOLLOWING CONVENTIONAL RADIOTHERAPY: A RETROSPECTIVE STUDY

Abstract OBJECTIVE To evaluate the safety and efficacy of stereotatic radiosurgery (SRS) in treating residual lesions of pineal non-germinomatous germ cell tumors (NGGCTs) after conventional radiotherapy. METHODS The patients admitted to Guangdong Sanjiu Brain Hospital from 1 January 2008 to 31 December 2018 who diagnosed with pineal NGGCTs pathologically or clinically were retrospectively analyzed. Among those, the patients received conventional radiotherapy with or without SRS were included. The residual lesions after radiotherapy were defined with a maximum diameter > 10mm. Prognosis related parameters such as local control rate, progress-free survival, overall survival and treatment-related toxicity were determined. RESULTS The median follow-up time was 34 months (range 8-142 months). The objective response rate and disease control rate were 71.4% and 95.2%, respectively. Three-year progression-free survival rate was 85.2% and 3-year total survival rate was 88.0%. The univariate analysis revealed that both age and concurrent chemotherapy were not correlated with the prognosis (P=0.286, 0.824). Partial tumor resection before radiotherapy and chemotherapy, AFP >500ng/ml, and no more than 4 cycles of adjuvant chemotherapy were poor prognostic factors (P=0.037, 0.010, 0.006). Moreover, no acute radiation response was observed after treatment with SRS. Only 1 out of 27 patients (3.7%) had brain neurotoxicity related to a prolonged course of radiochemotherapy. CONCLUSION SRS for residual lesions of NGGCTs following conventional radiotherapy appears to be well tolerant and improved local control. However, the therapeutic efficacy of conventional radiotherapy combined with SRS warrants further investigations in a large-scale randomized controlled clinical trials.

RADT-44. STEREOTATIC RADIOSURGERY FOR RESIDUAL LESIONS OF PINEAL NON-GERMINOMATOUS GERM CELL TUMORS AFTER CONVENTIONAL RADIOTHERAPY: A RETROSPECTIVE STUDY

Abstract OBJECTIVE To evaluate the safety and efficacy of stereotatic radiosurgery (SRS) in treating residual lesions of pineal non-germinomatous germ cell tumors (NGGCTs) after conventional radiotherapy. METHODS The patients admitted to Guangdong Sanjiu Brain Hospital from 1 January 2008 to 31 December 2018 who diagnosed with pineal NGGCTs pathologically or clinically were retrospectively analyzed. Among those, the patients received conventional radiotherapy with or without SRS were included. The residual lesions after radiotherapy were defined with a maximum diameter > 10mm. Prognosis related parameters such as local control rate, progress-free survival, overall survival and treatment-related toxicity were determined. RESULTS The median follow-up time was 34 months (range 8-142 months). The objective response rate and disease control rate were 71.4% and 95.2%, respectively. Three-year progression-free survival rate was 85.2% and 3-year total survival rate was 88.0%. The univariate analysis revealed that both age and concurrent chemotherapy were not correlated with the prognosis (P=0.286, 0.824). Partial tumor resection before radiotherapy and chemotherapy, AFP＞500ng/ml, and no more than 4 cycles of adjuvant chemotherapy were poor prognostic factors (P=0.037, 0.010, 0.006). Moreover, no acute radiation response was observed after treatment with SRS. Only 1 out of 27 patients (3.7%) had brain neurotoxicity related to a prolonged course of radiochemotherapy. CONCLUSION SRS for residual lesions of NGGCTs following conventional radiotherapy appears to be well tolerant and improved local control. However, the combination of conventional radiotherapy and SRS warrants further investigations in a large-scale randomized controlled clinical trials.

Stereotatic radiosurgery for residual lesions of pineal nongerminomatous germ cell tumors after conventional radiotherapy: A retrospective study.

e14516 Background: To evaluate the safety and efficacy of stereotatic radiosurgery (SRS) in treating residual lesions of pineal non-germinomatous germ cell tumors (NGGCTs) after conventional radiotherapy. Methods: The patients admitted to Guangdong Sanjiu Brain Hospital from 1 January 2008 to 31 December 2018 who diagnosed with pineal NGGCTs pathologically or clinically were retrospectively analyzed. Among those, the patients received conventional radiotherapy with or without SRS were included. The residual lesions after radiotherapy were defined with a maximum diameter > 10mm. Prognosis related parameters such as local control rate, progress-free survival, overall survival and treatment-related toxicity were determined. Results: The median follow-up time was 34 months (range 8-142 months). The objective response rate and disease control rate were 71.4% and 95.2%, respectively. Three-year progression-free survival rate was 85.2% and 3-year total survival rate was 88.0%. The univariate analysis revealed that both age and concurrent chemotherapy were not correlated with the prognosis (P = 0.286, 0.824). Partial tumor resection before radiotherapy and chemotherapy, AFP>500ng/ml, and no more than 4 cycles of adjuvant chemotherapy were poor prognostic factors (P = 0.037, 0.010, 0.006). Moreover, no acute radiation response was observed after treatment with SRS. Only 1 out of 27 patients (3.7%) had brain neurotoxicity related to a prolonged course of radiochemotherapy. Conclusions: SRS for residual lesions of NGGCTs following conventional radiotherapy appears to be well tolerant and improved local control. However, the combination of conventional radiotherapy and SRS warrants further investigations in a large-scale randomized controlled clinical trials.

Ion chambers compliance results of Brazilian radiation therapy facilities

The Brazilian Nuclear Energy Commission (cnen) has been making a constant effort to keep up to date with international standards and national needs to strengthen the status of radiological protection of the country. The guidelines related to radiation therapy facilities have been revised in the last five years in order to take into consideration the most relevant aspects of the growing technology as well as to mitigate the accidents or incidents observed in practice. Hence, clinical dosimeters have gained special importance in this matter. In the present work, we discuss the effectiveness of regulation and inspections to the enforcement of instrument calibration accuracy for the improvement of patient dosimetry and quality control. As a result, we observed that the number of calibrated instruments, mainly well chambers, is increasing each year. The same behavior is observed for instruments employed in technologically advanced radiation treatments such as intensity modulated radiotherapy, volumetric therapy and stereotatic radiosurgery. We ascribe this behavior to the new regulation.

In-Field Maximum Point Dose Could be a Risk Factor of Radionecrosis in Patients With Brain Metastases Treated by Linear Accelerator-Based Stereotatic Radiosurgery

In-Field Maximum Point Dose Could be a Risk Factor of Radionecrosis in Patients With Brain Metastases Treated by Linear Accelerator-Based Stereotatic Radiosurgery

Stereotatic radiosurgery – A review of literature

Stereotatic radiosurgery – A review of literature

Remineralization in a case of Spinal Metastasis following Radiation Treatment with CyberKnife Stereotactic Radiosurgery

In evaluating the outcomes of stereotatic radiosurgery (SRS) in the treatment of spinal metastases, authors have looked primarily at endpoints of pain relief and tumor growth suppression. The question of structural stability has been raised, but the pattern of bone remineralization has not been investigated in detail. With traditional radiation, both tumor control and pain relief are modest, and resulting bone remineralization can reach 80% with responsive tumors. SRS offers higher rates of both tumor growth control and pain relief (88%), even for radioresistant tumors, but the protection from vertebral fracture is not improved when there is more than 40% of the vertebra involved. We report a case of a partially collapsed C2 vertebral body affected by multiple myeloma, which was surgically stabilized and treated with CyberKnife SRS. Upon a 12-month follow-up period including CT imaging, remineralization of the vertebral body was observed starting at three months post-SRS that significantly progressed during the 12-month follow-up period. Final radiographic evaluation showed almost complete restoration of the structure of the vertebral body and the associated bone densities with significantly increased stability. This pattern of remineralization is contrasted with reported results of traditional radiation therapy, and its implications for stabilization are noted.

SU-E-T-13: An Evaluation of RadCal Software in Its Monitor Unit Calculation Accuracy for Small Dynamic Fields Using HDMLC

Purpose: To investigate the accuracy of an independent monitor unit (MU) verification program for small fields used in dynamically modulated highdefinition multileaf-collimator (HDMLC)-based stereotatic radiosurgery (SRS). Methods: HDMLC-SRS patient-treatment plans were calculated using the BrainLab-pencil beam dose-calculation algorithm implemented in the BrainLab-iPlan treatment planning system (TPS) (v.4.1.2) for the Novalis-TX 6X-SRS beam. Percent depth doses, beam profiles and output tables from this clinical beam were utilized to commission the RadCalc software (v.6.2) for independent MU verification. The MU difference between the MU calculation of the treatment planning system and the independent MU verification program for 187 dynamic arcs and 44 intensity modulated beams corresponding to 41 intracranial lesions from 35 patients was calculated. Field sizes of the arcs and beams studied ranged from 15 to 34 mm in their longest extension. Results: The average difference in the MUs with one standard deviation was −0.1% +/− 1.0% for the dynamic arcs and −0.0%+/− 2.7% for the intensity-modulated beams. The intensity modulated beams verifications showed a much higher spread in the difference compared to the non-modulated dynamic arcs; however, the average results can be considered clinically acceptable. The MU difference correlated inversely with the lesion size, indicating the limitation of the TPS algorithm with smaller field sizes. Conclusion: Use of the RadCalc software as an independent monitor unit verification system for both modulated and non-modulated small fields based on high-definition multileaf collimation is adequate to independently validate the point dose calculation accuracy. The system can be utilized as a part of the SRS quality assurance program.

Neurosugical complications of stereotatic radiosurgery treatment in brain AVMS

Neurosugical complications of stereotatic radiosurgery treatment in brain AVMS

Successful treatment of cervical dystonia induced by basal ganglion venous angioma with Gamma Knife thalamotomy

Stereotatic radiosurgery is typically not the first line of treatment for cervical dystonia. We present a patient with a rare cervical dystonia induced by a venous angioma in the right basal ganglion. The patient was successfully treated with a gamma knife thalamotomy after failed treatments of botulinum toxin injections and peripheral denervation.

Postoperative radiotherapy for ependymoma

PurposeTo evaluated the patterns of failure, survival rate, treatment-related toxicity and prognostic factors in postoperative radiotherapy of patients with ependymoma.Materials and MethodsThirty patients who underwent surgery and postoperative radiotherapy for ependymoma between the period of June 1994 and June 2008 were reviewed retrospectively. The age of patients ranged from 21 months to 66 years (median, 19 years). Seventeen patients had grade II ependymoma, and 13 had grade III anaplastic ependymoma according to the World Health Organization grading system. The postoperative irradiation was performed with 4 or 6 MV photon beam with median dose of 52.8 Gy (range, 45 to 63 Gy), and radiation field including 2 cm beyond the preoperative tumor volume. Median follow-up period was 51 months (range, 12 to 172 months).ResultsFourteen out of 30 (46.7%) patients experienced recurrence, and 12 of those died. Among those 14 patients who experienced recurrence, 11 were in-field and 3 were out-of-field recurrence. The 5-year overall survival (OS) and progression-free survival (PFS) rates were 66.7% and 56.1%, respectively. On univariate analysis, tumor grade was a statistically significant prognostic factor for OS and PFS. There were two complications after surgery and postoperative radiotherapy, including short stature and facial palsy on the left side.ConclusionWe observed good survival rates, and histologic grade was a prognostic factor affecting the OS and PFS. Almost all recurrence occurred in primary tumor site, thus we suggest further evaluation on intensity-modulated radiotherapy or stereotatic radiosurgery for high-risk patients such as who have anaplastic ependymoma.

SU-E-T-541: A Clinical Approach to Account for the Attenuation of Varian Exact IGRT Couch Top for Spine Stereotatic Radiosurgery Patients

Purpose: The purpose of this work is to develop an approach to account for the attenuation of Varian Exact IGRT couch top for spine cancer patients in spine stereotatic radiosurgery. Methods: Varian Exact IGRT couch which has carbon fiber plates sandwiched with a plastic foam core was used for this study. Transmission of 6MV x‐rays through the couch was measured at various oblique beam angles. Based on the measured values, we modeled the couch top as a stored organ in Pinnacle treatment planning system (TPS) for spine stereotatic radiosurgery (SSRS) patients. A planner can load the virtual couch top and override the density when designing a treatment plan to account for the couch attenuation explicitly. The dosimetric impact of the couch top on DVHs was investigated in 3 representative patients. Results: At normal incidence, percentage of the attenuation of the Exact IGRT couch for a 6MV beam was measured to be 2.40% and 2.68% for field size of and , respectively. The attenuation was found to be gantry angle dependent, with maximum attenuation 3.90% at 120° for field size of and 4.25% at 130° for , respectively. By using a fixed density of 1.05 within the thin carbon fiber layers, the calculated attenuation for the virtual couch top were 2.38% and 2.94% for field, 4.15%, and 4.57% for field, respectively, which agreed well with the measurement. Without considering the couch attenuation, the average loss of target coverage was 7.1% in three representative cases we analyzed. Conclusions: The attenuation of Varian Exact IGRT Couch Top should not be ignored when using the couch top for SSRS patients. A clinical approach was developed to account for the attenuation. A calibrated virtual couch model can be used to account for the attenuation in the treatment planning process.

A phase II trial of vinorelbine and intensive temozolomide for patients with recurrent or progressive brain metastases

To investigate the efficacy and safety of the combination of vinorelbine and intensive temozolomide for recurrent or progressive brain metastases from solid tumors. Patients > or =18 years of age and with Karnofsky performance scale (KPS) > or = 60, adequate organ function and progressive or recurrent brain metastases were eligible. This was a phase II trial with 28-day cycles using temozolomide (150 mg/m(2), days 1-7 and 15-21) and vinorelbine 25 or 30 mg/m(2 )on days one and eight. The primary endpoint was objective radiographic response. Thirty-eight patients (15 men, 23 women) with a median age of 57 years (range, 39-75) and median KPS of 80 were enrolled. The primary tumor sites were lung (n = 20), breast (n = 11), colorectal (n = 2), kidney (n = 2), bladder (n = 1), endometrium (n = 1), head and neck (n = 1). Prior therapies included chemotherapy (97%), whole-brain radiation therapy (79%), brain metastasis resection (53%) and stereotatic radiosurgery (47%). Objective radiographic response rate was 5% (one complete response and one minor response); five patients had stable disease, 29 progressive disease and two patients were not evaluable. Twenty-nine patients (76%) have died and the median follow-up of survivors was six months. Median progression-free and overall survivals were 1.9 and 5 months, respectively. Grade 3/4 toxicities were mainly hematological and two patients discontinued the study due to myelosuppression. In this heavily pretreated population of patients with brain metastases, adding vinorelbine and increasing the intensity of temozolomide do not improve response rates compared to previous studies with single-agent temozolomide at standard doses.

SU‐FF‐T‐78: Analysis of Setup Accuracy for Invasive Frame‐Based Stereotatic Radiosurgery (SRS) Patients Using Cone Beam Computed Tomography (CBCT)

Purpose: To evaluate the setup accuracy of invasive frame‐based stereotactic radiosurgery (SRS) patients using cone‐beam computed tomography (CBCT). Method and Materials: Each patient participating in this institutional‐approved prospective protocol was immobilized with a Brown‐Roberts‐Wells (BRW) frame and scanned on a CT simulator for treatment planning (2mm slice thickness). The patient was transferred to the treatment room and setup to the BRW coordinates of the planning isocenter. Before treatment was delivered, the patient was CBCT scanned with the CT localizer attached to the BRW frame. A CBCT scan of a BB at the treatment isocenter was also acquired to evaluate the apparatus accuracy of the BRW frame system. Systematic shifts between CBCT and treatment isocenters were measured independently from an orthogonal pair of projection images of a BB at the treatment isocenter, and were used to identify the treatment isocenter in the patient CBCT scan. BRW coordinates of the treatment isocenter of the patient scan were compared with the planning BRW coordinates to evaluate the localization accuracy. The patient CBCT scan was then co‐registered with simulation CT to determine the setup accuracy. Results: Three patients were successfully recruited to date. The average apparatus accuracy (Euclidean distance between the BRW coordinates of the planning isocenter and the BB) was 0.46±0.39 mm (mean ± one standard deviation). The average localization accuracy was 0.88±0.18 mm. The total setup accuracy of the invasive SRS frame was 1.63±1.39 mm with major sources of error in the superior‐inferior (0.43±2.18 mm) and anterior‐posterior (0.33±0.79 mm) directions. Conclusion: The apparatus error generated by the BRW frame system was comparable to earlier reports. Although the localization accuracy for patient treatment was slightly worse, significant setup errors were observed due to patient sag. Volumetric CBCT scan was therefore recommended even for invasive frame‐based SRS to correct this problem.

Stereotatic radiosurgery of 468 brain metastases ≤2 cm: implications for SRS dose and whole brain radiation therapy

Purpose The national standard stereostatic radiosurgery (SRS) dose for brain metastases ≤2 cm is 24 Gy as established by the Radiation Therapy Oncology Group study 90–05, in which planned whole brain radiotherapy (WBRT) was not used. On the basis of our institutional experience, the goal of this study was to determine the optimal SRS dose and influence of WBRT on local tumor control among 468 ≤2-cm metastases. Methods and materials Between October 1992 and May 2001, 468 newly diagnosed or recurrent ≤2-cm brain metastases, among 160 patients, were treated with SRS (dose range, 7–30 Gy; median, 20). A total of 240 metastases received planned WBRT (range, 6.75–50.4 Gy; median, 40.5) vs. 228 metastases that did not. The variables tested by multivariate analysis for their potential effect on tumor control included histologic type, site of metastasis, primary diagnosis, tumor volume, SRS dose, newly diagnosed vs. recurrent metastasis, and planned WBRT vs. no planned WBRT. Results Follow-up ranged from 1 to 82 months (median 7). On multivariate analysis, the addition of WBRT was the most significant predictor of local tumor control. Overall, patients who received WBRT had superior local tumor control rates (97% vs. 87% in those who did not receive WBRT; p = 0.0001). Patients receiving WBRT and SRS ≥20 Gy achieved local control rates of 99% compared with 91% control rates when treated with WBRT and SRS <20 Gy ( p = 0.0029). Increasing the SRS dose to >20 Gy resulted in no improvement in local tumor control and a higher rate of Grade 3 and 4 neurotoxicity, approaching statistical significance (5.9% vs. 1.9%, p = 0.078). Conclusion First, optimal control of brain metastasis ≤2 cm was seen with 20-Gy SRS combined with planned WBRT. Second, SRS doses >20 Gy resulted in no obvious improvement in local control and appeared to be associated with a greater rate of complications.

An analysis of treatment result for brain metastasis of stereotactic radiosurgery plus radiotherapy

Objective To compare the effect in the treatment of brain metastasis between stereotatic radiosurgery puls radiotherapy (SRS+R) and radiotherapy (R) alone. Methods From May 1995 to December 2000, a total of 84 patients with brain metastasis were evaluated in this study . In SRS+R group, 38 patients were given SRS with the center dose of 50～60Gy and the bound dose of 20～25Gy, whole brain irradiation were given the dose of 30～40Gy in 3～4 weeks. In R group , 46 patients received a total dose of 40～60Gy with 30～40 Gy entire brain irradiation puls a boost of 10～20Gy. Results The median survival period were 10 months in SRS+R group and 5.3 months in R group. The one year survival rate were 60.5%(23/38) and 17.4%(8/46) in SRS+R group and in R alone group ( P 0.01). The local control rate were 92.1%(35/38) and 21.7%(18/46) in SRS+R group and R alone ( P 0.01). Conclusion SRS is superior to R alone in prolong the survival period and local control treatment of brain metastasis.