Factors influencing local control after MR-guided stereotactic body radiotherapy (MRgSBRT) for adrenal metastases

Purpose

Stereotactic body radiotherapy (SBRT) is an effective treatment for adrenal gland metastases, but it is technically challenging and there are concerns about toxicity. We performed a multi-institutional pooled retrospective analysis to study clinical outcomes and toxicities after MR-guided SBRT (MRgSBRT) using for adrenal gland metastases.

Methods and Materials

Clinical and dosimetric data of patients treated with MRgSBRT on a 0.35 T MR-Linac at 11 institutions between 2016 and 2022 were analyzed. Local control (LC), local progression-free survival (LPFS), distant progression-free survival (DPFS) and overall survival (OS) were estimated using Kaplan-Meier method and log-rank test.

Results

A total of 255 patients (269 adrenal metastases) were included. Metastatic pattern was solitary in 25.9 % and oligometastatic in 58.0 % of patients. Median total dose was 45 Gy (range, 16-60 Gy) in a median of 5 fractions, and the median BED10 was 100 Gy (range, 37.5-132.0 Gy). Adaptation was done in 87.4 % of delivered fractions based on the individual clinicians' judgement. The 1- and 2- year LPFS rates were 94.0 % (95 % CI: 90.7-97.3 %) and 88.3 % (95 % CI: 82.4-94.2 %), respectively and only 2 patients (0.8 %) experienced grade 3 + toxicity. No local recurrences were observed after treatment to a total dose of BED10 > 100 Gy, with single fraction or fractional dose of > 10 Gy.

Conclusions

This is a large retrospective multi-institutional study to evaluate the treatment outcomes and toxicities with MRgSBRT in over 250 patients, demonstrating the need for frequent adaptation in 87.4 % of delivered fractions to achieve a 1- year LPFS rate of 94 % and less than 1 % rate of grade 3 + toxicity. Outcomes analysis in 269 adrenal lesions revealed improved outcomes with delivery of a BED10 > 100 Gy, use of single fraction SBRT and with fraction doses > 10 Gy, providing benchmarks for future clinical trials.

Dosimetric comparison of stereotactic MR-guided radiation therapy (SMART) and HDR brachytherapy boost in cervical cancer

PURPOSE

The standard of care in locally advanced cervical cancer (LACC) is concomitant chemoradiotherapy followed by high-dose-rate brachytherapy (HDR-BT). Although previous studies compared HDR-BT with stereotactic body radiotherapy (SBRT), there is scarce data regarding the dosimetric outcomes of stereotactic MR-guided adaptive radiation therapy (SMART) boost in lieu of HDR-BT.

METHODS AND MATERIALS

In this single-institutional in-silico comparative study, LACC patients who were definitively treated with external beam radiotherapy followed by HDR-BT were selected. Target volumes and organs at risk (OARs) were delineated in MRI and HDR-planning CT. An HDR-BT and a SMART boost plan were generated with a prescribed dose of 28 Gy in four fractions for all patients. The HDR-BT and SMART boost plans were compared in regard to target coverage as well OARs doses.

RESULTS

Mean EQD2 D90 to HR-CTV and IR-CTV for HDR-BT plans were 89.7 and 70.5 Gy, respectively. For SMART, the mean EQD2 D90 to HR-PTV, HR-CTV, and IR-CTV were 82.9, 95.4, and 70.2 Gy, respectively. The mean D2cc EQD2 of bladder, rectum, and sigmoid colon for HDR-BT plans were 86.4, 70.7, and 65.7 Gy, respectively. The mean D2cc EQD2 of bladder, rectum, and sigmoid colon for SMART plans were 81.4, 70.8, and 73.6 Gy, respectively. All dose constraints in terms of target coverage and OARs constraints were met for both HDR-BT and SMART plans.

CONCLUSIONS

This dosimetric study demonstrates that SMART can be applied in cases where HDR-BT is not available or ineligible with acceptable target coverage and OAR sparing. However, prospective clinical studies are needed to validate these results.

Robotic male and laparoscopic female sphincter-preserving total mesorectal excision of mid-low rectal cancer share similar specimen quality, complication rates and long-term oncological outcomes

The aim of this study was to compare perioperative and long-term oncological outcomes between laparoscopic sphincter-preserving total mesorectal excision in female patients (F-Lap-TME) and robotic sphincter-preserving total mesorectal excision in male patients (M-Rob-TME) with mid-low rectal cancer (RC). A retrospective analysis of a prospectively maintained database was performed. 170 cases (F-Lap-TME: 60 patients; M-Rob-TME: 110 patients) were performed by a single surgeon (January 2011-January 2020). Clinical characteristics did not differ significantly between the two groups. Operating time was longer in M-Rob-TME than in F-Lap-TME group (185.3 ± 28.4 vs 124.5 ± 35.8 min, p < 0.001). There was no conversion to open surgery in both groups. Quality of mesorectum was complete/near-complete in 58 (96.7%) and 107 (97.3%) patients of F-Lap-TME and M-Rob-TME (p = 0.508), respectively. Circumferential radial margin involvement was observed in 2 (3.3%) and 3 (2.9%) in F-Lap-TME and M-Rob-TME patients (p = 0.210), respectively. Median length of follow-up was 62 (24-108) months in the F-Lap-TME and 64 (24-108) months in the M-Rob-TME group. Five-year overall survival rates were 90.5% in the F-Lap-TME and 89.6% in the M-Rob-TME groups (p = 0.120). Disease-free survival rates in F-Lap-TME and M-Rob-TME groups were 87.5% and 86.5% (p = 0.145), respectively. Local recurrence rates were 5% (n = 3) and 5.5% (n = 6) (p = 0.210), in the F-Lap-TME and M-Rob-TME groups, respectively. The robotic technique can potentially overcome some technical challenges related to the pelvic anatomical difference between sex compared to laparoscopy. Laparoscopic and robotic approach, respectively in female and male patients provide similar surgical specimen quality, perioperative outcomes, and long-term oncological results.

The effect of P53 expression and smoking/alcohol in P16(+) and P16(-) oropharyngeal carcinoma and risk classification: the Turkish Society of Radiation Oncology Head & Neck Study Group 01-002

OBJECTIVE

The aim of this study is to categorize the risk groups of patients with oropharyngeal carcinoma (OPC) according to p16 and p53 status, smoking/alcohol consumption history, and other prognostic factors.

STUDY DESIGN

The immunostaining of p16 and p53 of 290 patients was retrospectively evaluated. The history of smoking/alcohol consumption of each patient was noted. p16 and p53 staining patterns were reviewed. The results were compared with demographic findings and prognostic factors. Risk groups have been classified for the p16 status of patients.

RESULTS

The median follow-up was 47 months (range 6-240). Five-year disease-free survival (DFS) rates for patients with p16 (+) and (-) were 76% and 36%, and overall survival rates were 83% vs 40%, respectively (HR = 0.34 [0.21-0.57], P < .0001), HR = 0.22 [0.12-0.40] P < .0001, respectively). p16(-), p53(+), heavy smoking/alcohol consumption, performance status; advanced T and N stages in patients with p16(-), and continuing smoking/alcohol consumption after treatment were found to be unfavorable risk factors. Five-year overall survival rates were 95%, 78%, and 36% for low, intermediate, and high-risk groups, respectively.

CONCLUSIONS

The results of our study have shown that p16 negativity in patients with oropharyngeal cancer was found to be an important prognostic factor, especially for those with lower p53 expression and not smoking/consuming alcohol.

A multicenter retrospective analysis of patients with nasopharyngeal carcinoma treated in IMRT era from a nonendemic population: Turkish Society for Radiation Oncology Head and Neck Cancer Group Study (TROD 01-001)

BACKGROUND

We aimed to evaluate patients with nasopharyngeal carcinoma (NPC) in a nonendemic population.

METHODS

In a national, retrospective, multicenteric study, 563 patients treated with intensity modulated radiotherapy at 22 centers between 2015 and 2020 were analyzed.

RESULTS

Median age was 48 (9-83), age distribution was bimodal, 74.1% were male, and 78.7% were stage III-IVA. Keratinizing and undifferentiated carcinoma rates were 3.9% and 81.2%. Patients were treated with concomitant chemoradiotherapy (48.9%), or radiotherapy combined with induction chemotherapy (25%) or adjuvant chemotherapy (19.5%). After 34 (6-78) months follow-up, 8.2% locoregional and 8% distant relapse were observed. Three-year overall survival was 89.5% and was lower in patients with age ≥50, male sex, keratinizing histology, T4, N3 and advanced stage (III-IVA).

CONCLUSIONS

Patients with NPC in Turkey have mixed clinical features of both east and west. Survival outcomes are comparable to other reported series; however, the rate of distant metastases seems to be lower.

Stereotactic Radiotherapy for Adrenal Metastases: A Multi-Institutional Review of Patient Characteristics and Outcomes - Turkish Society for Radiation Oncology SBRT Group Study (Trod SBRT 10-004)

INTRODUCTION

This study aimed to report the outcomes of stereotactic body radiotherapy (SBRT) for adrenal metastasis in a retrospective multi-institutional cohort.

METHODS

The outcomes of 124 patients with 146 adrenal metastases who underwent SBRT within 11 years (2008-2019) were retrospectively evaluated. Survival outcomes were analyzed by the Kaplan-Meier method. Patient, tumor, and treatment characteristics and their effects on survival, local control (LC), and toxicity outcomes were analyzed by log-rank and multivariate Cox regression methods.

RESULTS

The median age was 60 years. The most frequent primary tumor site was the lung, followed by the gastrointestinal system and breast. The adrenal gland was the only metastatic site in 49 (40%) patients. Median biologically effective dose (BED)10 was 61 Gy. The overall LC rate was 83%, and it was positively correlated with the BED10 and fraction dose. The 1- and 2-year local recurrence-free survival, overall survival (OS), and progression-free survival (PFS) rate was 79% and 69%, 83% and 60%, and 31% and 12%, respectively. OS significantly improved with non-lung cancer and <4-cm lesion and PFS with a fraction dose ≥8 Gy, BED10 >65 Gy, and an isolated adrenal metastasis. Fourteen patients reported an acute toxicity, and late toxicity was observed in 3 patients, including one grade 5.

CONCLUSION

A satisfactory LC rate was achieved for adrenal metastasis via SBRT. A higher BED10 and fraction dose were positive prognostic factors for tumor control. However, the main problem is DM in these patients, and systemic treatment options are needed to be improved.

Outcomes of carotid sparing intensity-modulated radiotherapy for early stage glottic cancer in 201 patients: Multicenter study of Turkish Radiation Oncology Society/TROD-01-007

BACKGROUND

To assess and report clinical outcomes after carotid sparing intensity-modulated radiotherapy for early stage laryngeal cancer.

METHODS

We retrospectively analyzed 201 patients with early stage glottic laryngeal cancer treated with carotid sparing intensity-modulated radiotherapy (IMRT)/volumetric modulated arc therapy (VMAT) techniques in six TROD centers.

RESULTS

After a median follow-up of 31 months the actuarial 1- and 3-year local and locoregional control rates were 99.4% and 94.7%, 98.4% and 93%, respectively. T classification, anterior commissure involvement, IMRT technique, and type of fractionation were not found to be prognostic for local control. Overall, eight patients had lost their organ function due to recurrence or toxicity. Grade 3 and 4 acute laryngeal edema was seen in eight (4%) and one (0.5%) of patients, respectively. Grade 3 and 4 late laryngeal edema developed in two (1%) and one patient (0.5%), respectively.

CONCLUSION

Oncologic outcomes of patients treated with carotid sparing IMRT were excellent; comparable with historical series, with acceptable side effects. Longer follow-up is needed to estimate long term effect on stroke.

Watch and Wait Strategy for Rectal Cancer: How Long Should We Wait for a Clinical Complete Response?

BACKGROUND

The objective of this study was to determine how long to wait in locally advanced rectal tumor (LARC) patients who receive total neoadjuvant therapy (TNT) and achieve a clinical complete response (cCR), and to identify the clinical parameters that affect the waiting period for the watch-and-wait strategy (W &W).

MATERIALS AND METHODS

The data of patients who achieved cCR between February 2015 and June 2020 were examined retrospectively. The week in which patients with cCR at the end of TNT achieved clearance was determined by reanalyzing recorded endoscopy video images. In the assessment at the time of the initial diagnosis, tumor characteristics, such as digital rectal examination findings, MRI stage, location with respect to the puborectalis muscle, annularity, and tumor size, were recorded prospectively.

RESULTS

A total of 54 patients were included in this study. According to the MRI-T stage, 14 cases were cT3a, 22 were cT3b, and 18 were cT3c-T4. Forty-four percent of the cases achieved cCR at 8-10 weeks, 19% at 12-16 weeks, 20% at 16-22 weeks, and 17% at 20-26 weeks. Patients with tumors that were early MRI-T stage (cT3a), negative clinical circumferential resection margin, mobile, small (≤4 cm), located above the puborectalis muscle and showed <180 degrees annularity achieved cCR significantly earlier than those with other tumors (p<0.05).

CONCLUSION

In this study, cCR was achieved in less than half (44%) of the cases during the 8-10 week waiting period. In the W&W strategy, the initial assessment for cCR seems insufficient, and we may need to wait up to 26-30 weeks, especially in patients with advanced-stage tumors.

Magnetic Resonance Image-Guided Hypofractionated Ablative Radiation Therapy for Hepatocellular Carcinoma With Tumor Thrombus Extending to the Right Atrium

Hepatocellular carcinoma (HCC) presenting with tumor thrombus (TT) and inferior vena cava (IVC)/right atrium (RA) infringement point to an advanced-stage disease that is deemed inoperable. Stereotactic body radiotherapy is an emerging treatment option for this group of patients with promising outcomes in recent studies that are comparable to conventional treatment methods, namely, transarterial chemoembolization and transarterial radioembolization. Here, we report a case of HCC with RA extension through the IVC. The patient was referred to our clinic for treatment options, and he was found suitable for magnetic resonance imaging-guided radiotherapy (MRgRT). We treated the patient with MRgRT in five fractions to a total dose of 40 Gray. The tumor was tracked during the treatment sessions, and adaptive treatment planning was performed before each fraction. The patient tolerated the treatment well with no acute grade 3-4 toxicities. The last follow-up showed that the patient had a complete biochemical response and is now a candidate for an orthotopic liver transplant. To our knowledge, this report is the first to document the MRgRT treatment of an HCC with TT and RA extension. MRgRT is safe and feasible for this patient group and can be an effective bridging therapy for liver transplants.

Risk of symptomatic radiation necrosis in patients treated with stereotactic radiosurgery for brain metastases

INTRODUCTIO

Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modality. We thus examined risk factors associated with the development of symptomatic RN in patients treated with SRS for brain metastases.

PATIENTS AND METHODS

We performed a retrospective review of our institutional database to identify patients with brain metastases treated with SRS. Diagnosis of symptomatic RN was determined by appearance on serial MRIs, MR spectroscopy, requirement of therapy, and the development of new neurological complaints without evidence of disease progression.

RESULTS

We identified 323 brain metastases treated with SRS in 170 patients from 2009 to 2018. Thirteen patients (4%) experienced symptomatic RN after treatment of 23 (7%) lesions. After SRS, the median time to symptomatic RN was 8.3 months. Patients with symptomatic RN had a larger mean target volume (p<0.0001), and thus larger V100% (p<0.0001), V50% (p<0.0001), V12Gy (p<0.0001), and V10Gy (p=0.0002), compared to the rest of the cohort. Single-fraction treatment (p=0.0025) and diabetes (p=0.019) were also significantly associated with symptomatic RN.

CONCLUSION

SRS is an effective treatment option for patients with brain metastases; however, a subset of patients may develop symptomatic RN. We found that patients with larger tumor size, larger plan V100%, V50%, V12Gy, or V10Gy, who received single-fraction SRS, or who had diabetes were all at higher risk of symptomatic RN.

Magnetic resonance image-guided hypofractionated ablative radiation therapy for extrahepatic cholangiocarcinoma: Plan adaptation in changing anatomy

Extrahepatic cholangiocarcinoma is an aggressive malignancy of biliary duct epithelium which typically has a poor prognosis. Although surgical resection improves overall survival, many patients are deemed medically inoperable or have unresectable tumors. Herein, we report a case of an 84-year-old Caucasian male who was diagnosed with medically inoperable extrahepatic cholangiocarcinoma. Magnetic resonance image-guided hypofractionated ablative radiotherapy was administered which has the advantages of superior soft tissue resolution, better visualization of the target and organ at risk, daily online adaptive planning and continuous cine MR tracking of the target during irradiation. Concomitant chemotherapy was used. On the first fraction the patient presented with a broken arm that forced the patient take a treatment position much different than the one used for simulation CT and planning. The patient was able to finish the treatment without the need of another simulation by adapting the plan according to the new anatomy. The patient is being followed up until today and is alive with no evidence of disease.

Stereotactic MR-guided online adaptive radiation therapy (SMART) for the treatment of liver metastases in oligometastatic patients: initial clinical experience

Purpose

We aimed to present our initial clinical experience on the implementation of a stereotactic MR-guided online adaptive radiation therapy (SMART) for the treatment of liver metastases in oligometastatic disease.

Materials and Methods

Twenty-one patients (24 lesions) with liver metastasis treated with SMART were included in this retrospective study. Step-and-shoot intensity-modulated radiotherapy technique was used with daily plan adaptation. During delivery, real-time imaging was used by acquiring planar magnetic resonance images in sagittal plane for monitoring and gating. Acute and late toxicities were recorded both during treatment and follow-up visits.

Results

The median follow-up time was 11.6 months (range, 2.2 to 24.6 months). The median delivered total dose was 50 Gy (range, 40 to 60 Gy); with a median fraction number of 5 (range, 3 to 8 fractions) and the median fraction dose was 10 Gy (range, 7.5 to 18 Gy). Ninety-three fractions (83.7%) among 111 fractions were re-optimized. No patients were lost to follow-up and all patients were alive except one at the time of analysis. All of the patients had either complete (80.9%) or partial (19.1%) response at irradiated sites. Estimated 1-year overall survival was 93.3%. Intrahepatic and extrahepatic progression-free survival was 89.7% and 73.5% at 1 year, respectively. There was no grade 3 or higher acute or late toxicities experienced during the treatment and follow-up course.

Conclusion

SMART represents a new, noninvasive and effective alternative to current ablative radiotherapy methods for treatment of liver metastases in oligometastatic disease with the advantages of better visualization of soft tissue, real-time tumor tracking and potentially reduced toxicity to organs at risk.

Multi-institutional validation of the ESMO-ESGO-ESTRO consensus conference risk grouping in Turkish endometrial cancer patients treated with comprehensive surgical staging

In this study, 683 patients with endometrial cancer (EC) after comprehensive surgical staging were classified into four risk groups as low (LR), intermediate (IR), high-intermediate (HIR) and high-risk (HR), according to the recent consensus risk grouping. Patients with disease confined to the uterus, ≥50% myometrial invasion (MI) and/or grade 3 histology were treated with vaginal brachytherapy (VBT). Patients with stage II disease, positive/close surgical margins or extra-uterine extension were treated with external beam radiotherapy (EBRT)±VBT. The median follow-up was 56 months. The overall survival (OS) was significantly different between LR and HR groups, and there was a trend between LR and HIR groups. Relapse-free survival (RFS) was significantly different between LR and HIR, LR and HR and IR and HR groups. There was no significant difference in OS and RFS rates between the HIR and HR groups. In HR patients, the OS and RFS rates were significantly higher in stage IB - grade 3 and stage II compared to stage III and non-endometrioid histology without any difference between the two uterine-confined stages and between stage III and non-endometrioid histology. The current risk grouping does not clearly discriminate the HIR and IR groups. In patients with comprehensive surgical staging, a further risk grouping is needed to distinguish the real HR group.Impact statementWhat is already known on this subject? The standard treatment for endometrial cancer (EC) is surgery and adjuvant radiotherapy (RT) and/or chemotherapy is recommended according to risk factors. The recent European Society for Medical Oncology (ESMO), European Society of Gynaecological Oncology (ESGO) and European Society for Radiotherapy and Oncology (ESTRO) guideline have introduced a new risk group. However, the risk grouping is still quite heterogeneous.What do the results of this study add? This study demonstrated that the current risk grouping recommended by ESMO-ESGO-ESTRO does not clearly discriminate the intermediate risk (IR) and high-intermediate risk (HIR) groups.What are the implications of these findings for clinical practice and/or further research? Based on the results of this study, a new risk grouping can be made to discriminate HIR and IR groups clearly in patients with comprehensive surgical staging.

Magnetic resonance image-guided adaptive stereotactic body radiotherapy for prostate cancer: preliminary results of outcome and toxicity

OBJECTIVE

Using moderate or ultra-hypofractionation, which is also known as stereotactic body radiotherapy (SBRT) for treatment of localized prostate cancer patients has been increased. We present our preliminary results on the clinical utilization of MRI-guided adaptive radiotherapy (MRgRT) for prostate cancer patients with the workflow, dosimetric parameters, toxicities and prostate-specific antigen (PSA) response.

METHODS

50 prostate cancer patients treated with ultra-hypofractionation were included in the study. Treatment was performed with intensity-modulated radiation therapy (step and shoot) technique and daily plan adaptation using MRgRT. The SBRT consisted of 36.25 Gy in 5 fractions with a 7.25 Gy fraction size. The time for workflow steps was documented. Patients were followed for the acute and late toxicities and PSA response.

RESULTS

The median follow-up for our cohort was 10 months (range between 3 and 29 months). The median age was 73.5 years (range between 50 and 84 years). MRgRT was well tolerated by all patients. Acute genitourinary (GU) toxicity rate of Grade 1 and Grade 2 was 28 and 36%, respectively. Only 6% of patients had acute Grade 1 gastrointestinal (GI) toxicity and there was no Grade ≥ 2 GI toxicity. To date, late Grade 1 GU toxicity was experienced by 24% of patients, 2% of patients experienced Grade 2 GU toxicity and 6% of patients reported Grade 2 GI toxicity. Due to the short follow-up, PSA nadir has not been reached yet in our cohort.

CONCLUSION

In conclusion, MRgRT represents a new method for delivering SBRT with markerless soft tissue visualization, online adaptive planning and real-time tracking. Our study suggests that ultra-hypofractionation has an acceptable acute and very low late toxicity profile.

ADVANCES IN KNOWLEDGE

MRgRT represents a new markerless method for delivering SBRT for localized prostate cancer providing online adaptive planning and real-time tracking and acute and late toxicity profile is acceptable.

Risk of symptomatic radiation necrosis in patients treated with stereotactic radiosurgery for brain metastases

INTRODUCTIO

Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modality. We thus examined risk factors associated with the development of symptomatic RN in patients treated with SRS for brain metastases.

PATIENTS AND METHODS

We performed a retrospective review of our institutional database to identify patients with brain metastases treated with SRS. Diagnosis of symptomatic RN was determined by appearance on serial MRIs, MR spectroscopy, requirement of therapy, and the development of new neurological complaints without evidence of disease progression.

RESULTS

We identified 323 brain metastases treated with SRS in 170 patients from 2009 to 2018. Thirteen patients (4%) experienced symptomatic RN after treatment of 23 (7%) lesions. After SRS, the median time to symptomatic RN was 8.3 months. Patients with symptomatic RN had a larger mean target volume (p<0.0001), and thus larger V100% (p<0.0001), V50% (p<0.0001), V12Gy (p<0.0001), and V10Gy (p=0.0002), compared to the rest of the cohort. Single-fraction treatment (p=0.0025) and diabetes (p=0.019) were also significantly associated with symptomatic RN.

CONCLUSION

SRS is an effective treatment option for patients with brain metastases; however, a subset of patients may develop symptomatic RN. We found that patients with larger tumor size, larger plan V100%, V50%, V12Gy, or V10Gy, who received single-fraction SRS, or who had diabetes were all at higher risk of symptomatic RN.

Patient-Reported Tolerance of Magnetic Resonance-Guided Radiation Therapy

Purpose

Magnetic resonance-guided radiation therapy (MRgRT) has been incorporated into a growing number of clinical practices world-wide, however, there is limited data on patient experiences with MRgRT. The purpose of this study was to prospectively evaluate patient tolerance of MRgRT using patient reported outcome questionnaires (PRO-Q).

Methods

Ninety patients were enrolled in this prospective observational study and treated with MRgRT (MRIdian Linac System, ViewRay Inc. Oakwood Village, OH, United States) between September 2018 and September 2019. Breath-hold-gated dose delivery with audiovisual feedback was completed as needed. Patients completed an in-house developed PRO-Q after the first and last fraction of MRgRT.

Results

The most commonly treated anatomic sites were the abdomen (47%) and pelvis (33%). Respiratory gating was utilized in 62% of the patients. Patients rated their experience as positive or at least tolerable with mean scores of 1.0–2.8. The most common complaint was the temperature in the room (61%) followed by paresthesias (57%). The degree of anxiety reported by 45% of the patients significantly decreased at the completion of treatment (mean score 1.54 vs. 1.36, p = 0.01). Forty-three percent of the patients reported some degree of disturbing noise which was improved considerably by use of music. All patients appreciated their active role during the treatment.

Conclusion

This evaluation of PROs indicates that MRgRT was well-tolerated by our patients. Patients’ experience may further improve with adjustment of room temperature and noise reduction.

Management of symptomatic radiation necrosis after stereotactic radiosurgery and clinical factors for treatment response

PURPOSE

Approximately 10% of patients who received brain stereotactic radiosurgery (SRS) develop symptomatic radiation necrosis (RN). We sought to determine the effectiveness of treatment options for symptomatic RN, based on patient-reported outcomes.

MATERIALS AND METHODS

We conducted a retrospective review of 217 patients with 414 brain metastases treated with SRS from 2009 to 2018 at our institution. Symptomatic RN was determined by appearance on serial magnetic resonance images (MRIs), MR spectroscopy, requirement of therapy, and development of new neurological complaints without evidence of disease progression. Therapeutic interventions for symptomatic RN included corticosteroids, bevacizumab and/or surgical resection. Patient-reported therapeutic outcomes were graded as complete response (CR), partial response (PR), and no response.

RESULTS

Twenty-six patients experienced symptomatic RN after treatment of 50 separate lesions. The mean prescription dose was 22 Gy (range, 15 to 30 Gy) in 1 to 5 fractions (median, 1 fraction). Of the 12 patients managed with corticosteroids, 6 patients (50%) reported CR and 4 patients (33%) PR. Of the 6 patients managed with bevacizumab, 3 patients (50%) reported CR and 1 patient (18%) PR. Of the 8 patients treated with surgical resection, all reported CR (100%). Other than surgical resection, age ≥54 years (median, 54 years; range, 35 to 81 years) was associated with CR (odds ratio = 8.40; 95% confidence interval, 1.27-15.39; p = 0.027).

CONCLUSION

Corticosteroids and bevacizumab are commonly utilized treatment modalities with excellent response rate. Our results suggest that patient's age is associated with response rate and could help guide treatment decisions for unresectable symptomatic RN.

Multichannel Film Dosimetry for Quality Assurance of Intensity Modulated Radiotherapy Treatment Plans Under 0.35 T Magnetic Field

Purpose

To evaluate the intensity modulated radiotherapy (IMRT) quality assurance (QA) results of the multichannel film dosimetry analysis with single scan method by using Gafchromic™ EBT3 (Ashland Inc., Covington, KY, USA) film under 0.35 T magnetic field.

Methods

Between September 2018 and June 2019, 70 patients were treated with ViewRay MRIdian^® (ViewRay Inc., Mountain View, CA) linear accelerator (Linac). Film dosimetry QA plans were generated for all IMRT treatments. Multichannel film dosimetry for red, green and blue (RGB) channels were compared with treatment planning system (TPS) dose maps by gamma evaluation analysis.

Results

The mean gamma passing rates of RGB channels are 97.3% ± 2.26%, 96.0% ± 3.27% and 96.2% ± 3.14% for gamma evaluation with 2% DD/2 mm distance to agreement (DTA), respectively. Moreover, the mean gamma passing rates of RGB channels are 99.7% ± 0.41%, 99.6% ± 0.59% and 99.5% ± 0.67% for gamma evaluation with 3% DD/3 mm DTA, respectively.

Conclusion

The patient specific QA using Gafchromic™ EBT3 film with multichannel film dosimetry seems to be a suitable tool to implement for MR-guided IMRT treatments under 0.35 T magnetic field. Multichannel film dosimetry with Gafchromic™ EBT3 is a consistent QA tool for gamma evaluation of the treatment plans even with 2% DD/2 mm DTA under 0.35 T magnetic field presence.

New horizons from novel therapies in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a relatively rare, but highly lethal cancer of the pleural mesothelial cells. Its pathoge-nesis is integrally linked to asbestos exposure. In spite of recent developments providing a more detailed understanding of the pathogenesis, the outcomes continue to be poor. To date, trimodality therapy involving surgery coupled with chemotherapy and/or radiotherapy remains the standard of therapy. The development of resistance of the tumor cells to radiation and several che-motherapeutic agents poses even greater challenges in the management of this cancer. Ionizing radiation damages cancer cell DNA and aids in therapeutic response, but it also activates cell survival signaling pathways that helps the tumor cells to overcome radiation-induced cytotoxicity. A careful evaluation of the biology involved in mesothelioma with an emphasis on the workings of pro-survival signaling pathways might offer some guidance for treatment options. This review focuses on the existing treatment options for MPM, novel treatment approaches based on recent studies combining the use of inhibitors which target different pro-survival pathways, and radiotherapy to optimize treatment.

Evaluation of response to stereotactic radiosurgery in patients with radioresistant brain metastases

PURPOSE

Renal cell carcinoma (RCC) and melanoma have been considered 'radioresistant' due to the fact that they do not respond to conventionally fractionated radiation therapy. Stereotactic radiosurgery (SRS) provides high-dose radiation to a defined target volume and a limited number of studies have suggested the potential effectiveness of SRS in radioresistant histologies. We sought to determine the effectiveness of SRS for the treatment of patients with radioresistant brain metastases.

MATERIALS AND METHODS

We performed a retrospective review of our institutional database to identify patients with RCC or melanoma brain metastases treated with SRS. Treatment response were determined in accordance with the Response Evaluation Criteria in Solid Tumors.

RESULTS

We identified 53 radioresistant brain metastases (28% RCC and 72% melanoma) treated in 18 patients. The mean target volume and coverage was 6.2 ± 9.5 mL and 95.5% ± 2.9%, respectively. The mean prescription dose was 20 ± 4.9 Gy. Forty lesions (75%) demonstrated a complete/partial response and 13 lesions (24%) with progressive/stable disease. Smaller target volume (p < 0.001), larger SRS dose (p < 0.001), and coverage (p = 0.008) were found to be positive predictors of complete response to SRS.

CONCLUSION

SRS is an effective management option with up to 75% response rate for radioresistant brain metastases. Tumor volume and radiation dose are predictors of response and can be used to guide the decision-making for patients with radioresistant brain metastases.

First 500 Fractions Delivered with a Magnetic Resonance-guided Radiotherapy System: Initial Experience

Objectives

Improved soft-tissue visualization, afforded by magnetic resonance imaging integrated into a radiation therapy linear accelerator-based radiation delivery system (MR-linac) promises improved image-guidance. The availability of MR-imaging can facilitate on-table adaptive radiation planning and enable real-time intra-fraction imaging with beam gating without additional exposure to radiation. However, the novel use of magnetic resonance-guided radiation therapy (MRgRT) in the field of radiation oncology also potentially poses challenges for routine clinical implementation. Herein the early experience of a single institution, implementing the first MRgRT system in the country is reported. We aim to describe the workflow and to characterize the clinical utility and feasibility of routine use of an MR-linac system.

Methods

The ViewRay MRIdian MR-linac system consists of a split-magnet 0.35 T MR-imaging scanner with a double focused multi-leaf collimator (MLC) equipped 6MV linear accelerator. Unique to the system are the control console integrated on-table adaptive radiation therapy (oART) planning capabilities as well as automated beam gating based on real-time intra-fraction MR imaging. From the first day of clinical implementation, oART was performed according to physicians’ discretion when medically indicated. All fractions were delivered under real-time imaging with soft tissue-based automated beam gating with individualized gating boundary settings. Patients actively assisted in breath-hold beam gating with the help of custom designed prismatic glasses allowing sight of a computer monitor mounted on the back wall just behind the MRI system bore. Patient demographics and treatment experience, indications for MRgRT including diagnosis and disease site, radiation dose prescribed and fractionation scheme, utilization of oART, respiratory gating settings, as well as duration of each treatment phase were analyzed.

Results

Between September 2018 and May 2019, 72 patients with 84 tumor sites were treated with MRgRT in 500 total fractions. Median patient age was 66 years (range: 28-83 years). Among 84 tumor sites, the most frequently treated regions were upper abdominal and pelvic (n = 36, 43% and n = 29, 34%, respectively). The most common diagnosis was prostate cancer, with 14 patients treated. In 69 patients (93.2%) oART was used at least once during a treatment course. Twenty-nine targets (43.1%) with significant breathing-related motion were treated in breath-hold with patient visual feedback. Median prescribed dose was 36.25 Gy (range: 24-70 Gy) in median five fractions (range: 3-28 fractions). A gating boundary of 3 mm around a gating region of interest (gROI) was most commonly used (range: 3-5 mm) with 95% of the gROI (range: 93-97%) required to be within the gating boundary for the beam to automatically engage. Mean total treatment time was 47 min (range: 21-125 min) and mean beam-on time was 16.7 min (range: 6-62 min).

Conclusions

MRgRT afforded by an MR-linac system has been successfully implemented into routine clinical use at our institution as the first system of its kind in Turkey. While the overall number of patients treated and fractions delivered is still limited, we have demonstrated the feasibility of both on-table adaptive radiation therapy as well as automated real-time beam gating on a daily basis in acceptable time schedules.

Output factors of ionization chambers and solid state detectors for mobile intraoperative radiotherapy (IORT) accelerator electron beams

Purpose

The electron energy characteristics of mobile intraoperative radiotherapy (IORT) accelerator LIAC^® differ from commonly used linear accelerators, thus some of the frequently used detectors can give less accurate results. The aim of this study is to evaluate the output factors (OFs) of several ionization chambers (IC) and solid state detectors (SS) for electron beam energies generated by LIAC^® and compare with the output factor of Monte Carlo model (MC) in order to determine the adequate detectors for LIAC^®.

Methods

The OFs were measured for 6, 8, 10, and 12 MeV electron energies with PTW 23343 Markus, PTW 34045 Advanced Markus, PTW 34001 Roos, IBA PPC05, IBA PPC40, IBA NACP‐02, PTW 31010 Semiflex, PTW 31021 Semiflex 3D, PTW 31014 Pinpoint, PTW 60017 Diode E, PTW 60018 Diode SRS, SNC Diode EDGE, and PTW 60019 micro Diamond detectors. Ion recombination factors (k_sat) of IC were measured for all applicator sizes and OFs were corrected according to k_sat. The measured OFs were compared with Monte Carlo output factors (OF_MC).

Results

The measured OFs of IBA PPC05, PTW Advanced Markus, PTW Pinpoint, PTW microDiamond, and PTW Diode E detectors are in good agreement with OF_MC. The maximum deviations of IBA PPC05 OFs to OF_MC are −1.6%, +1.5%, +1.5%, and +2.0%; for PTW Advanced Markus +1.0%, +1.5%, +2.0%, and +2.0%; for PTW Pinpoint +2.0%, +1.6%, +4.0%, and +2.0%; for PTW microDiamond −1.6%, +2%, +1.1%, and +1.0%; and for PTW Diode E −+1.7%, +1.7%, +1.3%, and +2.5% for 6, 8, 10, and 12 MeV, respectively. PTW Roos, PTW Markus, IBA PPC40, PTW Semiflex, PTW Semiflex 3D, SNC Diode Edge measured OFs with a maximum deviation of +5.6%, +4.5%, +5.6%, +8.1%, +4.8%, and +9.6% with respect to OF_MC, while PTW Diode SRS and IBA NACP‐02 were the least accurate (with highest deviations −37.1% and −18.0%, respectively).

Conclusion

The OFs results of solid state detectors PTW microDiamond and PTW Diode E as well as the ICs with small electrode spacing distance such as IBA PPC05, PTW Advanced Markus and PTW Pinpoint are in excellent agreement with OF_MC. The measurements of the other detectors evaluated in this study are less accurate, thus they should be used with caution. Particularly, PTW Diode SRS and IBA NACP‐02 are not suitable and their use should be avoided in relative dosimetry measurements under high dose per pulsed (DPP) electron beams.