Thymic Tumours in Children

Thymomas are very rare neoplasms in children and they represent less than 1% of mediastinal tumours in the paediatric population. The aim of our study was to assess the long-term treatment results of children with thymic tumours. A total number of eight children (four boys and four girls) with thymic tumours were identified. Median age at diagnosis was 7 years. In seven of them, thymoma was diagnosed; in one, a thymic carcinoma was diagnosed. In five of them, the WHO type was assessed: in two of them, the B1 type was found; in one, B2 was found; in one, AB was found, and in one, C was found. In all but one, surgery was the first-line treatment, but six patients had only partial resection. One patient started treatment with chemotherapy and four others received chemotherapy after the surgery. Radiotherapy was applied in six patients, with a median total dose of 37.5 Gy. Follow-up ranged from 8.5 to 273.5 months, with a median of 6.1 years. During this time, four patients died: one due to progression of the disease, and in the other three, the reason for death was unknown. In all evaluated patients, complete regression was observed (100% local control). Two-, 5- and 10-year OS and PFS were 85% and 72%, 51% and 54%, 51% and 54%, respectively. Combined treatment could provide satisfactory results in thymoma patients. There is a need for further, larger studies, which could help to establish optimal management strategies.

P.038 Impact of Disease Severity on Presentation Subtype and OnabotulinumtoxinA Utilization in Patients with Cervical Dystonia in the CD PROBE Completer Population

Background: The impact of cervical dystonia (CD) severity on presentation subtype and onabotulinumtoxinA utilization was examined in the completer population from CD PROBE (CD Patient Registry for Observation of BOTOX® Efficacy). Methods: In this multicenter, prospective, observational registry, patients with CD were treated with onabotulinumtoxinA according to injectors’ standard of care. Completers were patients that completed all 3 treatment sessions and had accompanying data. Results: Of N=1046 patients enrolled, n=350 were completers. Completers were on average 57.3 years old, 74.9% female, 94.6% white, and 60.6% toxin-naïve. Baseline severity was mild in 32.6%, moderate in 54.3%, and severe in 13.1%. Torticollis was the most common presentation at baseline (mild: 44.7%, moderate: 55.8%, severe: 63.0%), followed by laterocollis (mild: 42.1%, moderate: 32.6%, severe: 26.1%). Median onabotulinumtoxinA dose increased over time; 160U–200U for torticollis and 170U–200U for laterocollis. For all severities, median total dose increased from injection 1 to injection 3 (mild: 138U–165U, moderate: 183U–200U, severe: 200U–285U). Eighty-one patients (23.1%) reported 139 treatment-related adverse events. There were no treatment-related serious adverse eventsand no new safety signals. Conclusions: CD severity impacted presentation subtype frequency and onabotulinumtoxinA utilization in CD PROBE, with higher and tailored dosing observed over time and with increasing disease severity.

Radiation Dose Reduction in CT Torsion Measurement of the Lower Limb: Introduction of a New Ultra-Low Dose Protocol

This study analyzed the radiation exposure of a new ultra-low dose (ULD) protocol compared to a high-quality (HQ) protocol for CT-torsion measurement of the lower limb. The analyzed patients (n = 60) were examined in the period March to October 2019. In total, 30 consecutive patients were examined with the HQ and 30 consecutive patients with the new ULD protocol comprising automatic tube voltage selection, automatic exposure control, and iterative image reconstruction algorithms. Radiation dose parameters as well as the contrast-to-noise ratio (CNR) and diagnostic confidence (DC; rated by two radiologists) were analyzed and potential predictor variables, such as body mass index and body volume, were assessed. The new ULD protocol resulted in significantly lower radiation dose parameters, with a reduction of the median total dose equivalent to 0.17 mSv in the ULD protocol compared to 4.37 mSv in the HQ protocol (p < 0.001). Both groups showed no significant differences in regard to other parameters (p = 0.344–0.923). CNR was 12.2% lower using the new ULD protocol (p = 0.033). DC was rated best by both readers in every HQ CT and in every ULD CT. The new ULD protocol for CT-torsion measurement of the lower limb resulted in a 96% decrease of radiation exposure down to the level of a single pelvic radiograph while maintaining good image quality.

A survey among German-speaking radiation oncologists on PET-based radiotherapy of prostate cancer

Background Positron emission tomography-(PET) has evolved as a powerful tool to guide treatment for prostate cancer (PC). The aim of this survey was to evaluate the acceptance and use of PET—especially with prostate-specific membrane antigen (PSMA) targeting tracers—in clinical routine for radiotherapy (RT) and the impact on target volume definition and dose prescription. Methods We developed an online survey, which we distributed via e-mail to members of the German Society of Radiation Oncology (DEGRO). The survey included questions on patterns of care of RT for PC with/without PET. For evaluation of doses we used the equivalent dose at fractionation of 2 Gy with α/β = 1.5 Gy [EQD2(1.5 Gy)]. Results From 109 participants, 78.9% have the possibility to use PET for RT planning. Most centers use PSMA-targeting tracers (98.8%). In 39.5%, PSMA-PET for biochemical relapse after prior surgery is initiated at PSA ≥ 0.5 ng/mL, while 30.2% will perform PET at ≥ 0.2 ng/mL (≥ 1.0 ng/mL: 16.3%, ≥ 2.0 ng/mL: 2.3%, regardless of PSA: 11.7%). In case of PET-positive local recurrence (LR) and pelvic lymph nodes (LNs), 97.7% and 96.5% of the participants will apply an escalated dose. The median total dose in EQD2(1.5 Gy) was 70.00 Gy (range: 56.89–85.71) for LR and 62.00 Gy (range: 52.61–80.00) for LNs. A total number of ≤ 3 (22.0%) or ≤ 5 (20.2%) distant lesions was most often described as applicable for the definition as oligometastatic PC. Conclusion PSMA-PET is widely used among German radiation oncologists. However, specific implications on treatment planning differ among physicians. Therefore, further trials and guidelines for PET-based RT are warranted.

DIPG-01. REIRRADIATION PRACTICES FOR DIFFUSE INTRINSIC PONTINE GLIOMA

INTRODUCTION Diffuse intrinsic pontine gliomas (DIPG) are a leading cause of brain tumor deaths in children. Current standard of care includes focal radiation therapy (RT). Despite clinical improvement in the majority of patients, the effect is temporary and median survival is less than one year. The use of reirradiation and possible benefit has been reported in progressive DIPG, yet standardized approaches are lacking. We conducted an internet-based survey to assess physicians’ practices in pediatric DIPG. METHODS A 14-question REDCap survey regarding re-irradiation practices was emailed to 396 physicians identified through an International Pediatric Neuro-Oncology and Radiation-Oncology database. RESULTS Response rate was 35% overall (radiation-oncologists, 28%; pediatric oncologists, 57%). Two participants were excluded (did not treat DIPG). Participants included radiation-oncologists (62%), pediatric oncologists (7%), and pediatric neuro-oncologists (29%). Most physicians (62%) treated 1–5 DIPG patients per year, with 10% treating &gt;10/year. Reirradiation was considered a treatment option in 88%. Progressive disease or worsening clinical status were the most common reasons to consider reirradiation. The majority (84%) considered reirradiation a minimum of 6 months following initial RT. Doses varied, with median total dose 24Gy (range 12–60); 2Gy/fraction (range 1–9). Concurrent use of systemic agents with reirradiation was considered in 46%, mainly with targeted agents (37%), biologics (34%), or immunotherapy (25%). One-time reirradiation was the most common practice (71%). Interestingly, 9% of respondents would not consider reirradiation. CONCLUSION Although, the vast majority of physicians agree with re-irradiation as a treatment option for DIPG the total doses varied, and further clinical trials are needed.

Patient outcomes and tumor control in single-fraction versus hypofractionated stereotactic body radiation therapy for spinal metastases

OBJECTIVEStereotactic body radiation therapy (SBRT) offers efficient, noninvasive treatment of spinal neoplasms. Single-fraction (SF) high-dose SBRT has a relatively narrow therapeutic window, while hypofractionated delivery of SBRT may have an improved safety profile with similar efficacy. Because the optimal approach of delivery is unknown, the authors examined whether hypofractionated SBRT improves pain and/or functional outcomes and results in better tumor control compared with SF-SBRT.METHODSThis is a single-institution retrospective study of adult patients with spinal metastases treated with SF- or three-fraction (3F) SBRT from 2008 to 2019. Demographics and baseline characteristics, radiographic data, and posttreatment outcomes at a minimum follow-up of 3 months are reported.RESULTSOf the 156 patients included in the study, 70 (44.9%) underwent SF-SBRT (median total dose 1700 cGy) and 86 (55.1%) underwent 3F-SBRT (median total dose 2100 cGy). At baseline, a higher proportion of patients in the 3F-SBRT group had a worse baseline profile, including severity of pain (p < 0.05), average use of pain medication (p < 0.001), and functional scores (p < 0.05) compared with the SF-SBRT cohort. At the 3-month follow-up, the 3F-SBRT cohort experienced a greater frequency of improvement in pain compared with the SF-SBRT group (p < 0.05). Furthermore, patients treated with 3F-SBRT demonstrated a higher frequency of improved Karnofsky Performance Scale (KPS) scores (p < 0.05) compared with those treated with SF-SBRT, with no significant difference in the frequency of improvement in modified Rankin Scale scores. Local tumor control did not differ significantly between the two cohorts.CONCLUSIONSPatients who received spinal 3F-SBRT more frequently achieved significant pain relief and an increased frequency of improvement in KPS compared with those treated with SF-SBRT. Local tumor control was similar in the two groups. Future work is needed to establish the relationship between fractionation schedule and clinical outcomes.

Reirradiation practices for children with diffuse intrinsic pontine glioma

Background Diffuse intrinsic pontine gliomas (DIPGs) are a leading cause of brain tumor deaths in children. Current standard of care includes focal radiation therapy (RT). Despite clinical improvement in most patients, the effect is temporary and median survival is less than 1 year. The use and benefit of reirradiation have been reported in progressive DIPG, yet standardized approaches are lacking. We conducted a survey to assess reirradiation practices for DIPG in North America. Methods A 14-question REDCap survey was disseminated to 396 North American physicians who care for children with CNS tumors. Results The response rate was 35%. Participants included radiation-oncologists (63%; 85/135) and pediatric oncologists/neuro-oncologists (37%; 50/135). Most physicians (62%) treated 1 to 5 DIPG patients per year, with 10% treating more than 10 patients per year. Reirradiation was considered a treatment option by 88% of respondents. Progressive disease and worsening clinical status were the most common reasons to consider reirradiation. The majority (84%) surveyed considered reirradiation a minimum of 6 months following initial RT. Doses varied, with median total dose of 2400 cGy (range, 1200-6000 cGy) and fraction size of 200 cGy (range, 100-900 cGy). Concurrent use of systemic agents with reirradiation was considered in 46%, including targeted agents (37%), biologics (36%), or immunotherapy (25%). One-time reirradiation was the most common practice (71%). Conclusion Although the vast majority of physicians consider reirradiation as a treatment for DIPG, total doses and fractionation varied. Further clinical trials are needed to determine the optimal radiation dose and fractionation for reirradiation in children with progressive DIPG.

Proton re-irradiation of unresectable recurrent head and neck cancers

Purpose: This study presents a retrospective analysis (efficacy and toxicity) of outcomes in patients with unresectable recurrence of previously irradiated head and neck cancers, treated with proton therapy.Methods: From November 2015 to January 2020, 30 patients with in-field recurrence of head and neck cancer, who were not suitable for surgery, due to medical contraindications, tumor localization or extent, received re-irradiation with intensity-modulated proton therapy (IMPT). Sites of retreatment included the aerodigestive tract (60%) and base of the skull (40%). The median total dose of prior radiotherapy was 55.0 Gy. The median time to the second course was 38 months. The median re-irradiated tumor volume was 158.1 cm3. Patients were treated with 2.0, 2.4 and 3.0 GyRBE per fraction, with a median EQD2 of 57.6 Gy (α/β=10). Radiation-induced toxicity was recorded according to the RTOG/EORTC criteria.Results: The 1- and 2-years LC, RFS, and OS were 52.6/21.0, 21.9/10.9 and 73.4/8.4%, respectively, with a median follow-up time of 21 months. The median overall survival was 16 months. Acute grade 3 toxicity was observed in 1 patient (3.3%). There were 5 late severe side effects (16.6%), with one death associated with re-irradiation.Conclusion: Re-irradiation with a proton beam can be considered a safe and efficient treatment even for a group of patients with unresectable recurrent H&N cancers.

A randomized phase II feasibility study of individualized stereotactic body radiation therapy (SBRT) versus transarterial chemoembolization (TACE) with DEBDOX beads as a bridge to transplant in hepatocellular carcinoma (HCC).

4586 Background: For HCC pts undergoing LT, loco-regional treatment as a "bridge" is standard. The best bridging modality is unclear. SBRT is safe and effective when used in pts with advanced HCC. We prospectively compared SBRT to TACE as a bridge for HCC pts undergoing LT. Methods: From 9/2014-10/2019, 60 pts within Milan Criteria with CTP Class A/B8 cirrhosis were consented. 54 pts were randomized to TACE vs. SBRT. TACE pts (n =30) were scheduled to receive 2 treatments one month apart utilizing DEBDOX beads. TACE pts were hospitalized after each TACE. Pts receiving SBRT (n =24) received a median total dose of 45Gy delivered over 5 fractions using fiducials. Mean liver dose, Veff, and NTCP determined prescription dose. Pts were assessed by using mRECIST criteria at 2 months and every 3 months thereafter until LT or death. Toxicity and QOL were assessed before treatment, during treatment, two weeks post-treatment, and then every three months using the PIQ-6 Pain Impact Questionnaire and the SF-36v2 Health Survey. The 1° endpoint was time to recurrent or residual dz. Secondary endpoints were toxicity, pathologic response, radiologic response, number of subsequent treatments, cost, and QOL. 50 pts are evaluable for review. Results: See table. Conclusions: For early stage HCC patients with CTP Class A/B liver cirrhosis, SBRT appears as effective as TACE at controlling HCC prior to LT, may engender less toxicity, and eliminates the need for hospitalization. A larger multi-center trial is ongoing. Clinical trial information: NCT02182687. [Table: see text]

Thoracic radiotherapy for renal cell carcinoma metastases.

409 Background: For patients with metastatic renal cell carcinoma (RCC), metastasis-directed local therapies can delay progression and need to initiate/switch systemic therapy. We examined our experience treating lung or mediastinal metastases from RCC with radiotherapy (RT). Methods: We reviewed patients with lung or mediastinal metastases from RCC treated with RT. Overall survival (OS) and local control (LC) was measured from the start of RT using the Kaplan-Meier method. Results: Seventy-one patients were treated with RT for 89 lung or mediastinal metastases. Median follow-up was 2.0 years (range 0.02-11.4 years) after RT for surviving patients. Most patients were male (n=53, 74.6%). Median age was 58.4 years at initial diagnosis. Histology was most frequently clear cell carcinoma (n=62, 89.9%). At the time of treatment, 18 patients (25.4%) had 1-3 metastases, and the remainder (74.6%) had 4 or more metastases. Forty-one patients (57.5%) received systemic therapy prior to thoracic radiation. Initial systemic therapy was most commonly sunitinib (45%) or pazopanib (32.5%). Median time from starting systemic therapy to initiation of radiation was 2.0 years. Fifty-eight lung metastases and 31 mediastinal metastases were treated with a median 5 fractions (range 1-40), to a median total dose of 4800 cGy (range 400-7000), with a median fraction size of 500 cGy (range 150-2000). Thirty-three lesions were treated with concurrent systemic therapy, which was most commonly nivolumab (n=16). Of 89 treated lesions, 11 (12%) had local tumor recurrence, at a median of 1.6 years (range 0.4-2.9 years) after initiation of radiation. 1, 3, and 5 year MC (metastasis control) were 96.6%, 83.5% and 67.9%, respectively. Nine patients were treated with radiation in order to delay initiation of systemic therapy. Of these, 3 eventually received systemic therapy, initiated at a median 2.5 years after radiation. At last follow-up, 41 patients (57.7%) had died. Median OS was 2.6 years. Survival at 1, 3, and 5 years was 65.2%, 48.5%, and 38%, respectively. Conclusions: Radiation achieves high metastasis control rates for lung and mediastinal metastases from RCC, potentially delaying the need for systemic therapy.