Stereotactic Radiosurgery (SRS) for Large Brain Metastases: Dosimetric and Clinical Predictors of Local Progression and Radionecrosis

PURPOSE/OBJECTIVE(S)

Stereotactic radiosurgery (SRS) provides high rates of local control for small brain metastases with low rates of radionecrosis (RN). Larger targets are associated with increased risk of both local progression (LP) and RN. In this analysis, we hypothesized that dosimetric and clinical parameters predict for risk of LP and RN in SRS targets larger than two centimeters.

MATERIALS/METHODS

We retrospectively reviewed patients with one or more targets with either an intact versus post-operative cavity larger than 2.0 cm treated with LINAC-based SRS between 2017 and 2022 at one institution. We assessed for association between patient, treatment, and disease variables with LP and RN. Variables assessed included tumor resection status, PDL1 positivity, target volume, maximum and minimum target dose, EQD2 and BED (a/b = 2 for necrosis and a/b = 10 for tumor control), as well as receipt of steroids, bevacizumab, or systemic therapy before or after SRS. Radionecrosis was determined by characteristic radiographic changes. Analyses were performed for the entire cohort and within subsets including by resection status and dose fractionation.

RESULTS

A total of 178 lesions in 143 patients were included. Targets with volume diameters measuring at least 2 cm were used. Median follow-up was 2.3 years. Overall survival at 1 and 2 years was 56% and 32%, respectively. Most lesions (n = 119) were resected and treated with SRS post-operatively. The most common dose and fractionation schemes used were 30 Gy in 5 fractions (n = 89) and 27 Gy in 3 fractions (n = 63). For the entire cohort, the cumulative incidence of LP 1 and 2 years was 26% and 34%, respectively. The cumulative incidence of radiographic radionecrosis at 1 and 2 years was 12% and 17%, respectively. There was no difference in LP or RN between 27 Gy in 3 fractions versus 30 Gy in 5 fractions (p>0.5 for both). Median planning target volume (PTV) size was 18.5 cc for the 27 Gy in 3 fraction group compared to 21.9 cc in the 30 Gy in 5 fraction group. Minimum or maximum dose within the target was not associated with increased risk of LP or RN. Among patients receiving 27 Gy in 3 fractions, patients treated with resection followed by SRS had lower risk of LP compared to those treated with SRS alone (HR: 0.15, 95% CI: 0.03-0.64, p = 0.011). Among patients receiving 30 Gy in 5 fractions, patients who received corticosteroids prior to SRS had a lower risk of RN (HR: 0.14, 95% CI: 0.03-0.66, p = 0.013). For the entire cohort as well as within all subgroups, PD-L1≥1% was associated with increased risk of RN (p<0.001 for all).

CONCLUSION

Selecting the optimal SRS dose fractionation and planning parameters to minimize both LP and RN remains a challenge for large targets. In this analysis, 27 Gy in 3 fractions appeared to provide equivalent LP and RN compared to 30 Gy in 5 fractions, and may be more convenient for patients. Patients with PD-L1≥1% with large brain targets treated with SRS may be at increased risk of RN; corticosteroid prophylaxis may be considered in this population.

Memantine for Pediatric Patients Receiving Cranial Irradiation: A Pilot Study

PURPOSE/OBJECTIVE(S)

While memantine has become standard in certain adults receiving brain RT to decrease the cognitive impacts of RT, it is unknown whether pediatric patients can take and tolerate memantine or experience benefit. In this prospective single-arm feasibility study, we hypothesized pediatric patients receiving brain RT would tolerate memantine with good treatment adherence.

MATERIALS/METHODS

Patients aged 4-18 years with a primary CNS malignancy (excluding WHO Grade IV astrocytoma and glioblastoma) receiving intracranial RT were eligible. A 6-month course of memantine was given during and after RT. Dosing began once daily at 5 mg with up-titration in 5 mg increments over 4 weeks to a weight-based maximum (0.4 mg/kg to the closest 5 mg), not to exceed 10 mg BID. To reduce patient and clinical research associate (CRA) burden, medication adherence was tracked via the Medisafe Pill and Reminder application which study staff helped install on the patient or parent's smart phone. A paper pill diary was provided for those unable to use the app. The primary endpoint was to achieve 80% adherence rate to memantine in 80% of patients measured 1-month post-RT.

RESULTS

Eighteen patients (14 male and 4 female, median age 11.5 years (range: 4-18)) were enrolled from 2020-2022. The study closed early after enrolling 18 of 20 planned patients to avoid competing with the phase III randomized Children's Oncology Group (COG) study AACL2031. One patient withdrew for cognition-altering substance-use, leaving 17 patients with data available for analysis. Histologies included germ cell tumor (n = 6), craniopharyngioma (n = 3), choroid plexus papilloma (n = 2), ependymoma (n = 2), glial/astrocytoma (n = 2), medulloblastoma (n = 1), and meningioma (n = 1). Thirteen had surgery, and 9 received chemotherapy. Eight received craniospinal irradiation (CSI). Median RT dose was 54 Gy (range 36-59.4) in 30 fractions (range: 20-33). At data freeze, all 17 had passed the 1-month post-RT time point. One patient discontinued memantine after a single dose due to nausea. Pill-reports were available for 14 of the remaining 16; two patients did not complete digital pill logs. For those with complete logs, all adherence rates were above 80%, with a median of 99.32% pill completion rate (range: 92.67-100). Seven (50%) took 100% of prescribed doses. Irrespective of adherence for the 2 unavailable for evaluation, the primary endpoint was still achieved. Grade 1 toxicities included headache (n = 6, 35%) and constipation (n = 1, 6%); there were no grade 2+ toxicities. At last follow-up, 15/16 have completed the full 6-month memantine course. Secondary endpoints including neurocognitive evaluations have not yet been met and will be the subject of future reports.

CONCLUSION

Memantine is a feasible and well-tolerated addition to multi-modality treatment for pediatric brain tumors. Secondary endpoints of this study and results of the ongoing COG study are awaited to define the value of memantine in this population.

The Role of Radiation Therapy in the Management of Gray Zone Lymphoma

PURPOSE/OBJECTIVE(S)

Gray zone lymphoma (GZL) is a relatively rare disease predominantly affecting young adults with purportedly poor outcomes with current treatment approaches. The role of radiation therapy (RT) in the management of GZL is not well established. This is the largest study to report on the outcomes of GZL patients treated with and without RT.

MATERIALS/METHODS

A retrospective review of 30 patients with GZL treated across 3 institutions from 2009 to 2021 was performed. Event-free survival (EFS) was defined from initiation of frontline chemotherapy (CHT) to disease progression/relapse, initiation of salvage therapy, or death. Local control (LC) was defined from RT start date to in-field recurrence.

RESULTS

The median age was 32 (range: 18-86) years, and 16 (53%) patients had early stage (I-II) disease. Bulky mediastinal disease was present in 63% of patients, and the median tumor diameter was 10 (range: 1.5-18) cm. Patients received ABVD (20%), RCHOP (33%), or REPOCH (47%) as frontline CHT. Among 25 patients with interim PET/CT scan, there were 6 rapid early responders and 14 slow early responders (SER), with 2-year EFS of 33% and 24%, respectively (p = 0.13). After the completion of CHT, 15 (50%) patients achieved complete response (CR) and 10 (33%) achieved partial response (PR), with 2-year EFS of 46% and 10%, respectively (p = 0.004). RT was given to 9 patients in CR (n = 3) or in PR (n = 6). The median RT dose was 36 (30.6-48.6) Gy, at 1.8-2 Gy/fraction. Those receiving RT had bulkier disease at diagnosis (p = 0.049) and lower rates of CR following CHT (p = 0.03). After RT, 3/6 (50%) PR patients converted to CR. At a median follow-up of 4 years, the 2-year EFS was 26% for all patients, 33% for RT and 23% for noRT (p = 0.44). Among patients who did not receive upfront RT and experienced progression (n = 17), 16 (94%) relapsed in pre-existing sites. The 5-year OS was 80% for all patients, 88% for RT and 78% for no RT (p = 0.63). Patients who achieved PR to CHT and received RT had better 2-year EFS (17% vs 0%, p = 0.007) compared to patients who did not receive RT. Similarly, patients with SER who received RT had superior 2-year EFS (33% vs 13%, p = 0.038). Patients with bulky mediastinal disease had a 2-year EFS of 43% with RT and 11% without RT (p = 0.08). After 1st line treatment, 22 (73%) patients relapsed and 18 were successfully salvaged with a sustained CR. The most common salvage regimen involved high dose CHT followed by hematopoietic cell transplantation (HCT) (n = 15). RT was given for 7 patients in the relapsed/refractory setting (consolidative peri-HCT n = 4; definitive salvage n = 3) and 5 (71%) achieved a sustained CR. Among the 16 patients who received RT in the upfront (n = 9) or salvage (n = 7) setting, 3 patients experienced in-field recurrence translating to 2-year LC of 79%.

CONCLUSION

GZL patients have high risk of relapse and maximal upfront combined modality therapy should be considered. RT provides good local control and improves EFS particularly for SER, PR, and bulky mediastinal disease.

Clinical Outcomes for Chest Wall Ewing Sarcoma: A Multi-Center Single Institution Experience

PURPOSE/OBJECTIVE(S)

We report tumor and treatment characteristics, oncologic outcomes, and treatment-associated toxicities in a cohort of chest wall Ewing sarcoma (cwES) patients treated at a single tertiary care institution.

MATERIALS/METHODS

After IRB approval, patients with cwES treated from 1997-2022 were retrospectively reviewed. Patient, tumor, treatment, outcomes, and toxicity data were abstracted. Local control (LC), progression-free survival (PFS), and overall survival (OS) were defined from end of treatment and assessed using the Kaplan-Meier method. Log-rank test and unadjusted Cox models were performed to determine factors associated with outcomes.

RESULTS

The cohort includes 45 patients. Median age at diagnosis was 19.8 years (range: 3.5 - 57.8 years). Five patients (11.1%) presented with pleural effusion and eight patients with lung metastases (17.8%). Two (4.4%) patients had metastatic disease outside the thorax. Median tumor volume (TV) was 138.6 mL (range: 3.0-6762.0 mL). All patients received VDC/IE chemotherapy. LC modality was surgery (S) in 21 patients (47%), radiation therapy (RT) in 5 (11%), and S+RT in 19 (42%). Median TV was larger in S+RT patients (319.4 mL, range: 5.3-6761.9 mL) compared to RT (152.3 mL, range: 20.4-366.9 mL) or S (70.4 mL, range: 3.1-1037.8 mL) (p = 0.03). R0 and R1 resections were performed in 36 (90%) and 4 (10%) patients, respectively. Proton beam therapy was used in 15 (63%) patients. Median dose was 50.40 Gy (range: 34.2 - 60 Gy) in 28 fractions to the primary tumor or post operative bed. Median dose for hemithorax (1 patient, 2.2%) and whole lung irradiation (7 patients, 15.6%) was 15.0 Gy (range: 15.0-15.0 Gy) in 10 fractions. Median follow-up was 2.38 years (range: 0 - 21.90 years). Five-year LC, PFS, and OS for all patients was 77.9% (95% CI, 65.3 - 92.9%), 54.2% (95% CI, 39.9 - 73.5%), and 63.5% (95% CI, 49.3 - 81.8%), respectively. In patients with localized disease, 5-year LC, PFS, and OS were 82.4% (95% CI, 67.9-99.8%), 66.4% (95% CI, 49.7-88.8%), and 71.3% (95% CI, 54.2-93.9%), respectively. Two-year LC by modality was 100% for RT (95% CI, 100-100%), 84.2% (95% CI, 69.3- 100%) for S and 73.3% (95% CI, 54 - 99.5%) for S+RT (p = 0.51). On univariate analysis, TV ≥ 200 mL was associated with a significantly worse 5-year OS (49.5%, TV ≥ 200 mL vs. 80.8%, TV < 200 mL; HR 4.44, p = 0.032) and PFS (35.2%, TV ≥ 200 mL vs. 76%, TV < 200 mL; HR 3.55, p = 0.025). TV ≥ 200 mL trended towards worse 5-year LC: 69.2% for TV ≥ 200 mL versus 81.5% for TV <200 mL [HR 2.26(95% CI 0.49 - 10.47), p = 0.287]. Overall, low rates of grade ≥2 toxicity were observed: 4 (8.9%) fatigue, 4 (8.9%) radiation dermatitis, 1 (2.2%) chyle leak, 3 (6.6%) scoliosis, 4 (8.9%) infection, 1 (2.2%) pneumonia, and 1 (2.2%) chest wall deformity.

CONCLUSION

RT is a safe, effective local therapy for small to moderate cwES tumors. Patients with TV ≥ 200 mL had significantly worse survival outcomes and an inferior LC rate. This suggests large cwES tumors may benefit from an aggressive multi-modality approach.

Scalable radiotherapy data curation infrastructure for deep-learning based autosegmentation of organs-at-risk: A case study in head and neck cancer

In this era of patient-centered, outcomes-driven and adaptive radiotherapy, deep learning is now being successfully applied to tackle imaging-related workflow bottlenecks such as autosegmentation and dose planning. These applications typically require supervised learning approaches enabled by relatively large, curated radiotherapy datasets which are highly reflective of the contemporary standard of care. However, little has been previously published describing technical infrastructure, recommendations, methods or standards for radiotherapy dataset curation in a holistic fashion. Our radiation oncology department has recently embarked on a large-scale project in partnership with an external partner to develop deep-learning-based tools to assist with our radiotherapy workflow, beginning with autosegmentation of organs-at-risk. This project will require thousands of carefully curated radiotherapy datasets comprising all body sites we routinely treat with radiotherapy. Given such a large project scope, we have approached the need for dataset curation rigorously, with an aim towards building infrastructure that is compatible with efficiency, automation and scalability. Focusing on our first use-case pertaining to head and neck cancer, we describe our developed infrastructure and novel methods applied to radiotherapy dataset curation, inclusive of personnel and workflow organization, dataset selection, expert organ-at-risk segmentation, quality assurance, patient de-identification, data archival and transfer. Over the course of approximately 13 months, our expert multidisciplinary team generated 490 curated head and neck radiotherapy datasets. This task required approximately 6000 human-expert hours in total (not including planning and infrastructure development time). This infrastructure continues to evolve and will support ongoing and future project efforts.

Volumetric modulated arc therapy for hippocampal-sparing radiotherapy in transformed low-grade glioma: A treatment planning case report

Timing of radiotherapy for low-grade gliomas is still controversial due to concerns of possible adverse late effects. Prevention of possible late cognitive sequelae by hippocampal avoidance has shown promise in phase II trials. A patient with progressive low-grade glioma with gradual dedifferentiation into anaplastic astrocytoma is presented along with description of radiotherapy planning process attempting to spare the hippocampus. To our knowledge, this is the first described case using volumetric modulated arc technique to spare hippocampus during transformed low-grade glioma radiotherapy. Using modern intensity-modulated radiotherapy systems it is possible to selectively spare hippocampus together with other standard organs at risk. For selected patients, an attempt to spare hippocampus can be considered as long as other dose characteristics are not significantly compromised compared to standard treatment plan created without any effort to avoid hippocampus.