Intracranial Disease Progression Research Articles

Abstract PO5-16-10: The efficacy of novel antibody-drug-conjugates on brain metastases in metastatic breast cancer patients – a multicenter real-world analysis

Abstract 15 – 30% of all patients with metastatic breast cancer (MBC) develop brain metastases (BMs). Treatment of BMs include radiation therapy and surgical resection while systemic treatment is challenging and prospective evidence for the treatment of active brain metastases is restricted to the small molecule Tucatinib. Recently, the antibody-drug-conjugates (ADCs) Sacituzumab-Govitecan (SG) and Trastuzumab-Deruxtecan (T-DXd) have shown to be highly effective in the treatment of triple-negative (SG), HER2-positive (T-DXd) and HR+/HER2- (SG and, in case of HER2-low-expression, T-DxD) MBC. However, there is only limited data, whether these macromolecules are also effective in patients with BMs. We therefore aimed to examine the efficacy of SG and T-DXd in patients with stable and active BMs in a multicenter real-world analysis. Female patients with stable or active BMs who were treated with either SG or T-DXd at the breast centers of Tuebingen University, Ulm University or Freiburg University in Germany before June 30, 2023 were included into this analysis. Data cut-off for this analysis was July 10, 2023. BMs were classified as active if they were newly diagnosed and did not require local treatment or if they were progressing and did not require local treatment. Preexisting BMs without intracranial disease progression or preexisting/newly diagnosed BMs that had been treated by surgery and/or radiotherapy directly prior to SG/T-DXd therapy were considered as stable. All patients underwent baseline magnetic resonance imaging (MRI) of the brain and received follow-up MRIs at least every three months. Growth dynamics of BMs were assessed by board certified neuroradiologists. Intracranial disease control rate (icDCR) was defined as the percentage of patients with at least intracranial stable disease at the first follow-up MRI. Intracranial progression-free survival (icPFS) was determined as the period between the first application of SG or T-DXd and intracranial disease progression or treatment cessation due to the patients’ will or the onset of intolerable toxicity. If ADC treatment was discontinued due to extracranial disease progression albeit at least stable intracranial disease patients were censored. Overall survival (OS) was defined as the period between the first application of SG or T-DXd and death. In total, 26 patients were included with a median of two prior therapy lines in the metastatic setting (range 2 – 15). 10 (38%) and 14 (54%) patients received SG and T-DXd, respectively. 2/26 (8%) patients receiving SG were consecutively subjected to T-DXd treatment. SG was applied to 12/12 patients (100%) due to triple-negative MBC and 12/16 patients (75%) treated with T-DXd were HER2-positive. The remaining 4/16 patients (25%) treated with T-DXd showed HER2 low tumor biology. 5/12 (42%) and 8/16 (50%) patients treated with SG or T-DXd had active BMs at treatment initiation. The icDCR was 33% (95% CI: 5% - 61%)/81% (95% CI: 62% - 100%) for all patients treated with SG/T-DXd and 40% (95% CI: 0% - 88%)/75% (95% CI: 43% - 100%) in case of active BMs. After a median follow-up of 7.2 months, 10/12 (83.3%) patients treated with SG and 4/16 (25%) patients subjected to T-DXd had discontinued treatment. Median icPFS was 3.1 months (95% CI: 0.4 – 5.8 months) for SG and not reached for T-DXd. 7/12 (58%) patients treated with SG and 4/16 patients (25%) treated with T-DXd died until data cut-off. Median OS was 7.2 months (95% CI: 3.0 – 11.4 months) for patients treated with SG and not reached for patients treated with T-DXd. SG and T-DXd showed promising clinical activity in both, stable and active cerebral breast cancer metastasis. Updated PFS and OS data will be reported at the meeting. Citation Format: Dominik Dannehl, Henning Schäffler, Tobias Engler, Lea Volmer, Arne Estler, Ilinca Popp, Stefanie Lorenz, Eva-Maria Grischke, Markus Hahn, Ghazaleh Tabatabai, Ingolf Juhasz-Böss, Wolfgang Janni, Sara Brucker, Florin-Andrei Taran, Andreas Hartkopf. The efficacy of novel antibody-drug-conjugates on brain metastases in metastatic breast cancer patients – a multicenter real-world analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-16-10.

Abstract PO5-19-05: A Phase II Trial of Stereotactic Body Radiation Therapy and Fluoroestradiol Positron Emission Tomography in Patients with Oligoprogressive Estrogen Receptor Positive Metastatic Breast Cancer

Abstract Background: The term oligoprogression (OP) refers to a clinical scenario in which patients with diffuse metastatic disease on systemic therapy have a limited number of metastases that have progressed or are new whereas the majority of metastases are stable or improved. OP disease is increasingly being encountered in clinical practice due to improvements in systemic therapy. Treating OP disease with local ablative therapies may therefore prolong the time to more diffuse progression necessitating a change in systemic therapy and may therefore lead to improved overall survival in these patients. Only one study has evaluated the role of SBRT in patients with OP MBC. This trial accrued 47 patients with OP MBC, with 2/3 having triple negative disease. There was no difference in PFS between patients that received SBRT versus those that did not (4.2 months vs. 4.4 months, p=0.2). Whether ablative therapies are beneficial in subtypes of breast cancer that have many effective systemic therapies available, such as ER+ breast cancer, remains an open question and an unmet clinical need. Design: Phase II study for patients with OP ER+ MBC (1-4 new and/or progressing metastatic lesions). Eligible patients will receive stereotactic body radiation therapy (SBRT) to the OP lesions. SBRT will be delivered to each lesion in 3-5 fractions. Each patient’s systemic therapy regimen will be held during study therapy and will resume upon completion of study therapy. Patients will then be restaged at 12 weeks post-SBSRT. Patients that have at least stable disease at that time point will continue on their systemic therapy and then be re-staged 12 weeks later (24 weeks after SBRT). This study will also study the role of ER-targeted positron emission tomography (PET) imaging with 16α-18F-Fluoro-17β-Fluroestradiol (FES) in the OP ER+ patient population with FES PET scans obtained at baseline, and at each of the 2 follow-up imaging timepoints. A key secondary hypothesis is that the use of FES PET in addition to standard imaging at baseline and in follow-up will help confirm patients have OP disease and will help assess for new lesions on subsequent restaging. Eligibility: Key inclusion criteria: age≥18 yo; histologically confirmed ER+/HER2- metastatic breast cancer; the presence of metastatic breast cancer at the time of study entry with progression in 1-4 lesions (including new lesions); SBRT must be feasible for all progressing lesions. Key Exclusion Criteria: >2 lines of systemic therapy for metastatic disease; intracranial disease progression Objective: To determine whether using SBRT to treat OP lesions allows ER+ breast cancer patients to continue on their current systemic therapy for at least 24 weeks post SBRT. Objective: To assess whether FES-PET increases the number of lesions found prior to SBRT; To determine the impact of SBRT on patient quality of life; time to next line systemic therapy; PFS Statistical Methods Simon 2 stage optimal design with α=0.05 and 1-β=0.80. The null hypothesis is that the proportion of patients that remain on their original systemic therapy ≥24 weeks (2 restaging scans) post-treatment is 20%. The alternative hypothesis is that the proportion of patients that remain on their original systemic therapy after 2 restaging scans is 50%. In stage 1, 8 patients that proceed to SBRT will be enrolled. The study will be terminated if only 0 or 1 subjects remain on original systemic therapy after 2 restaging scans. However, if ≥2 patients remain on original systemic therapy after 2 restaging, then an additional 10 patients would be enrolled for a total of 18 patients. The null hypothesis will be rejected if ≥6 patients remain on their original systemic therapy after 2 restaging scans. Contact Information: Jose G. Bazan (jbazan@coh.org) Funding Source: City of Hope Comprehensive Cancer Center Citation Format: Jose Bazan, Joanne Mortimer, Yun-Rose Li. A Phase II Trial of Stereotactic Body Radiation Therapy and Fluoroestradiol Positron Emission Tomography in Patients with Oligoprogressive Estrogen Receptor Positive Metastatic Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-19-05.

Progression of Intracranial Artery Stenosis and Cerebral Small Vessel Disease and Associations Between the Two Entities: A Prospective Community-based Cohort Study (S6.003)

Progression of Intracranial Artery Stenosis and Cerebral Small Vessel Disease and Associations Between the Two Entities: A Prospective Community-based Cohort Study (S6.003)

199 Gamma Knife Radiosurgery to Treat Neurofibromatosis Type 2-Associated Meningiomas: A 35 Year Experience and Paradigm for Future Treatment

INTRODUCTION: Management of neurofibromatosis type 2 (NF2)-associated meningiomas remains a case-by-case basis, and treatment options vary. METHODS: Forty-nine patients (22 male, 44.90%) with 213 NF2-associated meningiomas treated with SRS between 1987 and 2022 were retrospectively reviewed. The median age at SRS was 56 (range: 20-79) years. Twenty-nine (59.18%) patients had pre-SRS surgical resection, and 7 (14.29%) had prior radiotherapy. The median number of meningiomas per patient was 2 (range: 1-17), the median margin dose was 13 (range: 9-16) Gy, and the median cumulative tumor volume per patient was 8.30 (range: 0.10-74.26) cm3. RESULTS: Nine patients (18.37%) had local tumor progression. The 1- and 5-year local tumor control rates were 100% and 90.54%, respectively. Tumor volume < 8.30 cm3 was associated with better local tumor control (p = 0.02, HR: 1.06, 95% CI: 1.01-1.12) on multivariate analysis. Twenty-five patients (51.02%) had detection of new growing tumors (DNGT). The 1- and 5-year DNGT rates were 78.05% and 47.38%, respectively. On multivariate analysis, >2 meningiomas at SRS presentation per patient (p = 0.01, HR: 1.09, 95% CI: 1.02-1.17) was significantly associated with DNGT. Neurological symptoms improved in 20 patients (40.82%), remained stable in 28 patients (57.14%), and worsened in 1 (2.04%) patient at a median follow-up time of 81 (range: 6–267) months after SRS. Seventeen (34.69%) patients were deceased at last follow-up, and 4 patients expired due to intracranial disease progression. Two (4.08%) patients developed transient adverse radiation effects; no patients developed secondary malignancies. CONCLUSIONS: Single-session SRS can effectively be used to control tumor progression and improve neurological symptoms in NF2-associated meningioma patients while limiting adverse radiation effects.

Is Gamma Knife surgery, omitting adjunct whole brain radiation treatment, feasible for patients with 20 or more brain metastases?

The importance of the number of brain metastases (BM) when deciding between whole brain radiation treatment (WBRT) and radiosurgery is controversial. We hypothesized that the number of BM is of limited importance when deciding radiation strategy, and offered Gamma Knife surgery (GKS) also for selected patients with 20 or more BM. The outcome following single session GKS for 75 consecutive patients harboring 20 or more (20+) BM was analyzed. Data was collected both retro- and prospectively. The median survival time was 9 months. Two grade 3 complications occurred, 1 resolved and 1 did not. Sex and clinical condition at the time of GKS (ECOG value) were the only parameters significantly related to survival time. Eighteen patients developed leptomeningeal dissemination with or without distant recurrences (DR), and another 32 patients developed DR a total of 73 times. DR was managed with GKS 24 times, with WBRT 3 times and with systemic treatment or best supportive care 46 times. The median time to developing DR was unrelated to the number of BM, but significantly longer for patients older than 65 years, as well as for patients with NSCLC. GKS is a reasonable treatment option for selected patients with 20 or more BM. It is better to decide the optimal management of post-GKS intracranial disease progression once it occurs rather than trying to prevent it by using adjunct WBRT.

Abstract TP221: Progression of Intracranial Artery Stenosis and Cerebral Small Vessel Disease and Associations Between the Two Entities: A Prospective Community-Based Cohort Study

Background: Both intracranial artery stenosis (ICAS) and cerebral small vessel disease (CSVD) can cause heavy socioeconomic burdens. However, their longitudinal changes remain controversial. To investigate the risk factors for ICAS and CSVD progression and their associations in a community population. Methods: This longitudinal analysis included 756 participants who underwent both baseline and follow-up brain magnetic resonance imaging (MRI) and magnetic resonance angiography from Shunyi cohort. The follow-up duration was 5.58±0.49 years. Incident ICAS was defined as new stenosis occurring in at least one artery or increased severity of the original artery stenosis. CSVD markers included lacunes, cerebral microbleeds (CMB), and white matter hyperintensities (WMH). Results: Of the 756 participants (aged 53.7±8.0 years, 34.9% men), 8.5% had incident ICAS. Body mass index (BMI) and diabetes mellitus are independent risk factors for ICAS. Hypertension is an independent risk factor for incident lacunes and CMB, whereas WMH progression is primarily affected by BMI. Higher LDL cholesterol level independently protects against WMH progression. Baseline ICAS burden predicted an increased risk of incident lacunes (odds ratio [OR] = 2.17, 95% confidence interval [CI] = 1.10-4.29, p = 0.025) after adjusting for age, sex, follow-up time, vascular risk factors, and baseline lacunes burden. Incident ICAS was also significantly associated with incident lacunes (OR = 3.29, 95% CI = 1.61-6.72, p = 0.001). No significant correlation was identified between ICAS and CMB or WMH. Conclusions: Patients with ICAS and CSVD progression had different modifiable risk factor profiles. The disparate association between ICAS and progressions of different MRI markers of CSVD imply vital differences of their underline mechanism.

Brain Metastases in the Setting of Stable Versus Progressing Extracranial Disease Among Patients With Metastatic Breast Cancer

IntroductionWomen with metastatic breast cancer (BC) are at risk of developing brain metastases (BrM), which may result in significant morbidity and mortality. Given the emergence of systemic therapies with activity in the brain, more breast oncology clinical trials include patients with BrM, but most require extracranial disease progression for trial participation. MethodsWe evaluated the proportion of patients with BC BrM who have intracranial disease progression in the setting of stable extracranial disease in a retrospective cohort study of 751 patients treated between 2008 and 2018 at the Sunnybrook Odette Cancer. Extracranial disease progression was defined as any progression outside of the brain within 4 weeks of a patient's local/regional treatment. Clinical/pathologic characteristics and outcomes were also abstracted from patients’ medical records. ResultsOf 752 patients in the cohort, 691 were included in our study. Sixty-one patients were excluded due to the presence of a second primary tumor or uncertain tissue origin of the BrM. BC subtype based on the primary tumor was known for 592 (85.6%) patients; 33.1% (n = 196) had HER2+ disease, 40% (n = 237) had HR+/HER2- disease, and 26.9% (n = 159) had triple negative BC. Extracranial disease status was available for 677 patients (98%); 41.1% (n = 284/691) had stable extracranial disease and 56.8% (n = 393/691) had extracranial disease progression within 4 weeks of treatment for BrM. DiscussionA high proportion of patients with BC BrM (41.1%) would be excluded from clinical trials due to stable extracranial disease. Efforts should be made to design trials for this patient population.

The Role of Stereotactic Radiosurgery in Patients With Brain Metastases From Colorectal Cancers.

The role of stereotactic radiosurgery (SRS) in patients with brain metastases (BMs) from colorectal cancers (CRCs) has not been established. The authors present a single-institution experience of patients with CRC who underwent SRS with metastatic brain spread. We retrospectively analyzed 111 patients with metastatic CRC (64 female, 57.7%), with 449 BMs treated with Gamma Knife SRS between 2000 and 2022. The median age during SRS was 63 years (range: 28-86), and the median Karnofsky Performance Scale was 80 (range: 60-100). The primary sites were colon (85 patients, 76.6%) and rectal (26 patients, 23.4%). Three patients underwent hypofractionated SRS (3 sessions) with a median margin dose of 27 Gy (range: 27-30). All other patients underwent single-session SRS with a median margin dose of 18 Gy (range: 13-20). The median patient survival after SRS was 7 months (range: 1-174). Ninety-eight (88.3%) patients expired at last follow-up and 15 patients (15.3%) died related to progressive intracranial disease. A Karnofsky Performance Scale of <80 at SRS presentation ( P = .02, hazard ratio [HR]: 0.6, 95% CI: 0.4-0.9) and no previous surgical resection ( P < .01, HR: 0.4, 95% CI: 0.3-0.7) were associated with inferior overall survival using multivariate analysis. Seventeen patients (15.3%) had documented local tumor progression after SRS, at a median time of 7 months (range: 3-34) between SRS and progression. Twenty-six patients (23.4%) developed new BMs at a median of 5 months (range: 2-26) between SRS and new tumor detection. Less than three BMs at SRS presentation ( P = .02, HR: 2.6, 95% CI: 1.2-5.6) were associated with better distant tumor control on multivariate analysis. The incidence of adverse radiation effects was 5.4%. SRS effectively controls BMs from CRC with low risk of treatment-related toxicity. During follow-up, the development of additional metastases can be safely treated by repeat SRS.

Amivantamab plus chemotherapy with and without lazertinib in EGFR-mutant advanced NSCLC after disease progression on osimertinib: primary results from the phase III MARIPOSA-2 study

Amivantamab plus carboplatin-pemetrexed (chemotherapy) with and without lazertinib demonstrated antitumor activity in patients with refractory epidermal growth factor receptor (EGFR)-mutated advanced non-small-cell lung cancer (NSCLC) in phase I studies. These combinations were evaluated in a global phase III trial. A total of 657 patients with EGFR-mutated (exon 19 deletions or L858R) locally advanced or metastatic NSCLC after disease progression on osimertinib were randomized 2 : 2 : 1 to receive amivantamab-lazertinib-chemotherapy, chemotherapy, or amivantamab-chemotherapy. The dual primary endpoints were progression-free survival (PFS) of amivantamab-chemotherapy and amivantamab-lazertinib-chemotherapy versus chemotherapy. During the study, hematologic toxicities observed in the amivantamab-lazertinib-chemotherapy arm necessitated a regimen change to start lazertinib after carboplatin completion. All baseline characteristics were well balanced across the three arms, including by history of brain metastases and prior brain radiation. PFS was significantly longer for amivantamab-chemotherapy and amivantamab-lazertinib-chemotherapy versus chemotherapy [hazard ratio (HR) for disease progression or death 0.48 and 0.44, respectively; P < 0.001 for both; median of 6.3 and 8.3 versus 4.2 months, respectively]. Consistent PFS results were seen by investigator assessment (HR for disease progression or death 0.41 and 0.38 for amivantamab-chemotherapy and amivantamab-lazertinib-chemotherapy, respectively; P < 0.001 for both; median of 8.2 and 8.3 versus 4.2 months, respectively). Objective response rate was significantly higher for amivantamab-chemotherapy and amivantamab-lazertinib-chemotherapy versus chemotherapy (64% and 63% versus 36%, respectively; P < 0.001 for both). Median intracranial PFS was 12.5 and 12.8 versus 8.3 months for amivantamab-chemotherapy and amivantamab-lazertinib-chemotherapy versus chemotherapy (HR for intracranial disease progression or death 0.55 and 0.58, respectively). Predominant adverse events (AEs) in the amivantamab-containing regimens were hematologic, EGFR-, and MET-related toxicities. Amivantamab-chemotherapy had lower rates of hematologic AEs than amivantamab-lazertinib-chemotherapy. Amivantamab-chemotherapy and amivantamab-lazertinib-chemotherapy improved PFS and intracranial PFS versus chemotherapy in a population with limited options after disease progression on osimertinib. Longer follow-up is needed for the modified amivantamab-lazertinib-chemotherapy regimen.

Pattern of Failure and Re-Irradiation for Stereotactic Radiotherapy Treated Brain Metastases from Non-Small Cell Lung Cancer (NSCLC)

Hypofractionated stereotactic radiotherapy (SRT) has been increasingly used for brain metastases (BMs) from non-small cell lung cancer (NSCLC). However, the prognostic factors, pattern of failure and clinical utility of re-irradiation for these patients remain have not been fully understood. Metastatic NSCLC patients receiving SRT that covering all of the intracranial tumor lesions and without prior whole brain radiotherapy (WBRT) were retrospectively enrolled. Local recurrence free survival (LRFS), intracranial progression free survival (iPFS) and overall survival (OS) were calculated from the initiation of SRT. Post intracranial progression survival (OS2) was measured from the initial intracranial disease progression. From 2018/05 to 2022/05, 218 patients were identified, with 142 (65.1%) having only one BM and 76 (34.9%) harboring 2-5 BMs. With a median follow-up of 31.1 (range, 1.0-44.6) months, median LRFS, iPFS and OS was 39.1, 26.6 and 31.1 months, respectively. No statistical difference of LRFS, iPFS and OS were found between patients with different numbers of BM. Nevertheless, patients receiving concurrent systemic therapy had significantly longer LRFS (HR = 0.35, p = 0.002), iPFS (HR = 0.57, p = 0.044) and OS (HR = 0.37, p = 0.001), when compared with those receiving SRT alone. By now, intracranial disease progression (iPD) was documented in 59 patients, with original site PD (OPD), new site PD (NPD) and both sites PD (BPD) occurring in 20 (33.9%), 17 (28.8%) and 22 (37.3%), respectively. Among the 59 patients, 19 (32.2%) received second-course SRT (re-SRT) targeting the intracranial progressive tumor lesions and re-SRT led to improved OS2 (22.7 vs 12.1 months, HR = 0.29, 95% CI 0.08-0.97, p = 0.045), which remained as an independent prognostic factor after multiple-variate Cox analyses. The status of systemic therapy, but not the number of BMs, may impact the survival outcomes of SRT-treated BMs from NSCLC. Some patients may benefit from re-SRT, which warranted future validation.

Stereotactic Radiotherapy (SRT) in Combination with Aumolertinib to Treat Intracranial Oligometastatic Non-Small Cell Lung Cancer (NSCLC): An Update of a Phase II, Prospective Study

Stereotactic radiotherapy (SRT) is highly effective and less toxic for limited intracranial metastases. Aumolertinib is a tolerable third-generation epidermal growth factor receptor tyrosine kinase inhibitor that has CNS efficacy in patients with EGFR-mutant NSCLC. We aim to investigate the efficacy and safety of aumolertinib followed by SRT in patients with intracranial oligometastatic NSCLC. Intracranial oligometastatic Patients with EGFR sensitive mutations (EGFR-TKIs naive) were enrolled and received aumolertinib 110mg daily until intracranial disease progression. Then SRT (32-40 Gy total, 8 Gy/f) was given to intracranial oligo-progression disease if possible. The primary endpoint was intracranial objective response rate (iORR). Secondary endpoints included intracranial progression-free survival (iPFS), intracranial duration of response (iDOR)according to RECIST 1.1, cerebral radiation necrosis rate (CRNR) and overall survival (OS). Safety was evaluated according to Common Terminology Criteria for Adverse Events version 5.0 (CTCAE v5.0). This trial is registered with ClinicalTrials.gov, NCT04519983. To February 10, 2023, a total of 38 patients were enrolled and 35 patients were assessable followed for 3 months to 18 months. All patients received 110mg aumolertinib daily and received at least one independent imaging evaluation by a radiologist. After oral administration of aumolertinib, the best response of 94% patients in intracranial and extracranial lesions was partial response (PR). Two patients had stable intracranial disease. At data cut-off, one patient developed intracranial primary lesion progression at 12 months after oral administration of aumolertinib but stable in extracranial lesions. SRT treatment was given to this patient. No grade ≥3 adverse events occurred after continued oral administration of aumolertinib. The most common adverse reactions were rash and abnormal liver enzymes, 1 patient had grade 2 CK elevation. This report showed pronounced intracranial objective response benefit in patients with intracranial oligometastatic disease followed by SRT after intracranial oligo-progression and no new safety signals. Aumolertinib has promising efficacy and good tolerability in intracranial oligometastatic EGFR mutated NSCLC. [Keywords] Non-small cell lung cancer; epidermal growth factor receptor tyrosine kinase inhibitor; Aumolertinib; Stereotactic radiotherapy.

Prospective Feasibility Trial of Vertebral Body Sparing Pencil Beam Scanning Proton Craniospinal Irradiation in Growing Children

Advanced proton therapy techniques now allow for delivery of craniospinal irradiation (CSI) to the entire brain and thecal sac while sparing many of the anterior vertebral bodies from doses expected to inhibit growth, though this technique has not been prospectively studied. The purpose of this trial is to test the feasibility and robustness of vertebral body sparing (VBS) CSI in children with standard image guidance, to assess the dosimetric and toxicity benefits of this approach, and to report early clinical outcomes. Children 3-18 years old requiring CSI treatment were eligible for this IRB approved prospective clinical trial. The CSI clinical target volume (CTV) included the brain, entire thecal sac and neural foramina with no expansion. Select anterior vertebral bodies (AVB) could be included at the physician's discretion. The spinal portion of the CTV was treated with PA beam(s) with robust optimization (+/-3.5% range, 5mm positional uncertainty). Daily image guidance included kV/kV imaging. Cone beam CT (CBCT) was acquired weekly after final positioning and a virtual CT (vCT) was created for quality assurance (QA) analysis. Acute toxicity was prospectively assessed weekly during treatment and 1 month after per CTCAE v5.0. Ten children with a median patient age and CSI dose of 9 years (range 3-16) and 36 Gy (RBE) (range 15-36 Gy (RBE)) were enrolled. Common diagnoses were medulloblastoma (n = 4) and non-germinomatous germ cell tumor (n = 3). Seven patients received prior chemotherapy; 2 patients were treated with palliative intent. Dose statistics for the anterior vertebral body varied according to age, CSI dose and portion of the spine, with the greatest sparing in the lower thoracic and lumbar vertebrae for all patients. Nine patients completed all QA CTs; one patient required a replan due to weight gain. For all remaining patients the treatment was highly robust: CTV V95 reduction at the C-spine, T-spine, and L-spine was 0.0±0.1%, 0.6±1.3%, and 0.8±1.1%, respectively. The highest grade non-hematologic acute toxicity was grade 2 alopecia (n = 9) and grade 2 nausea/vomiting (n = 5). One patient reported transient grade 1 esophagitis during treatment. Hematologic toxicity included >/ = grade 3 lymphopenia in 7 patients, >/ = grade 3 leukopenia in 1 patient, >/ = grade 2 anemia in 6 patients, and >/ = grade 1 thrombocytopenia in 3 patients. Median follow-up is 16.6 months (range 10-36 months). Three patients experience intracranial disease progression: 2 local and 1 distant intracranial failure. There were no failures within the spine. Proton vertebral body sparing CSI targeting the thecal sac only is a highly robust treatment technique and is well tolerated. Weekly CBCT to assess changes in soft tissue posterior to the spine is recommended. Further follow-up is required to assess long-term growth outcomes.

LMAP-19 THE ROLE OF STEREOTACTIC RADIOSURGERY IN PATIENTS WITH BRAIN METASTASES FROM COLORECTAL CANCERS

Abstract BACKGROUND AND OBJECTIVES The role of stereotactic radiosurgery (SRS) for patients with brain metastases from colorectal cancers (CRC) has not been established. The authors present a single-institution experience of CRC patients who underwent SRS with metastatic brain spread. METHODS We retrospectively analyzed 112 metastatic CRC patients (64 female, 57.14%) with 450 brain metastases that were treated with Gamma Knife SRS between 2000-2022. The median age at SRS was 63 years (range: 28-86) and the median Karnofsky Performance Score (KPS) was 80 (range: 60-100). The primary sites were colon (86 patients, 76.79%) and rectal (26 patients, 21%). Three patients underwent hypo-fractionated SRS (3 sessions) with a median margin dose of 27 Gy (range: 27- 30). All other patients underwent single-session SRS with a median margin dose of 18 Gy (range: 11-20). RESULTS The median patient survival after SRS was 7 months (range: 1-174). Ninety-eight (87.5%) patients expired at last follow up and 15 patients (15.31%) died related to progressive intracranial disease. KPS &amp;lt; 80 at SRS presentation (p=0.03, HR: 0.63, 95% CI: 0.41-0.96) was associated with inferior overall survival using multivariate analysis. Seventeen patients (15.18%) had documented local tumor progression after SRS, at a median time of 7 months (range: 3-34) between SRS and progression. Twenty-six patients (23.21%) developed new brain metastases at a median of 5 months (range: 2-26) between SRS and new tumor detection. KPS ≥ 80 (p=0.05, HR: 0.96, 95% CI: 0.93-0.99), and &amp;lt; 3 brain metastases at SRS presentation (p&amp;lt;0.01, HR: 3.62, 95% CI: 1.53-8.56) were associated with better distant tumor control on multivariate analysis. The incidence of adverse radiation effects was 5.36%. CONCLUSIONS SRS effectively controls brain metastases from CRC with a low risk of treatment-related toxicity, allowing patients to focus on primary disease management. During follow-up, the development of progressive or additional metastases can be safely treated by repeat SRS.

XRT-04. THE ROLE OF STEREOTACTIC RADIOSURGERY FOR MENINGIOMAS IN PEDIATRIC PATIENTS

Abstract Despite the generally benign and slow-growing nature, meningiomas in pediatric populations often exhibit more aggressive behavior. Stereotactic radiosurgery (SRS) is a non-invasive modality that is widely used as an upfront or adjuvant treatment for patients with meningiomas. Due to the rarity of meningiomas in pediatric patients, the outcomes of SRS for childhood meningiomas have never been described. From 1987 to 2022, a total of 2,030 patients with meningiomas underwent SRS at the University of Pittsburgh Medical Center. Nine patients (2 female; incidence rate = 0.44%) with a median age of 14.5 years (range, 9—17 years) at SRS were identified. Three patients (33.3%) had a history of total body irradiation. Seven patients (77.8%) were asymptomatic at the time of SRS presentation. Seven patients (77.8%) had a pre-SRS craniotomy; two patients (22.2%) had pre-SRS fractionated radiotherapy. The median cumulative tumor volume was 3.65 cc (range, 0.01—11.84 cc). The median margin dose prescribed was 14 Gy (range, 11—25 Gy). The median follow-up time was 107 months (range, 24—194 months). Five patients (55.6%) experienced tumor progression at a median of 25 months (range, 13—161 months). Local tumor control at 1-, 5-, and 10 years was 100%, 55.56%, and 55.56%, respectively. After local tumor progression, 2 patients received repeat SRS, 2 patients had surgical resection and 1 was placed on hydroxyurea for an unresectable tumor. At the date of the last clinical follow-up, 5 patients (55.6%) were still alive while 4 patients (44.4%) expired due to the progression of intracranial disease. 1-, 5-, and 10-year survival was 100%, 88.89%, and 64.81%, respectively. Childhood meningioma is a rare tumor that exhibits aggressive behaviors. SRS should be considered as an upfront or adjuvant treatment option in the multi-modal management of childhood meningiomas for optimal tumor control and maximal quality of life preservation.

Pattern of failure and re-irradiation for stereotactic radiotherapy treated brain metastases from non-small cell lung cancer (NSCLC).

e14010 Background: Hypofractionated stereotactic radiotherapy (SRT) has been increasingly used for brain metastases (BMs) from non-small cell lung cancer (NSCLC). However, the prognostic factors, pattern of failure and clinical utility of re-irradiation for these patients remain have not been fully understood. Methods: Metastatic NSCLC patients receiving SRT that covering all of the intracranial tumor lesions and without prior whole brain radiotherapy (WBRT) were retrospectively enrolled. Local recurrence free survival (LRFS), intracranial progression free survival (iPFS) and overall survival (OS) were calculated from the initiation of SRT. Post intracranial progression survival (OS2) was measured from the initial intracranial disease progression. Results: From 2018/07 to 2022/05, 218 patients were identified, with 142 (65.1%) having only one BM and 76 (34.9%) harboring 2-5 BMs. With a median follow-up of 31.1 (range, 1.0-44.6) months, median LRFS, iPFS and OS was 39.1, 26.6 and 31.1 months, respectively. No statistical difference of LRFS, iPFS and OS were found between patients with different numbers of BM. Nevertheless, patients receiving concurrent systemic therapy had significantly longer LRFS (HR=0.35, p=0.002), iPFS (HR=0.57, p=0.044) and OS (HR=0.37, p=0.001), when compared with those receiving SRT alone. By now, intracranial disease progression (iPD) was documented in 59 patients, with original site PD (OPD), new site PD (NPD) and both sites PD (BPD) occurring in 20 (33.9%), 17 (28.8%) and 22 (37.3%), respectively. Among the 59 patients, 19 (32.2%) received second-course SRT (re-SRT) targeting the intracranial progressive tumor lesions and re-SRT led to improved OS2 (22.7 vs 12.1 months, HR=0.29, 95%CI 0.08-0.97, p=0.045), which remained as an independent prognostic factor after multiple-variate Cox analyses. Conclusions: The status of systemic therapy, but not the number of BMs, may impact the survival outcomes of SRT-treated BMs from NSCLC. Some patients may benefit from re-SRT, which warranted future validation.

Abstract 37: A novel technique to preclinically assess the ability of targeted therapies to inhibit both primary and metastatic non small cell lung carcinoma

Abstract Lung cancer remains a devastating cancer diagnosis around the world, resulting in 18% of all cancer-related deaths. Lung cancer often metastasizes to the brain, significantly reducing life expectancy. Up to 7% of patients with non-small cell lung cancer (NSCLC) already have brain metastasis when they are first diagnosed, and 20%-40% of patients with NSCLC will develop this complication during disease progression. Currently there are no targeted therapies specific for brain metastases, and the blood-brain barrier can pose a physiologic impediment to many cytotoxic drugs and antibody-based therapies. Here, we will discuss the development and use of xenograft models to address metastatic brain disease via a direct intracranial implant coupled with a subcutaneous “primary” tumor to effectively allow evaluation of the response to treatment at both locations. Treatment with targeted therapies could have significantly different penetration and absorption rates, which will alter pharmacokinetic and/or pharmacodynamic (PK/PD) assessment across either tissue. The dual implant technique can be a powerful tool to assess the simultaneous impact of treatment on established metastatic disease and primary tumor. We have characterized the dual disease induction parameters for two human NSCLC cell lines: NCI-H1975-Luc and PC-9-Luc. Both cell lines have been transfected with luciferase to allow for bioluminescence imaging (BLI) to monitor the intracranial disease progression. Both NCI-H1975-Luc and PC-9-Luc are of interest to the research community due to their unique mutational EGFR T790M status. Consistent with the historical and published data, the H1975-luc and PC-9-luc models behaved as expected, producing reliable tumor progression with minimal intragroup variability. In each case, subcutaneous tumors (primary site) reached an evaluation size of ~1000 mm3 in ~20 days, and intracranial tumors (metastatic site) exhibited a total flux doubling time of ~2 days by BLI. Treatment with Osimertinib, an approved first-line treatment for EGFR+ NSCLC patients, was effective against both the subcutaneous and intracranial tumors. Treatment with Osimertinib at 25 mg/kg, given orally, produced 100% complete regressions (CR) against the subcutaneous tumors, which never re-grew prior to study termination on Day 26 post implant and 100% partial regressions (PR) against the established intracranial tumors, which re-grew following the conclusion of treatment at the same rate as the control brain tumors. These data show a difference between the responsive nature of subcutaneous and intracranial NSCLC tumors representing the difference in responsiveness of primary tumors and brain metastases. Utilizing this in vivo dual implant technique can be effective in comparing and assessing the ability of targeted therapies to inhibit both primary and metastatic diseases. Citation Format: Erin Trachet, Scott Wise. A novel technique to preclinically assess the ability of targeted therapies to inhibit both primary and metastatic non small cell lung carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 37.

Decoding molecular programs in melanoma brain metastases

Melanoma brain metastases (MBM) variably respond to therapeutic interventions; thus determining patient’s prognosis. However, the mechanisms that govern therapy response are poorly understood. Here, we use a multi-OMICS approach and targeted sequencing (TargetSeq) to unravel the programs that potentially control the development of progressive intracranial disease. Molecularly, the expression of E-cadherin (Ecad) or NGFR, the BRAF mutation state and level of immune cell infiltration subdivides tumors into proliferative/pigmented and invasive/stem-like/therapy-resistant irrespective of the intracranial location. The analysis of MAPK inhibitor-naive and refractory MBM reveals switching from Ecad-associated into NGFR-associated programs during progression. NGFR-associated programs control cell migration and proliferation via downstream transcription factors such as SOX4. Moreover, global methylome profiling uncovers 46 differentially methylated regions that discriminate BRAFmut and wildtype MBM. In summary, we propose that the expression of Ecad and NGFR sub- classifies MBM and suggest that the Ecad-to-NGFR phenotype switch is a rate-limiting process which potentially indicates drug-response and intracranial progression states in melanoma patients.

CNSC-04. CEREBROSPINAL FLUID-DERIVED CIRCULATING TUMOR DNA IS SUPERIOR TO PLASMA IN NSCLC PATIENTS WITH CNS PROGRESSION

Abstract Introduction Central nervous system (CNS) metastases are devastating neurologic complications. However, the clinical value of cerebrospinal fluid (CSF) as liquid biopsy medium in EGFR-mutated or ALK-rearranged patients with brain metastases (BM) or leptomeningeal metastases (LM) remains unclear. Patients and Methods We retrospectively analyzed the gene map of 14/48 NSCLC-BM patients and 34/48 NSCLC-LM patients. Compare the clinical predictive value of CSF and matched plasma (PLA) for patients with single CNS progression (cohort 1) or intracranial progression simultaneously with extracranial disease progression (cohort 2). Circulating cell-free tumor DNA (ctDNA) in CSF and matched PLA underwent next-generation sequencing targeting 168 cancer-relevant genes. Results For patients with single CNS progression, the mutation rate of major driver genes is much higher than the rate in matched PLA. Besides, CSF also demonstrated higher levels of potential prognostic markers in comparison with matched PLA samples, showing EGFR-amp presented more than two times the rate compared to matched PLA, and the detection rate of TBX3, PTEN were almost double the rate in CSF than paired PLA samples. In addition, poor outcomes associated with makers including CDKN2A/B, PIK3CA/G, CDK4/6, and MET showed exclusively in CSF samples.Almost all mutations identified in the PLA could detect in matched CSF samples in NSCLC-LM patients with both intracranial and extracranial disease progression. In addition, detection rates of driver mutations, consisting of EGFR or ALK are much higher in CSF compared to matched PLA, and these potential survival marker genes like CDK4/6, CDKN2A/B, EGFR-amp, MET, and PIK3CA identified uniquely in CSF samples. Conclusion CSF is more comprehensive in genomic mutation profile than matched PLA in NSCLC -LM regardless of single intracranial progression or intracranial progression simultaneously with extracranial evolution.

Resection with intraoperative cesium-131 brachytherapy as salvage therapy for recurrent brain tumors.

The authors' objective was to examine the safety and efficacy of salvage intracranial cesium-131 brachytherapy in combination with resection of recurrent brain tumors. The authors conducted a retrospective chart review of consecutive patients treated with intraoperative intracranial cesium-131 brachytherapy at a single institution. Permanent suture-stranded cesium-131 seeds were implanted in the resection cavity after maximal safe tumor resection. The primary outcomes of interest were local, locoregional (within 1 cm), and intracranial control, as well as rates of overall survival (OS), neurological death, symptomatic adverse radiation effects (AREs), and surgical complication rate graded according to Common Terminology Criteria for Adverse Events version 5.0. Between 2016 and 2020, 36 patients received 40 consecutive cesium-131 implants for 42 recurrent brain tumors and received imaging follow-up for a median (interquartile range [IQR]) of 17.0 (12.7-25.9) months. Twenty patients (55.6%) with 22 implants were treated for recurrent brain metastasis, 12 patients (33.3%) with 16 implants were treated for recurrent atypical (n = 7) or anaplastic (n = 5) meningioma, and 4 patients (11.1%) were treated for other recurrent primary brain neoplasms. All except 1 tumor (97.6%) had received prior radiotherapy, including 20 (47.6%) that underwent 2 or more prior radiotherapy treatments and 23 (54.8%) that underwent prior resection. The median (IQR) tumor size was 3.0 (2.3-3.7) cm, and 17 lesions (40.5%) had radiographic evidence of ARE prior to salvage therapy. Actuarial 1-year local/locoregional/intracranial control rates for the whole cohort and patients with metastases and meningiomas were 91.6%/83.4%/47.9%, 88.8%/84.4%/45.4%, and 100%/83.9%/46.4%, respectively. No cases of local recurrence of any histology (0 of 27) occurred after gross-total resection (p = 0.012, log-rank test). The 1-year OS rates for the whole cohort and patients with metastases and meningiomas were 82.7%, 79.1%, and 91.7%, respectively, and the median (IQR) survival of all patients was 26.7 (15.6-36.4) months. Seven patients (19.4%) experienced neurological death from progressive intracranial disease (7 of 14 total deaths [50%]), 5 (13.9%) of whom died of leptomeningeal disease. Symptomatic AREs were observed in 9.5% of resection cavities (n = 4), of which 1 (2.4%) was grade 3 in severity. The surgical complication rate was 16.7% (n = 7); 4 (9.5%) of these patients had grade 3 or higher complications, including 1 patient (2.4%) who died perioperatively. Cesium-131 brachytherapy resulted in good local control and acceptable rates of symptomatic AREs and surgical complications in this heavily pretreated cohort, and it may be a reasonable salvage adjuvant treatment for this patient population.

Factors associated with progression and mortality among patients undergoing stereotactic radiosurgery for intracranial metastasis: results from a national real-world registry.

Stereotactic radiosurgery (SRS) has been increasingly employed in recent years to treat intracranial metastatic lesions. However, there is still a need for optimization of treatment paradigms to provide better local control and prevent progressive intracranial disease. In the current study, the authors utilized a national collaborative registry to investigate the outcomes of patients with intracranial metastatic disease who underwent SRS and to determine factors associated with lesion treatment response, overall progression, and mortality. The NeuroPoint Alliance SRS registry was queried for all patients with intracranial metastatic lesions undergoing single- or multifraction SRS at participating institutions between 2016 and 2020. The main outcomes of interest included lesion response (lesion-level analysis), progression using Response Assessment for Neuro-Oncology criteria, and mortality (patient-level analysis). Kaplan-Meier analysis was used to report time to progression and overall survival, and multivariable Cox proportional hazards analysis was used to investigate factors associated with lesion response, progression, and mortality. A total of 501 patients (1447 intracranial metastatic lesions) who underwent SRS and had available follow-up were included in the current analyses. The most common primary tumor was lung cancer (49.5%, n = 248), followed by breast (15.4%, n = 77) and melanoma (12.2%, n = 61). Most patients had a single lesion (44.9%, n = 225), 29.3% (n = 147) had 2 or 3 lesions, and 25.7% (n = 129) had > 3 lesions. The mean sum of baseline measurements of the lesions according to Response Evaluation Criteria in Solid Tumors (RECIST) was 35.54 mm (SD 25.94). At follow-up, 671 lesions (46.4%) had a complete response, 631 (43.6%) had a partial response (≥ 30% decrease in longest diameter) or were stable (< 30% decrease but < 20% increase), and 145 (10%) showed progression (> 20% increase in longest diameter). On multivariable Cox proportional hazards analysis, melanoma-associated lesions (HR 0.48, 95% CI 0.34-0.67; p < 0.001) and larger lesion size (HR 0.94, 95% CI 0.93-0.96; p < 0.001) showed lower odds of lesion regression, while a higher biologically effective dose was associated with higher odds (HR 1.001, 95% CI 1.0001-1.00023; p < 0.001). A total of 237 patients (47.3%) had overall progression (local failure or intracranial progressive disease), with a median time to progression of 10.03 months after the index SRS. Factors found to be associated with increased hazards of progression included male sex (HR 1.48, 95% CI 1.108-1.99; p = 0.008), while administration of immunotherapy (before or after SRS) was found to be associated with lower hazards of overall progression (HR 0.62, 95% CI 0.460-0.85; p = 0.003). A total of 121 patients (23.95%) died during the follow-up period, with a median survival of 19.4 months from the time of initial SRS. A higher recursive partitioning analysis score (HR 21.3485, 95% CI 1.53202-3.6285; p < 0.001) was found to be associated with higher hazards of mortality, while single-fraction treatment compared with hypofractionated treatment (HR 0.082, 95% CI 0.011-0.61; p = 0.015), administration of immunotherapy (HR 0.385, 95% CI 0.233-0.64; p < 0.001), and presence of single compared with > 3 lesions (HR 0.427, 95% CI 0.187-0.98; p = 0.044) were found to be associated with lower risk of mortality. The comparability of results between this study and those of previously published clinical trials affirms the value of multicenter databases with real-world data collected without predetermined research purpose.