Neuro-Oncology Brain Metastases Criteria Research Articles

A Phase II Study of Atezolizumab, Pertuzumab, and High-Dose Trastuzumab for Central Nervous System Metastases in Patients with HER2-Positive Breast Cancer.

Patients with HER2-positive breast cancer brain metastases have few effective systemic therapy options. In a prior study, pertuzumab with high-dose trastuzumab demonstrated a high clinical benefit rate (CBR) in the central nervous system (CNS) in patients with brain metastases. The current trial evaluated whether the addition of atezolizumab to this regimen would produce further improvements in CNS response. This was a single-arm, multicenter, phase II trial of atezolizumab, pertuzumab, and high-dose trastuzumab for patients with HER2-positive breast cancer brain metastases. Participants received atezolizumab 1,200 mg i.v. every 3 weeks, pertuzumab (loading dosage 840 mg i.v., then 420 mg i.v. every 3 weeks), and high-dose trastuzumab (6 mg/kg i.v. weekly for 24 weeks, then 6 mg/kg i.v. every 3 weeks). The primary endpoint was CNS overall response rate per Response Assessment in Neuro-Oncology Brain Metastases criteria. Key secondary endpoints included CBR, overall survival, and safety and tolerability of the combination. Among 19 enrolled participants, two had a confirmed intracranial partial response for a CNS overall response rate of 10.5% (90% confidence interval, 1.9%-29.6%). The study did not meet the prespecified efficacy threshold and was terminated early. The CBR was 42.1% at 18 weeks and 31.6% at 24 weeks. Seven patients (36.8%) required a dose delay or hold, and the most frequent any-grade adverse events were diarrhea (26.3%) and fatigue (26.3%). The addition of atezolizumab to pertuzumab plus high-dose trastuzumab does not result in improved CNS responses in patients with HER2-positive breast cancer brain metastases.

Pertuzumab plus high-dose trastuzumab for HER2-positive breast cancer with brain metastases: PATRICIA final efficacy data

The PATRICIA study (NCT02536339) examined the efficacy and safety of pertuzumab plus high-dose trastuzumab in patients with HER2-positive metastatic breast cancer (MBC) with progressive central nervous system (CNS) metastases following radiotherapy. Primary analysis confirmed CNS objective response rate (ORR) was 11% (95% confidence interval [CI]: 3–25); clinical benefit rate (CBR) was 68% (4 months) and 51% (6 months). We report final efficacy data after a further 21-months of follow-up, updated safety, survival, and patient-reported outcomes (PROs). Patients received standard-dose pertuzumab plus high-dose trastuzumab (6 mg/kg weekly) until CNS or systemic disease progression or unacceptable toxicity. Primary endpoint: confirmed ORR (CNS) per Response Assessment in Neuro-Oncology Brain Metastases criteria. Secondary endpoints were response duration, CBR, progression-free survival (PFS), overall survival (OS), safety, and PROs. By clinical cut-off, 39 patients had completed or discontinued treatment. Confirmed ORR (CNS) was 11% (95% CI: 3.0–25.4). Median CNS-PFS was 4.6 months (95% CI: 4.0–8.9), as was median CNS-PFS or systemic PFS (95% CI: 4.0–8.9); median OS was 27.2 months (95% CI: 16.1–not reached). CBR in the CNS was 51% (19 patients, 95% CI: 34.4–68.1) at 6 months. Two patients remained on treatment until study closure, achieving stable disease for 4.1 and 4.8 years. Treatment-related grade 3/4 adverse events occurred in 7.7% of patients. Patients with confirmed partial response or stable disease (≥4 months) in the CNS had stable PROs over time. Pertuzumab plus high-dose trastuzumab represents a reasonable non-chemotherapeutic treatment option for selected patients with HER2-positive MBC with CNS metastases.

Outcomes Following Early Postoperative Adjuvant Radiosurgery for Brain Metastases

Adjuvant stereotactic radiosurgery (SRS) enhances the local control of resected brain metastases (BrM). However, the risks of local failure (LF) and potential for posttreatment adverse radiation effects (PTRE) after early postoperative adjuvant SRS have not yet been established. To evaluate whether adjuvant SRS delivered within a median of 14 days after surgery is associated with improved LF without a concomitant increase in PTRE. This prospective cohort study examines a clinical workflow (RapidRT) that was implemented from 2019 to 2022 to deliver SRS to surgical patients within a median of 14 days, ensuring all patients were treated within 30 days postoperatively. This prospective cohort was compared with a historical cohort (StanRT) of patients with BrM resected between 2013 and 2019 to assess the association of the RapidRT workflow with LF and PTRE. The 2 cohorts were combined to identify optimal SRS timing, with a median follow-up of 3.3 years for survivors. Timing of adjuvant SRS (14, 21, and 30 days postoperatively). LF and PTRE, according to modified Response Assessment in Neuro-Oncology Brain Metastases criteria. There were 438 patients (265 [60.5%] female patients; 23 [5.3%] Asian, 27 [6.2%] Black, and 364 [83.1%] White patients) with a mean (SD) age of 62 (13) years; 377 were in the StanRT cohort and 61 in the RapidRT cohort. LF and PTRE rates at 1 year were not significantly different between RapidRT and StanRT cohorts. Timing of SRS was associated with radiographic PTRE. Patients receiving radiation within 14 days had the highest 1-year PTRE rate (18.08%; 95% CI, 8.31%-30.86%), and patients receiving radiation between 22 and 30 days had the lowest 1-year PTRE rate (4.10%; 95% CI, 1.52%-8.73%; P = .03). LF rates were highest for patients receiving radiation more than 30 days from surgery (10.65%; 95% CI, 6.90%-15.32%) but comparable for patients receiving radiation within 14 days, between 15 and 21 days, and between 22 and 30 days (≤14 days: 5.12%; 95% CI, 0.86%-15.60%; 15 to ≤21 days: 3.21%; 95% CI, 0.59%-9.99%; 22 to ≤30 days: 6.58%; 95% CI, 3.06%-11.94%; P = .20). In this cohort study of adjuvant SRS timing following surgical resection of BrM, the optimal timing for adjuvant SRS appears to be within 22 to 30 days following surgery. The findings of this study suggest that this timing allows for a balanced approach that minimizes the risks associated with LF and PTRE.

RADIOMICS TO PREDICT THE RESPONSE OF BRAIN METASTASES TO STEREOTACTIC RADIOTHERAPY

Abstract AIMS Radiomics converts routinely obtained medical imaging into mineable, high-dimensionality data. We assessed its utility for incorporation into a multivariate model to predict the likelihood of response of brain metastases (BMs) to stereotactic radiotherapy (SRT). METHOD Patients treated with SRT over a ten-year period for BMs at three tertiary centres were retrospectively analyzed. SRT planning MRI scans were pre-processed, and radiomic features were extracted from each BM using PyRadiomics software. Follow up scans were analyzed for response and quantified by a modification of the Response Assessment in Neuro-Oncology Brain Metastases criteria. A radiomic signature predictive of BM response was created by a stepwise process involving correlation coeffcients and a binary least absolute shrinkage and se- lection operator regression analysis. A clinical predictive multivariate model for predicting response was com- pared against a combination clinical/radiomic model by McFadden’s pseudo-R-squared test. RESULTS 520 patients were included contributing a total of 1891 BMs. 1131 radiomic features were extracted from each BM. 12 features were used to construct a radiomic signature. Mean dose and BM volume were independent predictors of response in both the clinical and radiomics models. The radiomic signature was an independent prognostic predictor for response in the radiomic model (HR=1.095-1.231). Goodness of fit for predicting response was greater in the radiomics model (McFadden’s pseudo-R-squared score 0.243 vs 0.211), and statistically significant by likelihood ratio test (p=0.021). CONCLUSIONS This multi-centre retrospective analysis created a unique radiomic signature for predicting BM response to SRT and is the first study to incorporate clinical factors. A prospective validation study is planned.

Trastuzumab deruxtecan in HER2-positive breast cancer with brain metastases: a single-arm, phase 2 trial

Trastuzumab deruxtecan is an antibody–drug conjugate with high extracranial activity in human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. We conducted the prospective, open-label, single-arm, phase 2 TUXEDO-1 trial. We enrolled patients aged ≥18 years with HER2-positive breast cancer and newly diagnosed untreated brain metastases or brain metastases progressing after previous local therapy, previous exposure to trastuzumab and pertuzumab and no indication for immediate local therapy. Patients received trastuzumab deruxtecan intravenously at the standard dose of 5.4 mg per kg bodyweight once every 3 weeks. The primary endpoint was intracranial response rate measured according to the response assessment in neuro-oncology brain metastases criteria. A Simon two-stage design was used to compare a null hypothesis of <26% response rate against an alternative of 61%. Fifteen patients were enrolled in the intention-to-treat population of patients who received at least one dose of study drug. Two patients (13.3%) had a complete intracranial response, nine (60%) had a partial intracranial response and three (20%) had stable disease as the best intracranial response, with a best overall intracranial response rate of 73.3% (95% confidential interval 48.1–89.1%), thus meeting the predefined primary outcome. No new safety signals were observed and global quality-of-life and cognitive functioning were maintained over the treatment duration. In the TUXEDO-1 trial (NCT04752059, EudraCT 2020-000981-41), trastuzumab deruxtecan showed a high intracranial response rate in patients with active brain metastases from HER2-positive breast cancer and should be considered as a treatment option in this setting.

Abstract CT558: Capmatinib vs docetaxel as second- or third-line therapy in patients with locally advanced or metastatic METex14-mutated NSCLC: The GeoMETry-III trial

Abstract Background: MET dysregulation is a poor prognostic factor in advanced non-small cell lung cancer (NSCLC). MET exon 14 skipping (METex14) mutations occur in ~3% of patients with NSCLC. There is limited evidence of the efficacy of standard therapies, such as chemotherapy or immunotherapy, in patients with METex14-mutated advanced NSCLC. Capmatinib, a MET inhibitor (METi), is approved for the treatment of adult patients with metastatic METex14-mutated NSCLC, based on the results of the phase 2 GEOMETRY mono-1 study. Results (data cutoff: September 18, 2020) of this study in patients with METex14-mutated NSCLC treated with capmatinib showed an overall response rate (ORR) of 66.7% in first line (N=60), 51.6% in second line (N=31) and 40.6% in second- or third-line (2/3L; N=69). GeoMETry-III (NCT04427072) is a multicenter, open-label, randomized, controlled, global, phase 3 trial that is further evaluating the efficacy and safety of capmatinib vs docetaxel in the 2/3L setting in patients with METex14-mutated NSCLC. Methods: This study began enrollment in September 2020 and is currently recruiting adult patients with EGFR wild-type, ALK-negative, stage IIIB/IIIC/IV METex14-mutated NSCLC, who have progressed on 1 or 2 prior lines of systemic therapy for advanced/metastatic disease and are candidates for single-agent docetaxel. Other eligibility criteria include ≥1 measurable lesion per the Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1), an Eastern Cooperative Oncology Group performance status of ≤1 and no prior treatment with any METi or hepatocyte growth factor-targeting therapies. Patients with neurologically unstable, symptomatic central nervous system (CNS) metastases or those requiring increasing doses of steroids ≤2 weeks prior to study entry to manage CNS symptoms are excluded. Around 90 patients will be randomized 2:1 to receive either oral capmatinib 400 mg twice daily or intravenous docetaxel 75 mg/m2 every 21 days. Randomization is stratified by number of prior lines (1 or 2) of systemic therapy. Patients meeting protocol-specified eligibility criteria can cross over from the docetaxel to the capmatinib arm after blinded independent review committee (BIRC)-confirmed progressive disease as per RECIST 1.1.The primary endpoint is progression-free survival (PFS) by BIRC per RECIST 1.1. The key secondary endpoint is ORR by BIRC per RECIST 1.1. Other secondary endpoints include investigator-assessed ORR and PFS; duration of response, time to response and disease control rate (DCR) by BIRC and investigator; overall survival; safety; pharmacokinetics; patient-reported outcomes; overall intracranial response rate, intracranial DCR, duration of- and time to- intracranial response by BIRC per the Response Assessment in Neuro-Oncology Brain Metastases criteria in patients with baseline CNS lesions. Citation Format: Pierre Jean Souquet, Sang-We Kim, Johan F. Vansteenkiste, Anna Robeva, Aline Jary, Sabine Glaser, Alejandro Yovine, Juergen Wolf. Capmatinib vs docetaxel as second- or third-line therapy in patients with locally advanced or metastatic METex14-mutated NSCLC: The GeoMETry-III trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT558.

Multimodality MRI-based radiomics approach to predict the posttreatment response of lung cancer brain metastases to gamma knife radiosurgery.

To develop and validate a multimodality MRI-based radiomics approach to predicting the posttreatment response of lung cancer brain metastases (LCBM) to gamma knife radiosurgery (GKRS). We retrospectively analyzed 213 lesions from 137 patients with LCBM who received GKRS between January 2017 and November 2020. The data were divided into a primary cohort (102 patients with 173 lesions) and an independent validation cohort (35 patients with 40 lesions) according to the time of treatment. Benefit result was defined using pretreatment and 3-month follow-up MRI images based on the Response Assessment in Neuro-Oncology Brain Metastases criteria. Valuable radiomics features were extracted from pretreatment multimodality MRI images using random forests. Prediction performance among the radiomics features of tumor core (RFTC) and radiomics features of peritumoral edema (RFPE) together was evaluated separately. Then, the random forest radiomics score and nomogram were developed through the primary cohort and evaluated through an independent validation cohort. Prediction performance was evaluated by ROC curve, calibration curve, and decision curve. Gender (p = 0.018), histological subtype (p = 0.009), epidermal growth factor receptor mutation (p = 0.034), and targeted drug treatment (p = 0.021) were significantly associated with posttreatment response. Adding RFPE to RFTC showed improved prediction performance than RFTC alone in primary cohort (AUC = 0.848 versus AUC = 0.750; p < 0.001). Finally, the radiomics nomogram had an AUC of 0.930, a C-index of 0.930 (specificity of 83.1%, sensitivity of 87.3%) in primary cohort, and an AUC of 0.852, a C-index of 0.848 (specificity of 84.2%, sensitivity of 76.2%) in validation cohort. Multimodality MRI-based radiomics models can predict the posttreatment response of LCBM to GKRS. • Among the selected radiomics features, texture features basically contributed the dominant force in prediction tasks (80%), especially gray-level co-occurrence matrix features (40%). • Adding RFPE to RFTC showed improved prediction performance than RFTC alone in primary cohort (AUC = 0.848 versus AUC = 0.750; p < 0.001). • The multimodality MRI-based radiomics nomogram showed high accuracy for distinguishing the posttreatment response of LCBM to GKRS (AUC = 0.930, in primary cohort; AUC = 0.852, in validation cohort).

QOLP-02. PATIENT-REPORTED OUTCOMES FOLLOWING PERTUZUMAB PLUS HIGH-DOSE TRASTUZUMAB IN PATIENTS WITH HER2-POSITIVE METASTATIC BREAST CANCER (MBC) AND CENTRAL NERVOUS SYSTEM (CNS) PROGRESSION POST-RADIOTHERAPY

Abstract Effective therapies are needed for the treatment of patients with HER2-positive MBC who develop brain metastases. In the open-label, phase II PATRICIA study (NCT02536339), 40 patients with HER2-positive MBC with CNS metastases and CNS progression post-radiotherapy (median age 48 years [range, 34–69]; prior CNS treatment [whole brain radiotherapy 71%, stereotactic radiosurgery 59%, both 31%]) were enrolled to receive pertuzumab plus high-dose trastuzumab (6-mg/kg weekly) until CNS or systemic disease progression or unacceptable toxicity. Following a median (range) treatment duration of 4.5 (0.3–37.3) months, the CNS-confirmed objective response rate per Response Assessment in Neuro-Oncology Brain Metastases criteria (primary endpoint) was 11% (95% confidence interval: 3.03, 25.42), and the clinical benefit rate at 4 months was 68%, indicating sustained clinical stability. Patient-reported outcomes (PROs) were evaluated using the MD Anderson Symptom Inventory-Brain Tumor (MDASI-BT), which includes sub-scales for symptom severity (average of 13 core symptom and 9 brain-tumor specific items) and symptom interference (average of 6 interference-with-life items representing overall symptom distress). Among 36 patients included in the PRO analyses, mean (standard deviation [SD]) symptom severity scores at baseline and weeks 12 and 28 were 1.65 (1.62), 2.24 (2.14), and 1.94 (2.55), respectively. Mean (SD) symptom interference scores at baseline and weeks 12 and 28 were 2.51 (2.63), 2.81 (3.39), and 1.76 (2.43), respectively. Mean (SD) changes in symptom severity and interferences scores from baseline to week 12 were 0.34 (1.54) and 0.33 (3.08), respectively. On average, patients who did not achieve stable disease or better in the CNS following treatment had worsened symptom severity and symptom interference scores over 12 weeks, while those with stable disease or better in the CNS exhibited stable or improving scores. Pertuzumab plus high-dose trastuzumab provided clinical benefit to the majority (68%) of patients in PATRICIA, without a decrement in quality of life.

Use of radiomics for the prediction of local control of brain metastases after stereotactic radiosurgery.

Local response prediction for brain metastases (BM) after stereotactic radiosurgery (SRS) is challenging, particularly for smaller BM, as existing criteria are based solely on unidimensional measurements. This investigation sought to determine whether radiomic features provide additional value to routinely available clinical and dosimetric variables to predict local recurrence following SRS. Analyzed were 408 BM in 87 patients treated with SRS. A total of 440 radiomic features were extracted from the tumor core and the peritumoral regions, using the baseline pretreatment volumetric post-contrast T1 (T1c) and volumetric T2 fluid-attenuated inversion recovery (FLAIR) MRI sequences. Local tumor progression was determined based on Response Assessment in Neuro-Oncology‒BM criteria, with a maximum axial diameter growth of >20% on the follow-up T1c indicating local failure. The top radiomic features were determined based on resampled random forest (RF) feature importance. An RF classifier was trained using each set of features and evaluated using the area under the receiver operating characteristic curve (AUC). The addition of any one of the top 10 radiomic features to the set of clinical features resulted in a statistically significant (P < 0.001) increase in the AUC. An optimized combination of radiomic and clinical features resulted in a 19% higher resampled AUC (mean = 0.793; 95% CI = 0.792-0.795) than clinical features alone (0.669, 0.668-0.671). The increase in AUC of the RF classifier, after incorporating radiomic features, suggests that quantitative characterization of tumor appearance on pretreatment T1c and FLAIR adds value to known clinical and dosimetric variables for predicting local failure.

1586TiP - Phase III ALTA-3 study of brigatinib (BRG) vs alectinib (ALC) in patients (pts) with advanced anaplastic lymphoma kinase (ALK)−positive non–small cell lung cancer (NSCLC) that progressed on crizotinib (CRZ)

BackgroundThe second-generation ALK tyrosine kinase inhibitor (TKI) ALC has demonstrated efficacy and acceptable safety in ALK+ NSCLC pts who have progressed on CRZ. However, resistance to ALC eventually develops, with secondary resistance mutations detected in approximately 50% of pts and a median progression-free survival (PFS) <1 year. BRG is a next-generation ALK TKI designed to have potent and broad activity against ALK mutants. Post-CRZ, BRG demonstrated high systemic and central nervous system (CNS) objective response rates (ORRs) and the longest reported median PFS of any ALK inhibitor in this setting (16.3–16.7mo) (Huber. J Clin Oncol 2018;36; Bazhenova. Ann Oncol 2017;28). The current trial was designed to compare efficacy and safety of BRG vs ALC in pts with ALK+ NSCLC that has progressed on CRZ. Trial designThe second-generation ALK tyrosine kinase inhibitor (TKI) ALC has demonstrated efficacy and acceptable safety in ALK+ NSCLC pts who have progressed on CRZ. However, resistance to ALC eventually develops, with secondary resistance mutations detected in approximately 50% of pts and a median progression-free survival (PFS) <1 year. BRG is a next-generation ALK TKI designed to have potent and broad activity against ALK mutants. Post-CRZ, BRG demonstrated high systemic and central nervous system (CNS) objective response rates (ORRs) and the longest reported median PFS of any ALK inhibitor in this setting (16.3–16.7mo) (Huber. J Clin Oncol 2018;36; Bazhenova. Ann Oncol 2017;28). The current trial was designed to compare efficacy and safety of BRG vs ALC in pts with ALK+ NSCLC that has progressed on CRZ.Table1586TiPTablePrimary EndpointBlinded independent review committee (BIRC)−assessed PFS per RECIST v1.1Secondary EndpointsBIRC-assessed intracranial PFS Overall survival Investigator- and BIRC-assessed ORR, time to response, and duration of response (DOR) BIRC-assessed intracranial ORR and DOR Safety/tolerability Health-related quality of lifeSelected Exploratory EndpointsBIRC-assessed CNS efficacy per Response Assessment in Neuro-Oncology Brain Metastases criteria (intracranial ORR, DOR, and PFS) Molecular determinants of efficacy and safety with BRG and ALC Clinical trial identificationNCT03596866. Editorial acknowledgementPeloton Advantage, LLC, an OPEN Health Company; funded by Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited. Legal entity responsible for the studyARIAD Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited. FundingARIAD Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited. DisclosureS. Popat: Research grant / Funding (institution): Boehringer Ingelheim, Epizyme, BMS, Clovis Oncology, Roche, Lilly, Takeda; Honoraria (self): Boehringer Ingelheim, AstraZeneca, Roche, Takeda, Chugai Pharma; Advisory / Consultancy: Boehringer Ingelheim, Roche, Novartis, Pfizer, AstraZeneca, BMS, MSD, Guardant Health, AbbVie; Travel / Accommodation / Expenses: Boehringer Ingelheim, BMS, Merck Sharp & Dohme. G. Liu: Research grant / Funding (institution): Takeda, AstraZeneca, Roche, Bayer, Boehringer Ingerheim; Honoraria (self): Roche, Takeda, AstraZeneca, Bristol-Myers Squibb, AbbVie, Pfizer, Merck,Novartis, EMD Serano, Bayer; Advisory / Consultancy: Roche, Novartis, Pfizer. S. Lu: Advisory / Consultancy: AstraZeneca, Boehringer Ingelheim, Hutchison MediPharma, Simcere, Roche, JS InnoPharm; Speaker Bureau / Expert testimony: AstraZeneca, Roche; Research grant / Funding (self): AstraZeneca, Hutchison MediPharma. G. Song: Full / Part-time employment: Takeda. V. Samnotra: Full / Part-time employment: Takeda. J.C. Yang: Advisory / Consultancy: Boehringer Ingelheim, Eli Lilly, Bayer, Roche/Genentech/Chugai, Astellas, MSD, Merck Serono, Pfizer, Novartis, Celgene, Merrimack, Yuhan Pharmaceuticals, BMS, Ono Pharmaceutical, Daiichi Sankyo, Takeda, AstraZeneca, Hansoh Pharmaceuticals.

Interval Change in Diffusion and Perfusion MRI Parameters for the Assessment of Pseudoprogression in Cerebral Metastases Treated With Stereotactic Radiation

Apparent increases in the size of cerebral metastases after stereotactic radiosurgery (SRS) can be caused by pseudoprogression or true disease progression, which poses a diagnostic challenge at conventional MRI. The purpose of this study was to assess whether interval change in DWI and perfusion MRI parameters can differentiate pseudoprogression from progressive disease after treatment with SRS. Patients with apparent growth of cerebral metastases after SRS treatment who underwent pre- and post-SRS DWI, dynamic susceptibility contrast (DSC)-MRI, and perfusion dynamic contrast-enhanced (DCE)-MRI were retrospectively evaluated. Final assignment of pseudoprogression or progressive disease was determined at 6-month follow-up imaging using the Response Assessment in Neuro-Oncology Brain Metastases criteria. Mean values of apparent diffusion coefficient (ADC), DCE-MRI-derived volume transfer constant (Ktrans), and DSC-MRI-derived relative cerebral blood volume (CBV) from pre- and post-SRS MRI scans were compared between groups using univariate and regression analysis. Fisher exact test was used to compare interval change of imaging biomarkers. Of 102 cerebral metastases evaluated, 32 lesions in 29 patients met our inclusion criteria. The mean duration of follow-up was 7.2 months (range, 6-14 months). Twenty-two lesions were determined as pseudoprogression, and 10 lesions were determined as progressive disease using the Response Assessment in Neuro-Oncology Brain Metastases criteria at 6-month follow-up MRI. The interval change pattern of our imaging parameters matched the expected patterns of treatment response for ADC (23/32 lesions; 72%; p = 0.055; odds ratio, 5.1), Ktrans (24/32 lesions; 75%; p = 0.006; odds ratio, 19.2), and relative CBV (27/32 lesions; 84%; p = 0.001; odds ratio, 25.3). Pseudoprogression can be distinguished from disease progression in cerebral metastases treated with SRS via an interval decrease in relative CBV and Ktrans values.