OS03.5.A Characterization of the inflammatory tumor microenvironment composition in solid cancer patients with brain metastases after progression to immune checkpoint inhibitor therapy

Background

Immunotherapy (IO) has changed the treatment landscape of metastatic cancer patients, however, treatment resistance is frequent. We aimed to characterize the inflammatory tumor microenvironment in brain metastases (BM) after IO to gain a deeper understanding of immunologic escape mechanisms.

Material and Methods

Solid cancer patients who had BM resection after IO progression (IO cohort) were retrospectively identified. We analyzed tumor-infiltrating immune cell subsets (CD3, CD8, CD45RO, FOXP3) and expression of immune checkpoint molecules (PD-L1, PD-1, LAG-3) by immunohistochemistry. A control cohort of BM tissue samples without prior IO served for comparison (no immunotherapy cohort, NIO).

Results

Twenty-eight IO patients (12/28, 42.9% females; 16/28, 57.1% males; median 61 years; 14/28, 50% lung cancer; 5/28, 17.9% melanoma; 4/28, 14.3% renal cell carcinoma; 1/28, 3.6% breast cancer; 4/28, 14.3% other cancer entities) and 57 NIO patients (28/57, 49.1% females; 29/57, 50.9% males; median 58 years; 35/57, 61.4% lung cancer; 9/57, 15.8% breast cancer; 4/57, 7.0% melanoma; 3/57, 5.3% renal cell carcinoma; 6/57, 10.5% other cancer entities) were included. IO patients had a median of one (range 0-4) systemic therapy line prior to IO. Median time from last IO application until BM resection was 5.6 months (range 0.2-49.8 months). Patients received a median number of 7 (range 1-56) IO applications (14/28, 50% PD-1-targeting IO; 8/28, 28.6% PD-L1; 2/28, 7.1% CTLA4; 4/28, 14.3% CTLA4+PD-1; 3/28, 10.7% IO+chemotherapy). No statistically significant differences in the densities of investigated TILs or PD-L1 expression between the IO and the NIO cohort were observed. Patients of the IO cohort showed higher PD-L1 expression compared to the NIO cohort (57.1 vs. 42.1%, Chi-square, p>0.05). Overall survival (OS) was similar in both cohorts, with a median OS of 11.0 months (range 5.0-17.0) in the IO cohort and 11.0 months (range 5.5-16.5) in the NIO cohort.

Conclusion

Our findings show an upregulation of PD-L1 in BM occurring after prior IO therapy in the absence of other overt changes in the inflammatory microenvironment. Ongoing analyses in this cohort are investigating possible molecular driver of resistance by analyzing DNA methylation profiles of pre-and post-IO tissue samples of the IO cohort to potentially gain insights on inflammatory IO resistance mechanisms in BM patients.

P14.03 Shifting trends and entity-specific aspects in patients with brain metastasis: real-life analysis from 6031 individuals over an observation period of 30 years

BACKGROUND

We aimed to investigate the changing clinical characteristics of patients with brain metastases (BM) over the last three decades as the foundation for modern BM specific clinical trial planning.

MATERIAL AND METHODS

6031 patients with newly diagnosed BM from different solid tumors treated between 1986–2020 were identified from the Vienna Brain Metastasis Registry.

RESULTS

The fraction of BM originating from the most common BM causing primary tumors (lung cancer, breast cancer and melanoma) was stable over the observation period from 1986–2020. BM from renal cell carcinoma, colorectal cancer and cancer of unknown primary (CUP) decreased over time (p<0.001). Synchronous diagnosis of BM and primary tumor was more frequently observed in lung cancer and CUP patients compared to breast cancer patients (p<0.001). An increasing fraction of patients presented with asymptomatic BM (1986–1999: 20.2% vs. 2010–2020: 30.4%; p<0.001), specifically in lung cancer (p<0.001), melanoma (p<0.001) and renal cell cancer (p=0.004). A decrease of neurosurgical procedures (1986–1999: 39.3% vs. 2010–2020: 20.4%) and an increase of radiation treatments (1986–1999: 56.5% vs. 2010–2020: 73.0%) and systemic therapies (1986–1999: 0.6% vs. 2010–2020: 2.4%; p<0.001) was observed. Furthermore, median overall survival significantly increased across entities (1986–1999: 5 months vs. 2010–2020: 7 months; p=0.001). Intracranial progression as the cause of death increased across entities (p< 0.001). The prognostic DS-GPA (Hazard ratio [HR] 1.42; p< 0.001) and the Lung-molGPA (HR 1.67; p<0.001) could be validated.

CONCLUSION

We observed changes of BM presentation and clinical parameters during the observation period depending on primary tumor origins. Future BM studies should follow an entity-specific approach and address the characteristics of modern BM cohorts.