To evaluate the characteristics, diagnosis, and prognosis lung cancer leptomeningeal metastasis (LM).

LM is an uncommon but grim complication of lung cancer. CSF positivity has been proposed as a poor prognostic factor.

In this single-center retrospective cohort study, we reviewed patients with LM secondary to lung cancer diagnosed 1/1/2010-2/27/2024. We included patients that had an LM diagnosis based on imaging findings, positive CSF cytology for malignant cells, or both. Kaplan-Meier log-rank test was used to assess prognostic factors.

For 106 patients with lung cancer LM, median survival was 3.2 months from LM diagnosis. Most (n=91) had non-small cell lung cancer (NSCLC). Median survival for patients with NSCLC was slightly longer (3.7 months) compared to patients with SCLC (2.1 months, p-value=0.02). Most (93%) NSCLCs were adenocarcinoma. LM was detected at initial cancer diagnosis in 13 patients (12%). Intraparenchymal metastases were present in most (n=84/106, 79%) patients at LM diagnosis but were not associated with worse prognosis (3.1 months with concurrent metastases compared to 4.2 months without, p-value=0.87). Of the 65 patients with CSF cytology completed, 48 patients had at least one positive cytology, and 17 had no positive cytology. Sensitivity increased slightly with repeat cytology (1 sample=62%, 2 samples= 68%, 3 samples= 72%, and 4 samples= 74%). Survival was marginally longer in patients with negative cytology (5.7 months) compared to patients with positive cytology (2.6 months), but this was not statistically significant (p-value= 0.18). Patients with an Eastern Cooperative Oncology Group performance status of 0-2 (n=68) had a longer median survival (5.0 months) compared to patients with a performance score of 3-4 (n=38, median survival=2.0 months, p-value<0.001).

Lung cancer LMD has a poor overall prognosis of 3.2 months, worse for patients with SCLC and poor performance status. More data is needed to assess if CSF positivity is a poor prognostic factor.