RDTA-04 STEREOTACTIC RADIOSURGERY FOR FOCAL LEPTOMENINGEAL DISEASE: A SINGLE-INSTITUTION STUDY

Abstract Leptomeningeal disease (LMD) refers to the dissemination of cancer within the leptomeninges, specifically involving the subarachnoid space, pia mater, and CSF, and represents an aggressive and advanced stage of malignancy. Despite advances in diagnostic and therapeutic approaches, the prognosis for LMD remains poor. Chemotherapy and whole-brain radiation have remained the traditional mainstays of treatment for LMD, although recent studies have suggested that stereotactic radiosurgery (SRS) may also play a role in management. We present 7 cases of adult patients with focal LMD who underwent SRS as a primary treatment. Focal LMD was defined as a disease that was either confined to a single sulcus or a single region within the CSF. All patients in this cohort were female, with a median age of 58 years at the time of treatment (range: 40–68 years). Non-small cell lung cancer (NSCLC) was the most common primary tumor, accounting for 71.4% of cases, while the remaining patients had breast cancer. The time from primary tumor diagnosis to the detection of LMD had a median of 15.2 months (range: 0.77–54.67 months). The median tumor diameter was 17 mm (range: 3–46 mm). The median lesion volume was 0.79 cm3 (range: 0.02–15.70 cm3). The median prescribed radiation dose was 22 Gy (range: 16–27 Gy) with a maximum dose of 30.56 Gy (range: 19.34–36.44 Gy). The median isodose line was 74% (range: 70–98%). The median MRI-based radiological follow-up was 8.07 months (range: 1.73–90.13 months). Four out of 7 lesions (57.1%) demonstrated recurrence. The 3-month and 6-month LTC rates are 85.71% and 68.57%, respectively. One patient underwent surgical resection for radiation necrosis. SRS may be beneficial for a subset of LMD patients with focal disease, helping to delay the need for WBRT and avoid its potential side effects.