The purpose of this study is to confirm the safety and efficacy of linac based Volumetric Modulated Arc Therapy (VMAT) for craniospinal irradiation (CSI) in solid tumor cancer patients with leptomeningeal metastasis. The primary aim is to determine if linac based VMAT CSI for leptomeningeal metastasis improves central nervous system (CNS) progression free survival (PFS) compared to the historical standard control CNS PFS in patients treated with Involved Field Radiation Therapy (IFRT).

Inclusion Criteria:

1. Solid tumor cancer primary with leptomeningeal metastases established radiographically and/or by CSF cytology

2. Candidate for radiation therapy for the treatment of leptomeningeal metastases

3. If patient had prior radiation, a treatment plan can be generated that will not exceed normal tissue tolerances

4. Patient must have reasonable systemic treatment options, as confirmed by their medical oncologist

5. Age ≥ 18 years old

6. Able to provide informed consent

7. Karnofsky Performance Scale (KPS) ≥ 60

8. Adequate hematologic baseline

   1. Hemoglobin > 8g/dL
   2. Absolute neutrophil count >1,000/mm3
   3. Platelet count > 100,000/mm3

9. Female subjects must either be of

   1. Non-reproductive potential (over 60 years old, or without menses for at least 1 year without an alternative medical cause)
   2. Have history of hysterectomy, bilateral tubal ligation, or bilateral oophorectomy
   3. Must have negative serum/urine pregnancy test
   4. If of reproductive age, must practice effective contraceptive method

Exclusion Criteria:

1. Patient has multiple severe neurologic deficits per physician assessment
2. Patient has diffuse systemic disease without reasonable systemic therapy options
3. Patient is unable to undergo MRI brain and spine with gadolinium contrast
4. Prior radiation that would preclude development of a treatment plan that respects normal tissue constraints
5. Pregnant or lactating women
6. Prisoners

The de-identified participant data from the final research dataset will be shared upon reasonable request beginning 9 to 36 months after publication or as required by a condition of awards or supporting agreements, provided the requesting investigator executes a data use agreement with NYU Langone Health. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's Data Sharing Strategy Board (DSSB). Requests should be directed to: Benjamin.cooper@nyulangone.org. The protocol and statistical analysis plan will be posted on Clinicaltrials.gov only as required by federal regulation or supporting awards and agreements.

Beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research.

The investigator who proposed to use the data will be granted access upon reasonable request. Requests should be directed to Benjamin.cooper@nyulangone.org. To gain access, data requestors will need to sign a data access agreement. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's DSSB.