Stanislav Lazarev Highlights Key Insights from Proton vs Photon CSI for Leptomeningeal Disease
Stanislav Lazarev, Radiation Oncologist, Associate Professor at Mount Sinai Health System, shared a post on X about a paper by Kelsey M. Frechette et al. published in Practical Radiation Oncology:
“New study: Proton vs Photon CSI for leptomeningeal disease (Mayo Clinic, n=36)
- No difference in serious CSI-related cytopenias
- OS ~3.0 mo (proton) vs 1.7 mo (photon), NS
- Photon VMAT-based CSI – a viable alternative when protons aren’t available or can’t be started quickly
Important real-world data
OS here was very poor compared with MSKCC (Yang et al, JCO 2022) Phase II trial, where proton CSI yielded ~10 months OS in breast and NSCLC LMD.
So here’s the key question: why is that, and what’s missing from the paper?
I searched the main text and appendix and couldn’t find it – the extent of extra-CNS disease and available systemic options for extra-CNS disease at the time of diagnosis with LMD. It is probably THE most important factor when deciding on CSI for LMD.
CSI only makes sense if:
- Extra-CNS disease is controlled or has adequate systemic options
- You’re treating both compartments (craniospinal + systemic)
If systemic disease is uncontrolled, CSI’s benefit is minimal. It doesn’t help to put out 50% of the fire. Any potential gain of CSI is quickly negated by extra-CNS progression.
Patient selection is key.
In contrast to this Mayo study, recently published real-world data from Baptist Health South Florida and MDACC show very encouraging survival outcomes after proton CSI for LMD when patients are well-selected:
- Baptist Health South Florida (PMID: 40149379) – OS 10.1 mo
- MDACC (PMID: 39866593) – OS 13.7 mo
- Parallels MSKCC Ph II RCT (PMID: 35802849) – OS 9.9 mo
With the right patient selection, proton CSI can offer meaningful survival benefit.”
Title: Real-World Experience Using Proton Versus Photon Craniospinal Irradiation for Leptomeningeal Disease
Authors: Kelsey M. Frechette, Amanda F. Meyer, Sara B. Leier, William S. Harmsen, Sydney D. Pulsipher, Witold Matysiak, Thomas B. Bradley, Ugur T. Sener, Lauren M. Webb, David M. Routman, Elizabeth Yan, Nadia N. Laack, Paul D. Brown, Eric J. Lehrer, William G. Breen, Roman O. Kowalchuk, and Anita Mahajan
You can read the Full Article on Practical Radiation Oncology.
You can find more posts on Leptomeningeal Disease on OncoDaily.
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