A Prescriber-Concentration Study Reads Different Once You Trace It to Medicare's Reporting Floor

A paper posted online September 2 by the Journal of the American Academy of Dermatology reports that prescriptions for mechlorethamine gel, the topical chemotherapy sold as Valchlor for early-stage cutaneous T-cell lymphoma, cluster among a small number of specialists. The full text sits behind Elsevier's paywall, but the shape of the finding can be traced through a companion data set the same research group presented months earlier, and that earlier document shows where the headline number comes from and why it should be read as a lower bound rather than a count.

The lead author on the JAAD article, Joshua A. Kent, working with Larisa J. Geskin and colleagues at Columbia University's Cutaneous Lymphoma Center, also co-authored an abstract presented at the American Society of Hematology's 2025 annual meeting, titled "Utilization and cost trends of topical mechlorethamine for cutaneous T-cell lymphoma in the United States: A Medicare Part D analysis." Drawing on 2018-2023 Medicare Part D claims, that abstract counted 3,945 total claims for the drug, with dermatologists filing 79% of them at an average cost of about $7,220 per claim and hematology-oncologists filing a smaller share at the highest average cost, $9,346. In 2023, the abstract states, only 44 individual prescribers nationwide met the volume threshold Medicare requires before a provider's claims become publicly reportable.

That threshold is worth sitting with before treating 44 as a census. Medicare's public prescriber files only name physicians who filed more than 10 claims for a given drug in a given year; anyone below that line disappears into an unnamed aggregate. Cutaneous T-cell lymphoma is diagnosed in roughly 3,000 Americans annually, an incidence of 0.3 to 0.5 per 100,000, which guarantees a long tail of dermatologists writing a handful of Valchlor prescriptions a year for their own patients. Those prescribers never surface in the CMS data the Columbia group analyzed. The 44-prescriber figure describes who was visible to the reporting rule in 2023, not how many physicians actually prescribed the drug.

The Medicare data also can't distinguish between two different bottlenecks that produce the same concentration pattern. One is that few dermatologists know to reach for the drug or have built the workflow to do so. The other is structural: Valchlor has been distributed exclusively through specialty pharmacy networks rather than retail pharmacies since its 2013 FDA approval, a channel that only certain practices have set up to use regardless of how many physicians are otherwise qualified to prescribe it. A Medicare claims count, whatever else it establishes, cannot separate a knowledge gap from a distribution chokepoint, and the JAAD paper's abstract-stage precursor does not appear to try.

What the underlying data can support is a cost trend: per-claim spending climbing toward $9,300 among the specialists who prescribe it most, for a drug whose 2013 approval trial used a decades-old compounded 0.02% ointment as its non-inferiority comparator. That older, non-branded version of the same nitrogen-mustard compound has never gone away and remains a legal, cheaper option that these Medicare figures don't track at all, since compounded prescriptions don't generate the same claims data. Whatever conclusions the new JAAD paper draws about access to cutaneous T-cell lymphoma care, they rest on a data set that only sees the branded drug, and only sees the prescribers writing enough of it to clear a reporting bar built for an entirely different purpose.