Dr Barta on Treatment-Related Rashes vs New Mycosis Fungoides Lesions in CTCL

“[T-cell receptor arrangements] are like a barcode for the cutaneous lymphoma, and if we see that the T cells that are in the rash don’t have that barcode, then we are fairly confident that this is MAR. There can be a little bit of the disease still left, which makes [diagnosing the rash] somewhat more complicated, and in general it takes a discussion with the dermatologist and a biopsy [of the rash] to be certain.”

Stefan K. Barta, MD, MS, director of the T-cell lymphoma program, Executive Officer of the Consortium for Advancing Management and Pervention of Cancer in People with HIV, and an Associate Professor of Medicine at the Hospital of the University of Pennsylvania, discussed rashes in patients with the cutaneous T-cell lymphoma (CTCL) subtype mycosis fungoides, specifically outlining his approach to distinguishing between rashes associated with treatments like mogamulizumab-kpkc (Poteligeo) and simply new mycosis fungoides lesions.

Barta began by laying out the basics of mogamulizumab-associated rash (MAR), a rash that occurs in patients with CTCL with mycosis fungoides who receive the treatment. MAR is experienced by approximately 30% to 40% of patients, a rate that can be increased by combination regimens with mogamulizumab that stimulate the immune system, he said. Barta continued by explaining that the presence of MAR is not entirely negative, since it indicates an active immune system that is helping to fight mycosis fungoides. Moreover, data have indicated that patients who experience MAR also achieve better responses to mogamulizumab, he noted.

Barta then moved into a conversation about which features of rashes indicate MAR, like rashes occurring in the head and neck, photosensitivity, granuloma-like appearance, and increased ratios of CD8-positive cells relative to CD4-positive cells. Barta compared T-cell receptor arrangements to barcodes for disease, pointing out that if certain T-cell receptor patterns are not present in the rash, then it is likely MAR. However, he noted that there can still be small amounts of disease present in MAR, and thus conducting a biopsy and consulting with a dermatologist is an important step in properly differentiating between rashes.

Barta concluded by reassuring that with the use of topical steroids, treatment interruptions, and combinations with other drugs like methotrexate, MAR is manageable for patients with mycosis fungoides.