The researchers are doing this study to test the safety of combining bexarotene with TSEB radiotherapy in people who have a common form of CTCL called mycosis fungoides (MF).

Bexarotene is a form of vitamin A that activates proteins called retinoid X receptors, which may stop the growth of cancer cells and kill them. TSEB radiotherapy is a type of radiation therapy that treats the entire surface of the skin with very low doses of radiation to kill cancer cells and shrink tumors. This type of radiation does not pass through the outer layers of the skin into the tissues and organs below the skin.

The study researchers think that giving bexarotene treatment at the same time as treatment with TSEB radiotherapy may be more effective against MF than either treatment given alone or in sequence (one after the other).

Inclusion Criteria:

• Age ≥18 years
• Pathologically confirmed cutaneous T-cell lymphoma consistent with mycosis fungoides (MF) based on biopsy done or reviewed at MSKCC
• Stage IB or higher MF per ISCL/EORTC criteria; concurrent diagnosis of Sézary syndrome permissible. Patients who have not had prior systemic therapies and refractory/relapsed patients are eligible.
• Baseline mSWAT score of at least 10
• Stable topical steroids or systemic antipruritic agent (e.g. antihistamines, doxepin, GABA analogs) preceding study entry is permissible, but no new prescribed or over the counter topical or systemic anti-pruritics started post-enrollment
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
• Ability to provide informed consent

Exclusion Criteria:

• Any oral retinoid therapy for any indication within 3 weeks of the first dose of study drug
• Prior TSEB (prior focal skin-directed RT acceptable)
• Concurrent diagnosis of systemic anaplastic large cell lymphoma (ALCL) or another non-Hodgkin lymphoma
• Concurrent diagnosis of additional non-skin malignancy
• Pregnancy
• Patients unwilling to use two forms of barrier contraception while taking study medication
• Receipt of treatment with another investigational device or drug (at present or within 2 weeks of enrollment)
• Familial hypertriglyceridemia or other medical conditions in which use of bexarotene would be contraindicated
• High likelihood of protocol non-compliance (in opinion of investigator)
• Systemic steroids within two weeks of first dose of study drug (patients on systemic steroids for non-disease related conditions will be permitted per investigator discretion)

Prohibited concurrent medications

• Gemfibrozil is contraindicated as may increase bexarotene concentrations
• Bexarotene is a minor CYP3A4 substrate: avoid strong/moderate CYP3A4 inducers and inhibitors, if possible, but concomitant use is not a contraindication Bexarotene is a moderate CYP3A4 inducer: avoid concurrent administration with CYP3A4 sensitive substrates, for which minimal concentration changes may lead to therapeutic failures of the substrate (e.g. cyclosporine, tacrolimus, sirolimus, quinidine, fentanyl), if possible

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.