Targeted Radiotherapy in Primary Cutaneous Lymphomas: Precision, Efficacy, and Evolving Strategies.

Primary cutaneous lymphomas (PCLs), including cutaneous T-cell lymphomas (CTCL) and primary cutaneous B-cell lymphomas (PCBCL), are a diverse group of non-Hodgkin lymphomas that primarily affect the skin. Radiotherapy (RT) plays a pivotal role in the treatment of these lymphomas, particularly for localized disease, due to its ability to deliver precise, skin-directed treatment. Mycosis fungoides (MF) and Sézary syndrome (SS), the most common subtypes of CTCL, often require skin-directed therapies such as electron beam therapy and superficial brachytherapy to manage localized lesions. Electron beam therapy, including total skin electron beam therapy (TSEBT), has been utilized for decades, offering high response rates but with the risk of cumulative skin toxicity. Recently, low-dose radiotherapy (LDRT) has gained attention as an effective alternative that reduces toxicity while maintaining durable responses. Superficial brachytherapy is another modality that delivers radiation through custom molds, allowing for homogeneous dosing over complex anatomical areas like the face. Both teleradiotherapy and brachytherapy have demonstrated high complete response rates, with low recurrence rates observed when higher doses are used. In the context of primary cutaneous B-cell lymphomas, such as primary cutaneous marginal zone lymphoma (PCMZL) and primary cutaneous follicle center lymphoma (PCFCL), radiotherapy also offers excellent local control, particularly for indolent subtypes. However, more aggressive subtypes, such as diffuse large B-cell lymphoma, leg type (PCDLBCL-LT), may require systemic therapies in addition to radiation. Overall, teleradiotherapy and brachytherapy are essential components of the therapeutic arsenal for primary cutaneous lymphomas, offering effective disease control with manageable toxicity, while ongoing research focuses on optimizing treatment strategies and exploring novel combinations with systemic therapies.