Low Dose Radiotherapy in Primary Indolent Cutaneous B-cell Lymphoma

Primary cutaneous B-cell lymphomas (PCBCL) represent approximately 20% of all primary cutaneous lymphoma and are defined by a restricted disease spread to the skin without evidence of extracutaneous involvement at diagnosis. They encompass three main types: primary cutaneous marginal zone lymphoma (PCMZL), primary cutaneous follicle center lymphoma (PCFCL) and primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL, LT), of which the first two entities are indolent. Radiotherapy (RT) is part of the therapeutic mosaic for PCBCL and recommended by both national and international guidelines for a localized disease pattern, conferring high local control rates with a conservative approach . Curative doses cover a range of 18-54 Gy and complete remission is common regardless of which treatment is used. There is accumulating evidence for a possible de-escalation of RT dose while maintaining high response rates and thereby opening a role for low-dose RT (LDRT), which has been successfully shown for other indolent non-Hodgkin lymphoma. However, the rarity of indolent PCBCL and retrospective nature of studies make a definitive dose recommendation troublesome.

Inclusion criteria

• Age greater than or equal to 18 years
• Histological diagnosis of indolent B-cell lymphoma (follicular, marginal, NOS)
• Primary cutaneous location
• Early stage (I-II)
• First diagnosis or recurrence
• Low-dose radiotherapy treatment (4 Gy/2 sessions)

Exclusion criteria

• Aggressive histology lymphomas
• Advanced stages
• Extracutaneous localisation
• Radiotherapy dose administered > 4 Gy
• Patients without histological typing
• Patients without follow-up