Pediatric Hypopigmented Mycosis Fungoides: A Narrative Literature Review of Phototherapy Dosing Regimens

Background: Mycosis fungoides is the most common type of childhood-onset primary cutaneous T-cell lymphoma, and hypopigmented mycosis fungoides (hMF) is a rare, diversely presenting form of mycosis fungoides that is more common in young populations. Although phototherapy is the most used treatment for pediatric patients with hMF, there are currently no existing guidelines for dosing or duration of treatment. Methods: We performed a comprehensive narrative literature review on June 11th, 2024, utilizing the PubMed database of the current literature on the treatment of pediatric hMF with phototherapy. The search yielded 87 unique studies which were subsequently reviewed for relevancy. Twelve studies describing the results of phototherapy treatment for 285 pediatric patients were ultimately analyzed. Results: The median age range of patients was 5–18 years. Most patients presented with early-stage disease (Stage IA or IB) characterized by hypopigmented patches and plaques, often located on the trunk and extremities. Narrowband ultraviolet B (NB-UVB) therapy was the most common treatment modality. The majority of patients experienced complete or partial remission with phototherapy, with 61% of patients achieving complete remission and 31% of patients achieving partial remission with NB-UVB, while 61% of patients achieved complete remission and 29% of patients achieved partial remission for PUVA. Relapse was common, with many patients requiring multiple treatment cycles. PUVA phototherapy had a higher relapse rate of 63%, compared to a 44% relapse rate for NB-UVB phototherapy. The average cumulative dose was 60.31 J/cm² (53 cases) for NB-UVB and 62.3 J/cm² (11 cases) for PUVA. The number of treatment sessions ranged from 17 to 146 sessions for NB-UVB and from 21 to 258 sessions for PUVA. Adverse effects were reported in only one case, with most patients tolerating NB-UVB well. Conclusion: This narrative review identified limitations with current reporting of phototherapy modalities, number and frequency of phototherapy dosing sessions, number of cycles of treatment, and cumulative dosages administered of phototherapy dosing in pediatric patients with hMF. Further research is warranted to better characterize phototherapy dosing for pediatric patients and improve the standardization of phototherapy treatment protocols.