What is the recommended radiotherapy (RT) treatment approach for an adult patient with confirmed mycosis fungoides?

Radiotherapy Treatment for Mycosis Fungoides

Radiotherapy is highly effective for mycosis fungoides and should be selected based on disease extent: use localized radiotherapy (8 Gy in 2 fractions for small lesions, 20-30 Gy in 10-15 fractions for larger areas) for limited disease, or total skin electron beam therapy (TSEB) at 30-36 Gy for widespread involvement. 1

Treatment Selection by Disease Extent

Localized Disease (Few Lesions)

For patients with one or few tumors or plaques, local radiotherapy alone is the preferred initial approach. 2

• Single lesions or small areas: Use palliative low-dose radiotherapy of 8 Gy in 2 fractions for excellent local control 1
• Larger tumors or extensive areas: Employ 20-30 Gy in 10-15 fractions to minimize acute toxicity while maintaining efficacy 1
• Solitary patch/plaque (rare presentation): Consider curative-intent radiotherapy at 20-30 Gy in 2-Gy fractions 1
• Single fractions of 7-8 Gy are effective and convenient but allow less opportunity for re-treatment 1

Site-Specific Dosing Considerations

Critical anatomic sites require modified fractionation to limit toxicity:

• Lower legs: Use smaller doses per fraction due to poor skin tolerance 1
• Eyelids: Consider 4 Gy in 2 fractions to minimize acute and long-term toxicity 1
• Hands and feet (erythrodermic background): Local radiotherapy is effective for symptomatic fissured lesions 1

Widespread Cutaneous Disease (TSEB)

Total skin electron beam therapy achieves excellent complete response rates across all stages, with outcomes dependent on dose and energy delivered. 1

Standard High-Dose Protocol

• Conventional Stanford regimen: 36 Gy delivered via six dual-field technique, 2-Gy fractions per 2-day cycle over 9 weeks 1
• Higher doses (32-36 Gy) with higher energy (4-6 MeV electrons) produce superior complete response rates and 5-year relapse-free survival 1

Stage-Specific TSEB Outcomes

• Stage IA: 97% complete response rate, 50-month median relapse-free survival 1
• Stage IB: 59-75% complete response rate, 18-29 months median relapse-free survival 1
• Stage IIB: 47% complete response rate, 9 months median relapse-free survival 1
• Stage III: 33-60% complete response rate, 6-9 months median relapse-free survival 1

Low-Dose TSEB Alternative

• 12 Gy regimen: Achieves 87% overall response rate with 18% complete response, median duration of clinical benefit 132 months 1
• Low-dose protocols produce fewer side effects and allow opportunity for re-treatment 2

Stage-Specific Treatment Algorithms

Stage IA-IIA (Early Disease)

• Local radiotherapy is highly effective as monotherapy or combined with other skin-directed therapies 1
• Minimum effective dose approach is appropriate given MF's multifocal nature and need for potential re-treatment 1
• TSEB can be used but is not always necessary for limited disease 1

Stage IIB (Tumor Stage)

• For one or few tumors: Local radiotherapy at 20-24 Gy suffices as initial treatment 2
• For extensive tumors: Low-dose palliative radiotherapy (12 Gy in 3 fractions) is very effective 1
• Combined modality preferred: TSEB or local RT plus systemic therapy (PUVA with interferon-alpha or retinoids) for extensive disease 2

Stage III-IVA (Erythrodermic/Advanced Disease)

• Local radiotherapy for isolated symptomatic lesions or tumors on erythrodermic background 1
• Localized nodal disease: Treat with external beam radiotherapy per standard non-Hodgkin lymphoma protocols 1
• Visceral metastases: External beam radiotherapy using same dosing schedules; low doses or single fractions provide effective palliation 1

Stage IVB (CNS/Widespread Visceral)

• Central nervous system involvement: Palliative low-dose whole-brain radiotherapy for patients with good performance status 1
• Prognosis is very poor (0-15% 5-year survival) 1

Critical Treatment Principles

Avoid aggressive approaches that compromise quality of life:

• MF is highly radiosensitive; minimum effective doses achieve local control while preserving re-treatment options 1
• Do not use TSEB with adjuvant topical mechlorethamine—recent evidence shows no clinical advantage 1
• Radiotherapy can be administered concurrently with phototherapy and other skin-directed therapies 1

Important caveats for radiotherapy planning:

• Treatment depth must be determined by tumor thickness and invasion depth (assessed via ultrasound, CT, or MRI) 1
• Field margins should account for multifocal disease nature 1
• Consider overlapping field risks when planning repeat treatments, especially in areas with poor tolerance 1

Maintenance and Long-Term Considerations

Maintenance therapy after TSEB is a critical unresolved issue requiring individualized approaches 1

• Most patients will relapse after TSEB, but timing varies by stage 1
• Earlier therapeutic interventions may contribute to mutations increasing tumor proliferative capacity 2
• Quality of life should be prioritized over aggressive re-treatment in elderly patients with comorbidities 2