What is the recommended radiation therapy (RT) dosing for nodular lymphocyte-predominant Hodgkin's lymphoma (NLPHL)?

Radiation Therapy Dosing for Nodular Lymphocyte-Predominant Hodgkin Lymphoma (NLPHL)

For nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL), the recommended radiation therapy dose is 30 to 36 Gy for involved regions when used as a single modality treatment, and 25 to 30 Gy for uninvolved regions. 1

Treatment Approach Based on Disease Stage

Stage IA NLPHL

• Primary treatment: Involved-site radiation therapy (ISRT) alone
  • Dose: 30-36 Gy 1
  • In emergency situations (e.g., COVID-19 pandemic), hypofractionation to 27 Gy in 9 fractions may be considered 1

Early-Stage NLPHL (other than Stage IA)

• Primary treatment: Combined-modality therapy
  • Chemotherapy (typically ABVD) followed by ISRT
  • Dose: 20-30 Gy following ABVD 1

Advanced-Stage NLPHL

• Primary treatment: Chemotherapy alone (typically ABVD)
  • Radiation may be added for residual or bulky disease
  • Dose: 30-36 Gy for residual disease 1

Modern Radiation Field Concepts

The radiation field approach has evolved significantly over time:

• Extended Field (EF) and Involved Field (IF): Older approaches treating larger volumes based on nodal stations
• Involved Node RT (INRT): Targets only originally involved lymph nodes; requires optimal pre-chemotherapy imaging
• Involved Site RT (ISRT): Current standard approach; targets initially involved nodal and extranodal sites while sparing adjacent uninvolved organs 1, 2

ISRT requires:

• CT-based simulation
• Integration of PET/CT and MRI when available
• Proper definition of:
  • Gross tumor volume (pre-treatment disease)
  • Clinical target volume (accounting for subclinical disease)
  • Planning target volume (accounting for setup variations)

Treatment Planning Considerations

• Technique: 3D conformal RT, intensity-modulated RT, or proton therapy based on clinical circumstances 1
• Field design: Target the initially involved nodal sites and possible extranodal extensions 1
• Dose fractionation: Typically 1.8-2.0 Gy per fraction
• Areas to avoid: High cervical regions in all patients and axillae in women should be excluded if uninvolved 1

Special Considerations

1. Completely excised NLPHL: Radiation therapy may be omitted in cases of completely excised localized NLPHL, especially during resource-constrained situations 1

2. Relapsed disease: Treatment options include:

   • Conventional chemotherapy
   • Anti-CD20 antibodies (rituximab)
   • Radiation therapy
   • High-dose chemotherapy with autologous stem cell transplantation for early relapses 3

3. Treatment toxicity: Modern smaller radiation fields (ISRT/INRT) aim to reduce treatment volume and dose while maintaining efficacy and minimizing both acute and late sequelae 2

Monitoring and Follow-up

• Regular follow-up visits for at least 5 years after therapy
• Monitor for potential late effects, including secondary malignancies and cardiac toxicity
• Annual thyroid function tests if neck was irradiated
• Surveillance imaging as clinically indicated

Pitfalls to Avoid

1. Using outdated extended fields: Modern ISRT targets only involved nodes and possible extensions, significantly reducing normal tissue exposure

2. Inadequate imaging for planning: Proper pre-treatment imaging with CT, PET/CT, and/or MRI is essential for accurate target delineation

3. Overlooking the distinct nature of NLPHL: NLPHL has a different natural history and treatment approach compared to classical Hodgkin lymphoma

4. Excessive dose: In the era of combined modality therapy, historical higher doses may not be necessary for disease control

By following these guidelines for radiation therapy dosing in NLPHL, clinicians can optimize treatment outcomes while minimizing treatment-related morbidity and preserving quality of life.