What are the current guidelines for radiation therapy contouring in post-operative head and neck cancer patients?

Current Guidelines for Post-Operative Head and Neck Cancer Radiation Therapy Contouring

For post-operative head and neck cancer patients, radiation therapy should target the primary tumor bed and involved lymph node regions with a dose of 60-66 Gy (2.0 Gy/fraction) for high-risk features, with concurrent cisplatin recommended for patients with extracapsular nodal extension and/or positive surgical margins. 1

Dose and Fractionation Guidelines

High-Risk Features (Extracapsular Extension and/or Positive Margins)

• Postoperative radiotherapy should deliver 60-66 Gy (2.0 Gy/fraction) to regions with microscopically positive surgical margins and extracapsular nodal extension 1
• Concurrent chemotherapy (typically cisplatin 100 mg/m² every 3 weeks for 3 doses) should be added for patients with these high-risk features 1, 2
• The time from surgery to completion of radiotherapy should be kept as short as possible, ideally less than 6 weeks 1

Intermediate-Risk Features

• For tumor bed and involved lymph node regions without extracapsular extension or positive margins, a total dose of 60 Gy (2.0 Gy/fraction) is recommended 1
• Risk factors warranting postoperative radiotherapy include: advanced T stage, depth of invasion, multiple positive nodes, or perineural/lymphatic/vascular invasion 1
• Consider chemoradiation for patients with multiple positive nodes (without extracapsular spread), vascular/perineural invasion, or pT4 primary tumors 1

Low-Risk Nodal Regions

• Elective irradiation to low- and intermediate-risk nodal stations requires 44-64 Gy, depending on estimated tumor burden and fraction size 1
• For suspected subclinical spread areas (low to intermediate risk of recurrence), IMRT or 3D conformal RT is recommended 1

Target Volume Delineation

Primary Site Considerations

• Contouring should encompass the entire surgical bed of the primary tumor with appropriate margins 1
• Technical precision of IMRT has increased, requiring thorough understanding of natural history, anatomy, clinical circumstances, and imaging to guide target delineation 1
• For oral cavity tumors, a new classification of lateralized and non-lateralized OCSCC has been proposed to guide postoperative nodal CTV delineation 3

Nodal Considerations

• For well-lateralized (no soft palate extension or base of tongue involvement) T1-T2 tonsillar cancer with N0-N1 nodal category, unilateral radiotherapy is recommended 1
• For lateralized (<1 cm soft palate extension without base of tongue involvement) T1-T2 N0-N2a tonsillar cancer without extracapsular extension, unilateral radiotherapy may be delivered after careful discussion of risks and benefits 1

Radiation Techniques

IMRT Recommendations

• IMRT is now widely used in head and neck cancer and is the predominant technique at NCCN Member Institutions 1
• IMRT is useful in reducing long-term toxicity by reducing dose to major salivary glands, temporal lobes, mandible, auditory structures, and optic structures 1
• Dose painting techniques with IMRT allow for 54-63 Gy depending on dose per fraction 1
• Despite technical advantages, overall survival is similar between IMRT and conventional RT 1

Altered Fractionation

• Altered fractionation should be used in patients with T3 N0-1 oropharyngeal squamous cell carcinoma (OPSCC) treated with definitive radiotherapy who do not receive concurrent systemic therapy 1
• For radiotherapy-alone settings, schedules delivering at least 1000 cGy/week are recommended 1
• Hyperfractionation (1.15 Gy twice daily, total 80.5 Gy over 7 weeks) has shown improved local control compared to conventional fractionation in some studies 1

Follow-up Recommendations

• Post-treatment baseline imaging of primary site and neck (if treated) is recommended within 6 months of treatment 1
• Complete head and neck examination should be performed at regular intervals: every 1-3 months in year 1, every 2-6 months in year 2, every 4-8 months in years 3-5, and annually thereafter 1
• For patients who do not have a complete clinical response to therapy, salvage surgery plus neck dissection is recommended as indicated 1
• Thyroid-stimulating hormone (TSH) should be checked every 6-12 months if the neck was irradiated 1

Important Considerations and Pitfalls

• External radiation doses exceeding 75 Gy using conventional fractionation (2.0 Gy/fraction) may lead to unacceptable rates of normal tissue injury 1
• Radiation-related tissue changes may make it difficult to detect local or regional recurrence, potentially resulting in delayed diagnosis of persistent or recurrent disease 1
• While concurrent chemoradiation improves cancer-specific mortality, it may increase other-cause mortality, highlighting the need to carefully select patients who will benefit most from this approach 4
• Salvage surgery following radiation carries increased risk of complications, including delayed wound healing, skin necrosis, or carotid exposure 1
• The use of concurrent chemoradiation carries a high toxicity burden; altered fractionation or multiagent chemotherapy will likely further increase this burden 1