Role of Adjuvant Radiation Therapy in pT2N0 Tongue Cancer Post-WLE with 6mm DOI, No PNI, No LVSI
Adjuvant radiation therapy is NOT indicated in this case, as the patient lacks high-risk pathologic features that would warrant postoperative radiotherapy. 1
Risk Stratification Based on Pathologic Features
Your patient's pathology demonstrates intermediate-risk features only:
- Depth of invasion 6mm: This exceeds the 5mm threshold that increases nodal metastasis risk, but does not independently mandate adjuvant therapy when margins are adequate and nodes are negative 2, 3
- No perineural invasion (PNI): PNI is a critical high-risk feature that would require adjuvant RT to 56-60 Gy 1, 4
- No lymphovascular space invasion (LVSI): LVSI is strongly associated with locoregional failure (3-year LRC of 38.8% with LVSI vs 81.9% without) and would warrant consideration of adjuvant therapy 5
- pN0 disease after nodal dissection: Pathologically negative nodes significantly improve prognosis 6
Guideline-Based Indications for Adjuvant RT
High-risk features requiring adjuvant RT (60-66 Gy): 7
- Microscopically positive surgical margins
- Extracapsular nodal extension
- Multiple positive nodes (≥2 nodes)
Intermediate-risk features requiring adjuvant RT (56-60 Gy): 1, 4
- Close margins (<5mm)
- Perineural invasion
- Lymphovascular invasion
- Single positive node without extracapsular extension
Your patient has NONE of these indications, assuming adequate surgical margins were achieved (≥5mm). 1
Evidence Supporting Observation
The American Society for Radiation Oncology guidelines specifically recommend adjuvant RT only when adverse pathologic features are present 7. For pN0 disease without PNI or LVSI, single-modality surgical treatment is appropriate 1.
Research data support this approach: in node-negative oral tongue cancer, the absence of LVSI is associated with excellent 3-year locoregional control (81.9%) without adjuvant therapy 5. While DOI >5mm increases occult nodal metastasis risk (62% vs 13% for DOI <5mm), this risk is mitigated by the completed nodal dissection showing pN0 disease 2, 3.
Critical Caveats
Verify margin status carefully: If margins are close (<5mm) or positive, adjuvant RT becomes indicated at 56-60 Gy or 60-66 Gy respectively 1, 4, 8. This is the most common pitfall leading to local recurrence 2.
If adjuvant RT were indicated, it must begin within 6 weeks (ideally <85 days total from surgery to completion of RT), as timing may be more prognostically important than dose 7, 4.
Surveillance Strategy
Active clinical surveillance is appropriate for this patient with:
- Physical examination every 1-3 months for year 1-2
- TSH monitoring is NOT needed unless neck irradiation is performed 1, 4
- Imaging as clinically indicated for concerning findings
The recurrence risk in early tongue lesions with these favorable pathologic features (pN0, no PNI, no LVSI) is approximately 18% at 28 months, with most being salvageable local recurrences rather than regional failures 2.