What is the recommended management for a patient with T1 (tumor size) N0 (no regional lymph node metastasis) carcinoma (ca) of the tongue with perineural invasion (PNI) and no other adverse features?

Management of T1N0 Tongue Carcinoma with Perineural Invasion

For T1N0 tongue cancer with perineural invasion (PNI) as the sole adverse feature, adjuvant postoperative radiotherapy to the tumor bed and neck should be administered at 56-60 Gy in standard fractionation, as PNI independently predicts neck recurrence and poor disease-specific survival in early tongue cancer.

Primary Treatment Considerations

The initial surgical management should have included:

• Wide local excision (partial glossectomy) with adequate margins (≥5 mm when possible) 1
• Elective neck dissection is strongly indicated given that PNI correlates with occult cervical lymph node metastasis even in T1 disease 2
• For tongue tumors, ipsilateral selective neck dissection (levels I-IV) is appropriate for well-lateralized lesions 1

Significance of PNI in T1 Disease

PNI represents a critical adverse prognostic factor that fundamentally changes management, particularly in T1 tongue cancer:

• PNI independently predicts cervical lymph node metastasis, neck recurrence, and poor disease-specific survival in T1 oral cavity cancer 2
• In pathologically N0 necks, PNI is associated with significantly worse disease-free interval and locoregional control 3
• The presence of PNI in T1 disease carries similar prognostic weight to higher T-stage disease 2
• T1 patients with PNI who undergo observation alone have substantially higher neck recurrence rates compared to those receiving adjuvant treatment 2

Adjuvant Radiation Therapy Protocol

Adjuvant radiotherapy is indicated for T1N0 tongue cancer with PNI, based on the following evidence:

Radiation Parameters

• Total dose: 56-60 Gy to the tumor bed and ipsilateral neck using standard once-daily fractionation of 2 Gy per fraction 4
• Treatment should encompass the tumor bed and involved/at-risk lymph node regions 4
• For well-lateralized tongue tumors, unilateral radiotherapy may be considered 4

Evidence Supporting Radiation in PNI-Positive Disease

• Patients with pN0/PNI+ disease who received adjuvant radiation demonstrated significantly improved disease-free interval (6.5 years vs 1.7 years) and locoregional control (6.7 years vs 1.9 years) compared to observation 3
• The benefit of radiation therapy is most pronounced in PNI-positive patients, with END improving 5-year disease-specific survival by 16.2% in PNI-positive versus only 5.4% in PNI-negative T1 patients 2

Alternative Management if Neck Dissection Not Initially Performed

If elective neck dissection was not performed at initial surgery:

• Strongly consider completion neck dissection given the high risk of occult metastasis with PNI 2
• If neck dissection is declined or not feasible, prophylactic radiation to the neck (levels I-IV ipsilaterally) is mandatory 4, 5
• The median interval to neck recurrence is approximately 13 months, emphasizing the need for early intervention 5

Treatment Timing

Adjuvant radiation should begin within 6 weeks of surgery, as delays beyond this timeframe negatively impact outcomes 4

Surveillance Considerations

Following adjuvant radiation:

• TSH levels should be monitored every 6-12 months as hypothyroidism occurs in 20-25% of patients receiving neck irradiation 1
• Close monitoring for neck recurrence is essential, particularly in the first 2 years 5

Common Pitfalls to Avoid

• Do not treat T1N0 tongue cancer with PNI as "low-risk" disease requiring observation only - PNI fundamentally changes the risk profile 2
• Do not omit neck treatment - the presence of PNI indicates significant risk of occult nodal disease even in clinically N0 necks 3, 2
• Do not rely solely on margin status - even with clear margins, PNI independently predicts recurrence 3
• Avoid the misconception that T1 disease is inherently low-risk; PNI in T1 disease carries prognostic significance equivalent to more advanced disease 2