Is radiation therapy indicated for High-grade Squamous Intraepithelial Lesions (HSIL) of the vocal cord and if so, what is the typical fractionation schedule?

Radiation Therapy for High-Grade Squamous Intraepithelial Lesions (HSIL) of the Vocal Cord

Radiation therapy is NOT indicated for HSIL (carcinoma in situ) of the vocal cord as a first-line treatment, but when used after failed surgical approaches or patient preference, delivers excellent local control rates of 88-98% using 51-66 Gy in 20-30 fractions over 4-6 weeks. 1, 2, 3, 4

Treatment Algorithm for HSIL of the Vocal Cord

First-Line Management

• Primary treatment should be surgical: vocal cord stripping or laser excision, NOT radiation therapy 1, 2
• Radiation therapy is reserved for:
  • Recurrent HSIL after one or more failed surgical procedures (most common indication - approximately 60-70% of radiated patients) 2, 3, 4
  • Patient refusal of surgery 1
  • Medical contraindications to surgery 2

When Radiation Therapy IS Indicated

Standard Fractionation Regimen:

• Dose: 51-66 Gy (mean 59-62 Gy) 1, 2, 3, 4
• Fractions: 20-30 fractions 1, 2, 3
• Fraction size: 2.0-2.25 Gy per fraction 2, 3, 4
• Duration: 4-6 weeks 1, 2

Most Common Successful Regimen:

• 60 Gy in 27 fractions at 2.25 Gy per fraction (approximately 5.5 weeks) 3, 4
• Alternative: 51 Gy in 20 fractions over 4 weeks 1

Technical Specifications

• Field size: Small fields, typically 5 x 5 cm 3, 4
• Equipment: Megavoltage photons (Cobalt-60 or 2-6 MV linear accelerator) 2, 3
• Target: Limited to the true vocal cord(s) involved 5

Expected Outcomes

Local Control Rates

• 5-year local control: 88-98% 1, 2, 3, 4
• Ultimate local control with salvage surgery: 91-100% 2, 3, 4
• Cause-specific survival at 5 years: 100% 3, 4

Progression to Invasive Cancer

• Risk of progression to invasive squamous cell carcinoma: 10-11% 3, 4
• Time to progression: 6 months to 13 years (median approximately 2-4 years) 3, 4
• All invasive recurrences are salvageable with total laryngectomy 2, 3, 4

Critical Caveats

When Radiation Should NOT Be Used

• Extensive disease beyond the true vocal cords (supraglottic, infraglottic, or bilateral extensive involvement with anterior commissure) carries significantly higher failure rates 5
• The single failure in one series involved extensive extraglottic spread, resulting in death despite salvage surgery 5

Toxicity Profile

• Acute toxicity: Minimal, well-tolerated 1, 2
• Late complications: Rare 2, 3, 4
• Voice quality: Good-to-excellent in 90% of patients 2
• No serious long-term side effects reported 1, 4

Follow-Up Considerations

• Most recurrences occur within 5 years 2
• Risk of second aerodigestive tract malignancy: 11% at 10 years 2
• Close surveillance required for early detection of progression to invasive disease 3, 4

Comparison to Laryngeal Cancer Guidelines

The evidence provided for invasive laryngeal cancer 6 is NOT applicable to HSIL/CIS, as these guidelines address T1-T4 invasive disease requiring higher doses (66-70 Gy for early-stage, up to 81.6 Gy with hyperfractionation for advanced disease) 6. HSIL requires lower doses and smaller fields than invasive disease 1, 2, 3, 4.