O'Sullivan 2001 (Princess Margaret Ipsilateral RT)

Background

Retrospective single-institution analysis (Princess Margaret, Toronto). 642 tonsillar carcinoma patients 1970–1991; 228 selected for ipsilateral (unilateral) RT. Selection: well-lateralized T1–T3 N0–N2b, minimal/no base-of-tongue extension, no contralateral adenopathy, no midline involvement.

Interventions and follow up

Treatment: ipsilateral (unilateral) RT to primary + ipsilateral neck only, in 228 well-lateralized T1–T3 N0–N2b tonsillar carcinomas
Primary endpoint: contralateral neck failure rate; local control; disease-specific survival
mFollow up: 5+ yr

Results

Contralateral neck failure (ipsilateral RT): 4.8% at 5 yr
5-yr local control: ~92%
Disease-specific survival: comparable to bilateral RT in matched patients
Contralateral failure predictors: T3 and N2b higher risk

Adverse events

Xerostomia: significantly reduced vs bilateral RT (contralateral parotid spared)
Contralateral neck failure: 4.8%, acceptably low; salvage achievable in most nodal recurrences
Late dysphagia/feeding-tube dependence: lower with ipsilateral RT (reduced constrictor dose)

Conclusions

Carefully selected well-lateralized tonsillar carcinoma can be safely treated with ipsilateral RT (contralateral neck failure 4.8%) while reducing xerostomia and other bilateral-RT toxicities; patient selection is critical.

Key Limitations

Single-institution retrospective, non-randomized with selection bias; pre-HPV/pre-IMRT era; outcomes apply only to strictly selected lateralized tumors.

Clinical Context

Landmark support for ipsilateral RT in well-lateralized tonsil cancer to spare contralateral parotid; continues to inform unilateral neck treatment selection in the IMRT/HPV era.

References