Abstract

Background

No randomised evidence exists to guide treatment of SCCUP. Two main approaches with RT exist – treating involved neck only (INO) or the addition of an elective dose to potential primary sites and contralateral neck (MUC). The rationale for this is to reduce the likelihood of the primary tumour emerging in the future but results in increased toxicity. If the frequency of mucosal primary emergence remains low without elective irradiation, we may be able to spare our patients toxicity.

Method

This was a retrospective cohort study; patients with histologically confirmed SCCUP with unilateral neck disease staged with FDG PET-CT scan were eligible.

Results

26 patients were evaluated. 16 patients received INO RT, 10 patients received MUC RT, all treated with VMAT. 37.5% patients receiving INO RT had HPV/p16 positive disease. 50% patients receiving MUC RT had HPV/p16 positive disease. 56.3% patients in INO group received concurrent cisplatin, 50% in the MUC cohort.

Median follow up is 35 months (range 30-46mths). No mucosal primaries in either group have emerged. 1 patient in the MUC group relapsed in contralateral neck in the elective dose volume. 2 year OS is 81.3% in INO group, 80% in MUC group.

Dose to organs at risk are as below:

INO RT

(n=16)

MUC RT

(n=10)

Mean dose contralateral parotid

1217cGy

3336cGy

p<0.01

Maximum dose brain stem

3270cGy

4191cGy

p<0.01

Maximum dose spinal cord (

3686cGy

4023cGy

p=0.056

Mean dose midline mucosa (hyoid-cricoid)

4040cGy

5068cGy

p<0.01

Mean dose midline mucosa (cricoid – sternum)

2658cGy

3324cGy

p=0.07

Conclusion

RT to INO does not result in more frequent emergence of mucosal primary or contralateral recurrence in SCCUP. The observed reduction in dose to OARs with INO approach may represent an opportunity to spare patients toxicity and would support further research to confirm the benefits of RT to INO.