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Table 2 Specific RT volume definition volumes for Arm 1 (Primary RT)

From: Treatment de-escalation for HPV-associated oropharyngeal squamous cell carcinoma with radiotherapy vs. trans-oral surgery (ORATOR2): study protocol for a randomized phase II trial

Radiotherapy VolumeDefinition
GTV_PGross tumour volume
GTV_NGross nodes:
 – >  1.5 cm long axis
 – >  1 cm short axis
 – Necrotic
 – PET positive
CTV60Combination of GTV_P and GTV_N with a 5 mm expansion, excluding natural boundaries of spread
CTV54 – A 1 cm expansion on the GTV_P
 – Any nodal level that contains a positive node.
 – Any node < 1 cm in short axis the radiation oncologist deems suspicious for harbouring disease. This node plus an additional 5 mm margin will be included in the CTV54.
 – The first echelon draining nodal levels. This is nearly always level 2, but should include the lateral retropharyngeal nodes (RP) for soft palate and posterior pharyngeal wall extension.
CTV48 – Patients that are node negative:
  ◦ Ipsilateral: II-IV. RP only if extension to posterior pharyngeal wall or soft palate
  ◦ Contralaterala: II-IV, RP only if extension to posterior pharyngeal wall or soft palate
 – All patients with N1 (ipsilateral) nodal disease:
  ◦ Ipsilateral: Ib, II-V, RP
  ◦ Contralaterala: II-IV, RP only if extension to posterior pharyngeal wall or soft palate
 – All patients with N2 disease:
  ◦ Ipsilateral and contralateral: Ib, II-V, RP
  1. aIf treating the contralateral neck