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

GTV_P

Gross tumour volume

GTV_N

Gross nodes:

 – >  1.5 cm long axis

 – >  1 cm short axis

 – Necrotic

 – PET positive

CTV60

Combination 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

  ◦ Contralateral^a: 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

  ◦ Contralateral^a: 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