Table 1 Delineation of clinical target volume of nasopharyngeal carcinoma according to various institutions’ practice, international guidelines, and clinical protocols
| Â | NRG HN001 protocol | Our Institutional protocol | International guidelines | Suggestions based on current study |
|---|---|---|---|---|
GTVp + 8 mm + whole NP | GTVp + 8 mm + whole NP | GTVp + 10 mm + whole NP | GTVp + 8 mm + whole NP | |
T1-2 | Â | Â | Â | Â |
 Lateral | Bilateral parapharyngeal space Bilateral pterygoid fossa | Bilateral parapharyngeal space Bilateral lateral pterygoid plates | Bilateral parapharyngeal space Cover pterygoid muscle by 5 + 5 mm expansion from GTVp only, unless there is gross muscular invasion; Cover the whole muscle in case of invasion of the deep fascia/ epimysium of the pterygoid muscle | Bilateral parapharyngeal space Bilateral lateral pterygoid plates (including medial pterygoid muscle) |
 Anterior | Posterior 1/4 of nasal cavity Posterior 1/4 of maxillary sinus | At least 5 mm from choana, posterior wall of maxillary sinus If nasal cavity is involved, then posterior part of ethmoid sinus should be included Pterygoid process PP fossa | At least 5 mm from choana, posterior wall of maxillary sinus Include vomer and the surrounding ethmoid sinus PP fossa | At least 5 mm from choana, posterior wall of maxillary sinus Include vomer and the surrounding ethmoid sinus PP fossa |
 Superior | Skull base (including foramen ovale and rotundum bilaterally) Inferior sphenoid sinus | Skull base including foramen ovale and rotundum, lacerum, petrous apex bilaterally Inferior sphenoid sinus | Skull base including foramen ovale and rotundum, lacerum, petrous apex bilaterally Inferior sphenoid sinus (1/2) | Skull base including foramen ovale and rotundum, lacerum, petrous apex bilaterally Inferior sphenoid sinus (1/2) |
 Posterior | Anterior 1/3 clivus | Prevertebral muscle Anterior 2/3 clivus | Anterior 1/3 clivus Spare jugular foramen and hypoglossal canal in the absence of extensive posterior-lateral infiltration of primary tumor or high jugular lymphadenopathy | Prevertebral muscle Anterior 1/3 clivus Spare jugular foramen and hypoglossal canal in the absence of extensive posterior-lateral infiltration of primary tumor or high jugular lymphadenopathy |
 Inferior | Not stated | The caudal border of palatine uvula or the midpoint of C2 If oropharynx involved, the downward at least 10 mm | Not stateda | The caudal border of palatine uvula or the midpoint of C2 If oropharynx involved, the downward at least 10 mm |
T3–4 |  |  |  |  |
 Lateral | Bilateral parapharyngeal space Bilateral pterygoid fossa | Bilateral parapharyngeal space Bilateral lateral pterygoid plates If medial pterygoid muscle involved, then lateral pterygoid muscle should be included If lateral pterygoid muscle involved, then infratemporal fossa should be included | Bilateral parapharyngeal space Cover pterygoid muscle by 5 + 5 mm expansion from GTVp only, unless there is gross muscular invasion; Cover the whole muscle in case of invasion of the deep fascia/ epimysium of the pterygoid muscle | Bilateral parapharyngeal space Bilateral lateral pterygoid plates (including medial pterygoid muscle) If medial pterygoid muscle involved, then lateral pterygoid muscle should be included |
 Anterior | Posterior 1/4 of nasal cavity Posterior 1/4 of maxillary sinus | At least 5 mm from posterior wall of nasal cavity and maxillary sinus Include vomer and the surrounding ethmoid sinus Pterygoid process PP fossa | At least 5 mm from choana, posterior wall of maxillary sinus Include vomer and the surrounding ethmoid sinus If sphenoid sinus involved, then upper part of posterior ethmoid sinus should be covered PP fossa | At least 5 mm from choana, posterior wall of maxillary sinus Included posterior part of ethmoid sinus, in case of involvement of posterior nasal cavity or sphenoid sinus PP fossa Include inferior orbital fissure in case of involvement of PP fossa |
 Superior | Skull base including foramen ovale and rotundum bilaterally Entire sphenoid sinus Cavernous sinus (involved side only) | Skull base including foramen ovale and rotundum, lacerum, petrous apex bilaterally Entire sphenoid sinus If sphenoid sinus involved, then posterior part of ethmoid sinus If posterior ethmoid sinus involved, then anterior ethmoid sinus should be included Bilateral cavernous sinus | Skull base including foramen ovale and rotundum, lacerum, petrous apex bilaterally Entire sphenoid sinus Cavernous sinus (involved side only) | Skull base including foramen ovale and rotundum, lacerum, petrous apex bilaterally Entire sphenoid sinus Included posterior part of ethmoid sinus, in case of involvement of posterior nasal cavity or sphenoid sinus If posterior ethmoid sinus involved, then anterior sphenoid sinus should be included Cavernous sinus (involved side only) |
 Posterior | Anterior 1/3 clivus (entire if involved) | Prevertebral muscle Anterior 2/3 clivus (entire if involved) | Anterior 1/3 clivus (entire if involved) Spare jugular foramen and hypoglossal canal in the absence of extensive posterior-lateral infiltration of primary tumor or high jugular lymphadenopathy | Prevertebral muscle Anterior 1/3 clivus (entire if involved) Include jugular foramen in case of extensive posterior-lateral infiltration of primary tumor or high jugular lymphadenopathy If clivus or jugular foramen involved, then hypoglossal canal should be included |
 Inferior | Not stated | The caudal border of palatine uvula or the midpoint of C2 If oropharynx involved, the downward at least 10 mm | Not stateda | The caudal border of palatine uvula or the midpoint of C2 If oropharynx involved, the downward at least 10 mm |