The prescription dose was delivered as follows : gross target volume ( GTVnx ) 67-76 Gy in 30-33 fractions , positive neck lymph nodes ( GTVln-R/L ) 60-70 Gy in 30-33 fractions , high-risk clinical target volume ( CTV1 ) 60-66 Gy , low-risk clinical target volume ( CTV2 ) 54-60 Gy , and clinical target volume of cervical lymph node regions ( CTVln ) 50-55 Gy .