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Table 1 Volumes at risk in HNC

From: Technical guidelines for head and neck cancer IMRT on behalf of the Italian association of radiation oncology - head and neck working group

Burden of disease Description ICRU definition Adopted definition Finality T – level N – level Dose level definition Dose level NTD Solution examples (Total-dose Gy/single-fraction Gy/numbers of fractions
Definitive Postoperative
Conventional Slightly accelerated Conventional Slightly accelerated
Macroscopic Known gross disease GTV GTV Definitive Primary tumor Each Positive-nodes High Dose 70 Gy 70/2/35[18] 70/2.12/33[20]   
High risk of microscopic disease Risk of relapse > 10-20% [54],[55] CTV CTVHD^ Definitive Peri-GTV areas considered to contain potential microscopic disease [38] (T + 10 mm)* Positive Nodes + 5[41]-10[53]mm     66/2.2/30[17],[18]   
    (CTV1)        65/2.17/30[77]   
     Post-S Surgical bed with soft tissue involvement (Positive or close margins): PTB +0.5-1 cm according to anatomical barriers [41]. Nodal region with extracapsular extension [41]: PTB plus 1 cm up to the skin [56].ç   66-70 Gy    ≥63/1.8/35[78] 65/2.17/30[77]
    CTVHR Definitive Preferential areas of diffusion.(Optional) [56] Border-line lymph-nodes [51],[57] Intermediate Dose 60 Gy 63/1.8/35[18] 60/2/30[17],[18]   
    (CTV2) Post-S Surgical bed without soft tissue involvement [41] Nodal region without extracapsular extension   66§ Gy   59.4/1.8/33[20] ≥63/1.8/35[78]  
Low risk of microscopic disease Risk of relapse 5-10% [41],[80] CTV CTVLR Definitive Structure or compartment adjacent to tumor [56] Elective nodal regions, defined for each primary-tumor subsite# Low dose 50 Gy 58.1/1.66/35[18] 54/1.8/30[17],[18],[77]   54/2/27[79]
    (CTV3) Post-S     50 Gy   50.4/1.8/28[20] 57.6/1.8/32[78] 54/1.8/30[77]
  1. *Depending from anatomic barrier;§ though one prospective study failed to show a benefit for 66 Gy over 60 Gy in the high risk post-operative region [78], this is the dose recommended by some cooperative groups (EORTC [79]); PTB: postoperative tumour bed; ^ definition of the high-risk region is controversial [18] ; D = Definitive RT; Post-S = postoperative. CTVHD: High Disease; CTVHR=High Risk; LR = Low risk. Çin case of muscular infiltration (i.e. sternocleidomastoid muscle) at least the portion of the muscle surrounding the node [47] should be included. # Similarly, it would be appropriate to include the whole muscle (i.e. sternocleidomastoid muscle) in CTV3/LR or when grossly infiltrated at some level.