CTV-P delineation consensus guidelines (laryngeal, hypopharyngeal, oropharyngeal, oral cavity SCC)
TL;DRCTV-P1 = GTV-P + 5 mm and CTV-P2 = GTV-P + 10 mm, both anatomically edited, for definitive RT of laryngeal, hypopharyngeal, oropharyngeal and oral cavity SCC.
The volume is edited, not just expanded: air, mandible, hyoid, vertebrae and fascia trim it unless they are invaded. Two exceptions change the contour: T1 glottic disease gets no CTV-P2, and hypopharynx gets an optional 15 mm cranio-caudal CTV-P2 margin because submucosal spread reaches 20-30 mm.
In intact laryngeal, hypopharyngeal or oropharyngeal SCC treated with definitive RT, this supports a high-dose CTV of GTV-P plus 5 mm inside a lower-dose CTV of GTV-P plus 10 mm, both anatomically edited; it does not extend to the postoperative bed or to recurrent disease.
The volume is edited, not just expanded: air, mandible, hyoid, vertebrae and fascia trim it unless they are invaded. T1 glottic disease gets no CTV-P2, and hypopharynx gets an optional 15 mm cranio-caudal margin for submucosal spread of 20-30 mm. PTV expansion stays a centre decision.
7 details 1 trial watching
Multi-society consensus guideline for primary-tumour CTV (CTV-P) delineation, illustrated with endoscopic and planning-CT cases by subsite and T stage (UICC 8th edition).
CTV-P1 = GTV-P + 5 mm (high dose, typically 70 Gy in 2 Gy fx). CTV-P2 = GTV-P + 10 mm (50 Gy prophylactic with 2 levels, or 60 Gy intermediate with 3 levels, adding a 50 Gy CTV-P3). Delineate CTV-P2 first, then CTV-P1 inside it.
The margins rest on surgical evidence: Zanoni et al. found a 2.2 mm margin optimal for loco-regional recurrence-free survival, and laser microsurgery with 2-3 mm mucosal margins gave 85-95% local control without PORT. Tonsillar TORS/laser series with at least 2-3 mm margins report local control above 90%.
Margin data come mostly from T1-T2 tumours in selected high-volume surgical series, and the HPV effect on required margin is unknown. Infiltrative-border tumours and tumour budding are acknowledged as sources of GTV uncertainty the 5 + 5 mm concept does not resolve.
The main gain is a shared nomenclature tying CTV-P1/P2/P3 to dose level plus stage-specific editing rules. It does not settle margin adequacy under RT, and PTV expansion is explicitly left to each centre.
| Subsite / T | CTV-P1 | CTV-P2 | Editing note |
|---|---|---|---|
| Glottic T1 | GTV-P + 5 mm | Not recommended | Excludes thyroid cartilage and air cavity |
| Glottic T2 | GTV-P + 5 mm | GTV-P + 10 mm; may omit if small/superficial, not from anterior commissure | Excludes cricoid cartilage |
| Glottic T3-T4 | GTV-P + 5 mm | GTV-P + 10 mm | Stops at strap muscles unless macroscopically invaded |
| Supraglottic T1 | GTV-P + 5 mm | GTV-P + 10 mm | Includes pre-epiglottic and para-laryngeal space |
| Supraglottic T4 | GTV-P + 5 mm | GTV-P + 10 mm | Stops at strap muscles unless invaded; T4b may enter vertebral body |
| Subglottic T1 | GTV-P + 5 mm | GTV-P + 10 mm; optional | e.g. 2 mm into cricoid cartilage adequate |
| Subglottic T2-T4 | GTV-P + 5 mm | GTV-P + 10 mm | Excludes vertebral body except T4b |
| Hypopharynx T1 | GTV-P + 5 mm | GTV-P + 10 mm; optional if small/superficial | Excludes retro-pharyngeal space |
| Hypopharynx T2-T4 | GTV-P + 5 mm | GTV-P + 10 mm; consider 15 mm cranio-caudal | Not through pre-vertebral fascia unless T4b |
| Oropharynx T1 | GTV-P + 5 mm | GTV-P + 10 mm | Excludes air, bone, mobile tongue |
| Volume | 2 dose levels | 3 dose levels |
|---|---|---|
| CTV-P1 | 70 Gy in 2 Gy fx over 7 wk | 70 Gy in 2 Gy fx over 7 wk |
| CTV-P2 | 50 Gy in 2 Gy fx over 5 wk (prophylactic) | 60 Gy in 2 Gy fx over 6 wk (intermediate) |
| CTV-P3 | Not used | 50 Gy in 2 Gy fx over 5 wk (prophylactic) |
- Is the 5 + 5 mm margin adequate in HPV-positive oropharynx?
- Pattern-of-failure validation of edited CTV-P volumes under IMRT
- CTV-P definition in postoperative and recurrent settings n=104 · primary completion 2027-10 · post-TORS RT allowing primary resection bed sparing
📚 Sources · 📄 1 paper
The longer read
Read as a contouring document, this guideline does two things at once. It replaces the habit of large, often uniform primary margins with a two-tier volume tied to dose level, and it insists that the geometric expansion is only a starting point, to be cut back against air, bone, fascia and neighbouring subsites. The second point carries more practical weight than the first. Two planners who both apply GTV-P plus 10 mm can produce very different CTV-P2s depending on how aggressively they edit, and the subsite-by-stage text works as an editing manual: which cartilage is in, which is out, where the strap muscles stop the volume unless they are invaded.
The evidence base deserves a careful read. The margins rest on two kinds of data: pathology specimens showing how far tumour cells extend beyond the visible edge, and surgical series in which small resection margins still delivered high local control. Neither is a radiotherapy outcome study. The surgical series are selected, high-volume institutional experiences, and the surgeon has on-line visual feedback the radiation oncologist lacks. The authors also concede that most tonsillar cases were HPV-positive and that the effect of HPV status on the required margin is unknown. The 85-95% local control quoted for laser microsurgery with 2-3 mm mucosal margins is reassuring about the biology of microscopic extension. It is not proof that a 5 mm CTV-P1 under IMRT, with daily set-up variation absorbed by a centre-specific PTV, yields equivalent control.
Where the panel departs from its own rule is informative. Hypopharyngeal SCC gets an optional 15 mm cranio-caudal margin because surgical series report submucosal extension of 20-30 mm, and T1 glottic disease gets no CTV-P2 at all. These exceptions show the panel tailoring volumes to known spread patterns rather than imposing uniformity, which raises confidence in the rest. The stated limit of validity matters as much: postoperative and recurrent anatomy are excluded, and the authors say the 5 + 5 mm concept may not hold there.
What would make it wrong? A pattern-of-failure signal showing marginal recurrences clustered just outside CTV-P1 or CTV-P2 in pts contoured to these rules, especially in infiltrative-border tumours, where the authors admit GTV delineation is itself uncertain and inter-observer variability is larger. The authors attribute the 10-15% local relapse seen after selective surgery to tumour biology rather than margin, but that is an inference, not a measurement. Conversely, the smaller volumes this document endorses are the substrate any HPV-positive oropharynx de-escalation effort would build on, so the absence of HPV-stratified margin data is the most consequential gap.
For practice, the guideline mainly standardises. Its value lies less in any single margin than in a shared vocabulary (CTV-P1, CTV-P2, CTV-P3 mapped to dose level) that lets centres and trials compare volumes like for like, and in worked endoscopic-plus-CT examples by stage that make the editing reproducible. A centre still using undifferentiated primary margins should read it as a reason to audit its contours. A centre already working this way should read it as confirmation, not new evidence.