Lecture 28 - Oropharynx Contouring

ONCOL 306 - Imaging. University of Alberta

What are the two options for the treatment of T1-2N0 OPC

1. preferred: definitive RT with consolidative surgery (in case of < complete response)

2. alternatively: Surgical resection of primary ± neck dissection

When is Post-Op RT indicated for T1-2N0 OPC?

• pT3-T4

• close margins

• multiple nodes

• level IV - V nodes

• perineural invasion

• LVSI

When is Post-op chemoRT indicated for T1-2N0 OPC?

• positive margin

• extracapsular extension

What are the two options for T3-4 or LN+ OPC?

1. preferred: concurrent chemoRT with consolidative surgery (in case of < complete response)

2. alternatively: surgical resction of primary ± neck dissection

when is post-op RT indicated for T3-4 or LN+ OPC?

• pT3-4

• close margins

• multiple nodes

• level IV-V nodes

• perineural invasion

• LVSI

when is post-op chemoRT indicated for T3-4 or LN+ OPC?

• positive margins

• extra capsular extension

what two things are done for sim prep?

• dental care: custom dental tray or dental putty mold as needed

• thermoplastic and shoulder mask made prior to simulation

  • neck extended and shoulders down

How is the patient set up for sim?

simulate supine with neck gently extended, shoulders down. immobilize with the thermoplastic head and shoulder mask

• bolus if skin is involved

• shield metal crowns or fillings with custom dental tray or dental putty mold

what size of slices are used in CT sim

3 mm

what other modality can be used to help guide contours?

PET

what is included in the GTV for OPC?

gross tumor and involved lymph nodes (often GTVnode)

• clincial and radiographic gross disease

what is included in the CTV66 for OPC?

primary tumor and involved nodes

what is the formula for the CTV66?

CTV66 = GTV + 0.5-1 cm on primary + 0.3-0.5 cm on nodes

• typically 5 mm expansion

what is included CTV60 for OPC?

nodal areas at high risk of microscopic disease

• next nodal drainage site from involved nodes

what is included CTV54 for OPC?

nodal areas at low risk of microscopic disease

• elective nodal regions

what specific lymph node levels are included in CTV54 for OPC if there is no LNI? what if there is LNI?

• no LNI: levels II-IV + retropharyngeal

• LNI: levels Ib-V

what is included in the PTVs for OPC? what is the formula for the PTV?

CTV plus a margin for set-up variability

• PTV = CTV_x + 0.5 cm

do we crop the PTVs for OPC?

yes: crop PTV 3 mm from the skin

ensure PTV54 is cropped out of PTV66 region

what is the typical clinical presentation of OPC?

• painless neck mass common

  • trouble swallowing

  • pain swallowing

  • ear pain (CN IX involvemet)

  • tongue fixation (deep tongue muscle invasion)

  • Trismus (medial pterygoid invasion)

what are the anterior, posterior, superior, inferior, and lateral borders of the oropharynx?

• anterior = circumvallate papillae, anterior tonsillar pillars, and border of hard/soft palate

• posterior = posterior pharyngeal wall (retropharyngeal space)

• superior = superior surface of the soft palate

• inferior = superior surface of the hyoid bone / floor of the valecula

• lateral = tonsillar fossae and pillars

What are the names of the levels I-V lymph nodes

• Ia = submental

• Ib = submandibular

• II = upper jugular group

• III = middle jugular group

• IVa = lower jugular group

• V = posterior triangle group

what is the sup and inf border of level IA - submental

sup = mylohyoid muscle

inf = plastysma muscle (inf edge of the anterior belly of the digastric)

what is the sup and inf border of level IB - submandibular

sup = sup edge of submandibular gland

inf = plane through inf edge of hyoid bone/mandible; alternatively the inf edge of the submandibular gland

what is the sup and inf border of level II - upper jugular group

sup = inf edge of C1

inf = inf edge of hyoid bone

what is the sup and inf border of level III - middle jugular group

sup = inf edge of hyoid bone

inf = inf edge of cricoid cartilage

what is the sup and inf border of level IVa - lower jugular group

• sup = inf edge of cricoid cartilage

• inf = 2 cm sup to sternal manubrium

what is the sup and inf border of level IVb - medial supraclavicular group

• sup = inf border of level IVa (2 cm sup to sternal manubrium)

• inf = sup edge of sternal manubrium

what is the sup and inf border of level V - posterior triangle group

• sup = sup edge of body of hyoid bone

• inf = plane just below transverse cervical vessels

Prior to RT, what assessments will OPC patients get?

• Pre-RT dental assessment

• dietician assessment and baseline establishment

• SLP assessment

• Audiology referrla: cisplatin is ototoxic so baseline hearing needs to be established

what is the most common lymph node levels that OPC cancer typically spreads to?

levels II and III

which patients have a better prognosis, HPV+ or HPV-

HPV+