Hats and Scarves 2 Flashcards
What are the general signs and symptoms of Head and neck cancer?
Pain/ soreness
Difficulty swallowing (dysphagia)
Neck mass
Voice changes
Classic patient presentation vs New patient presentation?
Generally older males
Significant history of smoking and drinking
Generally, don’t look after themselves
VS
Younger
Generally better socio-economic status
Limited or no previous smoking or alcohol history
Now make up majority of head and neck cancer population
Immobilization devices
Thermoplastic mask Standard head rests/ custom ( e.g. 2 part foam) Vac loc bags Shoulder supports/fixation Hand grips Mouthpieces/ mouth bites
Purpose of mouthpiece
keeps tongue in/out of field, can improve immobilisation
Purpose of Shoulder retractors/ fixation?
can affect shoulders in field, relax, weight loss
What are the important aspects of immobilisation for a head and neck patient?
adequate neck support intricate moulding of shell around important anatomical features and anomalies (i.e. nose, ears, chin, sup of skull) chin position shoulder position shell integrity
What are the CT simulation considerations for head and neck patients?
length of time elapsed after surgery (potential residual swelling, tenderness, wound healing)
Dentures and plates
Dental extractions required (important this is done prior to planning due to its effect on patient positioning)
What are the CT simulation problems?
anatomical and surgical anomalies claustrophobia no teeth! Tracheostomy Potential shell shrinkage
What are the imaging requirements for Head and Neck CT simulation?
Ensure all appropriate marks are on the patient CT zero/PR marks
Nodal areas
Scars
Bolus (some centres scan with bolus on)
IV contrast
Ensure the entire potential treatment area is imaged
Important to remember basic CT principles
Don’t alter kV settings due to impact on HU value and dose
calculation
FOV size
Image artifacts
What are the final considerations for CT simulation?
ensure all marks are on patient shell
comprehensive record of position (devices, positioning measurements- ITN position, C-SSN)
Other pertinent information (photos)
What are the most common conventional fractionations for head and neck cancer (3DCRT)?
70Gy in 35# to high risk area
50Gy in 25# to elective areas
sometimes 54-60Gy in 27-30# to intermediate areas
What are the most common IMRT fractionations?
70Gy in 35# to high risk area
56Gy in 35# to elective areas
63Gy in 35# to intermediate areas
What is the common post-operative fractionation
66Gy in 33# to positive margin area
54-60Gy in 27-30# to operative bed
What is the DAHANCA protocol for head and neck cancer?
68Gy in 34# (2Gy boost given once per week for final 4 weeks of phase 1 and remaining 5# delivered immediately after the completion of phase 1)
For IMRT: bi-daily treatment once per week in last 4 weeks of treatment
Why use altered fractionation dose schedules?
- Both dose per fraction and irradiation time influence the response to radiation of malignant tumours and acute-responding tissues
- Altered fractionation radiotherapy improves survival in head and neck patients. Comparison of the different types of altered radiotherapy suggests that hyper fractionation provides the greatest benefit
- consider treatment side effects
What are the surrounding OAR in head and neck treatment?
spinal cord brainstem parotid glands lenses optic nerves optic chiasm
Dose to spinal cord?
45Gy
Dose to brainstem?
max <54Gy
Dose to parotids?
26-30Gy median dose
Dose to Lenses?
6-8Gy
Dose to optic nerves?
50.4Gy
Dose to optic chasm?
54Gy
What is the field arrangement for larynx?
opposing lateral fields
generally requires bolus on anterior surface
Field placement considerations (collimation along angle of spinal cord, shoulder position)
What is a typical field arrangement for unilateral volumes for head and neck cancer (e.g. parotid)?
3 -field arrangement
Traditional wedged pair
Generally include lower neck therefore junction required
What is a typical field arrangement for Bilateral volumes for head and neck cancer (e.g. oropharyngeal tumour)?
multi field arrangement (anterior, anterior obliques, posterior obliques)
Junctioning technique
Parotid sparing technique
For lower neck : anterior +/- posterior beam
Field weightings: deliver as much dose as possible through the large anterior field and use obliques to keep to spinal cord tolerance
Bilateral face (parotid sparing)
multi field arrangement (6-8 fields)
Split posterior, posterior obliques, laterals, anterior obliques
Lateral fields given largest weighting
Posterior and posterior obliques used to come off spinal cord
What do you need to consider with lenses?
exit beam
IMRT for Head and Neck?
gold standard treatment for complex, radical head and neck cancer
7-9 beams
no opposing fields with IMRT
What are the two types of IMRT?
static (step and shoot)
Dynamic (sliding window)
(refers to the way the MLCs move during treatment)
What are the benefits of VMAT compared to IMRT?
Potential benefits with VMAT compared to IMRT are obtained through enhanced flexibility in delivery by facilitating alternating dose rate and gantry speed during dynamic movement of jaws and MLCs
Provide more conformal dose distribution than conventional techniques
Provides steep dose gradients (or dose drop off) between different areas
Very beneficial for tumours that are prescribed a high dose but are in close proximity to critical structures.
Generally 2x 360degree
After applying the specific dose constraints to each structure which are given the highest priority for IMRT/VMAT?
PTV should always be of high priority followed by critical structures.
What are the implications of IMRT/ VMAT?
increased potential of over and underusing of tumour volume and critical structures
importance of accurate and reproducible patient positioning
importance of target and critical structure margins
How many phases of treatment are typical for head and neck patients?
2 -phases
Therefore, don’t take all critical structures to tolerance in first phase
Multiple phases treated simultaneously
