Head and Neck Cancer FRCR CO2A Flashcards
What are the major RFs for H&N Cancers?
- Tobacco smoking
- Alcohol consuption
- Viruses HPV for oropharnx and EBV for nasopharnx
- Wood dust (adenocarcinoma)
- Nitrosamines (Npx)
- Genetic factors like fanconi anemia
- Betel nut chewing
what are the subsites of oral cavity?
Lips, Buccal Mucosa, Oral Tongue, RMT, Floor of Mouth, Alveolus/gingiva, hard palate
what are the sub sites of Pharynx?
Nasopharynx
Oropharnx
Hypopharynx
what structures do oropharynx include
Tonsils, BOT and Vallecula, Soft Palate, postr pharyngeal wall above hyoid
Which cancers involve LN level VIII, Ix and X?
skin of head and neck region
what are neck levels VIII, IX and X
VIII: Parotid group
IX: Bucco facial group
Xa: Retroauricular LN
XB: OCCIPITAL NODES
what are premalignant lesions of H&N Cancer
Leukoplakia
Erythroplakia
Dysplasia
CIS
whats the transformation rate of dysplasia to malignancy?
12 -14 %
what are common benign tumors of H&N Cancer
Pleomorphic adenoma of parotid
hemangioma
juvenile angiofibroma
ameloblastomoa
what are malignant histologic types in H&N Cancer
Sq Cell Carcinoma > 90%
Adenocarcinoma
Salivary GLand: Adenocarcinoma, MEC, Ad cyctic Carcinoma, Acinic cell Carcinoma
melanoma
NEC like olfactory neuroblastoma and Merkell cell carcinoma
Lymphoma
Metastatic deposits
how does H&N Cancer spread?
Local Spread
Lymphatic spread
Hematogenous spread
Whats the MC clinical Presentation of. H&N Cancer
Painless neck mass
others wt loss, failure to thrive, bone pain, rarely hypercalcemia related symptoms
How to proceed with Head and Neck Cancer Examination ?
- inspection of oral gavity and oropharynx, pay attention to mucosal extent of disease, closeness to midline
- Flexible Nasendoscope, to look at nasal cavity, NPx, HPx, Opx, and larynx
- Assess vocal cord mobility, involement of antr commisure, postr commisure, look for subglottic extension
Tongue base involvment is best examined by palpating
- Complete the examination by palpating the neck nodes
What investigations are commonly done in H&N Cancer ?
- USG of neck
- FNAC
- CECT H&N and Chest
- MRI of craniofacial region
- PET CT: not routinely used in UK, its useful for pts with neck nods without obvious primary on clinical and radiological exams
what are two recent surgical techniques in H&N Cancer
TLM (tranoral laser microsurgery)
TORS (Transoral robotic surgery)
what is the common surgical approach in H&N Cancer
WLE of local tumor with or without reconstruction and Neck dissection
How is node positive and node negative patients managed with surgery in H&N Cancer
Comprehensive neck dissection for N+ disease
Selective Neck dissection for N- disease
what assessments all pts should undergo before starting RT?
- Dental Assessment : removal of loose tooth
- Nutritional assessment
- Speech and swallowing assessment
what time interval is ideal in between extraction and start of RT
atleast 2 weeks gap
what are indications for post op CRT in H&N Cancer
+ margin (<1 mm)
+ ECS
They are also k/a High Risk factors
what are intermediate RFs in HPR of H&N Cancer?
Advanced Tumor (T3/T4), Close margin (<5 mm and > 1 mm), PNI and LVSI
what is indication of post op RT in H&N Cancer
Intermediate RFs
what are things to be considered while planning for RT in H&N Cancer ?
Mouth Bite
Bolus
Skin markings
when is mouth bite used during RT simulation?
treating oral cavity/nasal cavity and maxillary sinus tumors
why is mouth bite used during RT simulation
to reduce dose to adjacent normal structures
when is bolus used in H&N Cancer RT simulation
To treat glottic caner when Antr commisure is involved
To treat skin, if involved
How is skin marking helpful in RT simulation?
identify extent of scar, done with aid of a lead wire, can be visualised on planning CT scan
How are chin and shoulders positioned during simulation for H&N Cancer
Chin should be in normal position
shoulders should be kept as low as possible
How is Target Volume delineation done in Definitive setting of H&N Cancer for RT
- Delineate GTV: Primary and nodes, help from diagnostic imaging and C/E findings, coregistration of diagnostic images
- Delineate the CTV1 (GTV + 1 cm isotropic expansion in all directions, adjacent high risk regions and whole involved nodal level(s) in neck, crop out nature tissue barriers like bone, air and fascia, include the entire involved nodal levels , may be extended to include adjacent high risk regions eg parapharyngeal spaces and remaining oropharynx/larynx etc
- Delineate elective CTV2
- Delineate OARs
- Create PTV and PRV
How is PRV (planning Risk Volume) contoured?
Giving margin (3 to 5 mm) to OAR
How is Target Delineation done in post operative setting of H&N Cancer
- Recreate preoperative primary and nodal GTV: with the aid of coregistration of diagnostic scans, edit GTV based on post op changes, 1 to 1.5 cm isotropic margin in all directions to create CTVp and CTVn from GTVn, extend CTV to include all pathologically involved nodal levels and include sermas and other post op changes (CTV1)
- CTV2: uninvolved nodal levels in dissected neck and other at risk nodal levels
What are important in Inverse RT planning
setting objectives / constraints and order of priorities
what is an objective and constraint
an objective is a parameter desired to be met where compromise may be an option while constraint is a parameter that must be met, compromise is not an option
WHich organs priority are set at the highest priority?
Serial organs, Dmax cannot exceed a predetermined level even to achieve PTV coverage
what is the order of priorities in H&N Cancer RT planning?
- Serial Oragans Dmax
- PTV coverage
- Objectives for dose to the parallel structures
what are PTV objectives for H&N Cancer RT planning ?
V99%>90%
V95%>95%
V50% 100%
V5% < 105%
V2% < 107 %
What Precautions should H&N Cancer pts on RT take
- Avoid Sun Exposure, wet shaving and perfumed soap and toileratires
- Twice daily applicaiton of skin moisturizers to the H&N Cancer region
- maintaining oral hygiene by using regular mouth wash 3 to 4 times/day
- AVoid smoking, alcohol and certain foods like citrus, spicy, hot and hard food
- Avoid Chlorhexidine mouth wash, instead do with 1 cup of warm water + 1/2 tsf salt + 1/2 tsf baking Soda
what are acute and chronic S/Es post RT
S/Es within 90 days of Treatment: Acute,
thereafter Chronic
What are RT late side effects for H&N Cancer pts?
- Xerostomia
- Swallowing dysfunction
- Trismus
- Subcut fibrosis
- ORN
why should chlorhexidine mouth gargle be avoided in H&N Cancer pts?
it inhibits the regrowth of the mucosa
How are results of CRT Vs RT alone comparable in H&N Cancer Pts?
CRT improved survival by 6.5% at 5 years compared to RT alone
Whats the most common chemo regimen used in H&N Cancer Pts?
DCF (docetaxel, Cisplatin, 5 FU) in Neoadjuvant setting
How is two drug regimen (cisplatin and 5 FU) comparable to three Drug Regimen (DCF)
Improved outcomes but higher acute toxicity, 12% neutropenic sepsis
other s/e: mucositis, esophagitis, nausea and anorexia
whats the mc regimen used in UK for conc chemo in H&N Cancer Pts?
High Dose Cisplatin @ 100 mg/m2 on D1, D22
what are other conc cisplatin regimen
40 mg/m2 weekly for 6 weeks, Carboplatin AUC 5 on D1 and D22 or weekly at AUC 1.5 to 2
How is sequential therapy (NACT with TPF and RT) comparable to CRT for H&N Cancer pts?
Conflicting results
an italian study by Ghi et al 2014 showed sequential therapy improved 3 year survival 58% vs 46%
what group of patients should be treated with systemic treatment with palliative intent in H&N cancers?
- inoperable locoregionaly recurrent disease
- distant metastatic disease or
- combination of both
What is 1st L treatment for metastatic H&N cancer pts (non nasopharynx)? NCCN 2023
Pembrolizumab/platinum (cisplatin or carboplatin)/5-FU
Pembrolizumab (for tumors that
express PD-L1 with CPS ≥1)c
What is subsequent L treatment for metastatic H&N cancer pts (non nasopharynx)? NCCN 2023 post 1st L
- Nivolumab (if disease progression on or after platinum therapy) (category 1)
- Pembrolizumab (if disease progression on or after platinum therapy) (category 1)
what single agents can be used for metastatic/recurrent H&N Cancer pts ?
Cisplatin
* Carboplatin
* Paclitaxel
* Docetaxe
* 5-FU45 Methotrexate
progression on or after platinum therapy) (category 2B)
* Cetuximab
* Capecitabine5
whats the response rate of single agent treatment in H&N cancer pts and how is it comparable to combination regimens?
response rate single agent: 10 to 15 %
combination: 25 to 30 %
but increased incidence of toxicity
WHATS THE treatment of Early stage oral cavity cancer (I and II)?
Rx of choice: Surgery (WLE and with/without reconstruction and Neck dissection depending on the subsite of oral cavity.
Node negative: Prophylactic Neck dissection (U/L for lateralized tumors and B/L for midline tumors) for FOM and Tongue while observation for other subsites
what’s the rate of occult metastasis to neck nodes in Node negative FOM and tongue cancer?
25 to 45%
when is RT used in Stage I and II Oral Cavity cancer pts?
Pts not willing for surgery or not able to go for surgery due to comorbidities
How much margin is usually given for CTV from GTV in buccal mucosa carcinoma?
2 cm
When is elective nodal irradiation done in oral cavity, st I and II patients (as definitive treatment)
for FOM and Tongue
how is early stage Lip cancer treated with RT?
with electrons (9-15 MeV) or KV X rays (170-300 KV)
How to plan treatment with e- for lip cancer?
- determine depth of tumor
- Add 1 cm for microscopic disease and 5 mm for penumbra
- use internal shielding (lead in wax) (general rule - energy/2 in mm of lead)
- use mouth bite
- custom made end plate cut out to shape the field
- use a bolus of 5 to 10 mm thickness to ensure surface is covered
How do you define locally advanced oral cavity cancers?
More than 4 cm, and/or invasion of adjacent structures (extrinsic tongue muscles, bone) and/or regional LN involvement
How is Locally Advanced Oral Cavity cancer treated and why?
Combined Approach (Sx and RT)
high risk of locoregional Recurrence
when is ChT added to post op RT in Locally advanced oral cavity cancer?
ECS +
Margin + <1 mm
when is only I/L neck treated with in post op oral cavity cancer pts?
- Buccal mucosa
- Alveolus
- RMT
- lateral border of oral tongue
- Lateralized FOM
when is B/L neck Rx with RT in post op Oral Cavity Cancer Pts?
when tumor crosses the midline
what’s the 5 year survival rates for different stage of oral cavity cancers?
St I: 71.5%
St II: 57.9%
St III: 44.5%
St IV: 31.9%
What’s the anatomical boundaries of Nasopharnx?
Supr: Floor of sphenoid sinus and clavus
Infr: caudal edge of C1 or nasal aspect of soft palate
Antr: junction with nasal choanae
Postr: PPW
Lateral: Lat pharyngeal wall and medial border of parapharyngeal space
What’s the Lymphatic drainage of Nasopharynx?
Retropharyngeal nodes: 1st echelon
Then to Level II and upper V nodes
what’s the commonest site of origin of Npx Cancer?
lateral wall of roof of NPx
whats the commonest presentation of Ca NPx?
I/L palpable LAD (60-90%)
BL LAD (50%)
whats the rate of skull base involvment in Ca NPx?
30%
What are the RFs for Ca NPx?
- EBV and Nitrosamines (present in salt cured fish and meat and released during the cooking Process)
- Genetic predisposition and heavy alcohol intake
what are the common S/S of Ca NPx?
- Painless Neck Lump, the posterior triangle
- U/L otitis media, conductive deafness and tinnitus
- nasal obstruction, epistaxis
- sore throat
- Cranial Nerver dysfunction (II-VI or XI-XII)
what’s the common histology of Ca NPx?
Sq Cell Carcinoma, 3 types, type I keratinizing (west and 20% of NPC), type II non keratinizing (a/w EBV, 30% of NPx), type III (poorly differentiated)
other histologies: Adenocarcinoma, Lymphoma (T Cell)
What’s the Rx of Choice for Ca NPx?
RT with/without ChT
How is RT delivered for Ca NPx?
IMRT for all patients due to close proximity of vital organs
what’s the role of surgery in Ca NPx?
limited to Dx and salvage neck dissection for recurrent or persistent + nodes after CRT
What’s the Rx for early stage (I) Ca NPx?
Radical RT alone
What’s the Rx for intermediate stage (II) Ca NPx?
Concurrent ChemoRadiotherapy
due to higher incidence of distant failure with RT
What’s the treatment of Locally Advanced Ca NPx?
NACT often 2 cycles with PF followed by ChemoRT with cisplatin (100 mg/m2 3 weekly for 3 doses)
What’s the RT dose for Ca NPx?
70 Gy/ 35 # to CTV1
59.4 Gy/ 35# to CTV2
54 Gy/ 35# to CTV3
CTV1 includes GTV + 1 cm and whole NPx and all involved LNs
What structures are included in CTV2 for Ca NPx?
post: B/L Retropharyngeal Nodes
Antr: postr third nasal cavity, postr ethmoid and postr third maxillary antrum antrly
LaterallY: B/L parapharyngal spaces, pterygoid plates and /or pterygoid muscles
Supr: skull base and floor of sphenoid sinus suprly including b/l foramen ovale, carotid canal and foramen spinosum, clivus and petrous tips
What structures are included in CTV3 for Ca NPx?
- upper 1/2 of sphenoid sinus
- infraorbital fissure, orbital apex and supraorbital fissure
- uninvolved nodal levels (level Ib-Va, Vb, the retrostyloid space and the SCF)
How does Conc ChT increases mucositis added to RT?
by 30%
What RT dose to Tumor is required for NPC disease control?
at least 70 Gy
What’s the 5 yr survival Rate for NPC stage wise?
St I: 71.5%
St II: 64.2%
St III: 62.2 %
St IV: 38.4 %
What’s the Local Control Rate for NPC treated with IMRT ?
90 % at 2 to 5 years
What are the RFs for OPC?
HPV 16
smoking
Alcohol
What’s peculiar about HPV+ OPC?
- MC subsite: tonsil and tongue base
- early T stage and advanced N stage with LNs that are cystic in nature
How is Oropharynx anatomically defined?
extends from Plate to the hyoid
supr: jxn of hard and soft palate
Infr: the vallecula/hyoid
antr: circumvallate papillae
postr: the postr pharyngeal wall
lat: lateral pharyngeal wall
What are the subsites of Oropharynx?
Tonsils
Tongue Base
Valleculae
Soft palate
postr pharyngeal wall
What are the LNs drainage of OPC?
- Level II nodes: 1st echelon
What’s the S/S of OPC?
- difficulty in swallowing and odynophagia
- referred otalgia
- Trismus
- Impaired Tongue movement and altered speech
what are the common histology of OPC?
Sq Cell Carc
AC
Small Cell Carc
Lymphoma
Mucosal Melanoma
what is lateralized OPC?
Tonsillar fossa
whats the non lateralized tumors in OPC
Tonsullar tumor involving adjacent tongue/soft palate by > 1 cm or arising from midline, tongue base/soft palate/PPW/vallecula
Whats the Rx of Stage I and Stage II OPC?
Sx (TLM or TORS) with SND(I/L or B/L)
How is Locally Advanced OPC treated?
CRT or
RT with concomitant Cetuximab (where chemo is contraindicated) or
RT alone
or Induction Chemo f/b RT/CRT
when does benefit of concurrent chemo decreases in Rx of OPC?
after age 70
Which OPC Patients can be considered for Induction Chemo?
Higher chances of metastatic
1. T4
2. N2c/N3
What are the prognostic factors in OPC?
Stage of disease
HPV status
Smoking Hx
whats the 3 year survival for OCP
82.4% for HPV + compared to 57.1 % for HPV -
3 year OS 93% in HPV + with a low smoking Hx
What are subsites of Hypopharynx?
Pyriform sinus
PPW
Post Cricoid region
what’s the Lymphatic drainage of Hypopharynx?
Level II to V and RPLNs (PFS)
Level II, III and RPLN (PPW)
Levels III, V and paratracheal (post cricoid)
anatomy of PFS
medially and suprly by The AEF
antrosuperirly by the pharyngoepiglottic fold
Laterally by superior edge of thyroid cartilage
Inferiorly: the apex opens into the esophagus
65 to 75% Cancers here
Postr Pharyngeal Wall Anatomy (OPC)
tip of epiglottis to the infr border of cricoid 10 - 20 % cancer pts
Post Cricoid region Anatomy
Postr surface of arytenoids to the inferior border of the cricoid cartilage, 5 to 10 % of cancers
what are the RFs for Ca Hypopharynx?
Smoking
Alcohol
IRon and Vitamin defy
asbestos exposure
wood and coal dust
What are the S/S of Ca Hypopharynx?
Odynophagia
Wt loss
referred otalgia, hemoptysis
difficulty in breathing
painless neck swelling
How is Neck treated in Ca Hypopharynx?
Elective Rx of B/L Neck for all stages, even in clinically node negative neck due to high incidence of occult LN Mets (30 to 50%)
How is St I and St II Ca Hypopharynx Treated with Sx?
surgery either TLM or TORS
open surgical procedures not recommended
How is locally advanced Ca Hypopharynx Treated with Sx?
Total laryngectomy
partial or total pharyngectomy
permanent tracheostomy
b/l neck dissection and reconstruction
How is CTV drawn from GTV in Hypopharyngeal cancer
1 cm isotropic margin except supr and infr (2 cm)
What structures are included in CTV1 for Hypopharngeal Cancer
GTV and margin
whole hypopharynx (tip of epiglottis to bottom of cricoid or lower as dictated by tumor),
parapharyngeal space on I/L side with gross disesase involving the space
What are subsites of Larynx?
Glottis
Supraglottis and
Subglottis
which among glottic cancer present earlier?
Glottic cancer
which has rich lymphatic drainage among laryngeal subsites?
supraglottic larynx
what structures are included in supraglottis?
Arytenoids, AEF, Epiglottis, False cords
what structures are included in glottis?
Vocal Cords
antr commisure
postr comissure
what structures are included in subglottis?
below the vocal cords to the bottom of the cricoid
what’s the common symptom of Laryngeal Cancer?
Hoarseness of voice
Sore throat,
Odynophagia
Difficulty swallowing
painless neck swelling
what Sx is used in laryngeal Cancer, early stage?
Tranoral laser resection in supraglottic and glottic cancers
SND considered in N0 patients but not for glottic cancer due to the low risk of nodal mets
What’s the role of salvage surgery in laryngeal cancer?
Recurrent /persistent disease following RT
what Sx is for people not suitable for larynx preservation in LA laryngeal Cancer?
Total Laryngectomy and B/L Neck Dissection
what’s the role of RT in Laryngeal Cancer?
Primary RT is an alternative Rx option for early stage disease at all subsites and is Rx of Choice in patients with poor access to surgery
How is CIS of glottis treated?
RAdical RT
How is Locally Advanced Laryngeal Cancer Treated?
classified into two groups
1. with no extra laryngeal extension with useful laryngeal function
2. with gross cartilage destruction and/or extra laryngeal disease or with poor function
What’s Rx for patients with gross cartilage destruction and/or extra laryngeal disease or with poor function?
Total Laryngectomy and Neck dissection and Adj. RT or CRT
what’s Rx for pts with no extra laryngeal extension with useful laryngeal function?
CRT (larynx preservation)
NACT f/b CRT (large volume disease)
RT (over 70 yrs or not fit)
RT and Cetuximab (C/I for Chemo)
When is bolus used for RT in laryngeal Cancer?
If antr commissure is involved
Which subsites are involved by tumors in decreasing order?
Maxilla (70%)
Nasal Cavity (lateral wall)
Ethmoid sinuses (10%)
Tumors of frontal and sphenoid are rare
Boundaries of maxillary Sinus
Supr: floor of the orbit
Infr: alveolar process of maxilla
medial wall: the nasal cavity
antr wall: antr wall of maxilla
postr wall: pterygoid and pterygopalatin fossa
what’s ohngren’s line
line connecting medial canthus to angle of mandible (imaginery line)
divides maxilla into antroinferior and posterosuperior region
How does AnteroInfr and postrosupr region maxilla cancer difffer?
AntroInfr a/w earlier presentation and good prognosis and reverse is true for postr superior
Lymphatic drainage of Maxilla
Retropharyngeal LNs, level I and II, early stage: < 5%, advanced stage: 10 to 15%
what are the RFs for Paranasal Cancer?
leather, textile, wood dust and nickel dust air pollution, tobacco, virus
what does nikel dust cause and what does wood dust cause?
Nickel dust; Squmaous cell carcinoma
Wood Dust: Adenocarcinoma
Clinical Presentation of paranasal sinus carcinoma
Early disease: Asymptomatic
present at a later stage, with symptoms related to invasion of adjacent structures
Symptoms include:
1. nasal obstrn
2. anosmia, nasal discharge, epistaxis
3. Facial/cheek swelling
4. Eye symptoms: diplopia, watering of eyes, proptosis
5. Pain in face numbness,
6. loosening of teeth, non healing ulcer in the oral cavity
what are histologic subtypes of Paranasal carcinoma?
Squamous cell Carcinoma (50%), Mucosal Melanoma, olfactory esthesioneuroblastoma, Adenoid cystic carcioma
What’s the treatment for MAxillary Sinus Carcinoma?
Surgery for early stage
Sx followed by adjuvant RT for locally advanced
When is I/L neck dissection done in maxillary sinus cancer?
for clinically node negative and advanced stage disease
what’s alternative Rx for CA Maxilla for unresectable or pts not amenable for Sx
RT with/without Chemo
CTV for maxillary sinus cancer
GTV + 1 cm
the whole maxillary antrum, b/l ethmoid sinuses and I/L nasal cavity
pterygopalatine fossa and masticator space in maxillary sinus tumors
sphenoid sinus when the ethmoid sinus is involved
Entire orbit when there is gross orbital fat involvement
what are benign tumors of parotid?
Pleomorphic adenomas and Warthin’s tumor
which salivary gland is commonly affected by tumors?
70% parotid
10 % submandibular glands
< 1% in sublingual glands
where does most of the cancer in parotid arise?
superficial lobe
What’s the Lymphatic drainage of parotid gland malignancy?
Preauricular and intraparotid nodes
what nerve submandibular gland malignancy affect
Lingual nerve, marginal branch of facial nerve, and the hypoglossal nerve causing tongue weakness
Common Histology of salivary gland tumor
Benign: Pleomorphic Adenoma
Malignant: MEC, Adenoid Cystic Carcinoma, Adenocarcinoma, malignant mixed tumors and Acinic cell carcinomas
what is peculiar about Adenoid Cystic Carcinoma?
high incidence of PNI
what’s the Rx for parotid gland malignancy?
Surgery involves superficial parotidectomy or total parotidectomy for tumors arising in the parotid glands, facial nerve is preserved where possible
When is Modified or Selective Neck dissection done for Salivary Gland Tumors?
- Node involvement
- locally advanced tumors (> 4 cm, T3/T4 disease)
- High grade tumors like undifferentiated carcinoma and high grade MED, AdenoCarc, malignant mixed tumors
What’s the role of RT in salivary gland tumors?
As an alternative in pt’s with locally advanced, inoperable or where surgery could not be done
Post op Setting:
1. close or + resection margins
2. residual disease
3. + nodes
4. High Grade Histology, MEC, Adenoid Cystic Carcinoma, High grade Adenocarcinoma, malignant mixed tumors except T1 tumors with clear margins
5. Tumors > 4 cm, T3/T4 tumors, bone and nerve involvment, skin involved, PNI, Close proximity to facial nerve where nerve is involved
When is RT indicated for Pleomorphic Adenomas post Op?
Positive or close margins
Isolated Supraclavicular LN?
Most of the metastasis from below the clavicle
What Investigations are done for unknown primary with neck node?
- History
- C/E
- Flexible Endoscopy
- EUA: to look at postnasal space, tongue base, hypopharynx, and take biopsies from there
- USG Neck and FNAC
- CT Neck and Chest
- MRI craniofacial region
- PET for patients for radical Rx when other Ivestigations failed to reveal a primary site
PET identifies 25% fo patients
what should be tested in biopsy for neck node?
HPV P26 and EBV
How is CUP with neck node Rx?
MRND followed by post op RT depending on histologic findings or
CRT or
RT alone
How is Target delineation done in CUP with neck node?
varies widely
most oncologists do total mucosal irradiation
what dose is given for Thyroid eye disease?
20 Gy/ 10#
what RT field is used for Thyroid Eye disease?
single lateral field angled 5 degree away from lens or with 1/2 beam blocking or
antr field with central axis blocking
what’s the improvement rate post RT in Thyroid eye disease?
75%
what’s the role of RT in macular degeneration?
15 Gy in 5 fractions, visual acquity is improved or stabilised in 66% of patients at 12 month follow upw
what is macular degeneration?
elderly patients, choroidal vessels prolferation causing subretinal H’ge and retinal detachment
leading cause of blindness in developed countries
what is thyroid eye disease?
Autoimmune response, activated T cells invade the orbit and stimulate the production of Glycosaminoglycan in fibroblasts
