Skin Flashcards
What are the 2 types of skin cancer?
Melanoma
Non Melanoma Skin Cancer NMSC
What are the two types of NMSC?
Basal Cell carcinomas
Squamous cell carcinomas
Where do melanomas commonly metastasise to?
brain
lung
small bowel
liver
What are some characteristics of melanomas?
very aggressive
unpredictable pattern of spread
blood & lymphatic spread early
Highly Radioresistant
What are the general ways for treating melanomas?
surgery and chemo
immunotherapy
megavoltage for metastases
What are the common melanoma dose fractionations for adjuvant RT after LN dissection?
50Gy/ 20#, 60Gy/ 30#
What are the common melanoma dose fractionations for palliative RT?
8Gy single fraction
20Gy/ 5#
36Gy/6# once weekly
What are the common melanoma dose fractionations for metastasis whole brain RT?
12Gy/ 2 daily fractions given on consecutive days
20Gy/ 5#
For NMSC what is the ratio of BCCs to SCCs?
3:1
What are the treatment options for BCC & SCC?
Surgery (cryosurgery, electrodessication & curettage, Moh’s micrographic surgery, wide local excision, skin grafting, LN dissection)
Topical chemotherapy
Photodynamic therapy
RT
What is Cryosurgery?
Liquid Nitrogen spray
Used for small superficial lesions (tissue dies, scab forms and drops off)
Cost-effective but not suitable near organs such as eyes
What is Electrodessication and Curettage (ED&C)?
Electrodessication burns tumour tumour is then scraped away Electric need to cauterise & kill margin Good cosmetic outcome Used on small lesions, multiple lesions
What is Moh;s Micrographic Surgery?
Microscopic examination of tumour slices so normal tissue is spared
Tracks and removes cancer and its roots
Good for the nose, eyelids, lips, hairline, hands, feet & genitals
What is a Wide Local Excision?
For incomplete excision or inadequate margins
may require a skin graft
local or general anaesthetic
What is Topical Chemotherapy?
5FU (fluorouracil) or Imiquimod creams
home application
steroid creams added if necessary (for swelling)
What is Photodynamic Therapy (PDT)?
hypersensitise cells to light then inject or topical application of drug (5-ALA)
Laser then kills cells
keep covered and dry for 36hours, scab forms and falls off in 3 weeks
What are the advantages of surgery?
can have good cosmetic result,
quick and safe
Good for lesions that recur after RT
Usually SCC needs wider excision due to possible lymphatic spread
Treatment of choice for nodal involvement
What are the disadvantage of surgery?
general anaesthetic for large tumours
skin grafting may be necessary
risk of post-op complications
difficult sites (inner canthus of eye)
What are some indications for using radiation therapy?
-patients who are medically unfit for surgery or anaesthetic
-Cosmesis (face)
preserve function (lower eyelid, lip, nose, inner canthus)
-patients prone to keloid
-recurrence
-positive margins
-perineural or lymphovascular spread invasion
-Large superficial tumours where: surgery would cause major loss of function (e.g. mouth dribbling, numbness) or mutilation would be involve (e.g. ear amputation, nasectomy)
In what circumstances would you not use RT?
young people (scar less noticeable than shape of RT field + telangiectasisa, risk of 2nd malignancy, fibrosis)
previous RT
area prone to trauma
upper eyelid
What is superficial treatment?
superficial (kV photons)
Electron
HDR Brachytherapy
What are superficial kV photons used for?
small tumours
frail patients
lesions <3cm diameter and <5mm thick
What are common fractionations for SXRT (superficial x-ray RT)?
36Gy/ 8# in 17 days (M/W/F)
30-32Gy/ 4# (one or two fractions/ week)
18Gy single fraction
What are the immoblisation restrictions for skin treatments?
any position as long as it’s reproducible and stable
supine, prone, decubitus, semi prone, seated
headrests, pillows, sandbages
Bolus/ rice bags
Head and neck cast for lesion on head
What is a clinical mark up?
must record enough info to reproduce set up
ususally not tattooed (especially if on face)
tracings required
photos
What shielding is used?
thickness depends on energy used (e..g. 4mm for electrons up to 10MeV)
individual cutouts for small lesions
LMPA cut out insert
secondary x-rays absorbed in lead
wax may be aded to provide build up to dose at skin
may need extra protection for eyes/ nasal cavity
When would direct field or fixed angles be used for electron treatment?
used if we want to avoid critical structures of match to another field
What is skin apposition?
best contact
want skin perpendicular to electron applicator
What are the advantages of electrons?
varying energy
can reach certain depth doses (depending on energy)
rapid fall off at depth
can treat lesions near bone and cartilage
What are the disadvantages of electrons?
difficult to match fields due to bowing isodose curves (treatment area is greater than that seen on skin surface)
Not possible to treat field sizes <4cm
What is the common dose fractionations for SCCs <5cm diameter?
45Gy /9# on alternate days over 3 weeks
54Gy/20# daily
What is the common dose fractionations for SCCs >5cm diameter?
50-54Gy/20#
66Gy/ 33#
What is the common dose fractionations for Post-Op XRT?
50Gy/ 20#
60Gy/ 30#
What are common acute side effects?
erythema
dry itchy skin
dry/moist desquamation
What are common chronic side effects?
pigmentation
telangiectasia
ischaemia
thickening
What are keloid scars?
follow surgical excision
RT indicated within 24-72 hours
6-9Gy/ 1#
What are the characteristics of BCC?
slow growing
rarely metastasize
What are the basal cell subtypes?
nodular/redent ulcer superficial subtype morpheic (sclerosing) infiltrative similar looking to morpheic pigmented = bluey/black looks similar to melanoma
What are the characteristics of SCC?
potential to metastasise
can be aggressive and grow quickly
What are the Squamous subtypes?
Bowen’s disease pre-invasive SCC in situ
verrucous
spindle cell variant
What are the different routes of spread for SCCs?
perineural spread (2.5-5%) (cancer spreading to space around nerve) lymph node dermal lymphatics local invasion pericartilageous spread distant metastases
What are the corresponding sizes for TNM staging for primary BCC?
T1 = ≤2cm T2 = >2cm but ≤5cm T3 = >5cm T4 = Deeply invades beyond s/c tissue
How do 5 year control rates reflect BCC size?
as the size increases the 5 year control rate decreases
How does RT with surgery benefit patients?
higher 5 year control rates for BCC & SCC
What are the causes of BCC, SCC or melanomas?
-UVA, UVB (sun exposure)
-immunosuppressants (organ transplant
-arsenic exposure
-genetic disorders (Gorlin’s syndrome, albinism)
Marjolin’s uler type scar cancer
Why might adjuvant RT be given more for SCC than BCC?
probability of locoregional recurrence is greater initially for SCC. With the addition of RT the probability can be reduced significantly
What target volume margin should BCC’s have?
No less than 5mm
What target volume margin should SCC’s have?
10mm
How do you select which filter to use for superficial
Higher HVL mm Al, the larger the lesion
For superficial RT what is the minimum % depth dose to the specified tumour depth?
80%
For superficial RT what varies the depth dose?
Filter
Field size
SSD
What are common dose fractionations for Superficial RT treatment?
18Gy/ 1# (can have bad side effects)
21Gy/ 3# (1#/ week)
24Gy/ (4# (1-2#/week)
36Gy/ 10-12 (4-5#/ week)
What is the second most common head and neck cancer after skin?
Lip
(1/4 of oral cavity tumours
90% affect lower lip
secondary to sun exposure and pipe smoking)
What do we look for in a lower lip cancer?
Non-healing ulcer
Direct extension (through skin to muscle)
Perineural involvement (involve mental nerve
Infrequently spread to LN
Where can the lip lymphatics spread to?
Upper: (Submandibular, Pre-auricular or Upper cervical jugulodigastric LN)
Midline lower: submental LN
Lower lateral : ipsilateral submandibular LN
How are lip cancer typically managed?
Surgery (very small lesion – primary closure if <30% involvement)
Larger lesions require transposition flap
Why would EBRT be used for lip lesions?
≥3cm (cosmetic benefit)
elderly
recurrence post-surgery
nodal involvement
What is a typical dose fractionation for electron beam to lip?
55-66Gy @100% in 20# over 4 weeks OR equivalent to 49.5-54Gy @90% in 20# over 4 weeks
wax build up with first 90% at the skin surface
When would photons be used?
If lymph node involvement
OR areas where difficult contour
When would brachytherapy be used?
Early T1 and small T2
What are the melanoma subtypes?
superficial spreading (most common)
Lentigo Maligna (most common in elderly on hands and face
Acral lentiginous melanomas (most common in darker skinned people)
Mucosal lentiginous melanoma
Nodular Melanoma
How does TNM staging differ for melanoma?
T level describes thickness (depth) of lesion
thicker the more aggressive
What are indications for RT for melanomas?
unresectable or residual lentigo maligna or lentigo maligna melanoma
desmoplastic/ neurotropic melanoma of the head and neck
in-transit disease (multiple nodules)
recurrences after surgery
nodal disease (high risk patients)
symptomatic metastasis
What are typical dose fractionations for primary and in-transit melanoma?
50Gy/ 20# for unresected disease
48Gy/ 20# for resected disease (most common)
What are the typical dose fractionation for resected nodal disease for melanoma?
30Gy/ 5# (twice weekly)
33Gy/ 6# (twice weekly)
48Gy/ 20# daily
What is merkel cell cancer?
Merkel cell carcinoma is a rare type of skin cancer that usually appears as a flesh-colored or bluish-red nodule, often on your face, head or neck.
Malignancy of primary neural cell found within the basal layer of the epidermis or grouped together to form the tactile hair disc of Pinkus and function as a type 1 mechanoreceptor
-high rate nodal involvement
What are the characteristic of MCC?
relatively uncommon
>65 years old
predominance in males and caucasians
occurs most commonly in sun-exposed areas (50% head and neck, 40% extremities)
How do you treat MCC?
surgery & RT
If RT is to be used as adjuvant, the adequacy of the surgical margin becomes less critical
When should RT commence after surgery for MCC?
rapid repopulation after surgery, RT should be commenced as soon as the wounds have healed
tumour is radiosensitive
