Radiotherapy Flashcards
How is Grenz ray treatment given?
Low kilovolt (kV) X-rays which are absorbed into epidermis usually 200 Roentgens given 1-2x per week for a total dose of 800-1000 Roentgens Rpt cycle at 4-6 month intervals
What derm conditions can Grenz rays be used for?
Psoriasis Eczema Darier's Hailey-Hailey MF Lichen planus acrodermatitis of Hallopeau have been used for LM but generally dont penetrate deep enough to ensure adequate Rx
How may radiotherapy be used in the treatment of keloids?
Can irradiate keloid
Can excise keloid and do early XRT to scar
85% success rate
Older keloids dont respond as well
Usually 3-4 fractions each of 3-4 Gray
Can use superficial X-rays, electron beam XRT or radioactive iridium wire implant
Surgery preferred over XRT as primary skin cancer Rx for which circumstances?
Younger pts (cosmesis better) Gorlins Bulky tumour (cure unlikely) field size >6cm (cure unlikely) tumour eroding cartilage or bone - unlikely to sure and if so low chance of re-epithelialization trunk or perineal tumours tumours below knee Pt unable to lie still CI in verrucous carcinoma at any site - risk of transformation to anaplastic SCC
XRT is preferred primary skin cancer Rx in which circumstances?
Elderly pts on warfarin or with significant comorbidities
Tumours of face where surgery may result in poor cosmesis or loss of function
Indications for post op XRT?
Tumour margins not clear further surgery not possible Tumour has poor prognostic factors - positive LNs, large primary SCC, head/neck region Perineural invasion
What information is necessary for XRT prescription or documentation?
total dose given energy of beam number of fractions given total number of days over which Rx given volume/are to be treated + margin
Should upper eyelids be treated with XRT?
No
can lead to keratinization of the conjunctivae and traumatic damage to eye
Lower eyelids usually okay
What are the AEs of Grenz ray therapy?
minimal AEs as only penetrates about 2mm deep
at doses >200 Roentgens can be mild sunburn rcn
pts may get a persisatnt dark tan lasting many months
What are the features of acute XRT rcn / radiodermatitis?
tissues w/ more rapid cell turnover show XRT rcn more quickly after Rx
skin reddens at day 5-7
peak rcn at 3-4 weeks after end of XRT Rx
brisker rcn seen if larger dose given in short time or in pts w/ a tendency to sunburn
rcn sttles in 2-3 wks w/ re-epithelialization starting in perifollicular areas
What is the management for acute radiation burn reaction (acute sunburn rcn)?
leave wound open as much as possible
apply vaseline only
avoid; trauma, extremes of temp, irritants or physical irritation (topicals, rubbing), TCS, repeated washing
What are the features of late XRT rcn (chronic radiodermatitis)?
Tissues with a slower cell division rate show effects of XRT later - months or years after Rx
e.g. subcut fat, fibrous tissues, small blood vessels
At 5-10 years post XRT may see;
pallor, increased pigmentation, reduced adnexal structures, atrophy, telys
Radionecrosis usually occurs approx 1 yr after complete healing of the skin following XRT
What is the max amount of superficial X-ray treatment a patient can have?
can safely have 3 course of 3Gy of superficial X-rays in lifetime
What is fractionation?
Why is XRT fractionated?
Simply means dividing the total dose into multiple smaller doses given at intervals
Allows selctive Rx of cancer cells as normal cells recover between Rx but cancer cells do not
What is treatment regime for XRT of lentigo maligna?
Sydney melanoma institute protocol;
Treatment field is gross tumour volume as dtermined by RCM + a 1cm margin
Total dose 50 Gy for adjuvant or 54-60 Gy for curative XRT
Given in 2-4 Gy fractions daily
