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FRCR2 > skin > Flashcards

skin Flashcards

1
Q

What genetic condition predisposes to non-melanoma skin cancer and for which RT is contraindicated
What is the defect

A

Xeroderma pigmentosa

Defect in nucleotide excision repair

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2
Q

What should be assessed for skin cancer on examination

A

Size & depth of tumour, fixation to underlying structures, bony involvement
Margins

Regional LN involvement

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3
Q

When is surgery preferred for a skin cancer

A

Young age < 60yrs – cancer risk, RT effect on cosmesis worsens with time
Poor Vascular supply: lower leg – shin/malleoli, dorsum of hand
Large lesions involving cartilage / bone - RT may cause osteoradionecrosis
Upper eyelid (overlying lacrimal gland) - risk of dry eye if gave RT
Prior burns / previous RT
DNA defect syndrome: Gorlin’s, XP, Ataxia telangiectasia - RT could induce tumours

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4
Q

When is RT preferred for skin cancer

A

Provides better cosmesis / functional outcome - nose, lower eyelid, ear, lower lip/commissure
Sites with potential for deep infiltration: inner canthus, nasolabial fold, ala nasi, tragus, post auricular area
Large superficial lesions
Elderly or unfit for surgery
Multiple lesions

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5
Q

When is adjuvant RT indicated for a skin cancer

A

R1 margin and no further surgery possible (6-10mm margin ideally)
Extensive or large PNI
Multiple risk factors - infiltrative growth pattern, poorly differentiated

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6
Q

How is a skin cancer best treated with kV

A

BCC - 5mm margin
SCC - 1cm margin
Deep margin the same - receiving at least 90% of the dose

Protective - Eye shield, mouthguard

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7
Q

What radical dose should a skin cancer receive

A

SCC - 45Gy/10# (if small can hypo fractionate to 35Gy/5#; if large, hyperfractionate to 60Gy/30#)
BCC - 40.5Gy/9#

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8
Q

How are margins altered when treating with electrons
What is the minimal lateral size

A

Need wider margins as dose distribution narrows with depth
40mm min lateral size

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9
Q

What protection is needed when treating eg a lip with electrons

A

lead mouthguard covered in wax due to backscatter of electrons

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10
Q

How dose the depth dose depend on energy for electrons

A

Dx2 = Dmax
Dx3 = D90
dx4 = D50
dx5 = practical range (tail)

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11
Q

What thickness of lead shielding is needed depending on electron energy

A

Energy / 2 = thickness in mm

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12
Q

For photons, where is Dmax in relation to energy

A

Energy/4 = Dmax in mm

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13
Q

How is a low risk BCC best treated
How is a high risk BCC best treated

A

Low risk - surgical curettage or cautery, topical imiquimod or 5FU

High risk - surgical excision (WLE, Moh’s) or RT

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14
Q

When is adjuvant RT needed for BCC

A

Positive margins
Perineural invasion

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15
Q

What margin is given for a BCC

A

Well defined - 5mm margin
Poorly defined or morphoiec - 10mm

If treating with electrons, allow an extra 5mm margin

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16
Q

What percentage of actinic keratosis will transform to SCC per year

A

1%

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17
Q

What radical primary RT dose would be given to an SCC

What margin should be included

A

45Gy/10#

Can consider 18-20Gy/1# if elderly & lesion <3cm
35Gy/5# if >4cm

If >5cm - 55Gy/20#
If >6cm - 60Gy/30#

Well defined SCC - 1cm
poorly defined or large (>4cm) - 2cm margin
1cm deep margin
For electrons, add an extra 1cm margin to these

18
Q

What are the indications for adjuvant RT for SCC

What dose should be given for adjuvant RT

A

Positive margins
Perineural invasion
Tumour depth >4mm
Poor differentiation / high grade

Dose: 50Gy/25# or 60Gy/30# or 66Gy/33# for high risk H&N SCC

19
Q

When should electrons be chosen as treatment modality

A

Over bone and cartilage due to the photoelectric effect
Lesions >4cm
Scalp - drop off of dose minimises dose to brain

20
Q

When should orthovoltage XRs be chosen as treatment modality

A

<1cm depth and <4cm lesion

21
Q

What systemic treatments can be used for metastatic SCC

A

Cisplatin & 5FU (capecitabine) – like head & neck
Cemiplimab – PDL1 inhibitor

22
Q

What is a Merkel cell carcinoma

A

Aggressive neuroendocrine cancer with high risk of spread, typically occurring within H&N area

23
Q

What is the treatment for a Merkel cell carcinoma

A

If operable, surgical resection with 3cm margin and SLNB
If positive LN -> nodal dissection and adjuvant RT

If inoperable - primary RT (60Gy/30#) with 3-5cm margin

24
Q

What are the indications for adjuvant RT for a Merkel cell carcinoma

What dose RT is given adjuvantly

A

Positive margins
Primary tumour >2cm
Node positive

Dose: 50Gy/25#

25
Q

What is the treatment for a metastatic Merkel cell carcinoma

A

Carboplatin/etoposide or avelumab
+/- RT to neck nodes

26
Q

What is the prognosis for a Merkel cell carcinoma

A

High rate of local recurrence
Median OS – 9 months in metastatic disease

27
Q

What are the 4 types of Kaposi sarcoma

How is it treated

A

HIV related
Immunosuppressed
Classical - indolent, lower limbs
Endemic - sub-saharan africa - aggressive and occurs in children with fulminant lymphadenopathy

Treatment:
HAART
Palliative RT to symptomatic lesions - 8Gy/1#, 20Gy/10#
If severe disease - systemic treatment with caelyx or paclitaxel

28
Q

How is a cutaneous angiosarcoma treated

A

Resection with side margin with 50Gy/25# adj RT
If inoperable, caelyx in combination with RT (60Gy/30#)

29
Q

How is a low grade cutaneous follicular or marginal-zone (MALT) lymphoma treated

A

Superficial RT or electrons
PTV = GTV + 2-3 cm margin
24Gy in 12# or 15Gy in 5#

30
Q

How are cutaneous T cell lymphomas classified

A

Indolent:
Mycosis fungoides / Sezary syndrome – erythroderma, poor prognosis (32m)

Aggressive:
Anaplastic large cell / NK cell lymphoma

31
Q

How are cutaneous T cell lymphomas treated

A

Observe until symptomatic, then PUVA or topical steroids

Palliative RT for symptomatic lesions - 8Gy/2# or 12Gy/3#

Systemic treatment - No benefit of combination treatment (eg CHOP) over single agents: methotrexate, liposomal doxorubicin, gemcitabine

32
Q

What is the treatment for mycosis fungoides

A

Total body electron therapy - 30Gy in 20# over 5 weeks

33
Q

How is T staging defined for skin SCC

A

T1 - <2cm
T2 - 2-4 cm
T3 - >4cm or bone invasion or perineural invasion
T4a - gross cortical bone or marrow invasion
T4b - Skull base or axial skeleton involvement

34
Q

How is nodal staging defined for skin SCC

A

N1 - single node and <3cm
N2a - single node 3-6cm
N2b - multiple ipsilateral nodes all <6cm
N2c - bilateral or contralateral nodes ≤6cm
N3 - ECS or LN >6cm

35
Q

What histological markers would suggest melanoma

A

HMB 45, S100

36
Q

What is the Van Herk recipe

A

used to calculate CTV-PTV margin to allow for setup error for EBRT photons

37
Q

What is the 10yr local control rate of BCC

A

<2cm - 95%
>2cm - 90%
deep invasion 50%

38
Q

What are the indications for post op RT for BCC

A

T3 (>4cm)
T4
Recurrence

39
Q

First line mx of SCC
Outcomes

A

Surgery - aiming 4mm margin at least

<2cm - 95% 5yr control
2-5cm - 65-85%
>5cm 50-60%

40
Q

Indicatiosn for adjuvant RT for SCC

A

<4mm margin for low risk (<2cm)
6mm for high risk (>2cm or >6mm depth, perineurial invasion)

41
Q
A

FRCR2 (28 decks)

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