Skin malignancy

1. Skin Cancer
Russell Banner
28nd September 2018

2. South West Wales Cancer Centre

3. How to approach?
• Patient Factors
– Performance status
– Co morbidities
• Tumour Factors
– Site
– Size
– Shape
– Adjacent structures
• Treatment Factors
– Outcomes
– Morbidity
– Modality
– Radiotherapy
• Photons
• Electrons
• Orthovoltage

4. Think about
• What modality
• What energy
• Blocks /Eye shields
• Bolus
• Advantages and disadvantages
• Morbidity
• Intent of treatment / Dose / Fractionation

5. Describe

6. Describe

14. Examine

16. Investigate

17. £153,034
Investigate
£444,129

18. Case 4
Investigate

19. Histology

22. Skin Cancers
• Squamous Cell Carcinoma
• Basal Cell Carcinoma
• Metastatic Deposits
• Melanoma
• Lymphoma
• Kaposi’s Sarcoma
• Merkel cell carcinoma

23. Treatment options

24. Moh’s, WLE, RT – Kv / MeV / MV
• Better cosmesis /
functional outcome nose,
lower eyelid, ear, lower lip
• Deep infiltration inner
canthus, nasolabial fold, ala
nasi, tragus, post auricular
area
• Larger superficial lesions,
elderly + frail, unfit,
adjuvant
• Cartilage and bone better
treated with MeV
PE effect of Kv
• Over air better treated
with kV Mev
Scatter
• Surgery younger,
Prev RT, vascular insufficiency
(shin / dorsum hand), lacrimal
gland, DNA repair syndrome

25. kV

26. 0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
120.0%
140.0%
0 2 4 6 8 10 12
Dose
Normalised
to
1
cm
deep
Depth (cm)
170 kV
90 kV
300 kV

27. kV
D90 (mm) D50 (mm) HVL
90 kV
5cm dia /30cm
5 27 2.6mm Al
170 kV
5cm dia /30cm
7 38 0.5mm Cu
170 kV
10cm dia/50cm
14 56 0.5mm Cu
300 kV
10cm dia/50cm
17 71 3.3mm Cu

28. Superficial
• Not technically ideal for Cartilage / Bone
• Eye Shield
• Stand off
• Stand in
• Inverse square law
• Change in SSD

29. Electrons

30. Electron PDD
Electron depth doses (10x10cmfield)
0
20
40
60
80
100
0 1 2 3 4 5 6 7 8 9 10 11
Depth in water (cm)
%
Dose
4MeV
6MeV
9MeV
12MeV
15MeV
18MeV

31. Skin Dose
Electron depth doses (10x10cm field)
0
20
40
60
80
100
0 1 2 3 4 5 6 7 8 9 10 11
Depth in water (cm)
%
Dose
6MeV
9MeV
12MeV
15MeV
18MeV
Build up curves for electron beams
70
80
90
100
110
0 0.5 1 1.5 2
Depth (cm)
%
Dose
6MeV
9MeV
12MeV
15MeV
18MeV

32. Characteristics of Electrons
• Sharp dose fall off
• Lateralised, Superficial lesions
• High skin dose (cf Photons)
• Pre requisite
– Flat surface
– Uniform density

33. Electrons
• In preference to KV over cartilage and bone
• Lateral scatter greatest at low energy
• Bolus superficial targets
• Wider margins
• Caution with air
• No beam <40mm as decreased penetration and loss
of beam flatness
• Decrease in energy by 2MeV/cm medium
• Back Scatter Factor 30-70%

37. Blocks

38. • Photons
• Electrons

39. Electrons
x 2 Dmax (mm)
x 3 D90 (mm)
x 4 D50 (mm)
x 5 Practical range (mm)
/2 Lead required for shielding (mm)
/2 Practical range (cm)
/3 Therapeutic range (cm)
/4 Dmax (cm)
4 6 9 12 18 25
Dmax 0.8 1.2 1.8 2.4 3.6 5.0
D90 1.2 1.8 2.7 3.6 5.4 7.5
Therap R 1.3 2.0 3.0 4.0 6.0 8.3
D50 1.6 2.4 3.6 4.8 7.2 10.0
Pract R 2.0 3.0 4.5 6.0 9.0 12.5
shielding 2mm 3mm 4.5mm 6mm 9mm 12.5mm

40. Photons
10x10field Dmax (cm) D50 (cm) 5DD at10cm
Cobalt 0.5 58.7
6Mv 1.5 15cm 67.5
10Mv 2.3 18cm 73
16MV 2.8 76.8
Dmax= Mv/4

42. Margins

43. Margins
2%

44. • Don’t forget
the deep
margin

46. Staging

47. Staging
T1 ≤ 2cm
T2 > 2cm
T3 Deep structure
T4 Skull base, axial skeleton
N1 Single, ≤3cm
N2 Single, > 3-6cm
Multiple, ≤ 6cm
N3 > 6cm

48. Prescription
• Dose
• Time
• Fractionation
• Energy
• Prescription point

49. Case 4
Small

50. Medium

51. Large

52. Palliative

57. Shielding

58. 3

63. Consent

64. Consent
• Acute
– fatigue
– erythema
– desquamation
– scabbing
– alopecia
– pigmentation
• Chronic
– (hypo)pigmentation
– atrophy
– telangectasiae
– alopecia
– nasolacrimal duct
stenosis / wet eye
– lacrimal gland failure /
dry eye
– cartilage necrosis
– second malignancy

65. Retreatment

66. Errors and Interruptions in Treatment
• Myocardial Infarction after 1st fraction 35Gy/5#
• SSD error – 50cm vs. 30cm

67. Good Luck!