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Radiation Oncology Factoids > Squamous cell and basal cell carcinoma of skin > Flashcards

Squamous cell and basal cell carcinoma of skin Flashcards

1
Q

What is the incidence of non-melanoma skin cancer (NMSC) in the United States?

A

> 2 million cases/yr in the United States (exceeds incidence of all other cancers combined)

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2
Q

Which is more common: basal cell carcinoma (BCC) or SCC?

A

BCC (80%) is more common than SCC (20%).

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3
Q

What is the sex predilection for skin cancers?

A

Males are more commonly affected than females (4:1).

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4
Q

What % of skin cancer deaths are attributable to cutaneous SCC?

A

20%

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5
Q

What is the primary etiology of NMSC?

A

Mutagenesis from UV light

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6
Q

What signaling pathway is involved in BCC pathogenesis?

A

Sonic hedgehog signaling pathway. Vismodegib, FDA approved for BCC, targets this pathway.

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7
Q

According to NCCN, how are anatomic skin areas divided? (see also Connolly et al., Dermatol Surg 2012)

A

H: “mask areas” (central face, eyelids, eyebrows, periorbital nose, lips, chin, mandible, preauricular, postauricular, temple, ear), genitalia, hands, feet
M: cheek, forehead, scalp, neck, pretibial
L: trunk and extremities (except pretibial, hands, feet, nails, ankles)

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8
Q

What is the “mask area” and why is it considered higher-risk?

A

It corresponds to the midface, where the embryologic fusion lines lie, and may represent a higher risk for deep invasion or LR.

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9
Q

According to NCCN, what are the risk factors for recurrence for BCC?

A

Area L ≥20 mm, area M ≥10 mm, area H (any size), poorly-defined borders, recurrent, immunosuppression, prior RT, PNI, and aggressive histology pattern (morpheaform, basosquamous, sclerosing, mixed infiltrative, and micronodular)

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10
Q

What are the high-risk factors for SCC?

A

Those listed above for BCC and rapidly growing, neurologic Sx, poorly differentiated, unfavorable histology (adenoid, adenosquamous, desmoplastic
or metaplastic), ≥2-mm thick or Clark level IV or V.

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11
Q

What genetic/inherited disorders are associated with skin cancer?

A

Phenylketonuria, Gorlin syndrome, xeroderma pigmentosa, and albinism have a genetic/inherited association with skin cancer.

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12
Q

What is the incidence of PNI and mets with BCC?

A

PNI: 1%
Mets: <0.1% (nodes or distant sites)

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13
Q

What is the incidence of PNI and mets with cutaneous SCC?

A

PNI: 2%–15%
Mets: nodes: 1%–30% (1% for grade 1, 10% for grade 3, 30% from burn associated SCC); distant: 2% (lung > liver > bones)

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14
Q

What are the major determinants of LN spread for cutaneous SCC?

A

Poor differentiation, size/depth (>3 cm/>4 mm), PNI/LVI, location (lips, scars/burns, ear), and recurrent lesions

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15
Q

What LN regions are most commonly involved in cutaneous SCC?

A

The (1) parotid and (2) upper cervical nodes are most commonly involved, mostly from H&N SCC.

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16
Q

Sun exposure at what stage of life correlates with BCC vs. SCC?

A

BCC: early in life/childhood
SCC: decade preceding Dx

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17
Q

What is Bowen Dz?

A

Bowen Dz is SCC in situ.

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18
Q

How often does actinic keratosis (AK) progress to invasive SCC?

A

AK (proliferation of atypical keratinocyte) lesions are on the continuum with SCC, and progress to invasive SCC at a rate of ∼0.6% per yr.

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19
Q

What is a Marjolin ulcer?

A

Marjolin ulcer is SCC arising in a burn scar.

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20
Q

What is the most common site for sebaceous carcinomas?

A

Ocular adnexa

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21
Q

What is the most common primary site in a pt with SCC of an intraparotid LN?

A

Cutaneous SCC of the H&N

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22
Q

What are the most common histologies of NMSC of the outer vs. the inner ear?

A

Pinna: BCC

Rest (canal, middle ear, mastoid): SCC (85%)

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23
Q

What are the high-risk features defining the primary tumor as T3 in the 8th edition AJCC for cutaneous SCC?

A

Large caliber PNI (≥0.1 mm or nerve beneath the dermis), deep invasion (>6 mm or beyond SQ fat), and minor bone erosion. Other high-risk features (poor differentiation, LVI, and anatomic location) no longer affect T stage.

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24
Q

What is the latest T staging according to the 8th edition of AJCC cancer staging manual (2017) for SCC/BCC?

A

There is no AJCC staging for SCC/BCC outside of the H&N. For cutaneous
SCC of the H&N (including BCC) the following T staging applies:
Tis: CIS
T1: <2 cm
T2: 2 cm or larger but smaller than 4 cm
T3: 4 cm or larger or minor bone erosion, deep invasion, or PNI
T4a: gross cortical bone or marrow invasion
T4b: skull base invasion and/or skull base foramen involvement

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25
Q

How is bone invasion staged per the 8th edition AJCC?

A

Minor bone erosion is stage T3, gross cortical bone or marrow invasion is stage T4a and skull base invasion is T4b.

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26
Q

How is PNI staged per the 8th edition AJCC?

A

Large caliber PNI (≥0.1 mm diameter or nerve beneath the dermis) or clinical or radiographic named–nerve involvement is T3, while skull base foramen involvement is T4b.

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27
Q

How is deep invasion staged per the 8th edition AJCC?

A

Deep invasion, defined as invasion beyond the SC fat or >6 mm from the granular layer, is T3.

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28
Q

What are 2 major changes in nodal staging for cutaneous cancers of the H&N in the 8th edition of AJCC?

A

Clinical (all pts) and pathologic (neck dissection pts) staging criteria and the addition of extranodal extension (ENE) as a major criteria of nodal staging.

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29
Q

What are the different clinical N-stages (cN) in the 8th AJCC for cutaneous carcinomas?

A 
N1: single, ipsi, ≤3 cm, ENE (–)
N2a: single, ipsi, 3–6 cm, ENE (–)
N2b: multiple, ipsi, ≤ 6 cm, ENE (–)
N2c: bilat or contralat LNs, ≤6 cm, ENE (–)
N3a: any LNs >6 cm, ENE (–)
N3b: any LN with ENE (+)
30
Q

What are the different pathologic N-stages (pN) in the 8th AJCC for cutaneous carcinomas?

A

N1: single, ipsi, ≤3 cm, ENE (–)
N2a: single, ipsi, ≤3 cm, ENE (+), or single, ipsi, 3–6 cm, ENE (–)
N2b: multiple, ipsi, ≤6 cm, ENE (–)
N2c: bilat or contralat LNs, ≤6 cm, ENE (–)
N3a: any LNs >6 cm, ENE (–)
N3b: single, ipsi >3 cm, ENE (+), or multiple, contralat or bilat LN, ENE (+)

31
Q

What defines stage groupings I, II, III, and IV?

A

Stage I: T1N0
Stage II: T2N0
Stage III: T3N0 or T1–3N1
Stage IV: N2–3, T4, or M1

32
Q

What anatomic sites are considered high-risk per the 8th edition of AJCC?

A

Lip (vermillion and hair-bearing), ear, temple, and cheek

33
Q

What cutaneous malignancy is often described as a “pearly papule”?

A

BCC

34
Q

How is cutaneous SCC often described clinically?

A

Flesh-toned and variably keratotic

35
Q

On H&P, what aspects should be the focus of the exam?

A

Hx: presence and distribution of paresthesias. Exam: Extent of tumor, CN exam, regional LN evaluation, audiometry/otoscopy for cancers of the ear, clinical ENE (+).

36
Q

When is it appropriate to obtain imaging, per NCCN?

A

Primary MRI with contrast if large nerve involvement suspected. If bone involvement is suspected, CT is recommended.

37
Q

Name 4 potential Tx options for NMSC.

A
  • Surgery (WLE, Mohs surgery, surgical excision with complete circumferential peripheral and deep margin assessment)
  • Curettage and electrodesiccation (C&E)
  • Superficial therapies
  • Primary RT
38
Q

Describe Mohs Sg.

A

In Mohs Sg, a superficial slice of skin is taken and then sectioned into quadrants. Tissue is examined microscopically in real time. Additional layers
are taken in the quadrants that show persistent Dz.

39
Q

When are C&E and superficial therapies appropriate for skin cancer?

A

Only low-risk NMSC. (Cannot evaluate histologic margins with these techniques.)

40
Q

List Tx considered superficial therapies.

A

Topical 5-FU, imiquimod, photodynamic therapy, and cryotherapy

41
Q

What % of BCC recurs if a margin is (+) at the time of resection?

A

BCC recurs in 30% for a (+) lat margin and >50% for a (+) deep margin.

42
Q

What % of SCC recurs if a margin is (+) at the time of resection?

A

Nearly 100% of SCCs recur if margin is (+).

43
Q

When is RT preferred as the primary Tx modality for skin cancer?

A

RT is preferred for pts >60 yo and who are not candidates for primary Sg. RT should be offered for lesions of the central face, lip, eyelid, and ears if Sg will
lead to inf cosmetic or functional outcomes.

44
Q

What is the best predictor of LC after definitive RT?

A

T stage is the best predictor for LC.

45
Q

What is the LC after definitive RT for BCC vs. SCC?

A

LC is similar for BCC and SCC with T1 lesions (95%) and lower for SCC than BCC if T2 (75%–85%) or T3 (50%).

46
Q

What should be done with a (+) margin resection?

A

Re-excise if possible, otherwise adj RT.

47
Q

What are 3 indications for adj RT to the primary site with skin cancer?

A

– (+) Margin
– Large nerve or extensive PNI
– Invasion of bone, cartilage, or skeletal muscle

48
Q

What are relative contraindications to RT in the Tx of skin cancers?

A

Relative contraindications to RT for skin cancer include areas prone to trauma (hands and feet, or beltline) or with poor blood supply (below knees/elbows), age <50 yrs, post-RT recurrence, Gorlin syndrome, CD4
count <200, high occupational sun exposure, and exposed area of bone/cartilage.

49
Q

When should adj nodal RT be considered after surgical resection?

A

Consider adj nodal RT after surgical resection for T3/T4 tumors, multiple +LNs, large (>3 cm) LNs, or close neck dissection margins.

50
Q

When should adj CRT be considered?

A

Consider for ENE (+), or neck dissection margins (+). Note: this is extrapolated from mucosal H&N cancers. There are no data demonstrating improved survival for cutaneous SCC of the skin.

51
Q

According to NCCN guidelines, what dose schemes are typically employed with the Tx of skin cancers <2 cm?

A

64 Gy in 32 fx over 6–6.4 wks
55 Gy in 20 fx over 4 wks
50 Gy in 15 fx over 3 wks
35 Gy in 5 fx over 5 days

52
Q

According to NCCN guidelines, what dose schemes are typically employed with the Tx of skin cancers >2 cm?

A

66 Gy in 33 fx over 6–6.6 wks

55 Gy in 20 fx over 4 wks

53
Q

According to NCCN guidelines, what dose schemes are typically employed for adj RT for skin cancers?

A

60 Gy in 30 fx over 6 wks

50 Gy in 20 fx over 4 wks

54
Q

What is the margin/dose modification if electrons are used? Why?

A

If electrons are used, add an additional 0.5-cm margin on the skin surface and use 10%–15% higher daily/total dose b/c of bowing in of isodose curves and a lower RBE (0.85–0.9) of electrons.

55
Q

What is the Rx point if orthovoltage (100–200 kV) RT is employed?

A

Dmax (90% of the IDL has to encompass the tumor). Do not use this if the lesion is >1 cm deep.

56
Q

When treating with electrons, how deep should the 90% IDL extend in relation to the lesion?

A

The IDL should extend at least 5–10 mm deeper than the deepest aspect of the lesion.

57
Q

When treating skin lesions with electrons, what rule is typically employed to choose the correct beam energy?

A

Electron energy (in MeV) should be >3 times the lesion depth (i.e., a 9-MeV beam is needed for a 2-cm lesion depth). Also, can use generality: Electron energy (in MeV)/4 is depth of 90% IDL. You must account for bolus in your depth calculation.

58
Q

What is the RT volume if a named nerve is involved by SCC?

A

The RT volume should include the nerve retrograde to the skull base. Consider IMRT/elective nodal RT.

59
Q

Where do basosquamous skin cancers occur? What is the Tx paradigm?

A

Basosquamous skin cancers occur on the face. These are treated like SCC, as they have similar rates of nodal mets.

60
Q

What kind of shields are used, and where should they be placed? Why?

A

Wax-covered lead shields are used b/c of backscattered electrons with low MeV beams. They are typically placed behind/downstream of tumor.

61
Q

How should fx size be tailored for skin cancer depending on the RT field size? On location of the tumor (face vs. extremity)?

A

In general, the larger the field, the smaller the fx size should be. For cosmetically sensitive areas like the face, smaller fx are typically used.

62
Q

If simple excision is performed for BCC, what are the min margins required?

A

Low risk: 4 mm

High risk: 10 mm

63
Q

What is the preferred RT modality for bone-invasive skin cancer? For cartilage invasion?

A

Megavoltage photons are the preferred Tx modality for bone invasion b/c of a more homogenous distribution compared to orthovoltage d/t the f-factor;
however, this is not so with cartilage invasion, as orthovoltage beams have little difference in distribution in cartilage regardless of energy.

64
Q

If treating recurrent BCC or morpheaform BCC, what type of margins should be used?

A

Because these tumors infiltrate more extensively, an extra 0.5–1-cm margin should be added on the surface.

65
Q

How should SCC of the mastoid be treated?

A

Mastoidectomy or temporal bone resection → PORT

66
Q

How long should a skin graft heal before starting RT?

A

6–8 wks of healing time is required after skin grafting before RT should be initiated.

67
Q

What are some toxicities expected after RT for skin cancer?

A

Telangiectasia, skin atrophy, changes in pigmentation, skin necrosis, fibrosis, osteonecrosis, chondritis, xerostomia, and hearing loss (if treating near the
inner ear).

68
Q

If cartilage is in the RT field, what should the dose/fx be kept below?

A

The dose should be kept at <3 Gy/fx to reduce the risk of cartilage necrosis.

69
Q

What is the incidence of skin necrosis after RT?

A

Skin necrosis occurs in 3% of pts (in 13% if fx size is >4–6 Gy).

70
Q

To what dose should middle ear/canal lesions be limited? Why?

A

Limit middle ear/canal lesions to 65–70 Gy b/c of higher rates (>10%) of osteoradionecrosis with doses >70 Gy.

71
Q

What can be done to reduce the toxicities to surrounding normal tissues from skin irradiation in the H&N region when using electrons?

A

To reduce toxicities to normal tissues, use lead shielding to block the lens, cornea, nasal septum, teeth, and gums. Use dental wax on the side from which the beam enters to absorb backscatter.

72
Q

Per the latest NCCN guidelines, what should be the f/u intervals for pts with non-melanoma skin cancers?

A

NCCN non-melanoma skin cancer f/u intervals:

  1. Complete skin exam for life at least once/yr
  2. For local Dz: H&P q3–12 mos for yrs 1–2, q6–12 mos for yrs 3–5, then annually
  3. For regional Dz: H&P q1–3 mos for yr 1, q2–4 mos for yr 2, q4–6 mos for yrs 3–5, then q6–12 mos for life

Radiation Oncology Factoids (44 decks)

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