Treatments for cSCC

Question 1

What are common treatments for cSCC?

Answer 1

Surgical excision
- remission rate > 90%
Cryotherapy w liquid N2
- for low risk SCC

Question 2

How does MOHS (micrographically controlled surgery) work?

Answer 2

• small, thin layers removed in sections
• only used in cases of high risk or where anatomic and functional preservation of area is needed

Question 3

What are some topical therapies for treating cSCC?

Answer 3

• 5-Fluorouracil (5-FU)
• Imiquimod
• Pembrolizumab

Question 4

5-FU mechanisms of action

Answer 4

• interferes w cell proliferation
• causes cell death
• disrupts DNA and RNA synthesis (inhibits enzymes involved w DNA synthesis)
• is an “antimetabolite”
• incorporated into DNA and RNA (interferes w function)

Question 5

What is the specific cellular mechanism of action of 5-FU

Answer 5

• taken up by transporter proteins
• converted into FUTP or FdUTP
• interfere w DNA and RNA synthesis
• interfere w cell proliferation and viability

Question 6

How does 5-FU inhibit TS (Thymidylate synthase)?

Answer 6

• 5-FU converted into FdUMP
• binds to TS
• inhibits TS (therefore inhibiting production of dTMP)
• decrease in dTMP = decrease in dTTP (dTTP is needed for DNA synthesis)
• sTTP depletion also causes imbalance in many other deoxynucleotides (disrupts DNA synthesis and repair = DNA damage and cell death)

Question 7

What does Imiquimod do?

Answer 7

• stimulates immune system which then eliminates tumour
  used for epidermal pre-cancerous lesions and carcinomas

Question 8

What does Pembrolizumab do?

Answer 8

• blocks ability of tumour cells to evade immune system
• binds to and blocks PD1 receptors on immune cells, activating them to kill cancer cells
• used for cSCC that cannot be treated surgically
• IV administration