Ch 82 SCC Flashcards
tumour type
- malignant, locally invasive skin tumor
- 2% to 15% of all cutaneous tumors in dogs
- 15% to 49% in cats
Etiology
mutation?
- actinic keratosis and SSC often coexist in dogs and cats
- risk factor: sun exposre
- Ultraviolet light–specific mutations in the p53 tumor suppressor gene in up to 80% in cats (40% in dogs)
- dogs is 8 years, cats is 12 years.
- White cats have a 13x higher risk
what is actitinic keratosis?
what is carcinoma in situ?
what is bowenoid in situ carcinoma?
- actinic keratosis = a precancerous solar-induced lesion
- carcinoma in situ (Tis) = preinvasive carcinoma confined to basement membrane
- bowenoid in situ: multicentric squamous cell carcinoma in situ in cats, multifocal, crusted plaques occurring anywhere on the body (pigmented as well as nonpigmented skin) and may contain melanin.
- 17% reported cases in cats progressed to invasive SCC
List the most common sites of SCC in dogs and in cats
forms?
Dogs: nail bed, scrotum, legs, anus
Cats: Pinnae, eyelids, temporal area, nasal planum
proliferative or erosive
tumor grade
- Histologically, usually classified as well, moderately, or poorly differentiated
- involving the facial skin > reported to be locally invasive but late to metastasize
- Tis and T1 less invasive = better tx success
- Aggressive surgery is best for stage T2 or higher
- Euthanasia usually dt extensive local progression or recurrence
Tis – preinvasive carcinoma
T0 – no tumour
T1 – tumour <2cm diameter, superficial or exophytic
T2 – tumour 2-5cm diameter or minimal invasion, irrespective of size
List some alternative treatment methods of SCC stage Tis or T1 (7)
- Cryotherapy - small, superficial lesions up to 5mm
- Plesiotherapy (strontium 90) -
- Radiation Therapy
- Photodynamic therapy - topical 5-aminolevulinic acis or systemic meta-tetrahydroxyphenylchlorin
- Electrochemotherapy - bleomycin
- Immunomodulatory therapy - Imiquimod, indirect antiviral and antitumour effects
- curretage
curettage and thermocauterization
- actinic keratosis and Tis and T1 of the nasal planum in 34 cats
- 94% disease-free at 1 year
Cryosurgery
- only for small superficial lesions of up to 5 mm
- 90 cats: 1- and 3-year DFI 84% and 81%, although many required multiple treatments
- Median survival of 682 days
- no histologic investigation of margins is possible
- Treatment outcome is strongly related to technique (freezing time) and tumor depth
strontium plesiotherapy
- 90Sr probe is held directly at the lesion.
- superficial form of radiation therapy
- rapid decrease in depth of the tissue, <10% of the surface dose reaching 3 mm of depth
- <3 mm diameter lesion, with 1- and 3-year control rates of 89% and 82%
external beam radiation
brachytherapy
- classified as orthovoltage or megavoltage based on the energy of the photon.
- Orthovoltage 150 to 500 kVp;
- Megavoltage >1 million electron volts. - Megavoltage radiation obtained from cobalt machines or linear accelerators.
- linear accelerators can allow radiation of deep seated tumours and have a skin sparing effect (orthovoltage at same dose would cause skin necrosis)
- linear accelerators can also deliver electron beam irradiation > excellent for surface tumours
brachytherapy
- a type of radiation therapy that involves placing radioactive seeds, wires, or capsules inside the body to treat cancer
- material emits gamma rays that destroy cancer cells
- The radiation dose is focused on the cancer cells, minimizing damage to nearby healthy cells
radiation
- nonresectable tumors, or marginal resected tumor beds
- high-dose brachytherapy: complete response in 36/58 (72%
- orthovoltage: 1 yr progression-free survival of 85% respectively, for stage T1. Higher stage tumors showed a poor response.
- electron beam: T2 and higher, 1yr disease-free-interval rates of 66% with 94% complete response.
photodynamic
- because photodynamic therapy uses visible light to excite photosensitized intracellular molecules, treatment efficacy decreases quickly with increasing lesion depth
- mainly T1: topical 5-aminolevulinic acid, 85% complete response, 18 cats second treatment after recurrence, and 45% of the cats were disease-free at a median 38 months
Chemotherapy and electrochemotherapy
- as sole treatment has not led to long-term responses
- Efficacy of adjuvant chemotherapy combined with surgery for invasive lesions needs further investigation
- Cyclooxygenase-2 (COX-2) is overexpressed in many epithelial tumors > inhibition (NSAIDs) has been proposed
- in 100% of canine and feline cutaneous
- oral SCC, no conclusions in cats
electrochemotherapy
- uses locally applied electrical field pulses to induce an increased uptake of a systemically administered chemotherapeutic
- bleomycin
- T2 and T3 : 81% had a complete response with median time to progression of 30 months.
de Castro Cunha 2023 – canine SCC treated with electrochemotherapy and surgery
VCO
sx+ECT → MST 884 days, sx alone 362 days, ECT alone not reached
- sx+ECT → 32% survival benefit vs sx alone
- side-effect = dehiscence 38.5%
- 34.6% nodal or distant metastasis → median DFI 394d vs no metastasis 945 days
- survival not influenced by staging
Immunomodulatory Therapy
Imiquimod
- immune response modifier with indirect antiviral and antitumor effects
- less favorable effects in 12 cats
- most partial response, (75%) developed new lesions, 2 cats showed systemic side effects.
surgery
- Infiltrative SCC of the nasal planum in dogs is generally more difficult to treat than in cats, and recurrence is likely
- no evidence-based criteria for the extent of surgical margins
nasal planum
- for invasive forms, radical resection recommended
- nasal planectomy
- aggressive rostral maxillectomy
- consider recon technqiues
eyelid
- lip-to-lid flap
- third eyelid lateral advancement combined with a local transposition cutaneous flap
angularis oris axial pattern skin flap can be used to cover rostral facial defects in dogs and cats
list reconstructive sx options for nasal planum
- lip-to-nose flap
- bilateral labial advancement flaps
- nasolabial island flap from the left labial tissue
- Labial Mucosal Inversion Technique
What are the recommended margins for SCC excision in dogs and cats?
Dogs: Atleast 2cm (more invasive than cats)
Cats: at least 5mm
prognosis
Description of outcome and adverse
events in 21 cats with locally
advanced nasal planum squamous
cell carcinoma treated with
electrochemotherapy
Ferrer-Jorda 2024
nasal planum SCC (T3N0M0 or T4N0M0)
overall response rate of 100%. Cats achieving a CR > DFI 182 days (range 128–327)
overall survival was 453 days for a
median follow-up of 341 days (range 191–989). Of the cats, 62% had grade 3 or 4 toxicities
Toxicities
reported can be severe in the short term; however, with
medical and/or surgical management, a complete resolution
without any sequelae is expected
Clinical features and outcome of dermal squamous cell carcinoma in 193 dogs (1987-2017)
Willcox 2019
VCO
- overall MST 1004 days, actinic change → longer survival (1359 vs 680 days)
- actinic change in 38% - presentation: younger, white coat colour, sun-exposed area- completeness of margins and surgical intervention not associated with survival
future prospective studies will be necessary to investigate whether adjunct therapies such as radiation or chemotherapy offer improvement in survival for dermal SCC in the dog
Clinical presentation and outcome in cats with aural squamous cell carcinoma: a review of 25 cases (2010-2021)
Alysha M McGrath 2022
MST: surgery+/-RT 168d vs other palliative (medical, RT, chemo, RT+chemo) 85d
- difference not statistically significant
Canine squamous cell carcinoma: Electrochemotherapy association with surgery and correlation with overall survival
Cunha 2023
VCO
- sx+ECT → MST 884 days, sx alone 362 days, ECT alone not reached
- sx+ECT → 32% survival benefit vs sx alone- side-effect of sx+ECT: dehiscence 38.5% - mild-moderate
- 34.6% nodal or distant metastasis → median DFI 394d vs no metastasis 945 days
- sun-exposed sites → more aggressive histologically but longer survival (MST 772 vs 199)
- survival not influenced by staging
