Quiz 3 Flashcards
3 main types of skin cancer
Basal cell
Squamous cell/cutaneous squamous cell
Malignant melanoma
Slower form of skin cancer, not very aggressive and doesn’t tend to metastasize
Most prevalent cancer in humans
If untreated, can create damage
Can appear anywhere on body; common on head, neck, and other sun-exposed areas
Younger with sunburns at greater risk
1-2 million cases yearly, RT when cosmesis is ideal (face)
Treatment technique selected depends on factors such as previous methods of treatment if any, location on body, risk of recurrence and metastasis, and the volume of tissue invasion
Surgery performed to remove nonmelanoma skin cancers from areas where cosmesis is not a factor, scarring is acceptable, and patient wants to expedite results
Basal cell (BCC)
Faster growing and more dangerous than basal but not as much as melanoma; tends to metastasize
Can appear anywhere on body; common on head, neck, and other sun-exposed areas
Younger with sunburns at greater risk
1-2 million cases yearly, RT when cosmesis is ideal (face)
Treatment technique selected depends on factors such as previous methods of treatment if any, location on body, risk of recurrence and metastasis, and the volume of tissue invasion
Surgery performed to remove nonmelanoma skin cancers from areas where cosmesis is not a factor, scarring is acceptable, and patient wants to expedite results
Squamous cell carcinoma (SCC)
Cutaneous squamous cell
Basal to squamous cell ratio in men to women
5:1 men, 10:1 women
One of the most lethal forms of skin cancer and very common
Most common sites: women’s legs and men’s trunk and face, can also occur in any melanin sites such as eyes, eyelids, mucosa, oral cavity, and anus
Key to treatment is treating it before it metastasizes; palliation; cure usually limited to surgical resection
Chemo and immunotherapy to prevent metastasis or if it’s already metastasized
RT limited to palliation for metastatic dose; radioresistant but can be used adjuvant to surgery or as treatment if surgery is not an option
Superficial, electron, or total skin electron irradiation (TSEI)
Malignant melanoma
Skin cancer that usually appear as firm, non-tender, pink-red lesion; nodular
Distinction has climbed and now has its own staging system
Rare, high rate of recurrence and morbidity greater than melanoma
In sun-exposed sites
Chemo and RT combination treatment if too expensive for surgery
Merkel cell
Stanford technique: treatment with 12 fields or 6 dual fields; extend SSD to 300-400 cm to include entire body
Using electrons, patient exposed
Mycosis fungoides
Total skin electron irradiation (TSEI)
Metastatic melanoma TSEI dose
36 Gy in 9 weeks, 1 Gy per fraction, 4 days a week
5 types of surgical treatments for basal and squamous cell cancers
Often the original excisional biopsy contains all of the tumor with acceptable margins Mohs surgery Electrodesiccation Cryosurgery Photodynamic therapy
Often used to treat BCC and early SCC; with local anesthesia, the cancer is scooped out with a curette and the destruction of any remaining tumor cells and process of bleeding is carried out with a probe emitting a high frequency electric current to destroy tissue and cauterize blood vessels
Electrodesiccation
Surgery with best success rate for BCC and SCC
Mohs sugery
Instrument in the form of a loop, ring, or scoop with sharpened edges
Curette
Treatment of early nonmelanoma skin lesions with liquid nitrogen or carbon dioxide applied to a lesion, lowering its temperature and thereby freezing and killing abnormal cells
Cryosurgery
Photosensitizing agent is injected into the body and absorbed by all cells; light from a laser is directed on the tumor area and causes a reaction within the cells that contain the photosensitizing agent that destroys the cells
Photodynamic therapy
4 factors that affect the choice between the use of electrons and kV x-rays for the treatment of skin cancer
Comes down to what is in clinic, may not have superficial/orthovoltage machine; electrons come from linac
Size of treatment volume, depth of lesion
Underlying anatomical structures, use electrons if critical structure under lesion
Physician preference
_________ have poor small dose field and don’t get good dose coverage
kV x-ray photons allow the target volume to be covered with a smaller field size than with that of a field producing similar effects near the skin surface through the use of electrons because of electron field physical properties
________ get good average to high dose, sharper beam edge
Electrons, photons
Surface dose less than ___-___% is generally unacceptable; ___-___% isodose lines encompassing what is being treated (always try to get 100% isodose line to lesion)
90-95%
With photons regardless of energy, Dmax always at ________; high energy electrons = ____ surface dose, low energy electrons = ____ surface dose
Surface; high, low
Deep tissue dose ______ for photons than electrons
Electrons have rapid falloff, kV x-rays penetrate much deeper and affect a greater volume of underlying tissue
Use electrons when critical structures beneath lesion
Higher
No significant difference exists between bone and soft tissue doses for electrons
Absorbed dose is _______ in bone and cartilage than in soft tissue with the use of kV x-rays; photoelectric effect dependant on Z^3/E^3
Higher
1 cm of bone = ____ cm of tissue; 1 cm of lung = ____ cm of tissue because of density
- 65 cm
0. 25 cm
Excellent or good cosmesis in ___% of patients treated with kV x-rays, compared with ___% of patients treated with electrons
95%
80%
Cosmetic results were superior for patients in whom less than ___% of the dose was delivered with bolus; with electrons bolus _______ surface dose and _______ cosmesis
50%
Increases
Decreases
Depth at which the tangent plotted through the steepest section of the electron depth dose curve intersects with the extrapolation line of the brems tail
Range of electrons (10%), where they stop/dissipate; electrons/2
Practical range (RP)
