Phar 653 Pharmacotherapeutics III
Spring 2002
DERMATOLOGY: Skin Cancer Screening & Prevention

Nina Han Cheigh, Pharm.D.
Clinical Assistant Professor
Coordinator, Academic Programs
University of Illinois College of Pharmacy
ncheigh@uic.edu

Goal:

To familiarize the student with general sun precaution information, and to be able to recognize those at higher risk for skin cancers.

Objectives

Identify different rays of the sun
Discuss skin and its distinguishable characteristics
Understand the damaging and beneficial effects of sun on the skin
Identify common skin cancer
Define Sun Protection Factor.
Identify chemical versus physical sunscreens
Provide proper information on skin protection

The Solar Spectrum

Sun spectrum includes: cosmic, gamma, Xrays, ultraviolet, visible light, infrared, microvwaves, radiowaves
Visible light: 400 - 800 nm (40%)
Infrared is above visible light: 800 - 10,000 nm (50%)
Ultraviolet is below visible light (10%)

Ultraviolet light

Ultraviolet A (UVA)
-320-400 nm
-Most abundant component of ultraviolet radiation (95%)
-Causes “tanning reactions”; rarely burns
-Penetrates skin deeper than UVB
-Contributes to chronic sun damage
-Considered much more harmful
Ultraviolet B (UVB)
-290-320 nm

-Consists of only 5% of ultraviolet rays reaching earth

-Causes “sunburn” reactions (see slide 2,3)
-Major spectrum associated with skin cancer development
Ultraviolet C (UVC)
-<290 nm
-Typically does not reach the earth
-From artificial sources

The Skin in the Sun

1) Skin consists of epidermis, dermis, and subcutaneous tissue

2) Aside from hair, there are three “barriers” in the skin that protect from the sun naturally

A) “horny” layer-keratinocyte proliferation

B) urocanic acid-secreted in perspiration; natural “filter”

C) surface lipids-absorb UV

MELANIN (pigment)

1) Definition: pigments contained in intracellular organelles known as melnosomes

2) Local at dermal-epidermal junction

3) 2 grades of pigment:

4) eumelanin (dark, causes dark tan)

5) phaeomelanin (light, causes light tan)

6) The darker the skin, the more resistant to damage by sunlight.

Skin Types
Type I          Always burns, never tans
Type II          Usually burn, tan less than average
Type III          Sometimes mild burn, tan average
Type IV          Tan more than average; minimal burns
Type V          Tans easily; rarely burns          (Brown skin)
Type VI          Tans profusely; never burns (Dark brown skin)

Beneficial effects of Sun on the Skin

1) Calorific effect: infrared rays causing vasodilation, which results in temperature regulation via perspiration

2) Antiarchitic effect: vitamin D synthesis

3) Anti-depressive effect: relationship of sun and mood

Damaging effects of Sun on the Skin

1) SUNTAN: ultraviolet radiation that stimulates melanocytes to produce more melanin

2) SUNBURN: inflammatory reactions involving histamine, kinins, prostaglandins

a) 1st degree: pink erythema

b) 2nd degree: bright red erythema

c) 3rd degree: swollen, painful, cyanic erythema leading to exfoliation

d) 4th degree: skin detachment, associated sometimes with fevers, headache, etc.

3) Phototoxicity & Photoallergy

4) Premature aging and wrinkling

5) Skin Cancers

SKIN CANCER
http://www.skincarephysicians.com/melanomanet/index.html

1) Incidence: skin cancer is the most common type of cancer (33%)

2) 90% of skin cancer is due to chronic, unprotected skin exposure

3) Incidence is rising from 1/1500 in 1935, to 1/75 projected for 2000 (FIGURE 1) (NYU Melanoma Cooperative Group)

FIGURE 1- Guttman, Cheryl. Are Derms Winning the Battle Against Melanoma? Dermatology Times 1997;S3.

Types of Skin Cancers

1) Actinic Keratosis:

-small, scaly “precancerous” lesions

2) Basal Cell Carcinomas (BCC)

-most common type of skin cancer

-lesions are solitary or multiple non-healing

-highly treatable and rarely metastasizes

-risk factors: cumulative sun exposure, family history, tanning booths

3) Squamous Cell Carcinomas (SCC)

-less common

-lesions are slowing growing; can also affect mucous membranes

-metastasis rate: 0.3-3.5% skin; 3-29% mucous

-risk factors: similar to that of BCC

4) Malignant Melanoma (MM)

-less common than SCC

-far deadlier

-incidence: whites>hispanics>blacks/asians

Risk Factors

1) Skin lesions-see ABCD’s of melanoma

2) Cumulative sun exposure-# sunburns, tanning booth use over life

3) Skin Types-type I> risk than others

4) Family History

ABCD’s of MELANOMA

http://www.afraidtoask.com/skinCA/abcde.html

-Asymmetry

-Border irregularity

-Color

-Diameter

How to prevent such damages?

1) Photoprotective measures

2) Sunscreens

3) Limit sun exposure and get skin examinations

4) Perform self-examinations (FIGURE 2)

FIGURE 2-Patient Information. American Academy of Dermatology. 1993.

Photoprotective measures

1) Clothing

2) Hats (brim should be 6 inches around), umbrellas

3) color and type of material -darker colors absorb UV rays while lighter will reflect

4) Time of day: avoid 11am to 3pm (highest UV intensity)

SUNSCREENS

1) Classified as “drugs”

2) Prevents: sunburn, skin damage, freckling, uneven colorations

3) http://telemedicine.org/Sundam/SunDam2.4.2.html
http://www.sunprecautions.com/

What is SPF?

Definition of SPF (sun protection factor): ratio of least amount of UVB required to produce a minimal erythematous (red) reactions through sunscreen to the amount of energy required to produce the same erythema without sunscreen.
Does greater than SPF 15 have a greater effect? YES-SPF 15 typically blocks ~93% harmful rays. SPF that is greater has a minimal incremental benefit (ie. SPF30 may block 96%), but this small benefit may be important in those high risk patients.

CHEMICAL sunscreens

1) These act as filters for UV penetration

2) Reflect mostly UVB rays, and not UVA

3) Colorless and cosmetically acceptable

4) Common ingredients:

-PABA (para-aminobenzoic acid)

-Anthranilates

-Benzophenones

-Cinnamates

-Salicylates

-Avobenzone (Parsol 1789)***

newest ingredient which is a chemical sunscreen, yet blocks UVA rays. The only chemical sunscreen to do so.

PHYSICAL sunscreens

1) Opaque and reflects / scatters light

2) Reflects both UVA and UVB

3) Sometimes difficult to apply

4) Common ingredients:

5) Zinc Oxide

6) Titanium Dioxide

7) Iron Oxide

8) Kaolin

9) Talc

Recommended Doses

· Depends on skin type (TABLE 1)

· Typically, routine use of SPF 15 is recommended. Typically, SPF 15 blocks approx. 93% of UV rays. An increase to SPF 30 may block up to 96%. Someone who has many risks (type I skin, family history, history of many burns, etc) may benefit from the small incremental increase of using SPF 30, 45, etc.

· Outdoor activities would vary the doses and vehicles

-Oily skin=gels may be better

-For swimming=waterproof products, but reapply frequently

TABLE 1- Moulds, M. Apply Yourself: How to use sunscreen. Sun & Skin News 1999;16(2):3.

Adverse effects of sunscreens

1) Contact dermatitis-common with chemical sunscreens; recommend physical sunscreens for these patients

2) Staining

3) Stinging / drying

4) Folliculitis

Common sun myths

· “suntan preparations increase tan”

· shade prevents sunburn

· no sunburns on cloudy days

no effect from altitude, snow, water, and sand

Primary Prevention Recommendations

1) Limit sun exposure

-avoid tanning facilities

-wear protective clothing

-wear sunscreen

2) American Cancer Society Recommendations:

-Monthly self-exams and 3-year physician exams for those 20-30 years