INTRODUCTION
Skin cancer is the most common cancer in both men and women. Most skin cancers are either basal cell or squamous cell carcinoma. Basal cell carcinoma (BCC) develops from the basal layer of the epidermis while squamous cell carcinoma (SCC) develops from the keratinocytes in the epidermis.
75 percent of these are BCC. SCC and BCC are usually slow growing tumours that are easily treated. However, both can become large and invade surrounding tissues if left untreated. While BCCs rarely spread to other organs, SCCs can occasionally be aggressive, in some cases spreading to surrounding lymph nodes. Early detection and treatment can cure most tumours and can prevent these complications.
Melanoma, another type of skin cancer, is potentially more serious, although it is much less common than basal or squamous cell carcinoma. Melanoma is not dealt with in this section.
RISK FACTORS
Both environmental and genetic factors can increase a person’s risk of developing skin cancer. Chronic exposure to the ultraviolet (UV) radiation in sunlight is the most important risk factor.
Sun exposure over time is the most common cause of SCC. In contrast, intense intermittent sun exposure (eg, sunburn, childhood exposure) is the most important risk factor for both BCC and melanoma. Tanning beds cause skin changes like those seen with chronic sun damage and can increase the risk of both BCC and SCC.
Weakened immune system
People with a weakened immune system have a significantly increased risk of developing both BCC and SCC. Examples of people with a weakened immune system include those who have undergone organ transplantation, have required long-term oral steroids or other immunosuppressant medications, or have HIV.
The risk of developing SCC can be 65 to 250 times higher in people with a weakened immune system compared to the general population; the risk of BCC is increased approximately 10-fold.
SIGNS AND SYMPTOMS
Most skin cancers have an abnormal appearance. BCC and SCC can occur anywhere on the skin surface, but occur most frequently on the head, face and neck, back of the hands, forearms, and legs.
Abnormal skin features that are often seen with SCC and BCC include pink discoloration, scaling, inflammation (swelling), ulceration, bleeding, thickening, or crusting. These changes can often mimic a benign skin condition such as eczema or a “pimple” that just won’t heal. Anyone who notices these changes should make an appointment with a GP as soon as possible. Referral to a dermatologist (a physician who specializes in skin conditions) may be recommended.
DIAGNOSIS
Although, BCCs and SCCs have characteristic features, they can share features with many benign skin conditions. As a result, the preferred method to diagnose BCC or SCC is to have a biopsy. A piece of tissue is removed and examined under a microscope. If the abnormal area is small, the entire lesion may be removed during the biopsy. If the area is large, only a small piece of tissue is removed.
TREATMENT OPTIONS
The optimal treatment for BCC/SCC depends upon several factors, including the following:
- The size, type, and location of the cancer
- The chances that the cancer is aggressive or likely to recur
- The person’s preferences regarding the appearance of the area after treatment
- The physician’s training, experience, and preference
Treatment requires a balance between the risk of recurrence and the extent of treatment. High-risk skin cancers must be treated aggressively to reduce the risk of recurrence and/or spread to surrounding lymph nodes. Incompletely treated tumours can become large, spread to surrounding areas and, in the case of SCC, metastasize. Large or metastatic tumours can require extensive, potentially disfiguring, treatment(s). Furthermore, metastatic SCC can potentially pose a life-threatening risk.
On the other hand, there may be little-to-no benefit to treating a low-risk cancer too aggressively because there may be no cure rate advantage to such overly aggressive treatment. Furthermore, excessive treatment may also cause a poor cosmetic result.
Treatment options are divided among those recommended for low-risk and high-risk basal cell or squamous cell skin cancers. Treatment recommendations are often based upon the physician’s experience and preference.
Treatment options for low-risk cancers
Cryosurgery
Cryosurgery uses liquid nitrogen to freeze the tumour. Cryosurgery is fast, relatively inexpensive, requires minimal anaesthesia, and has few disadvantages. After treatment, there is usually some pain, moderate-to-severe swelling, blister formation, and oozing that resolve over days to weeks. The treated area subsequently peels off, leaving behind an ulcer that heals over four to six weeks; areas on the lower leg may take longer to heal. Long-term side effects can include permanent hair loss in the treated area and a round, flat whitened scar.
The five-year cure rates for basal and squamous cell carcinomas treated with cryosurgery are high, generally 90 percent or better for properly selected tumours. This procedure is generally performed by a dermatologist.
Curettage and electrodessication (electrosurgery)
Curettage and electrodessication (C&D) is a procedure that can be done in the clinic with local anaesthesia. The clinician uses an instrument (a curette) and an electric current to remove the abnormal area. C&D may be recommended for low-risk areas on the chest and arms or legs; it is not usually recommended for use on the face or head.
The advantages of C&D are that it is relatively inexpensive, easy to perform, and well tolerated by most people. One disadvantage is that the treated area usually develops a circular pink to white, sometimes raised scar. C&D cannot be used in people with an implanted medical device, such as a pacemaker or defibrillator. Similar to cryosurgery, C&D is usually performed by a dermatologist.
Some studies have reported cure rates of greater than 95 percent for carefully selected people. However, higher recurrence rates have been reported by others, and the actual recurrence rate may be closer to 10 to 20 percent.
Surgical removal
Surgical removal (excision) is effective for the treatment of both low- and high-risk basal and squamous cell cancers. This can be performed by a dermatologist or a plastic surgeon. Lesions in cosmetically sensitive areas should probably be removed by a plastic surgeon. Larger lesions may need skin grafts or muscle flaps and this should always be done by a plastic surgeon. Results of surgery are good with cure rates > 90%
Radiation therapy (RT)
Radiation therapy may be a good option for well-defined, primary SCCs, especially for older people and those who could not tolerate a surgical treatment. RT is not usually recommended for low-risk BCCs. See below.
Topical 5-FU
5-Fluorouracil (5-FU) works by inhibiting the growth of rapidly dividing cells, such as cancer cells. Topical 5-FU is available as a cream or solution that is applied to the skin twice per day for three to eight weeks; treatment for 10 or more weeks is sometimes required. In some cases, the provider will recommend covering the treated area with a dressing (eg, gauze or tape) to enhance absorption.
Side effects of 5-FU can be bothersome, potentially limiting its use. Common side effects include stinging, burning, pain, redness, swelling, and development of skin ulcers or infections. The skin near the eyes, lips, and nose can be especially sensitive. Pain can be significant, and sometimes requires a break in treatment (temporarily or permanently). Applying cold petroleum jelly or a steroid ointment may help to soothe irritation. It is important to avoid intense exposure to the sun during treatment.
The main advantage of 5-FU is that it usually provides a favourable cosmetic outcome. After treatment ends, healing generally occurs over two or more weeks, leaving reddened and darkened skin (which usually fades with time).
Studies of topical 5-FU have reported cure rates of 80 to 92 percent for certain low-risk tumours.
Treatment options for high-risk cancers
High-risk cancers are generally treated by surgically removing the abnormal area and a small amount of surrounding normal tissue. The advantage of surgical removal over the treatments described above is that with surgery, the tissue that is removed can be examined with a microscope, allowing a pathologist to determine if the edges (margins) of the tissue contain any cancer cells. To minimize the risk of cancer recurrence, it is important that the tissue margins be free of cancer cells.
There are two types of surgical treatment: traditional surgical excision and Mohs surgery.
Surgical excision
Surgical excision (removal) is effective for the treatment of both low- and high-risk basal and squamous cell cancers. Surgery can usually be performed in the clinic with local anesthesia. The treated area is usually stitched closed immediately following removal, and the skin sample that was removed is sent to a lab for analysis. Results of the analysis are usually available a week or more following the surgery. Most people heal within two weeks of surgery.
The cosmetic appearance of the area after surgical excision depends upon the location and size of the cancer. Cure rates also depend upon the size, type, and location of the cancer:
- BCCs of the chest, arms, and legs and small BCCs that are located on lower risk areas of the head and neck have five-year cure rates exceeding 95 percent after surgical excision.
- Five-year cure rates for primary and recurrent SCCs treated with surgical excision are reported to be 92 and 77 percent, respectively.
- For large BCCs (ie, greater than 15 mm in diameter), cure rates after surgical excision range from 77 to 88 percent.
- Cure rates for BCCs located on high-risk areas of the face and head (ie, lips, nose, paranasal or periocular region, ears, scalp) range from 57 to 82 percent after surgical excision.
Mohs surgery
Mohs micrographic surgery (MMS) is a specialized surgical technique performed by a dermatologist. The procedure is usually performed in the clinic with local anaesthesia. MMS can be used for treating BCCs located anywhere, including the ears, nose and paranasal structures, lips, eyelids, fingers and nail beds, and genitalia. MMS is the treatment of choice for many high-risk skin cancers because of the high cure rates it offers for such high-risk lesions.
The advantage of MMS compared to traditional surgical excision is that 100 percent of the tissue margins are examined at the time of the procedure, which usually means that less tissue is removed and the surgeon can be certain that the margins are clear, reducing the chances of recurrence and that a second surgery will be needed. Standard surgical excision, on the other hand, examines less than 1 percent of the tissue margins.
MMS has a high cure rate for all types of skin cancers. Reported five-year cure rates for primary and recurrent SCCs are about 97 and 90 to 94 percent, respectively. For primary and recurrent BCCs, MMS results in five-year cure rates of about 98 and 95 percent.
Radiation therapy
Radiation therapy (RT) involves the use of focused, high energy x-rays to destroy cancer cells. The x-rays are delivered from a machine (called a linear accelerator) that is outside of the patient. Treatments are brief and not painful. The damaging effect of radiation is cumulative, and a certain dose is required to stop the growth of cancer cells.
For very large lesions small radiation doses are administered for a few minutes each day, five days per week, for several weeks. For smaller lesions higher doses can be given each time, so many patients will need 9, 6, 3 or even just one treatment. A lot depends on the patient’s preference and travelling distance from the hospital. The cosmetic outcome is better with more fractions and there will be less immediate skin soreness.
Five year cure rates after treatment with RT are greater than 90 percent. However, BCCs that recur following RT may behave more aggressively than those recurring after surgical procedures, with higher rates of second recurrence and distant metastasis.
Short term side effects of RT include redness and swelling, scaling skin, development of ulcers, pain, and occasionally infection. Healing generally occurs within three to four weeks following the final treatment, although these symptoms may persist for months in severe cases. Long-term side effects can include permanent hair loss, skin changes (dry, shiny, thickened skin), skin breakdown, and others. RT can also increase the risk of developing a new skin cancer (related to continued sun exposure).
FOLLOW UP
Risk of a second skin cancer — People who develop either BCC or SCC are at increased risk of developing another skin cancer (BCC, SCC, or melanoma) in the future.
Basal cell carcinoma
Approximately 20 percent of people with one BCC develop another primary BCC within one year, and roughly 40 percent develop a new BCC within five years. This risk is higher in fair-skinned individuals and in people who have had more than one BCC in the past.
Squamous cell carcinoma
After a primary SCC, the estimated risk for developing another SCC is about 18 percent at three years and 30 percent at five years.
Clinician monitoring
After treatment for skin cancer, it is important to have regular follow up appointments to monitor for treatment complications and for new or recurrent skin cancers. Appointments may be recommended every three to six months for two years, and then once yearly.
Self-examination
In addition to visits with a healthcare provider, self-examination is recommended to identify any new skin lesion and monitor for changes in existing skin lesions. If a new or changing lesion is detected, contact your GP or dermatologist to determine if further evaluation is needed.
Prevention
Because of the increased risk of developing a subsequent skin cancer, anyone who has had skin cancer is advised to take precautions to reduce exposure to the sun.
Despite the fact that few people die as a result of BCC or SCC, these cancers can significantly change a person’s appearance by destroying skin, cartilage, and even bone. Untreated advanced lesions typically become open sores or ulcers, requiring complicated, expensive, and time-consuming wound care treatments. As a result, it is important to seek treatment as soon as possible if an area of the skin appears abnormal, will not heal, or changes over time.