BASAL CELL CARCINOMA
Basal Cell Carcinoma (BCC) is one of the most common types of skin cancer. About 8 out of 10 skin cancers are basal cell carcinoma. According to www.skincancer.org, an estimated 3.6 million cases are diagnosed annually in the U.S. alone.
Basal cell cancer begins in the basal cell found at the bottom of the epidermis which is the outermost layer of the skin. This is where new skin cells are produced as old ones die off. Cancer develops from an abnormal overgrowth of the basal cells repopulating the epidermis which are normally located at the base. This is caused by errors or DNA damage occurring from exposure to ultraviolet (UV) radiation from the sun or indoor tanning devices, or from indirect DNA mutations through reactive oxygen species and immune suppression triggering changes in the basal cells.
Basal cell carcinoma often appears as a slightly transparent bump on the skin. However, they can also look like open sores, red patches, pink growths, shiny bumps, scars, or growths with slightly elevated, rolled edges with a central indentation, yet they can still take other forms. It can occur anywhere on the body, but these commonly develop in sun-exposed areas, especially the face, head, and neck. Other common sites are the scalp, shoulders, and back. They tend to grow slowly and it is very rare for basal cell cancer to spread to other parts of the body. However if left untreated, BCC can become locally aggressive, and grow wide and deep into the skin destroying skin, tissue, and even the bone.
There are a number of factors increasing the risk of basal cell carcinoma namely:
• Chronic sun exposure either from natural sunlight or artificial sunlight such as from tanning beds. This risk factor is greater if living in a sunny or high-altitude location, resulting to further exposure to UV radiation. Severe sunburn accelerates skin aging which then also increases risk.
• Radiation therapy. Current or previous radiation therapies to treat acne or other skin conditions may also trigger basal cell carcinoma at the treatment sites.
• Fair-skinned people have less protective pigment melanin hence the risk is deemed higher among people who freckle, burn easily, do not tan, or tan poorly. Also included here are people with very light skin, red or blond hair, or blue, green, or other light-colored eyes.
• Increasing age. Basal cell carcinoma often takes decades to develop thus the majority of BCC occurs in older adults. However, this does not exclude younger adults with the trend nowadays of skin cancer becoming more common in people in their 20s and 30s.
• Past medical or family history of skin cancer. There is a higher risk of developing basal cell carcinoma in those who’ve had it before or if there is any family member with a history of skin cancer.
• Immunosuppressive treatments. All immunosuppressant therapies, pharmacological or physical, can subdue or even impair the skin immune system network which significantly increases the risk for skin cancer.
• Exposure to arsenic which is a toxic metal naturally found in the environment increases the risk of BCC and other cancers. Everyone has some exposure to arsenic but some people may have higher exposure if they have drunk contaminated underground water or have an industrial job involving producing or using arsenic.
• Genetic syndromes. Certain rare genetic diseases increase the risk of BCC namely xeroderma pigmentosum, basal cell nevus syndrome also known as Gorlin syndrome, Bazex-Dupre-Christol syndrome, and Rombo syndrome.
Different types of treatment are available on an outpatient basis, using local anesthetics with minimal pain. Options include the following:
• Surgical excision. Using a scalpel, the entire cancerous lesionsare cut out along with a safety margin of surrounding tissue and sent to a laboratory for pathological analysis. For small BCCs which have not spread, excision is frequently the only treatment required with cure rates above 95% in most body areas.
• Mohs micrographic surgery. This surgery is performed in one visit but in stages. The surgeon removes the cancer layer by layer while examining each layer under a microscope until no more cancer cells remain. Mohs surgery is the gold standard and most effective technique for removing BCCs with minimal harm to healthy tissues with the highest cure rate up to 99% on the first BCC treatment. This method is more complex and time-consuming than other treatments but is recommended for high-risk recurrence BCCs.
• Curettage and electrodessication (C and E). With a curette, the BCC is scraped off and heat or chemical agent is used to destroy the remaining cancer cells subsequently stopping the bleeding and sealing off the wound. C and E treatment is one option for treating small BCCs with less likely recurrence. This procedure has cure rates of close to 95% similar to surgical excision.
• Radiation therapy. This treatment utilizes low-energy X-ray beams to destroy the tumor, without the need for an anesthetic or incision. Radiation is primarily used for BCCs that are hard to treat with surgery and in people with poor health for whom surgery is not recommended. However, there is no guarantee that all of the cancer cells have been destroyed resulting in an effectiveness of only 90%. Moreover, radiation therapy may require several treatments over a few weeks or daily for a specified time and is sometimes used after surgery when there is an increased risk that cancer will return.
• Cryotherapy. Cryosurgery therapy involves the application of liquid nitrogen to freeze and destroy the tumor. This treatment will result in blistering of the lesion and/or become crusted and then fall off, allowing healthy tissues to emerge. This is effective for small and superficial BCCs and may also be used after scraping the surface with a curette. This is particularly beneficial for those with bleeding disorders or those with hypersensitivity to anesthesia. The efficacy rate ranges from 85% to 90% as it may miss deeper portions of the tumor, and the scarring at the site makes recurrence difficult to detect.
• Photodynamic therapy (PDT). This therapy involves the application of photosensitizing drugs and light to the BCC. A physician applies a topical agent making the lesion sensitive to light or injecting the agent into the tumor. Once absorbed into the BCC, a light that destroys the skin cancer cells is shone on the area. After the procedure, there is a strict precaution to avoid sunlight for at least 48 hours, as UV exposure will activate the medication and cause severe sunburn. PDT is an option for treating superficial BCC but is not recommended for invasive cases.
• Topical medications. Topical immunotherapy. Topical chemotherapy. These are prescription medications in the form of creams or gels applied directly to the affected areas to treat superficial BCCs with minimal risk of scarring. These medications like Imiquimod activates the immune system to attack cancer cells while 5-FU, a topical chemotherapy agent, directly kills off cancerous cells. Cure rates are ranging from 80-90%.
• Targeted therapy with a signal transduction inhibitor. Vismodegib or sonidegib can shrink or slow down the growth of cancer cells. These are treatment options for BCCs which have spread to other parts of the body and cannot be cured by surgery or radiation therapy alone.
Recurrence of basal cell carcinoma depends on the histological subtype and type of treatment approach. The recurrence rate is low at less than 5% but increases among those treated with incomplete excisions. Assessing the histological type preoperatively through biopsy and an ultrasound evaluation assessing the exact size and depth are recommended for the success of appropriate treatment. Regular check-ups in specialized clinics are also very important for early diagnosis and treatment for first-time BCC and monitoring risks of recurrence.