Skin Cancer and Melanoma
Skin cancer is the most common cancer diagnosed in Australia and New Zealand. Skin cancer occurs when skin cells change into abnormal cells and grow at an uncontrolled rate. There are two main types of skin cancer: melanoma and non-melanoma skin cancer. The number of melanoma and non-melanoma skin cancer cases is increasing worldwide.
Melanoma skin cancer arises from pigment-producing cells (melanocytes). Even though melanoma is associated with sun exposure, it can occur anywhere on the skin including non-sun exposed areas. Rarely it can occur on the skin lining the nose, mouth and genitals. When melanoma cancer cells grow a lesion on the skin appears and it is often (but not always) brown or black in colour.
Melanoma can become locally destructive and invade nearby structures. Common sites that melanoma can spread to include nearby lymph nodes (glands) or distantly to bone, lung, liver and brain. When melanoma spreads throughout the body it is referred to as metastatic or secondary disease.
Non-melanoma skin cancers do not arise from melanocytes but instead arise from other cells in the upper layers of the skin. The two most common types of non-melanoma skin cancer are squamous cell carcinoma and basal cell carcinoma. Although non-melanoma skin cancer can occur anywhere on the skin, it is most commonly found in areas of long-term sun exposure such as the head, face, neck, arms, legs and back of the hands.
Basal cell carcinomas (BCC) are usually localised but can become locally aggressive and invade nearby structures. Basal cell carcinomas rarely spread to lymph nodes or other sites in the body. Squamous cell carcinomas (SCC) are usually localised but can become locally aggressive and invade nearby structures. Some high-risk squamous cell carcinomas have the potential to spread to lymph nodes, nearby nerves or distant sites in the body.
What Are the Causes of Skin Cancer?
Studies have shown that there are certain factors, called risk factors that increase the chance of developing skin cancer.
The list below outlines some of the risk factors for melanoma and non-melanoma skin cancer.
Risk Factors for Melanoma
- Sun exposure and UV radiation: This is the main risk factor for melanoma. Melanomas are associated with intermittent (occasional) intense sun exposure. Blistering sunburns in adolescence or childhood are strongly linked with an increased risk of melanoma
- Age: Melanoma is more common with increasing age and is rare in children and adolescents.
- Gender: Melanoma is more common in males than females.
- Skin type: Individuals with naturally darker skin colour have a lower risk of developing melanoma. It is thought that greater penetration of UV light into the skin is associated with a higher risk of melanoma. Individuals with darker skin have more healthy pigment producing cells (melanocytes) that act to protect against UV exposure.
- Naevi (moles): Naevi are non-cancerous lesions that can be present at birth (congenital) or be acquired later in life. Most typical naevi are brown or black, 5mm in diameter or less, flat or raised and have a uniform colour and rounded shape. Naevi can transform into melanoma, but this risk is small. The lifetime risk for an individual naevus to transform into melanoma is approximately 0.009% for women and 0.03% for men. Atypical naevi are similar to naevi but have an abnormal appearance including a larger size, varying shades of colour and/or an irregular shape or border. The risk of melanoma transformation is higher for atypical naevi than for typical naevi. There is an association between the number of naevi and risk of melanoma. The number most cited for an increased risk of melanoma is 50-100 naevi per individual.
- Personal history of melanoma: Individuals who have one melanoma are at a higher risk than the average person of developing another melanoma.
- Family history: 10% of melanoma cases are familial i.e. run in families. These cases are often a combination of genetic (inherited) and environmental factors. Some familial cases of melanoma are linked with FAMMM syndrome (familial atypical multiple mole and melanoma syndrome) or AMS (atypical mole syndrome). Both of these inherited conditions are associated with a large number of atypical (abnormal) appearing naevi.
- Immunosuppression: Individuals with a weakened immune system are at increased risk of developing melanoma. The immune system may be compromised due to immune suppressing medications, an underlying medical condition or in individuals who have had organ transplants.
- Tanning beds: Evidence from a number of studies has shown that tanning beds are associated with an increased risk of melanoma.
- PUVA therapy: Patients with psoriasis and a number of other skin conditions may have treatment with ultraviolet radiation (PUVA). There have been rare cases of melanoma reported after PUVA therapy.
Risk Factors for Non-Melanoma Skin Cancers
- Sun exposure and UV radiation: This is the main risk factor for non-melanoma skin cancers. Individuals with fair skin, light coloured eyes, red hair and European ancestry are at the highest risk for solar damage due to the lack of pigment (melanin) in the skin to protect them from UV rays. Traditionally non-melanoma skin cancers were linked to chronic (long term) low levels of sun exposure, occurring over many years. However newer research also suggests that early sun exposure during childhood and intense sun exposure (sunburns) also increase the risk of non-melanoma skin cancers.
- Age: non-melanoma skin cancer is most common in older individuals.
- Immunosuppression: Individuals with a weakened immune system are at increased risk of developing non-melanoma skin cancers and the non-melanoma skin cancers can behave more aggressively. The immune system may be compromised due to immune suppressing medications, an underlying medical condition or in individuals who have had organ transplants.
- Tanning beds: There is increasing research supporting tanning beds increase the risk of non-melanoma skin cancers.
- PUVA therapy: Patients with psoriasis and a number of other skin conditions may have treatment with ultraviolet radiation (PUVA). There have been rare cases of squamous cell carcinoma reported after PUVA therapy.
- Drugs: There are a number of drugs that increase the sensitivity of the skin to UV radiation. This can increase the risk of non-melanoma skin cancers.
- Arsenic: This is a poisonous substance that can be found in contaminated drinking water, medications or seafood. Non-melanoma skin cancers can develop years after exposure.
- Ionising radiation: Therapeutic radiation is used to treat cancers and a number of non-cancerous conditions and is associated with a very small risk of developing a non-melanoma skin cancer. The risk is limited to the region of the body that receives therapeutic radiation and the time from exposure to developing a non-melanoma skin cancer is approximately 10- 20 years.
- Actinic keratosis: This skin condition appears as rough, bumpy or scaly spots and is caused by long-term sun damage. It most commonly occurs on the scalp, face, arms and ears. If untreated sometimes actinic keratosis can change into non-melanoma skin cancer.
- Genetic conditions: There are a number of rare inherited conditions that can increase the risk of non-melanoma skin cancer.
- Chronic ulcers or burns: These conditions can increase the risk of developing a squamous cell carcinoma (type of non-melanoma skin cancer).
- Smoking: Is associated with an increased risk of squamous cell carcinoma.
What Are the Symptoms of Skin Cancer?
Melanoma often looks like a mole or birthmark that is brown or black but is different in a number of ways.
Use the ABCDE system to remember the features that are concerning for melanoma:
- Asymmetry: One side of the lesion looks different to the other side
- Border: An uneven or jagged edge
- Colour: Not uniform in colour, different colours
- Diameter: It is larger than the eraser on the end of a pencil
- Evolution: It is changing in shape, size and/or colour
Melanomas can also bleed and become red or crusty. They may be itchy. Rarely melanomas are not brown or black.
If you think that you have a mole or birthmark that looks abnormal, show it to your doctor.
Non-Melanoma Skin Cancer
A non-melanoma skin cancer may have one or more of the following features:
- Crusty or scaly
- Open sore
- Pimple-like spot
If you are concerned about unusual skin changes, especially if they don’t heal by themselves, see your doctor.
What Are the Treatments for Skin Cancer?
The treatments available for skin cancer include topical therapies (treatment applied to the skin cancer), surgery, radiation therapy, chemotherapy, immunotherapy and/or targeted therapy.
The choice of treatment will depend on the type of skin cancer, the extent of the cancer and patient preference. A team of doctors including surgeons, dermatologists, radiation oncologists and medical oncologists will decide together on the best treatment for an individual patient.
Cryotherapy can be used for small (<2cm), well-defined, low risk non-melanoma skin cancers. It is a topical treatment that destroys cancer cells by a freezing and thawing process. Liquid nitrogen is applied to the tumour and a small area of surrounding tissue. Cryotherapy is not used in the treatment of melanoma
Topical 5-FU can be used to treat the precursor lesions of non-melanoma skin cancer or very low risk, superficial non-melanoma skin cancers. The treatment involves the application of a topical form of chemotherapy (5-fluorouracil) up to twice a day for 4-8 weeks to the area of skin involved. Temporary inflammatory reactions are common with the treatment. Topical 5-FU is not used in the treatment of melanoma.
Photodynamic therapy can be used to treat the precursor lesions of non-melanoma skin cancer and occasionally very low risk, superficial non-melanoma skin cancers. This treatment involves the application of a cream on the skin that sensitises the pre-cancer cells or cancer cells to a selected light wavelength. An ultraviolet light is then focused on the localised area and this process is repeated for a number of sessions. Photodynamic therapy is not used in the treatment of melanoma.
Imiquimod is a topical therapy for the area of involved skin that can be used to treat the precursor lesions of non-melanoma skin cancer and low risk, superficial non-melanoma skin cancers. It kills cancer cells by stimulating the local immune environment. The treatment involves daily application for 6-16 weeks and temporary inflammatory reactions are common. Imiquimod is rarely used for superficial melanomas if surgery is not possible.
Surgery is used in the management of melanoma and non-melanoma skin cancers. Surgery is the most important curative treatment for melanoma when the melanoma is localised.
The aim of surgery is to remove the melanoma with a section of healthy tissue around the tumour (known as a margin). During surgery the lymph nodes may be sampled depending on the risk factors of the melanoma. This may involve the removal of one or two lymph nodes (a sentinel lymph node biopsy) and/or the removal of all of the lymph nodes in a specific region (lymph node dissection).
Many non-melanoma skin cancers are treated and cured with surgery. This involves removing the cancer with a margin of normal tissue around the cancer. The lymph nodes nearby may be sampled or removed if there is a suspicion that the lymph nodes contain cancer cells.
Radiation therapy is important in the management of melanoma and non-melanoma skin cancers. In the setting of melanoma, it can be used after surgery as “adjuvant” treatment (additional treatment used to reduce the risk of the cancer recurring). It is a localised treatment that aims to kill any ‘microscopic’ cancer cells or tumour deposits that may remain after surgery.
Radiation therapy can be used to target to the area in which the melanoma on the skin was surgically removed to reduce the risk of recurrence. Radiation therapy can also be used to target the area in which the lymph nodes were removed if the lymph nodes contained cancer cells.
The aim of radiation treatment in this setting is to reduce the risk of the melanoma recurring in the area in which the lymph nodes were removed. The recommendation for adjuvant radiation therapy will be based on a number of factors including the specifics of the cancer under the microscope, other treatments available and investigations aimed at imaging the rest of the body.
In the treatment of non-melanoma skin cancer radiation therapy can be used as the sole management (without the need for surgery) or it can be used in selected cases after surgery as “adjuvant” treatment to reduce the risk of the cancer recurring. For small, low risk non-melanoma skin cancers radiation therapy provides a high likelihood of cure with results similar to surgery.
For larger, high risk non-melanoma skin cancers surgery is usually recommended and radiation therapy may be used after surgery for the best chance of cure. If lymph nodes are removed during surgery and are found to contain cancer cells, radiation therapy may be recommended to where the lymph nodes were removed to reduce the risk of the cancer recurring.
External beam radiation therapy (EBRT) and superficial radiation therapy (SXRT) are the most common types of radiation therapy used in skin cancer treatment.
Radiation therapy is usually delivered once a day and the total length of treatment can range from a few treatments to 6 weeks of treatment. Another type of radiation therapy that is less commonly used to treat skin cancer is brachytherapy.
Systemic therapy refers to the use of medications (tablets or injections) that include chemotherapy, immunotherapy and/or biological therapy, the latter also known as ‘targeted’ therapy. In the setting of skin cancer, systemic therapy is mainly used if the melanoma or non-melanoma skin cancer has spread to lymph nodes or distant sites in the body. The choice of systemic therapy depends on the type of skin cancer and additional information including special tests done on the cancer tissue.
• Immmunotherapy can be used for the treatment of metastatic melanoma and non-melanoma skin cancers. Immune therapies are aimed at stimulating a patient’s own immune system to fight the melanoma.
• Targeted drug therapies can be used for the treatment of metastatic melanoma if the melanoma tests positive for a specific mutation. If a patient’s melanoma tests positive for a BRAF mutation, an oral medication that blocks the BRAF pathway in the melanoma cells can be used. If a patient’s melanoma tests positive for a c-kit mutation, an oral medication that blocks the c-kit pathway in the melanoma cells can be used.
• Chemotherapy can be used for melanoma and non-melanoma skin cancer if the cancer has spread to distant sites in the body such as the lung, bone and liver (metastatic disease). The type of chemotherapy will depend on the type of skin cancer and other factors specific to a patient’s medical history.
What Are the Side Effects of Radiation Therapy?
The potential side effects of radiation treatment are divided into acute side effects (can occur during and shortly after radiation treatment) and late effects (occur months to years after radiation treatment). The potential side effects depend on the site of radiation. Your Radiation Oncologist will explain the potential side effects of your treatment in detail.
Early Side effects (during/soon after treatment)
General – Fatigue is common in the second half of treatment and is very variable between patients. Fatigue may persist for several weeks after treatment.
Local –The acute side effects to the skin will be discussed here. However additional acute side effects may be relevant to you depending on what part of the body is being treated, the type of radiation being used and what tissues or organs are in the path of the radiation therapy.
Your Radiation Oncologist will explain what additional side effects are relevant to you based on what area of the body is being treated. For example, radiation to the skin on the face, scalp, groin, etc will have different tissues and organs nearby and therefore other possible acute side effects are specific to the area treated.
Skin reddening and irritation– The skin can become increasingly red and itchy during treatment. The peak of the skin reaction occurs 7-14 days after the treatment is completed. Skin blistering and peeling can also occur. Occasionally there may discomfort but strong pain medications are rarely required.
Loss of hair (alopecia)– Hair may fall out during or after radiation treatment. If hair loss occurs, it may be temporary or permanent.
What can help reduce acute side effects to the skin?
Resting as needed can help with fatigue. During treatment your Radiation Oncology team will provide advice on creams and dressings based on the degree of your skin reaction. Special creams can be used for itchy skin and if pain or discomfort occurs, pain medications can be prescribed. It is advised to keep the treatment area protected from the wind and sun. For sun protection during and immediately after treatment do not apply sunscreen to the skin receiving radiation. Instead wear a wide brimmed hat or loose-fitting protective clothing over the skin for sun protection.
Late or long-term side effects (Side effects well after treatment)
Late side effects may occur a few months to years after treatment. They are more uncommon than early side effects. Depending on the problem it may occur once and then go or may be more persistent over the long term or may come and go over time. The late side effects to the skin will be discussed here. However additional late side effects may be relevant to you depending on what part of the body is being treated, the type of radiation being used and what tissues or organs are beneath the skin being treated.
Your Radiation Oncologist will explain what additional late side effects are relevant to you based on what area of the body is being treated. For example, radiation to the skin on the face, scalp, groin, etc will have different tissues and organs nearby and therefore other possible late side effects are specific to the area treated.
Skin and underneath soft tissue changes – If permanent skin changes develop after treatment, they are mainly cosmetic and can be minimised. Occasionally the skin can be a little lighter or darker in the region that has received radiation. Tiny blood vessels under the skin may be come swollen and more prominent (telangiectasias) over time. Skin may become thinner and more easily injured with time. The tissues under the skin can become firmer and feel tighter.
Skin ulceration – This is a rare side effect of radiation treatment to the skin (usually less than 1%).
Radiation induced cancers – Second cancers occurring as a result of radiation therapy are an extremely rare side effect of radiation therapy, occurring more than 10-15 years after radiation therapy.
What can be done to minimise and treat late side effects?
To reduce the severity of late skin effects it is important to follow the detailed advice from your Radiation Oncologists & radiation therapy nursing staff regarding topical creams, dressings (if necessary) and general skin care.
Even after the acute skin reaction has resolved, the skin that has received radiation will always be more sensitive to the sun and more susceptible to slower healing. It is important to wear sunscreen with SPF 30 or higher to any previously treated skin if it is exposed while in the sun. In addition to sunscreen, a wide brimmed hat or protective clothing is a good idea. Makeup can be used to conceal skin paleness & telangiectasia. Massage and physiotherapy treatments can help soft tissue firmness. In the rare instance that a non-healing skin ulcer develops after radiation treatment, surgery can be performed to repair the skin.
The best person to speak to you about radiation therapy is a Radiation Oncologist. Your general practitioner, dermatologist or surgeon can refer you to a Radiation Oncologist close to you to discuss whether radiation therapy is appropriate for you.
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