Prognosis and survival for melanoma skin cancer
If you have melanoma skin cancer, you may have questions about your prognosis. A prognosis is the doctor’s best estimate of how cancer will affect someone and how it will respond to treatment. Prognosis and survival depend on many factors. Only a doctor familiar with your medical history, the type and stage of the cancer, the treatments chosen and the response to treatment can put all of this information together with survival statistics to arrive at a prognosis.
A prognostic factor is an aspect of the cancer or a characteristic of the person (such as sex) that the doctor will consider when making a prognosis. A predictive factor influences how a cancer will respond to a certain treatment. Prognostic and predictive factors are often discussed together. They both play a part in deciding on a treatment plan and a prognosis.
The following are prognostic and predictive factors for melanoma skin cancer.
Thickness of the tumour
The thickness of the primary tumour is an important prognostic factor. It helps predict the risk that the cancer will spread. The thicker the tumour, the poorer the prognosis. Melanoma skin cancer that is less than 1 mm thick has a low risk of spreading to other parts of the body. Melanoma skin cancer that is thicker than 4 mm has a higher risk of spreading to other parts of the body and coming back (recurring) after treatment.
Ulceration is when there is broken skin with an open wound. When there is ulceration of the primary tumour, it has a less favourable prognosis than a tumour without ulceration. The presence of ulceration increases the risk that the cancer will spread to others parts of the body and come back after treatment.
Mitotic rate measures how fast cancer cells are dividing and growing. It is the number of cells that divide (mitosis) in a certain amount of cancer tissue. An increased mitotic rate is linked with a poor prognosis.
Location of cancer on the skin
Having melanoma skin cancer on the arms or legs (extremities) has a better prognosis than having melanoma skin cancer on the central part of the body (trunk), head or neck. Melanoma skin cancer on the palms of the hands or soles of the feet also has a poorer prognosis compared to other locations.
Women with melanoma skin cancer tend to have a better prognosis than men with melanoma skin cancer. This may be because women more commonly develop melanomas that involve the extremities, while men more commonly develop melanomas that involve the trunk, head or neck.
People younger than 35 have a greater risk of melanoma skin cancer spreading to nearby lymph nodes. But overall, people who are older have a poorer prognosis.
Nodular melanoma skin cancer has a poor prognosis because it grows down into the skin (vertical growth pattern) and tends to be thick when diagnosed.
Lymph nodes with cancer
If the cancer has spread to nearby lymph nodes, the prognosis is poorer. The larger the number of lymph nodes that contain cancer, the poorer the prognosis. People with cancer in 4 or more nearby lymph nodes have a poorer prognosis than people with 1 to 3 cancerous lymph nodes.
If enlarged lymph nodes can be felt (are palpable) or found during imaging tests, the prognosis is poorer than when there is only a small amount of cancer (micrometastases) in the lymph nodes.
Melanoma skin cancer that has spread to other parts of the body (called distant metastases), such as the lung, the liver or the brain, has a poor prognosis. This prognosis is poorer than cancer that has spread to other places on the skin far from where it started, tissue under the skin (subcutaneous tissue) or distant lymph nodes.
For metastatic melanoma, a high lactate dehydrogenase (LDH) level in the blood has a poorer prognosis than when the LDH level is normal.