Prognosis and survival for eye cancer
If you have eye 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, stage and characteristics of your 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 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 factors for eye cancer.
Stage is an important prognostic factor for eye cancer. A lower stage eye cancer has a better prognosis.
Location of the cancer
The location of the eye cancer helps to predict a prognosis.
A melanoma of the iris often has a better prognosis than a melanoma of the choroid or ciliary body. This is because melanomas of the iris can be seen from the outside of the eye so they are often found at an early stage when they are small. Melanoma of the ciliary body or choroid is typically diagnosed at a more advanced stage so these tumours have a poorer prognosis. Melanoma that starts to grow in other parts of the eye and spreads (metastasizes) to the ciliary body also has a poorer prognosis.
Lymphoma of the eye
Lymphoma that develops outside of the eyeball (called extraocular lymphoma) generally has a better prognosis than lymphoma that develops inside the eyeball (intraocular lymphoma).
Cancer spread outside of the eye
Cancer that has spread outside of the eye has a less favourable prognosis than cancer that hasn’t spread outside of the eye.
Spindle cell intraocular melanoma has a better prognosis than epithelioid cell intraocular melanoma or mixed cell intraocular melanoma (this is a mix of both types of cells). Most melanomas of the iris are the spindle cell type so they tend to have a favourable prognosis.
Mitotic count is the number of cells that are in the process of dividing (called mitosis) when seen under a microscope. Tumours that have higher mitotic counts tend to grow more quickly than those with lower mitotic counts. Eye cancer that has a low mitotic count has a better prognosis than an eye cancer with a higher mitotic count.
Generally, a smaller eye tumour has a better prognosis than a larger tumour. Smaller intraocular melanomas have a lower chance of spreading than larger tumours.
People with small to medium-sized intraocular melanoma are also more likely to be able to see with the affected eye after treatment compared to people with larger tumours.
If any tissue is removed from the tumour during a biopsy or surgery, genetic tests may be used to look for changes to the chromosomes. Some changes to chromosomes are linked to a higher risk of the cancer spreading and a poorer prognosis. This includes:
- a missing chromosome 3 (called monosomy 3)
- loss of part of chromosome 6 (6q)
- an extra copy of part of chromosome 8 (8q)
People with intraocular melanoma who have lost all or part of one of the copies of chromosome 3 tend to have tumours that are larger, have spread to the ciliary body and have epithelioid cells.
People who have an extra part of chromosome 6, called a 6p gain, tend to have a better prognosis.
People whose tumours have certain gene mutations or too many copies (called overexpression) of certain genes tend to have a poorer outcome. The following genetic changes are linked to a worse prognosis in people with intraocular melanoma:
- too many copies of the DDEF1 gene on chromosome 8
- BAP1 mutations
Gene expression profiling to predict risk of cancer spreading
Gene expression profiling is a way for doctors to analyze many genes at the same time to see which are turned on and which are turned off. Doctors have found that gene expression profiling can help predict the risk of cancer spreading in people with uveal melanoma, a type of intraocular melanoma. This test helps to classify the cancer into 2 groups (called classes). Class 1 uveal melanoma has a better prognosis than class 2 uveal melanoma.
Ki-67 tumour marker
A tumour marker is a naturally occurring substance in the body. An abnormal amount of a tumour marker can indicate the presence of cancer or help predict prognosis. Ki-67 is a tumour marker that shows cells that are dividing. People with intraocular melanoma whose tumours have Ki-67 have a risk of the cancer spreading to other parts of the body.
Younger people have a better prognosis than older people.
What’s the lifetime risk of getting cancer?
The latest Canadian Cancer Statistics report shows about half of Canadians are expected to be diagnosed with cancer in their lifetime.