Prognosis and survival for eye cancer

A prognosis is the doctor’s best estimate of how cancer will affect you and how it will respond to treatment. Survival is the percentage of people with a disease who are alive at some point in time after their diagnosis. Prognosis and survival depend on many factors.

The doctor will look at certain aspects of the cancer as well as characteristics of the person. These are called prognostic factors. The doctor will also look at predictive factors, which influence how a cancer will respond to a certain treatment and how likely it is that the cancer will come back after treatment.

Prognostic and predictive factors are often discussed together. They both play a part in deciding on a prognosis and a treatment plan just for you. Only a doctor familiar with your medical history, the stage, type and other features 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 and chances of survival.

The following are prognostic factors for eye cancer.

The stage of eye cancer is the most important prognostic factor. People with eye cancer that is diagnosed at an early stage have a better prognosis than those with advanced eye cancer.

People with eye cancer that has grown outside of the eyeball (called extraocular extension) have a less favourable prognosis than people with cancer that is only in the eyeball. Those with eye cancer that has spread to other parts of the body (called distant metastases) also have a poorer prognosis.

Tumour characteristics (including size, thickness and margins) are important factors in predicting prognosis for melanoma of the eye. People with tumours that are smaller and thinner usually have a better prognosis than those with larger and thicker tumours. The edges of the tumour that separate the cancer cells from the non-cancerous tissue is called the margin. Eye cancers that have defined margins have a better prognosis than those with margins that are difficult to determine (called diffuse margins).

The location of the tumour, or where the cancer started in the eye, is an important factor in predicting prognosis.

Melanoma that starts in the iris (a type of uveal melanoma) typically has a better prognosis than melanomas that start in other parts of the eye.

Lymphoma of the eye in the conjunctiva (a type of orbital adnexal lymphoma) generally has a better prognosis than lymphoma that starts in other parts of the eye.

Cell type describes how the cells of the eye cancer look and behave. There are 3 main types of cells in posterior uveal melanoma (a type of melanoma of the eye that starts in the choroid or ciliary body):

• spindle cells (can be spindle A or spindle B), which are long and thin
• epithelioid cells, which are round
• intermediate cells, which look like epithelioid cells but are smaller

Some cancers will have only a single cell type and others will have a mix of these cell types. People with melanoma of the eye that is made up of spindle cells have a more favourable prognosis than people with melanoma of the eye that is made up of epithelioid cells or a mixture of 2 or more cell types.

Your healthcare team will do genetic tests on any tissue removed during a biopsy or surgery to treat eye cancer. These tests look for changes to genes and chromosomes in the cancer cells.

Melanomas with any of the following chromosomal changes tend to grow larger and are more likely to metastasize. They have a poorer prognosis than melanomas that don’t have these changes.

• missing chromosome 3 (called monosomy 3)
• extra copy of part of chromosome 8 (called gain of 8q)
• missing a part of chromosome 6 (called loss of 6q)
• missing a part of chromosome 8 (called loss of 8p)
• missing a part of chromosome 1 (called loss of 1p)

People who have an extra copy of part of chromosome 6 (called gain of 6p) often have a better prognosis.

Melanoma of the eye that has mutations (changes) to the BAP1 gene usually has a poorer prognosis than melanoma that doesn’t have mutations.

People who have the following gene mutations tend to have a better prognosis than those without them:

• splicing factor 3B subunit 1 (SF3B1) mutations
• eukaryotic translation initiation factor 1A X-linked (EIF1AX) mutations

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. The gene profile can then be used to classify melanoma of the eye into 2 groups (called classes) – class 1 and class 2. People with class 1 melanoma have fewer genetic changes that are associated with poorer prognosis. They usually have a better prognosis than people with class 2 melanoma.

Mitotic activity describes the amount of cell division (a process called mitosis) that is occurring at a certain time. The more cells that are in the process of dividing, the higher the mitotic activity is. Cancers that have higher mitotic activity tend to grow more quickly.

Mitotic count is the number of cells that are in the process of dividing when seen under a microscope. Eye cancers that have a lower mitotic count have lower mitotic activity and have a better prognosis than those with a higher mitotic count.

Ki-67 is an antigen that occurs normally in dividing cells. It can be used as a tumour marker. Eye cancers that have a higher level of Ki-67 have higher mitotic activity and have a poorer prognosis than those with a lower level of Ki-67.

Younger people usually have a better prognosis than older people.