Although it is commonly referred to as a gene mutation, ROS1+ cancer actually occurs when the ROS1 gene has been altered -- entire sections of its DNA have been swapped with another gene. This is called a gene fusion or gene rearrangement.
When the ROS1 gene fuses or joins with another gene it activates the ROS1 gene in a way that causes uncontrolled cell growth and cancer. ROS1 is tested for and found primarily in patients who have lung cancer; however, the ROS1 biomarker has been found in many other cancers, including melanoma, sarcoma, breast and brain cancer.
When ROS1 fuses or joins with another gene and causes lung cancer, a patient is said to be ROS1-positive.
How common is ROS1+ cancer?
ROS1+ cancer is not a common cancer. It occurs in approximately 2% of non-small cell lung cancers, and occurs with similar frequency in cancers that start in many other organs such as:
Brain: ROS1+ cancer was first discovered in glioblastoma
Blood vessels (angiosarcoma)
Skin (melanoma)
Bile ducts (cholangiocarcinoma)
Liver
Breast
Pancreas
Ovaries
However, testing for ROS1+ cancer is standard of care only for non-small cell lung cancer, so people with other types of cancer often are not tested for ROS1 gene fusions. We estimate that less than 1000 cases of ROS1+ lung cancer are diagnosed in the USA annually.
How do you get ROS1+ cancer?
Essentially, getting ROS1+ cancer is just bad luck. We don’t know what causes the ROS1 gene to fuse with another gene.
ROS1+ cancer is not known to be associated with any particular risk factor or behavior -- people who get ROS1+ cancer tend to be younger than the average cancer patient, and generally healthy (except for the cancer).
It’s likely the gene fusion arose when a cell made a random mistake in copying DNA while duplicating itself (which happens more often than we realize).
How do you know if you have ROS1+ cancer?
Not all lung cancers are the same. In order to know if your lung cancer is ROS1 positive, the tumor tissue, fluid from a pleural effusion, or a blood sample is sent for biomarker testing.
Biomarker testing is a way to look for genes, proteins, and other substances (called biomarkers or tumor markers) that can provide information about cancer. Biomarker testing includes testing tumor tissue for abnormalities in its DNA and levels of specific proteins in the tumor.
An error in the ROS1 gene is one biomarker that physicians look for in non-small cell lung cancer.
Can ROS1+ Cancer be Passed on From Parents to Children?
No. ROS1+ cancer cannot be passed from parents to children. ROS1+ cancer is due to what is known as a "somatic" gene alteration--it is damage that occurred to genes in individual cells during a person's life. Somatic gene alterations like ROS1+ cancer appear only in the cancer cells, and cannot be passed from parent to child. The cause of somatic mutations is unknown -- it could be completely random or may result from exposure to carcinogens.
How Can You Learn More?
ROS1+ cancer is so rare that oncologists can be forgiven for not knowing everything about it when they give you your diagnosis. Even very large cancer centers may have encountered only a few ROS1+ patients. That means that you may need to partner with your oncologist to stay on top of information about what’s needed and what’s new.
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