Having had a precancerous condition or a cancer in the past and certain treatments can increase your risk for cancer.
Precancerous conditions
Some precancerous conditions have the potential to develop into cancer over time if they are not treated. Sometimes people with precancerous conditions are checked regularly, so they can be treated quickly if the cell changes become more severe and turn into cancer.
Past history of cancer
Sometimes people can get more than one cancer during their lifetime. About 10% of people with cancer can get another different type of cancer (a second primary cancer) that is not the result of a metastasis or recurrence. Whether another primary cancer will occur can be affected by:
- chance
- the first (initial) type of cancer
- the effect of treatment for the initial cancer
- Some cancer treatments such as chemotherapy or radiation therapy can increase the risk of a second primary cancer developing.
- having risk factors that are linked to several types of cancers, such as smoking and cancer of the lung, mouth, or throat
- having a genetic predisposition to certain cancers, such as breast and ovarian cancer
Cancer treatment
Children and adults who have been treated with radiation therapy and certain types of chemotherapy have an increased risk of developing a second cancer. While these treatments can be life-saving, they alsocan:
- cause cell damage and mutations
- weaken the immune system so that it may not be able to recognize and destroy cancer cells
Only a very small percentage of people develop a second cancer because of receiving cancer treatments. The highest risk of developing a second cancer occurs in people who have received both chemotherapy and radiation therapy, because of cell damage and mutations that can occur. Most second cancers occur many years after the initial treatment.
Radiation therapy
Radiation therapy appears to increase the risk of a second solid tumour in the radiated area. Radiation exposure has also been linked to leukemia. The risk of cancer after radiation treatment depends on:
- the dose of radiation given (the risk can increase if higher doses are given)
- the area treated (some organs are more sensitive to the effects of radiation than others)
- if and how much of the bone marrow was exposed to radiation
- the age of the person at the time of treatment
Chemotherapy
Certain types of chemotherapy drugs can increase the risk of a second cancer. These include:
- alkylating drugs – an example is cyclophosphamide (Cytoxan, Procytox)
- anthracyclines – an example is doxorubicin (Adriamycin)
- cisplatin (Platinol AQ)
- topoisomerase II inhibitors – an example is etoposide (Vepesid, VP-16)
These drugs appear to increase the risk of cancers such as leukemia and lymphoma. The risk increases when higher doses are used and when chemotherapy is given for longer periods of time.
Hormonal therapy
Some hormonal therapies used to treat cancer in women may also increase their risk of developing a different cancer. For example, women who take tamoxifen (Nolvadex, Tamofen) for breast cancer have an increased risk of uterine (endometrial) cancer if they still have their uterus.
Benefits of treatment outweigh the risks
Even though there is a risk for a second cancer, chemotherapy and radiation therapy treatments are still the best tools doctors have to treat cancer. The benefit of treating a cancer outweighs the risk of developing a second cancer in the future.
Researchers continue to try to find better ways to treat cancer, such as creating more targeted approaches to therapy or seeing if using a lower dose of chemotherapy drugs or radiation is as effective as a higher one.