Ductal carcinoma in situ, DCIS, is a curable form of non-invasive breast cancer where the cancer cells do not leave the milk ducts.
Hormonal therapy may be part of your treatment plan if you have DCIS. Hormonal therapy is used to decrease the risk of cancer coming back in the breast that had the DCIS. Hormonal therapy is given for 5 years.
This blog post focuses on hormonal therapy for ductal carcinoma in situ.
What is Ductal Carcinoma in Situ?
Ductal carcinoma, also called DCIS, is non-invasive breast cancer. In situ means “in its original place.”
You will be told that you have DCIS when abnormal cancer cells are found in the lining of the breast duct but have not broken through the walls of the duct.
Picture adapted from: https://medicalxpress.com/news/2014-08-effective-treatment-dcis-vital-reduction.html
The first picture is a normal breast milk duct. The middle picture shows DCIS. Notice how the cancer cells (in red) are only inside the milk ducts. The last picture is when DCIS becomes invasive breast cancer. The cancer cells are spreading outside of the milk ducts.
About 1 in 4 new breast cancers will be DCIS. Most of these breast cancers can be cured with surgery alone or with surgery and radiation therapy.
If you have the type of surgery that removes just the abnormal cells and keeps the rest of your breast, there is a chance that breast cancer can happen again in the breast. Hormonal therapy can decrease that chance.
It is important to know that hormonal therapy has not been shown to improve survival in people who have had DCIS. That’s because DCIS is not invasive cancer and does not spread to other parts of the body.
Who Should Have Hormonal Therapy after DCIS?
We tend to consider giving every person who has had DCIS hormonal therapy.
If you have had removal of the entire breast (a mastectomy), hormonal therapy is not likely to help you. Although hormonal therapy can decrease the risk of cancer in the other breast, the risk of cancer in the other breast is low, and the benefit of hormonal therapy is minimal.
If you have had breast-conserving surgery (such as a lumpectomy) and are not going to had radiation therapy, hormonal therapy is an important part of your treatment. Hormonal therapy in people who are going to hold off on radiation therapy have a slightly higher risk of the DCIS returning, but hormonal therapy can offset the lack of radiation therapy.
What if I Don’t Want to Take Hormonal Therapy?
If you do not want to take hormonal therapy after DCIS, you are not increasing your risk of death from breast cancer. For example, you may have side effects that interfere with your quality of life. Stopping hormonal therapy is an option you can discuss with your medical team. If you want to delay hormonal therapy because you are hoping to get pregnant, discuss this with your medical team (see below).
How is Hormonal Therapy Given in DCIS?
Hormonal therapy is given after surgery or surgery and radiation therapy for DCIS.
In addition to these other treatments, you may also be offered hormonal therapy for 5 years or more to reduce the chance of developing another DCIS tumor or invasive breast cancer.
Hormonal drugs appear to be most helpful in people whose DCIS had the estrogen receptor. The cancer cells that have the estrogen receptor respond to estrogen in your body.
Hormonal therapy works by decreasing the amount of estrogen that can get to any developing cancer cells.
Types of Hormonal Therapy
There are two main types of hormonal therapy used for people who have had DCIS. One is called tamoxifen, which is a selective estrogen receptor modulator, or SERM. The second is a group of medications called aromatase inhibitors. The three aromatase inhibitors that are prescribed to people with breast cancer are anastrozole, letrozole, and exemestane.
Tamoxifen is used for pre-menopausal and post-menopausal people. In other words, for people with ovaries that are still functioning, tamoxifen is a good option. Tamoxifen is also a good option if your ovaries have been removed or if they are no longer functioning (after menopause).
Aromatase inhibitors (anastrozole, letrozole, or exemestane) are an option only in people who do not have ovarian function.
Tamoxifen (brand name Nolvadex) works by blocking estrogen receptors. It does not lower your estrogen levels.
Tamoxifen is taken by mouth once a day. For DCIS, tamoxifen 20 mg is taken by mouth once a day every day for 5 years. It can be taken with or without food.
Tamoxifen side effects include hot flashes, night sweats, leg cramps, or joint pain. Tamoxifen can also cause vaginal discharge or dryness, irregular periods, loss of libido, and sleep problems. Hair thinning is not common but is upsetting to many people.
Rare side effects are cancer of the uterus and blood clots.
It is important to let your medical team know which side effects you are having.
The aromatase inhibitors work by blocking the production of estrogen in tissues in your body, such as the adrenal glands (which sit on top of your kidneys) and fat tissue. Unlike tamoxifen, these medicines do lower the amount of estrogen in your body.
The aromatase inhibitor that has been used in studies with people who have had DCIS is anastrozole. However, all three aromatase inhibitors -anastrozole, letrozole, and exemestane – are considered equally effective.
Side effects of the aromatase inhibitors include joint and muscle pain, vaginal dryness, loss of libido, urinary problems, hot flashes, and night sweats.
Over time, the aromatase inhibitors can cause thinning of the bone that may be a problem in people who already have bone thinning. Calcium and vitamin D supplements may help protect your bone from thinning.
One advantage of the aromatase inhibitors is that they do not cause an increase in the risk of blood clots.
Anastrozole (brand name Arimidex)
Anastrozole 1 mg is taken by mouth once a day every day for 5 years.
Letrozole (brand name Femara)
Letrozole 2.5 mg a day is taken by mouth every day for 5 years.
Exemestane (brand name Aromasin)
Exemestane 25 mg a day is taken by mouth every day for 5 years. This medication should be taken after a meal.
It is important to let your medical team know which side effects you are having.
Which Hormonal Therapy Drug Should I Take?
Both types of hormonal therapy are effective. Which medicine is right for you depends on whether or not you have functioning ovaries, whether or not you are at risk for blood clots, and which side effects you experience.
Work with your medical team to discuss the pros and cons of both types of hormonal therapy.
Fertility & Contraception
People with functioning ovaries and a uterus are still able to become pregnant. People with functioning testicles are able to get another person pregnant. If either of these situations describes you, and you are still interested in having children after your DCIS therapy is completed, then you should discuss your options with a fertility specialist before starting DCIS treatment.
Hormonal drugs can cause harm to an unborn baby. If you have functioning ovaries, you will likely have to take a pregnancy test to make sure you are not pregnant.
If you have functioning ovaries or functioning testicles, then you and your partner should explore contraception options to avoid pregnancy. All oral contraceptives have hormones and should be avoided when taking hormonal drugs for DCIS. Non-hormonal contraception, such as a condom or copper IUD, should be used during DCIS treatment.
In general, we recommend avoiding pregnancy until you have been off hormonal therapy for 2 months.
- National Cancer Institute Dictionary of Cancer Terms. cancer.gov. https://www.cancer.gov/publications/dictionaries/cancer-terms. Published February 2, 2011. Accessed November 10, 2020.
- Breastcancer.org. Signs and Symptoms of DCIS. breastcancer.org. https://www.breastcancer.org/symptoms/types/dcis/symptoms. Modified February 18, 2016. Accessed November 10, 2020.
- The American Cancer Society Medical and Editorial Content Team. Ductal Carcinoma In Situ (DCIS). Cancer.org. https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/types-of-breast-cancer/dcis.html. Revised September 20, 2019. Accessed November 10, 2020.
- The American Cancer Society Medical and Editorial Content Team. ACS Recommendationsfor the Early Detection of Breast Cancer. Cancer.org. https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/american-cancer-society-recommendations-for-the-early-detection-of-breast-cancer.html. Revised March 5, 2020. Accessed November 10, 2020.
- Gradishar WJ, Anderson BO, Abraham J, et al. National Comprehensive Cancer Network Guidelines Breast Cancer. Version 5.2020 From the National Comprehensive Cancer Network; July 2020. https://www.nccn.org/professionals/physician_gls/pdf/breast.pdf. Accessed November 11, 2020.
- Lexi-drugs online [database on the Internet]. Hudson (OH): Lexicomp, Inc.; 2016 [cited 10 Nov 2020]. Available from: http://online.lexi.com. Subscription required to view.