Gestational trophoblastic disease is a pregnancy-related condition that can occur in the uterus after conception. The term gestational trophoblastic disease (GTD) actually describes a group of rare diseases that begin in the tissues that are created after conception, i.e., the joining of egg and sperm in the uterus. GTD is so named because the disease begins in the trophoblast, the layer of cells that surrounds the newly formed embryo.
Some types of gestational trophoblastic disease can develop into cancer, which is why it’s important that they be diagnosed as early as possible. With prompt diagnosis and proper treatment, the various forms of this disease can often be cured.
Since GTD can recur after treatment, it’s important to have follow-up exams on a regular basis.
Patients with GTD are treated at our Gynecological Cancer Unit. You can also review the tabs at top of this page for information on GTD symptoms and risks, diagnosis, and treatment.
Types of Gestational Trophoblastic Disease
- Hydatidiform mole (also known as molar pregnancy): While this is the most common form of GTD, it’s still relatively rare, occurring in about 1 of every 1,500 pregnancies. The sperm and egg join, but instead of developing into a fetus, the resulting tissue resembles grape-like cysts. Hydatidiform moles are benign (non-cancerous) but have the potential to develop into cancer. There are two types: A complete hydatidiform mole develops when a sperm fertilizes an “empty” egg (one that contains no nucleus or DNA). All the genetic material comes from the father’s sperm. Therefore, there is no fetal tissue. About 1% to 3% of complete moles may develop into choriocarcinoma, a malignant form of GTD (read more about choricarcinoma below). A partial hydatidiform mole develops when two sperm fertilize a normal egg. These contain some fetal tissue, but no viable fetus is formed. Partial moles rarely develop into malignant GTD.
- Invasive mole (or chorioadenoma destruens): This is a malignant form of hydatidiform mole that enters the myometrium (muscular wall of the uterus) and may cause the uterus to bleed. In some cases, these invasive moles result after a complete mole has been scraped away from the uterus via surgery. When an invasive mole is not cured through treatment, it is often called persistent gestational trophoblastic disease.
- Choriocarcinoma: This is a malignant form of GTD that most often forms from a complete hydatidiform mole. It can also begin in tissues that remain in the uterus after a normal pregnancy, after a fetus is lost early in pregnancy, or after an abortion. Although rare – occurring only in one pregnancy out of 20,000 to 40,000 in the U.S. -- choriocarcinoma is a serious cancer that is likely to spread to organs beyond the uterus.
- Placental-site trophoblastic disease: This very rare type of malignant GTD starts in the uterus where the placenta was attached. Most of these tumors do not spread to other sites in the body, but some may penetrate the muscle layer of the uterus.
Early symptoms of GTD can be hard to determine because some of them mimic normal pregnancy symptoms. The most common symptom is vaginal bleeding and you should alert your physician immediately if this occurs. Other symptoms can include:
- Excessive abdominal swelling during pregnancy
- Abdominal pain
- Preeclampsia or toxemia
- Hyperthyroidism (overactivity of the thyroid gland)
When reading about risk factors for gestational trophoblastic disease, it’s imperative to keep in mind that having one or more risk factors doesn’t mean you will develop the disease.
Risk factors for GTD may include:
- Age: The risk of complete molar pregnancy is highest in women over age 40 and younger than 20. Age is less a factor for partial moles. Since gestational trophoblastic tumors result from an abnormal pregnancy, all women of childbearing age are at some risk for the disease.
- Previous molar pregnancy: Once a woman has had a hydatidiform mole, there is about a 1 in 60 chance that she will have another one. However, 98% of subsequent pregnancies will be normal.
- Pregnancy history: Women with no previous pregnancies may be at slightly higher risk
- Blood type: Women with blood type A or AB are at slightly higher risk than those with B or O
- Oral contraceptives: Women taking birth control pills may be at slightly higher risk
- Sexual history: Women who have had more than 10 sexual partners may have increased risk
In order to diagnose GTD, your doctor may perform the following tests:
- Blood tests: These generally include a CBC (complete blood count) as well as a test to measure for human chorionic gonadotropin (HCG) levels. The HCG levels are generally elevated during pregnancy, but abnormally high levels can indicate GTD.
- Ultrasound imaging: Use of ultrasound can rule out presence of a fetus, and can detect a mole as well as determine whether it has spread
- Additional imaging tests such as computed tomography (CT) scan, magnetic resonance imaging (MRI), and/or positron emission tomography (PET) scan may be used to determine whether GTD may have spread to other organs.
A process called staging is used to determine whether your cancer has spread and if so, to what extent. Staging is also used to determine your treatment options.
In GTD, staging includes a number of factors, not just tumor size or progression. These factors include your age, your prior pregnancies, the exact site of the cancer and number of growths, and whether any previous treatments have failed. This information is incorporated into the following stages to determine a prognosis and course of treatment.
- Stage I: The tumor has not spread outside the uterus
- Stage II: The cancer has spread outside the uterus but is limited to the genital structures (vagina or pelvis or both)
- Stage III: The cancer has spread to the lungs and may or may not also involve genital structures such as the vagina or vulva
- Stage IV: The cancer has spread distantly to other organs (such as the brain, liver, kidneys and/or gastrointestinal tract)
No matter what stage of gestational trophoblastic disease you have, treatment is available. Depending on the exact type, location and extent of the disease, the most common treatments are surgery and chemotherapy. At UC San Diego Health, you and your physician will work together to determine the best approach for your specific cancer.
- Dilation and curettage (D&C): In this procedure, a speculum is inserted into the vagina to allow access to the cervix and uterus. The cervix is gently dilated (stretched) and an instrument called a curette is used to remove tissue from the uterus. Hydatidiform moles and placental-site trophoblastic tumors are the only types of GTD that can be treated in this way.
- Hysterectomy: This surgical procedure to remove the entire uterus can be used to treat hydatidiform moles in women who do not want to have any more children. It is also the standard treatment for all women with placental-site trophoblastic tumors, though a D&C may be an option in some cases. The ovaries are generally not removed, although they may be.
The American Cancer Society notes that gestational trophoblastic disease is one of the few cancers that can almost always be cured by chemotherapy, no matter how advanced it is.
Chemotherapy uses anticancer drugs that are injected into a vein or given by mouth. These drugs enter the bloodstream and reach all areas of the body, making this treatment useful for cancers that have spread to distant organs (metastasized).
One of the unique aspects of gynecologic oncology is that specialists in this field are specially trained in chemotherapy for cancers of women’s reproductive organs. With their advanced knowledge, gynecologic oncologists can select the best drug combinations for each patient, manage complications and minimize side effects.
Note: Chemotherapy is sometimes used in combination with, or after, surgery to assure all cancer cells have been destroyed.