Uterus Cancer PET Scan

Positron Emission Tomography is an important procedure in uterine cancer treatment. Uterine cancer is one of the leading causes of cancer death in women and the American Cancer Society estimates that 50,840 new cases of uterus cancer will be diagnosed in the United States of America during 2004. There are three types of uterine cancer: cervical cancer, uterine sarcoma, and endometrial cancer. Cervical cancer is treated and diagnosed in a different manner from uterine sarcoma and endometrial cancer as it effects the lower portion of the uterus, the cervix. Endometrial cancer is the most common form of cancer affecting female reproductive organs. Although the death rate of uterine cancer has decline in recent years due to improved forms of early detection and enhanced medical treatment, it is still one of the leading causes of cancer-related death in women. The American Cancer Society predicts that in 2004, uterine cancer will cause 10,990 deaths.

About Uterine Cancer

Uterine cancer is one of the most common causes of cancer death among women and it is estimated by the American Cancer Society that 58,840 new cases of uterine cancer will be diagnosed in the United States of America during 2004. Cancer of the uterus occurs when uterine cells become abnormal and form more cells in an uncontrolled manner. A tumor, which is a mass of tissue, develops out of these extra cells and can either be benign (non-cancerous) or malignant (cancerous). To understand uterine cancer, it is important to distinguish between the three types of uterine cancer:

  • Cervical Cancer:
    A form of uterine cancer that affects the cervix, the lower part of the uterus, which connects the body of the uterus to the vagina. Cervical cancer is treated and diagnosed in a different manner than the other types of uterine cancers and usually begins in the lining of the cervix. Cervical cancer occurs gradually and there are two main types of cervical cancer: squamous cell carcinomas, which accounts for 80% to 90% of all cervical cancer cases, and adenocarcinomas, which accounts for the other 10% to 20%. Cervical cancer, however, can feature both cervical cancer types and this is known as mixed carcinoma. The American Cancer Society estimates that in 2004 that 10,520 new cases of invasive cervical cancer will be diagnosed in the United States of America. The American Cancer Society also estimates that in 2004, cervical cancer will lead to 3,900 deaths.
  • Uterine Sarcoma:
    A form of uterine cancer that develops in the muscle (myometrium) and affects the connective tissues of the uterus. Like endometrial cancer, uterine sarcoma affects the upper part (or body) of the uterus. However, unlike endometrial cancer, uterine sarcoma is extremely rare. Most uterine sarcomas can be classified by the type of cell that they develop from: endometrial stromal sarcomas, which is the least common form of uterine sarcoma; uterine leiomyosarcomas, which begin in the muscle wall of the uterus; and uterine carcinosarcomas, which is the most common form of uterine sarcoma. A rare form of uterine cancer, it is estimated that in 2004 that 1,613 new cases of uterine sarcoma will be diagnosed in the Untied States of America.
  • Endometrial Cancer:
    A form of uterine cancer that develops from the endometrium, the inner lining of the uterus. Like uterine sarcoma, endometrial cancer affects the upper part (or body) of the uterus. The most form of cancer affecting female reproductive organs, endometrial cancer can be classified by the type of cell that they develop from: endometrial adenocarcinomas, the most common form of endometrial cancer that emerge from the glandular cells and comprises 90% of all endometrial cancer cases; clear cell, and papillary serous adenocarcinomas. The most common type of uterine cancer, it is estimated that in 2004 that 38,707 new cases of endometrial cancer will be diagnosed in the United States of America.

Currently, the cause of uterine cancer is unknown. However, medical studies have identified a variety of conditions that increases the odds of uterine cancer susceptibility. It is important to note that the presence of these risk factors do not necessarily lead to the development of uterine cancer. The risk factors of uterine cancer will be described pertaining to the type of uterine cancer:

Cervical Cancer Risk Factors

  • Human Papillomavirus Infection:
    Most doctors believe that a woman must be first infected by the human papillomavirus (HPV) before they develop cervical cancer. HPVs tend to cause warts (papillomas) but certain high-risk forms of HPVs like HPV 16, HPV 18, HPV 31, HPV 33, and HPV 45, can cause cancer of the cervix. HPVs are sexually transmitted diseases that do not have a cure. As it spreads from skin-to-skin contact, condoms are not particularly effective in protecting against HPVs. However, although it is believed that HPV infection is a necessity for the development of cervical cancer, most doctors feel that HPV infection is not the sole reason for cervical cancer to development and that other factors are required in cervical cancer development.
  • Smoking:
    Medical studies have shown that carcinogens (cancer-causing chemicals) in tobacco is absorbed by the lungs and carried in the bloodstream throughout the body. Researchers believed that these carcinogens damage the DNA of cervix cells and that women who smoke are twice as likely as nonsmokers to develop cervical cancer.
  • Human Immunodeficiency Virus (HIV) infection:
    HIV is a disease that damages the body’s immune system making women more susceptible to HPV infections.
  • Chlamydia Infection:
    A sexually transmitted disease that can infect the female reproductive system, recent studies have indicated that women with past or current chlamydia infection have a higher susceptibility to cervical cancer.
  • Diet:
    Women whose dietary intake is low in fruits and vegetables have been found to be more susceptible to cervical cancer. Additionally, overweight women have also been found to be more susceptible to cervical cancer development.
  • Oral Contraceptives:
    Studies have suggested that there is a correlation between using oral contraceptives for 5 years or more and an increased susceptibility of cervical cancer development.
  • Multiple Pregnancies:
    Many full-term pregnancies lead to an increased risk of cervical cancer development.
  • Family History:
    There is an increased risk of cervical cancer development for women whose immediate family members have had cervical cancer.

Uterine Sarcoma Risk Factors

  • Prior Pelvic Radiation Therapy: Cancer treatments that use ionizing (high-energy) radiation in the pelvic regions can damage DNA cells and leads to an increased risk in the development of a second type of cancer. These cancers are usually diagnosed 5 to 25 years following radiation exposure.
  • Age: Uterine sarcomas usually occur in women who are middle-aged or are elderly.
Endometrial Cancer Risk Factors
  • Early Menarche:
    Women who begin to have monthly periods before the age of 12 increase the number of years that their endometrium is exposed to estrogen, which increases their susceptibility to the development of endometrial cancer.
  • Late Menopause:
    Women who experience menopause after the age of 50 increase the number of years that their endometrium is exposed to estrogen, which increases their susceptibility to the development of endometrial cancer.
  • Total Length of Menstruation Span:
    Women who have a lengthy menstruation span increase the number of years that their endometrium is exposed to estrogen, which increases their susceptibility to the development of endometrial cancer.
  • History of infertility or nulliparity:
    Women who have never gave birth or unable to become pregnant are more susceptible to endometrial cancer as pregnancy creates a hormonal balance shift from estrogen to progesterone. Therefore, pregnancies reduce the risk of endometrial cancer development.
  • Obesity:
    Fat tissue can create changes within a woman’s body, changing other hormones into estrogen. A large amount of fat tissue can therefore increase a woman’s estrogen level, therefore increasing their susceptibility to the development of endometrial cancer.
  • Diabetes:
    Studies have shown that women who have diabetes are more likely to develop endometrial cancer.
  • Age:
    Endometrial cancer occurs in women who are 40 years of age or older, 95% of the time. As women age, their susceptibility to endometrial cancer development increases.
  • Family History:
    There is an increased risk of endometrial cancer development for women whose immediate family members have had cervical cancer.
  • Prior Pelvic Radiation Therapy:
    Cancer treatments that use ionizing (high-energy) radiation in the pelvic regions can damage DNA cells and leads to an increased risk in the development of a second type of cancer. These cancers are usually diagnosed 5 to 25 years following radiation exposure.
Symptoms of Uterine Cancer

Regardless of the type of uterine cancer, the PET scan is an important tool that can be used to reverse its effects. As the cause of uterine cancer is still unknown, early detection of uterine cancer is instrumental in uterine cancer treatment. Early detection of cervical cancer has increased over the last couple of decades through the increased use of Pap screening. Pap screening or Pap smear involves the collection of cervical cells to be examined under a microscope. Changes are detected that shows cancerous trends as well as infection or inflammation. However, for uterine sarcomas and endometrial cancer, early detection is difficult. In order to detect uterine cancer in its early stages, the American Cancer Society recommends these actions:

  • Cervical cancer screening should commence about 3 years after a woman has begun to have vaginal intercourse or when they are 21 years old, whichever comes first. A regular Pap test should be conducted annually or a liquid-based Pap test should be conducted biannually for cervical cancer screening.
  • At the age of 30, women who have had 3 continuous normal Pap test results can be screened biannually or tri-annually with either a regular Pap test or a liquid-based Pap test. For women who have not had 3 continuous normal Pap test results, it is advised that they continue to be screened annually.
  • For women who 70 years of age or older that have had at least 3 continuous, normal Pap test results, they are able to cease cervical cancer screening.

For women who are concerned about the development of uterine sarcomas and/or endometrial cancer, there is currently no early detection test that they can conduct. As uterine cancer often does not produce symptoms during its early stages, it is difficult to detect uterine sarcomas and endometrial cancer in its early stages. However, if any of these symptoms are present, it is highly recommended that a qualified doctor be notified for their diagnosis:

  • Abnormal vaginal bleeding
  • Bleeding following intercourse, douching, or a pelvic exam
  • Pain during intercourse
  • Unusual vaginal discharge such as bleeding or spotting
  • Pelvic pain
  • Mass and weight loss
PET and Uterine Cancer Diagnosis

Positron Emission Tomography is an effective procedure used in the various stages of treatment of uterine cancer. However, PET and other imaging tools are used rarely in the uterine cancer diagnosing stage. Early diagnosis of cervical cancer usually occurs through Pap screening. Pap screening or Pap smears are tests that involve the collection of cervical cells to be examined under a microscope. Through this procedure, changes within the uterus are detected that indicate cancerous activity as well as infection or inflammation.

Although Pap Screening is highly effective in the early detection of cervical cancer, it is limited in its capacity to detect the early stages of uterine sarcoma development or endometrial cancer. Pap tests are capable of finding early uterine sarcoma cases and endometrial cancer cases but for the most part do not detect most cases. Pelvic exams (an examination in which the doctor checks the vagina, uterus, bladder, and rectum for lumps or physical changes in the shape or size of these organs) are effective in finding advanced cases of uterine cancer but are limited in detecting uterine cancers in their early stages.

In most instances, uterine cancer is detected when a patient undergoes a physical examination from their physician after they detect uterine cancer symptoms. During this physical examination, a sample of the patient’s endometrial tissue or cervical tissue is taken and examined by medical professionals through a biopsy or dilation and cutting.

Although imaging tests are rarely performed on potential uterine cancer patients during the diagnosis stage, it is an instrumental procedure used during the uterine cancer screening stage. There has been one instance where PET imaging in a patient that suspected she had a recurrence of cancer in her lung actually found that she had a recurrence of cancer in her uterus. As clinical physicians become more comfortable with PET technology, it is likely that Positron Emission Tomography will become incorporated in uterine cancer diagnosing.

PET and Uterine Cancer Staging

PET scans are highly effective in the treatment of uterine cancer when it is used during the staging phase. Staging commences following uterine cancer diagnosis and is used to determine if or how much the uterine cancer has spread. The staging component of uterine cancer treatment is critical as it provides the necessary information for physicians in determining an appropriate medical course of uterine cancer treatment.

Through PET imaging, a physician is able to determine whether or not cancerous cells have spread from the uterus to other parts of the body. Most commonly, uterine cancer spreads into nearby lymph nodes, nerves, or blood vessels where it can spread into other lymph nodes and organs like the lungs, liver, and bones. Positron Emission Tomography involves the administration of a radioactive tracer that combines a radioisotope, a radioactive compound that is detected by a PET scanner, with a natural body compound, which the body is able to integrate into its system without any negative effects. In uterine cancer screening, the radioactive tracer used is Fluorodeoxyglucose (FDG) that combines the natural body compound glucose with the radioisotope Fluorine-18. Although many patients have concerns about the radioactive component contained in PET imaging, Fluorine-18 contains a short half-life and disappears from the body within hours. Consequently, the PET procedure is a safe one for patients.

In the staging process, PET scans are the most effective imaging tool in determining the spread of cancerous cells. Uterine cancer imaging tests such as x-rays, computed tomography (CT), and magnetic resonance imaging (MRI) are limited in their ability to detect only changes in the anatomical structure of the organs and tissue. Positron Emission Tomography, however, is a non-invasive procedure that determines cancer spread more comprehensively than these other screening procedures, as it detects biochemistry changes among organs and tissues. By tracing the spread of FDG in a patient’s body, PET imaging is able to establish patterns of cancer spread based on the body’s chemical reactions to FDG. As it is similar in structure to glucose, PET determines cancer spread by studying the absorption of FDG by the patient’s organs and tissues. FDG is absorbed at a faster rate by cancerous organs and tissue than healthy organs and tissues. By studying the biochemical reaction of the patient’s body, PET scan is able to produce the most accurate analysis of whether uterine cancer has spread to other areas of the body.

The information derived from uterine cancer staging is critical in determining an accurate outlook of patient recovery as well as forming the basis for further medical uterine cancer treatment. Uterine cancer treatment employs the FIGO (International Federation of Gynecology and Obstetrics) System of Staging, which is a comprehensive staging system based on a doctor’s physical examination and other tests such as PET imaging. The FIGO uterine cancer staging system employs different criteria for the different types of uterine cancers.

Cervical Cancer FIGO Staging System
  • Stage 0: The tumor is carcinoma in situ, meaning that the cancer is present only in the layer of cells lining the cervix and is not present in the deeper tissues of the cervix.
  • Stage I: The cancer is present in the cervix but has not spread to anywhere else in the body.
  • Stage IA: The earliest form of Stage I, this means that the cancer present is minute and only visible under a microscope.
  • Stage IA1: Cancer is less than 3 mm deep and less than 7 mm wide.
  • Stage IA2: Cancer is between 3 mm and 5 mm deep and less than 7 mm wide.
  • Stage IB: In this stage, the cancer usually is visible without a microscope, although this stage does include cancers that have spread deeper than 5 mm into the connective tissue of the cervix or are wider than 7 mm that is only visible with a microscope.
  • Stage IB1: Cancer is visible but is not larger than 4 cm.
  • Stage IB2: Cancer is visible and is larger than 4 cm.
  • Stage II: The cancer is still retained inside the pelvic area but has spread beyond the cervix to nearby areas.
  • Stage IIA: In this stage, the cancer has spread to the upper part of the vagina from the cervix but has not spread to the lower third of the vagina.
  • Stage IIB: In this stage, the cancer has spread from the cervix to the parametrial tissue, the tissue next to the cervix.
  • Stage III: The cancer has spread from the cervix to the lower part of the vagina or the pelvic water. During this stage, the ureters (tubes that carry urine from the kidneys to the bladder) may be blocked by cancer.
  • Stage IIIA: In this stage, the cancer has not spread to the pelvic wall but has spread to the lower third of the vagina.
  • Stage IIIB: In this stage, the cancer extends to the pelvic wall and/or blocks urine flow to the bladder by blocking the ureters.
  • Stage IV: The most advanced stage of cervical cancer, this stage represents cancer spread to other parts of the body.
  • Stage IVA: In this stage, the cancer has spread to organs close to the cervix, particularly the bladder or rectum.
  • Stage IVB: In this stage, the cancer has spread to organs that are distant from the pelvic area, such as the lungs.
  • Uterine Sarcoma FIGO Staging System
  • Stage I: The cancer is retained in the main body of the universe. If uterine sarcoma has been diagnosed at this stage, the five-year survival rate is 50%.
  • Stage II: The cancer has spread to the cervix from the body of the uterus. If uterine sarcoma has been diagnosed at this stage, the five-year survival rate is 20%.
  • Stage III: The cancer is retained in the pelvic area but has spread beyond or outside the uterus. If uterine sarcoma has been diagnosed at this stage, the five-year survival rate is 10%.
  • Stage IIIA: The cancer has spread to the serosa (the layer of tissue on the uterus’ outers surface) or to the adnexa (the tissues immediately to the uterus’ right and left sides). This stage can also indicate cancer cells present in the peritoneal fluid (fluid from the inner lining of the pelvis and abdomen) that has been detected through microscopic examination.
  • Stage IIIB: The cancer has spread to the vagina from the uterus.
  • Stage IIIC: The cancer has spread from the uterus to nearby lymph nodes such as the pelvic and/or para-aortic lymph nodes.
  • Stage IV: If uterine sarcoma has been diagnosed at this stage, the five-year survival rate is 10%.
  • Stage IVA: The cancer has spread from the uterus to the mucosa (inner surface) of the rectum or the urinary bladder.
  • Stage IVB: The cancer has spread from the uterus to lymph nodes in the groin area or has spread to organs that are distant from the uterus such as the bones or lungs.
Endometrial Cancer FIGO Staging System
  • Stage I: The cancer is retained in the body of the uterus and has not spread to lymph nodes. If endometrial cancer is diagnosed at this stage, the five-year survival rate is between 90% and 95%.
  • Stage IA: The earliest stage of Stage I, this means that the cancer is retained within the endometrium (the inner lining of the uterus).
  • Stage IB: The cancer has spread from the endometrium but has spread less than halfway through the myometrium (the muscular wall of the uterus).
  • Stage IC: The cancer is retained within the body of the uterus but is no longer limited to the endometrium and has spread more than halfway through the myometrium.
  • Stage II: The cancer has not spread to lymph nodes but is no longer contained in the body of the uterus and has spread to the lower part of the uterus next to the cervix. If endometrial cancer is diagnosed at this stage, the five-year survival rate is 75%.
  • Stage IIA: The cancer is present in the body of the uterus and the endocervical glands (the glands that form the inner lining of the cervix).
  • Stage IIB: The cancer is present in the body of the uterus and the cervical stroma (the supporting connective tissue of the cervix).
  • Stage III: The cancer is retained in the pelvic area but has spread beyond or outside the uterus. If endometrial cancer is diagnosed at this stage, the five-year survival rate is 60%.
  • Stage IIIA: The cancer has not spread to lymph nodes or distant sites but has spread to either the serosa of the uterus (the layer of tissue on the outer surface of the uterus) or the adnexa (the tissues immediately to the right and left sides of the uterus). This stage can also indicate that cancerous cells are present in the peritoneal fluid (the fluid from the inner lining of the pelvis and abdomen).
  • Stage IIIB: The cancer has not spread to the lymph nodes or distant sites but has spread to the vagina.
  • Stage IIIC: The cancer has spread to lymph nodes near the uterus but not to distant sites.
  • Stage IV: If endometrial cancer is diagnosed at this stage, the five-year survival rate is between 15% and 26%.
  • Stage IVA: The cancer may or may not have spread to lymph nodes but has not spread to distant sites. It has spread to the mucosa (inner lining) of the rectum or urinary bladder.
  • Stage IVB: The cancer has spread to distant sites away from the uterus including the bones or lungs. It may or not have spread to lymph nodes.
  • The information gathered in staging is critical in determining the correct medical action to take to treat uterine cancer. For staging, recent research studies have verified the effectiveness of PET imaging over other imaging techniques. A 2001 study conducted at the Washington University School of Medicine found that PET scans were able to confirm the presence of a cervical tumor in 100 of the 101 women that undertook the study compared to the 77 detected by CT scanning. Additionally, PET scanning was able to reveal abnormal pelvic nodes in 67 of the 101 women compared to the 20 found in CT scanning. As a more accurate imaging tool used in uterine cancer staging, PET is instrumental in influencing the correct medical treatment recommended by physicians. It helps prevent unnecessary surgery by revealing the proper information detailing the extent of a patient’s uterine cancer.

PET and Uterine Cancer Follow-Up

The information attained in uterine cancer staging forms the basis for further medical action to treat uterine cancer. In most instances, uterine cancer treatment involves three main methods: chemotherapy, radiation therapy, and surgery, or a combination of two of the three options. In cases of uterine sarcoma and endometrial cancer, hormone therapy can possibly be used. The stage of the uterine cancer, determined through staging, as well as the type of cancer determines the appropriate treatment to be performed. Although these treatments are usually effective, an important component of uterine cancer treatment is determining whether active cancer cells have remained in the body following treatment.

Prior to the clinical use of PET scan, physicians applied radiation therapy and chemotherapy according to standard rules. However, through the use of PET imaging, it is now possible for physicians to specifically cater uterine cancer treatments to a patient’s particular situation. This is because Positron Emission Tomography allows a physician to view the location, extent, and resilience of a patients’ uterine cancer.

Additionally, PET imaging is the most effective diagnostic tool in detecting uterine tumor response to therapy. PET scans study the chemical function of the uterus and other organs and tissues and is able to produce images that show visual biochemical changes in the body caused by uterine cancer. Unlike anatomic forms of imaging such as computerized tomography (CT) that details changes in body structure such as the presence of tumors, PET imaging is able to determine whether a tumor is benign (alive tissue and non-cancerous) or malignant (dead tissue and cancerous).

PET scans involve the administration of the radioactive tracer, Fluorodeoxyglucose (FDG) that combines the natural body compound glucose with the radioisotope Fluorine-18. FDG safely travels through the body where a PET scanner monitors its movement within the body. A radioactive tracer that disappears from the body within hours, FDG is able to detect cancer recurrence in successfully treated lesions as well as determine whether tumors identified in an anatomic imaging scan are cancerous or not.

This is because FDG is similar in structure to glucose, which cancerous cells absorb at a faster rate than healthy cells. By tracing the absorption rates of FDG by the targeted cells, a physician is able to determine whether successfully treated lesions are showing signs of cancer recurrence. Additionally, PET imaging is able to detect cancer recurrence in lymph nodes and/or scar tissue from surgery from surgery or another lesion sooner than an anatomical imaging procedure. PET scans are also able to distinguish between cancerous and non-cancerous tumors that are detected by anatomical imaging and are still present despite uterine cancer treatment.



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