Ovarian cancer is any of several cancers that begin growing in the ovaries, two symmetrical organs within the female reproductive system responsible for producing eggs, or ova.
Three Types Of Cell, Three Types Of Cancer
Ovaries play a double function in reproductive health. Beyond creating ova, and thus the material for reproduction, ovaries are also glands, producing the majority of female “sex hormones,” like estrogen and progesterone. These hormones are critical, encouraging the development of female sex characteristics during puberty and regulating the menstrual cycle, which maintains a woman’s fertility.
Ovaries also kick in during pregnancy, producing higher levels of hormones to prevent more eggs from being created, prepare the breasts for lactation and relax the pelvis prior to delivery.
On a very basic level, the ovaries are made up of three different types of cells:
- Epithelial cells, which line the outer surface of the organ
- Germ cells, which eventually develop into eggs
- Stromal cells, which serve as a sort of connective tissue, holding the ovary together, and also producing hormones
Any one of these three cell types can become cancerous; there are epithelial ovarian cancers, germ cell ovarian cancers and stromal cell ovarian cancers.
Cancers that begin in the epithelium, the outer layer of cells that covers an organ, are called “carcinomas.” Ovarian carcinomas account for the vast majority of ovarian cancer cases, between 85% and 90%, according to the American Cancer Society.
How Cancer Works
Cancer, fundamentally, is a malfunction in the way these cells grow. But more specifically, cancer is a change in how these cells behave.
Your cells are constantly dividing, creating new copies of themselves, but not every copy is exactly the same. Each time a cell divides, it has to duplicate the genetic information, or DNA, that serves as a set of instructions for what the cell will do and how the cell will interact with other cells. But sometimes this duplication process isn’t perfect, and the DNA itself changes. That’s called mutation, and specific mutations in a cell’s DNA change the specific ways in which a cell behaves.
Cells aren’t meant to live forever. In fact, under certain circumstances, they kill themselves, making room for newer cells that haven’t yet reached the point of suicide. Every time a cell divides, its chromosomes, the structures that hold onto DNA, become shorter. At a certain point, the chromosomes are so short that the cell dies. But cancer cells, through a genetic mutation, figure out a way around this naturally-encoded death. Instead of allowing their chromosomes to get shorter, cancer cells keep adding little bits back on, effectively allowing them to live forever.
Tumors, Benign Or Malignant
Cancer cells don’t work well with other cells. Normal cells are constantly responding to the cells that surround them. If they overstep their bounds, dividing more than they should, a little message from their neighbors will tell them to stop. But cancer cells have learned how to ignore those messages, which allows them to replicate endlessly. The real problem, though, is that when a cancer cell divides, its “children” will have the same genetic mutations as their “parent.” That’s why, instead of having only isolated cancer cells, we get tumors, abnormal masses of tissue.
Not every tumor is cancerous; some are benign. Indeed most tumors that begin in the ovary are benign. What separates benign from cancerous tumors is yet another genetic mutation, one that allows cancer cells to break away from their community and spread to other regions of the body. Normal cells, along with cells that make up benign tumors, commit suicide after leaving their neighbors. Cancer cells, on the other hand, have lost the set of genetic instructions that would tell them to commit suicide.
That’s why cancer is so dangerous. Not only can it divide, endlessly, it can also spread, in a process known as “metastasis.”
How Ovarian Cancer Spreads
Even after metastasizing to another part of the body, every cancer is classified by its “primary” or original site of growth. So cancers that have spread to the bladder or colon are still called ovarian cancers, if they started in the ovaries.
Usually, ovarian cancers don’t get very far. Ernst Lengyel, a gynecologic oncologist at the University of Chicago, defined the two primary ways ovarian carcinomas metastasize in a 2010 paper published by the American Journal of Pathology. According to Lengyel, these cancers spread either:
- directly to the Fallopian tubes, bladder or colon, organs that closely neighbor the ovaries, but remain a single, continuous tumor or
- by “exfoliating,” when a few cancer cells break off from the primary tumor and become disseminated throughout the abdominal cavity
Unlike most cancers, Lengyel says, ovarian cancers rarely get into the blood stream, which means they usually don’t spread to body parts far away from the ovaries. Some cancers, though, can reach lymph nodes and enter the lymphatic system, a network of vessels that carries white blood cells through the body, and filters body fluids of toxins.
We Catch Ovarian Cancer Too Late
When doctors talk about “cancer staging,” they’re mainly talking about whether or not a cancer has begun to spread, and if so, how far. While oncologists use several different staging systems to describe ovarian cancer, the most common has been developed by the International Federation of Gynecology and Obstetrics (FIGO):
- In Stage 1, the cancer is confined to the ovaries.
- In Stage 2, the cancer has spread from the ovaries to other regions of the pelvis. That can mean the Fallopian tubes, the uterus or elsewhere.
- In Stage 3, the cancer is found in the ovaries, the pelvis and the peritoneum, which is the layer of tissues lining the abdominal cavity
- In Stage 4, the cancer has spread even further, to distant organs
Most women who develop ovarian cancer aren’t diagnosed until a later, or “advanced,” stage, after the disease has metastasized. The National Cancer Institute, which keeps the most extensive statistics on cancer in the US, has found that between 2006 and 2012, only around 34% of the women diagnosed with ovarian cancer were diagnosed before the disease had spread, either to regional lymph nodes or more distant body parts.
That’s why ovarian cancer, in most cases, is deadly. We catch it too late. While only 19% of breast cancer patients will die as a result of their disease, around 69% of patients with ovarian carcinoma do. Despite being relatively rare, only the 17th most common cancer diagnosed in America, ovarian cancer is the fifth deadliest form of malignancy in women.
Why It’s Hard To Notice Ovarian Cancer Early
Ovarian tumors, when they begin to grow, often come to press on organs that neighbor the ovaries. Usually, that means portions of the intestines, and this pressure is what causes most of ovarian cancer’s earliest symptoms:
- bloating in the abdomen, sensations of pressure and / or pain
- difficulty eating, or feeling “full” very quickly
Tumors can also press against the bladder, leading to frequent urination. Of course, all of these symptoms are “nonspecific”; they can be caused by numerous conditions, most of which aren’t cancer. But according to WebMD, when these symptoms are caused by ovarian cancer, they follow a specific pattern. Ovarian cancer symptoms begin suddenly, occur every day for weeks on end and will feel oddly “different” from normal menstrual or digestive problems.
Other possible signs of ovarian cancer, like fatigue, back pain and painful intercourse, are also nonspecific. Many women experience a combination of these symptoms at some point, but don’t have cancer, and since the ovaries aren’t close to the surface of the abdomen, it can be very difficult to feel even moderately-sized tumors. Doctors miss them, too.
Once the symptoms become acute, impossible to ignore, it probably means the cancer has already metastasized. Advanced cancers, though, are harder to treat than ones diagnosed at an early stage, which is likely why ovarian cancer has such a poor prognosis for most actual patients.
The only conclusive way to diagnose ovarian cancer is with a biopsy, removing part of a tumor and looking at it under a microscope. Biopsies, however, can only be performed once a tumor has been identified which, again, is difficult until the cancer has progressed. After physical examinations, physicians use ultrasounds to look for tumors beneath the skin, and blood tests to measure for cancer antigen 125 (CA-125), a protein that ovarian cancer cells can produce. Neither of these tests are definitive; tumors can be benign and other conditions, including fibroids, can sometimes produce cancer antigen 125. Even regular menstruation can cause a bump in CA-125 levels.
Treating Ovarian Cancer
Once cancer is confirmed, always through a biopsy test, the first step in treatment is usually surgery. Removing as much of the tumor, or tumors, as possible is the goal. In general, the more ovarian cancer surgeons can remove, the longer a patient will survive.
That might sound intuitively obvious, but cancer is very complex and surgical interventions don’t always have the effect that you’d expect. For ovarian cancer at least, what you’d assume to be true is true. In 2002, cancer researchers at Johns Hopkins Medical School reviewed 81 different studies, and found that for every 10% increase in how much ovarian cancer doctors were able to remove, patients lived 5.5% longer. What’s really surprising is that ovarian cancer is one of the only malignancies for which surgical removal has any effect on survival.
After surgery, the vast majority of patients receive chemotherapy. For most, that means a cocktail of at least two drugs, usually carboplatin and a taxane. Carboplatin is a form of the element platinum. Researchers think it prevents cancer cells from repairing their own DNA. Taxanes, on the other hand, interrupt the process by which cancer cells divide. Taxol is the most common taxane used to treat ovarian cancer, although rarely, a different drug called Taxotere is used.
There’s no cure for cancer, and none of these treatments can promise anything more than prolonging a patient’s life. We are, however, getting better at diagnosing and treating ovarian cancer, although advances in this regard have been slower than for other forms of cancer. Still, survival rates are creeping up. In 1975, only 33.7% of ovarian cancer patients survived the first five years after they were diagnosed. Today, it’s more like 46%.
What Causes Ovarian Cancer?
On one level, genetic mutations within cells cause ovarian cancer. The real question is what causes those genes to mutate? The answer is we don’t really know.
In some cases, genes just mutate, because that’s what happens when cells divide. But the genetic mutations that lead to ovarian cancer are very specific, and researchers have been able to identify many of them. Most of these genes have been assigned names like BRCA1, BRCA2, PTEN and STK11, all of which are genes that, upon mutation, appear to increase the likelihood of a woman’s developing ovarian cancer. Some of these genetic mutations can be passed down from parent to child, although these “hereditary” risk factors cause a relatively small proportion of the ovarian cancers diagnosed every year.
Beyond resorting to general, and fairly unhelpful, causal factors like “genetic mutations,” researchers have developed a number of theories to explain why ovarian cancer happens, and seems to happen more often in certain women. For example, we now know that both experiencing a pregnancy and taking oral contraceptives reduce the risk for developing ovarian cancer. As the American Cancer Society explains, both being pregnant and being on birth control pills also reduces the number of times a woman’s ovary will actually release eggs. So one theory is that ovulation has something to do with ovarian cancer.
Hysterectomy and tubal ligation also reduce the risk for ovarian cancer. Another theory, based on that fact, is that substances in the environment can cause ovarian cancer, and having a hysterectomy or tubal ligation cuts off the pathway (from vagina to uterus to fallopian tubes) through which those substances eventually reach the ovaries. This may explain why many studies have found a link between ovarian cancer and talcum powder, which many women use as a feminine hygiene product. If talcum powder can cause cancer, then it likely reaches the ovaries by entering the vagina.
To learn more about risk factors, and potential causes, of ovarian cancer, click here.