Ovarian cancer is one of the most challenging diseases known to medicine. Early detection is difficult because symptoms can be mild and vague and could apply to a variety of conditions, such as irritable bowel syndrome or ovarian cysts. The most typical ovarian cancer symptoms include:
- Swollen or bloated abdomen
- Persistent pain in the abdomen or pelvis
- Difficulty eating, constantly feeling full
- Increased urination
These symptoms are also seen with many other common conditions, as a result, only about 24 percent of women with ovarian cancer are diagnosed early. The rest find out about their disease after it has spread outside the ovaries or fallopian tubes, making successful treatment more difficult to accomplish. However, if the symptoms are new and persistent you should see your health care provider. Other symptoms such as constipation or fatigue, diarrhea and spotting between periods are also often reported by women with ovarian cancer.
One of the most important steps in treating ovarian cancer is staging the disease. In other words, has it spread and, if so, how far? Staging is generally done during surgery, placing the cancer in one of four categories:
Stage 1 –
The cancer is limited to one or both ovaries or to the fallopian tubes.
Stage 2 –
The cancer has spread to other areas of the pelvis, uterus, bladder, colon or rectum.
Stage 3 –
The cancer has spread to the abdomen and may also be in the lymph nodes.
Primary peritoneal cancers are stage 3.
Stage 4 –
The cancer has spread to organs outside the abdomen, such as the liver or lungs.
There are three major ovarian cancer tumor types based on where the tumor develops:
- Epithelial tumors account for 90 percent of ovarian cancers and start from cells on the outside (the epithelium) of the ovaries or the fallopian tubes.
- Germ cell tumors originate inside the ovaries in the cells that create the eggs. These tumors are rare and generally affect younger women.
- Stromal tumors are also rare and originate in the connective tissue surrounding the ovaries.
There are also different types (or histologies) of epithelial ovarian cancer. The most common is serous (high grade) and the others are clear cell, mucinous, endometrioid, carcinosarcoma and low-grade serous.
High grade serous and endometriod cancers as well as carcinosarcomas are chemo-sensitive and are similarly treated.
Low grade cancers of serous, mucinous, and endometrioid histology have distinct biologies and different treatment strategies. For example, hormonal therapy is often used for low grade serous and endometrioid subtypes.
The Role of Genomic Mutations
When people talk about mutations, they are simply highlighting genomic changes. DNA can change relatively frequently through errors in replication during cell division or through environmental exposure to tobacco smoke, chemicals, the sun’s ultraviolet radiation or other agents. Mutation is not necessarily bad – it’s the force that drives evolution. However, in some cases, mutations can be harmful.
Doctors have known for many years that ovarian and breast cancers have a hereditary element –some women diagnosed with ovarian cancer have family members who have had breast or ovarian cancer. Germline (hereditary) mutations in BRCA1 and BRCA2 genes increase the risk of developing ovarian cancer. The standard of care is to test for mutations in these genes whenever a woman is diagnosed with ovarian cancer – even if there is no family history. If she is positive, drugs called PARP inhibitors may be effective.
Tumors have been likened to trees. Maple trees share many common traits, but each individual plant grows in a unique way, generating a branching pattern that is different from other trees. All cancers begin with mutations and, as they grow and spread, acquire even more genomic variations.
Some of these mutations make cells divide faster. Others prevent diseased cells from dying. Still others remove the quality control mechanisms that safeguard DNA, leading to even more mutations. As a result of these widespread variations, ovarian cancer is not one disease but many.
Today, we can differentiate these cancers based on the unique set of gene mutations and the levels of proteins encoded by the genes in each woman’s cancer.