Ovarian cancer is classified into four main stages, ranging from stage I (cancer confined to the ovaries or fallopian tubes) to stage IV (cancer that has spread to distant organs like the lungs or liver). The staging system used worldwide comes from the International Federation of Gynecology and Obstetrics, and each stage is further divided into substages based on exactly how far the cancer has spread. Staging is one of the strongest predictors of outcome, with five-year survival ranging from about 92% for localized disease down to roughly 32% for distant spread.
How Ovarian Cancer Is Staged
Unlike many cancers that can be staged with imaging alone, ovarian cancer almost always requires surgery to determine its true stage. During the procedure, a surgeon examines the abdominal cavity, takes tissue samples from multiple areas, and collects fluid from the abdomen to check for cancer cells under a microscope. Lymph nodes in the pelvis and along the major blood vessels are also biopsied. All of this information, combined with what the pathologist finds in the tissue, determines the final stage.
This means you may not know your exact stage until after surgery, even if imaging gave an initial estimate. Thorough surgical staging matters because it directly affects treatment decisions.
Stage I: Cancer Confined to the Ovaries
In stage I, the cancer has not spread beyond the ovaries or fallopian tubes. No cancer is found in nearby lymph nodes or distant organs. Within stage I, three substages capture important differences:
- Stage IA: Cancer is found in only one ovary or one fallopian tube. The tumor is entirely contained inside the organ, with no cancer on the outer surface and no cancer cells in abdominal fluid.
- Stage IB: Cancer is present in both ovaries or both fallopian tubes, but still entirely contained inside them, with no surface involvement and no cancer cells in abdominal fluid.
- Stage IC: Cancer is in one or both ovaries or fallopian tubes, but at least one higher-risk feature is present: the outer capsule of the ovary ruptured (either before or during surgery), cancer cells appear on the outer surface, or cancer cells are found in fluid collected from the abdomen.
These distinctions matter for treatment planning. Stage IA with a slow-growing tumor type may be treated with surgery alone, while stage IC typically warrants chemotherapy afterward because of the higher chance that microscopic cancer cells escaped into the abdominal cavity. Recurrence rates for stage IA are around 9%, and no recurrences were observed in a study of stage IB patients with low- to moderate-grade tumors.
Stage II: Spread Within the Pelvis
Stage II means the cancer has grown beyond the ovaries or fallopian tubes but is still limited to the pelvic area. This could mean the tumor has extended to the uterus, bladder, rectum, or other pelvic structures. It may also involve cancer cells found on pelvic tissue surfaces, called peritoneal implants.
Stage II is subdivided based on exactly where the pelvic spread has occurred, but the key boundary is this: the cancer has left the ovary but has not yet reached the upper abdomen or distant organs. Treatment at this stage typically involves surgery to remove as much cancer as possible, followed by chemotherapy.
Stage III: Spread Beyond the Pelvis
Stage III is the most commonly diagnosed stage because ovarian cancer often produces vague symptoms that go unrecognized until the disease has advanced. At this point, cancer has spread beyond the pelvis into the abdominal cavity, onto the lining of the abdomen (the peritoneum), or into lymph nodes behind the abdomen.
The substages reflect the extent of that spread:
- Stage IIIA: Cancer has reached retroperitoneal lymph nodes (confirmed under a microscope), or microscopic deposits are found on abdominal surfaces outside the pelvis. Lymph node involvement is further classified by whether the deposits are smaller or larger than 1 centimeter.
- Stage IIIB: Visible tumor deposits up to 2 centimeters are found on abdominal peritoneal surfaces outside the pelvis.
- Stage IIIC: Tumor deposits larger than 2 centimeters are found on abdominal surfaces outside the pelvis, including on the surface of the liver or spleen (but not inside those organs).
A common site for abdominal spread is the omentum, a fatty tissue layer that drapes over the intestines. Surgeons frequently remove it as part of the operation. The goal at stage III is “debulking,” which means removing as much visible tumor as possible. Ideally, no remaining deposits are larger than about a centimeter, a result that significantly improves the effectiveness of the chemotherapy that follows.
Stage IV: Distant Metastasis
Stage IV means the cancer has spread to organs outside the abdomen or into the interior tissue of the liver or spleen. It is divided into two substages:
- Stage IVA: Cancer cells are found in fluid around the lungs, a condition called malignant pleural effusion. This is the most common presentation of stage IV disease.
- Stage IVB: Cancer has spread to the inside of the liver or spleen, to lymph nodes outside the abdomen and pelvis, or to other distant sites such as the lungs, bones, or brain.
Even at stage IV, treatment typically begins with surgery to remove as much tumor as possible, followed by platinum-based chemotherapy. Some patients receive chemotherapy first to shrink the tumors before surgery, an approach called neoadjuvant chemotherapy. The five-year relative survival rate for distant-stage ovarian cancer is about 31.5%, though individual outcomes vary widely depending on tumor type, how well the cancer responds to chemotherapy, and how much tumor the surgeon can remove.
How Stage Affects Survival
The National Cancer Institute’s SEER database groups ovarian cancer survival into three categories rather than the four formal stages. Based on data from 2016 through 2022, the five-year relative survival rates are:
- Localized (roughly stage I): 91.9%
- Regional (roughly stage II and some stage III): 70.1%
- Distant (advanced stage III and stage IV): 31.5%
These numbers represent averages across all types of ovarian cancer. Some subtypes, particularly high-grade serous carcinoma (the most common type), tend to be diagnosed at later stages but often respond well to initial chemotherapy. Less common subtypes like mucinous ovarian cancer may behave quite differently. The grade of the tumor, which describes how abnormal the cells look, also affects prognosis independently of stage.
Why Most Cases Are Found at Later Stages
Only about 17% of ovarian cancers are caught at the localized stage. The ovaries sit deep in the pelvis, and early-stage disease rarely causes noticeable symptoms. When symptoms do appear, they tend to be nonspecific: bloating, pelvic pressure, feeling full quickly when eating, or urinary urgency. These overlap with dozens of common, benign conditions, which is why they’re often dismissed for weeks or months.
There is no reliable screening test for ovarian cancer in the general population. Pelvic exams, CA-125 blood tests, and transvaginal ultrasounds can help evaluate symptoms or monitor high-risk individuals, but none has proven effective as a population-wide screening tool. For people with BRCA1 or BRCA2 gene mutations or a strong family history, risk-reducing surgery to remove the ovaries and fallopian tubes is the most effective prevention strategy available.