When diagnosing ovarian cancer, doctors try to classify it by stage to describe how far along the cancer has progressed. Knowing what stage ovarian cancer is in helps them determine the best course of treatment.

Ovarian cancer has four stages, with stage 1 being the earliest.

Read on to learn the basics of ovarian cancer, what characterizes stage 1, and who’s at risk. We’ll also look at early symptoms, treatment options, and outlook for this stage.

Ovarian cancer begins in the ovaries. These are the two almond-shaped, egg-producing organs located on both sides of the uterus in the female reproductive system.

The cells where the cancer forms determines the specific type of ovarian cancer. The three types include:

  • epithelial tumors, which form in the tissue outside the ovaries and account for about 90 percent of ovarian cancers
  • stromal tumors, which begin in the tissue of hormone-producing cells and represent about 7 percent of ovarian cancers
  • germ cell tumors, which form in egg-producing cells and are more common in young women

The lifetime risk of a woman experiencing ovarian cancer is 1.3 percent. Genetic factors are responsible for about 10 percent of cases. Though exact causes are unknown, other risk factors include:

Ovarian cancers are classified by stages, which indicate where the cancer started and how it has potentially spread to other areas of the body.

Stage I ovarian cancer, the earliest stage, is commonly divided into three substages:

  • Stage 1A. Cancer is in one ovary or fallopian tube, but not on the outer surface.
  • Stage 1B. Cancer is in both ovaries or fallopian tubes, but not on the outer surfaces.
  • Stage 1C. Cancer is found in one or both ovaries or fallopian tubes, in addition to one of the following:
    • The outer capsule bursts during or before surgery, resulting in cancer cells possibly leaking into the stomach or pelvic area.
    • Cancer is found on the outer surface of the ovary(s).
    • Cancer is found in fluid washings from the abdomen.

The stage in which ovarian cancer is diagnosed affects treatment options and survival rates. Early diagnosis improves survival rates.

Ovarian cancer is difficult to detect in its early stages because there isn’t a screening test for it. Also, the symptoms are common for a number of noncancerous conditions.

That said, early symptoms of ovarian cancer may include:

Symptoms generally become more severe as ovarian cancer progresses. Consult your doctor if you experience unusual symptoms or believe they may be a result of ovarian cancer.

To diagnose possible ovarian cancer, your doctor will likely recommend a pelvic exam. Because small tumors in the ovaries may be difficult to detect, other tests may include:

The primary treatment for stage 1 ovarian cancer is surgery to remove the tumor. Your doctor might recommend also removing the fallopian tubes or nearby lymph nodes. A hysterectomy, which is a procedure to remove the uterus, is usually unnecessary.

Treatment plans for ovarian cancer may also include chemotherapy or radiation to kill cancer cells.

If other types of treatment aren’t effective or if the cancer has returned, your doctor might recommend targeted therapy, which kills certain molecules associated with the growth and spread of cancer.

The stage in which ovarian cancer is detected has an effect on survival rates, but only about 15 percent of those with ovarian cancer are diagnosed in stage 1.

According to the American Cancer Society, the relative survival rates for stage 1 invasive epithelial ovarian cancer are:

  • 1: 78 percent
  • 1A: 93 percent
  • 1B: 91 percent
  • 1C: 84 percent

For stage 1 ovarian stromal tumors, the relative five-year survival rate is 99 percent.

For stage 1 germ cell tumors of the ovary, that rate is 98 percent.

Relative survival rates decrease throughout each successive stage, so early detection is one of the most important factors in effective treatment. Speak with your doctor if you’re experiencing symptoms of ovarian cancer.