Cervical cancer is classified into four main stages (I through IV) based on how far the cancer has grown and whether it has spread beyond the cervix. The staging system used worldwide is the FIGO system, developed by the International Federation of Gynecology and Obstetrics. Your stage at diagnosis is the single biggest factor in determining treatment options and outlook. About 44% of cervical cancers are caught while still localized to the cervix, where the 5-year survival rate is 91.8%.
How Staging Works
Staging tells you and your care team how large the tumor is, how deep it has grown into surrounding tissue, and whether it has reached lymph nodes or distant organs. Doctors determine the stage using a combination of physical examination, imaging (typically MRI of the pelvis and PET-CT scans to check for spread), and biopsy results that measure exactly how deep the cancer has invaded.
Once a stage is assigned at diagnosis, it generally doesn’t change, even if the cancer later responds to treatment or progresses. If the cancer comes back, it’s described as recurrent rather than restaged.
Stage I: Cancer Confined to the Cervix
In stage I, cancer is found only in the cervix. It hasn’t spread to nearby tissues, lymph nodes, or distant organs. This stage is broken into substages based on how deep the tumor has grown and how wide it measures.
Stage IA is sometimes called “microinvasive” because the cancer can only be seen under a microscope. It’s divided further:
- IA1: The tumor has invaded no more than 3 mm deep into the cervical tissue and is no wider than 7 mm.
- IA2: Invasion is deeper than 3 mm but less than 5 mm, and still no wider than 7 mm.
These millimeter distinctions matter because IA1 tumors can often be treated with less extensive surgery, sometimes preserving the ability to have children.
Stage IB means the cancer is still confined to the cervix but is larger than the microinvasive threshold. It’s grouped by tumor size:
- IB1: The visible tumor is 4 cm or smaller.
- IB2: The tumor is larger than 4 cm.
Stage I cervical cancer falls under the “localized” category in survival statistics, where the 5-year relative survival rate is 91.8%.
Stage II: Spread Beyond the Cervix
In stage II, the cancer has grown beyond the cervix but hasn’t reached the lower third of the vagina or the pelvic wall. It’s divided into two substages based on where exactly the cancer has extended.
- Stage IIA: Cancer has spread to the upper two-thirds of the vagina but not into the tissue surrounding the uterus (called the parametrium).
- Stage IIB: Cancer has spread into the parametrium, the connective tissue that surrounds the uterus and helps hold it in place.
The distinction between IIA and IIB is important because IIB typically requires radiation and chemotherapy rather than surgery as the primary treatment. Stage IIA tumors, particularly smaller ones, may still be treated surgically in some cases.
Stage III: Reaching the Pelvic Wall or Lymph Nodes
Stage III means the cancer has spread further within the pelvis. This can happen in several ways, and any one of them qualifies:
- Stage IIIA: Cancer has reached the lower third of the vagina but not the pelvic wall.
- Stage IIIB: Cancer has grown into the pelvic wall, or it’s blocking one or both ureters (the tubes connecting the kidneys to the bladder). When a tumor blocks a ureter, the kidney can swell and stop working properly, a condition called hydronephrosis.
- Stage IIIC: Cancer has spread to pelvic or para-aortic lymph nodes, regardless of the tumor’s size or how far it extends locally. Pelvic lymph nodes sit near the cervix and uterus, while para-aortic nodes are higher up, near the large blood vessel running along the spine. Involvement of para-aortic nodes generally signals a more serious situation than pelvic nodes alone.
Stage IIIC was added to the FIGO system relatively recently to reflect the importance of lymph node involvement. Before this change, a small tumor with positive lymph nodes could be classified as an earlier stage, which didn’t accurately reflect the prognosis. Now, any cancer with confirmed lymph node spread is automatically stage III or higher.
Stages II and III fall under the “regional” category for survival statistics, with a 5-year relative survival rate of 64.0%.
Stage IV: Spread to Nearby Organs or Distant Sites
Stage IV is divided into two substages that represent very different situations:
- Stage IVA: Cancer has spread to nearby pelvic organs, specifically the bladder or rectum. The tumor has grown through the walls of these organs, not just pressed against them.
- Stage IVB: Cancer has spread to distant parts of the body. The most common sites are the lungs, liver, bones, and distant lymph nodes far from the pelvis.
The 5-year relative survival rate for distant cervical cancer is 20.5%. Treatment at this stage focuses on controlling the cancer’s growth, managing symptoms, and maintaining quality of life. Combinations of chemotherapy, radiation, immunotherapy, and targeted therapies are used depending on the specific situation.
Why Early Detection Changes Outcomes
The gap in survival between stages is dramatic. Localized cervical cancer has a 91.8% five-year survival rate, regional drops to 64.0%, and distant falls to 20.5%. This is why routine cervical screening (Pap tests and HPV tests) matters so much. Screening can catch precancerous changes years before they become invasive, and it can detect early-stage cancers when they’re most treatable.
Most early cervical cancers cause no symptoms at all. By the time symptoms like abnormal bleeding, pelvic pain, or unusual discharge appear, the cancer may have already progressed beyond stage I. Keeping up with recommended screening intervals is the most effective way to catch cervical cancer at a stage where treatment is most likely to succeed.