What Defines Cancer "Stages"?
Staging is a way to describe the severity of your cancer based on the extent of your original (primary) tumor and whether your cancer has spread to other areas of your body. Staging is important because it can enable your oncologist to work with you to develop an appropriate treatment plan. It can also help give some indication of your prognosis.
But remember, no one can tell you for sure what your prognosis will be.
There is a well-established cancer “staging system” that is widely used by oncologists, which is both a good thing and a bad thing. It’s a good thing because oncologists and pathologists around the world generally agree with the system.
As a result, you can be confident that if you’re given a “stage” for your cancer after a definitive evaluation by your oncologist, you would have received that same stage had that evaluation been conducted by another oncologist. This is because doctors follow agreed-upon criteria for staging, which is as follows:
Stage 0: The cancer is noninvasive.
Stages I, II, and III: The higher the number, the more extensive the disease. The tumor may be larger or may have spread beyond the organ in which it first developed to nearby lymph nodes and/or organs adjacent to the location of the primary tumor.
Stage IV: The cancer has spread to distant sites in the body.
Sometimes additional letters and numerical suffixes are used to subdivide cancer stages. For example, a stage IIIE+S tumor indicates extralymphatic spread (as marked by the E) and splenic involvement (as marked by the S).
Now the bad news. Because the fundamental concepts behind tumor staging haven’t changed substantially since the process was developed many decades ago, certain assumptions considered reasonable at that time don’t appear to be appropriate today. Perhaps the most important fact is that formal staging is only done at the initial diagnosis.
The drawback of this system is that it doesn’t account for recurrence or metastasis, which may occur sometime after a tumor is initially staged.
With the exception of blood-related malignancies (leukemia, myeloma, lymphoma), most cancers are staged based on findings at the time of initial surgery. Additional information to define the cancer stage may come from imaging studies (such as a CT scan of the lungs or abdomen) and specific blood tumor marker studies.
Patients who experience a cancer recurrence in a distant site commonly say that they have “stage IV cancer,” but this isn’t technically correct. A cancer that initially presents as a localized process (“stage I”) will always be labeled as stage I. Clearly, this situation can be quite confusing.
The stage of a cancer provides very general information about the extent of its spread and observed location within the body. In most cases, this information is essential in defining the best initial treatment plan.
For example, if you have a lung cancer that appears to be entirely localized without involvement of regional lymph nodes, it will be treated with surgery (assuming you’re medically able to tolerate it); on the other hand, if you have extensive lymph node involvement, you probably won’t undergo surgery, and you’ll have radiation plus chemotherapy instead.
The relevance of staging varies based on the specific tumor type in question and the available treatment options to be considered in that particular setting. For example, surgery may be used to treat one tumor type (such as ovarian cancer) even in the presence of documented stage IV cancer, while documented regional lymph node involvement (stage II) for other tumor types may modify the therapeutic strategy away from surgery and toward radiation.
These decisions are largely based on the results of large-scale clinical trials that have been conducted over the past several decades and have helped to define optimal disease management in particular clinical settings.
Blood tumors are all essentially “stage IV” at diagnosis, and treatment will be with anticancer drugs (possibly with external radiation to large masses) rather than surgery.
Unfortunately, despite improvements in diagnostics, it’s impossible to precisely know if an individual cancer truly remains localized at the time of diagnosis, despite negative imaging or tumor marker studies. Therefore, although you may have stage I breast cancer, you may, in fact, have microscopic (unable to be seen on imaging studies) metastatic cancer. This is why adjuvant chemotherapy is given for certain cancer types.
Despite the drawbacks and challenges of cancer staging, in general, prognosis is excellent when you’re found to have an early-stage cancer, rather than more advanced disease. However, with the increasing effectiveness of treatment options for multiple tumor types — even advanced cancers — you can experience genuinely meaningful benefits associated with treatment, including substantial improvement in cancer-related symptoms, improved quality of life, and prolonged survival.