Cancer Diagnosis, Staging and Monitoring
How is cancer diagnosed?
Initial evaluation for cancer is usually prompted either by suspicious signs and symptoms, or by abnormal findings during screening tests and routine medical exams. This initial evaluation might include Imaging studies (X-Rays, CT scans, MRIs, Ultrasound, etc) as well as blood and urine tests. However, with limited exceptions, diagnosis of cancer can not be made without obtaining and evaluating suspicious tissue (Pathology).
Pathology
Why is pathology necessary? There are several very important reasons, some of which are presented below:
- Sometimes diseases other than cancer may mimic cancer on imaging studies and laboratory tests.
- Appropriate treatment of cancer largely depends on where this cancer originated. For example, cancer of the liver, called hepatocellular carcinoma, is treated very differently from cancer of the colon which spread to the liver.
- Even cancers of the same origin may behave differently, have different prognosis and require different treatment depending on a more precise characterization of tumor cells. For example, if breast cancer cells are found to have hormone receptors, tumor growth can be controlled by hormone therapy. If hormone receptors are negative, hormone therapies will not work.
- Tissue obtained for pathology can also be used to perform genomic tests on the tumor cells. Genomic tests are already employed in some cases to characterize tumor aggressiveness, to decide on the best therapeutic strategy and to select medications which are likely to benefit the individual patient. As our knowledge grows, genomic testing on cancer cells will become an increasingly important tool for tailoring therapeutic approaches to a particular tumor.
- Note that genomic testing performed on tumor cells should not be confused with genetic testing for inherited diseases and cancer predisposition. Changes in the genes responsible for susceptibility to cancer are either passed on from parents, or occur early in the development of human embryo. They are present in normal cells and tissues of an individual and make these cells prone to acquire additional alterations required for development of a tumor. According to our present knowledge, the majority of adult cancer patients do not have inherited predisposition for cancer. Their tumors develop from a completely normal cell and therefore, genetic abnormalities identified in the tumor are not found in normal tissues of the same patient.
It is important to understand that, although Pathology is a crucially important and powerful tool, it is not a magic wand. Occasionally, it is not possible to determine the origin of the tumor despite all the arsenals of tests presently available to doctors.
Tumor Markers
Tumor markers are molecules that are produced by tumors and could be detected in the blood. Some of the commonly used markers are presented below:
- Carcinoembrionic Antigen (CEA)
- Prostate Specific Antigen (PSA)
- Alpha Fetoprotein (AFP)
- CA 19.9
- CA 27.29
- CA 125
Evaluation of the tumor markers can help direct the search for the cancer’s place of origin. For example, bone lesions in conjunction with elevated PSA will prompt evaluation for prostate cancer. However, tumor markers are not a substitute for Pathology in the majority of cases. Use of tumor markers in monitoring responses to therapy and in the follow up of cancer survivors is discussed below.
Cancer Staging
Cancer Staging describes how big the cancer is and how far did it spread. The most widely used staging system is called TNM.
- “T” characterizes the size of the primary tumor, how deep it penetrates into the tissue and whether it involves neighboring organs and structures.
- “N” reports the number of lymph nodes involved with cancer and where they are located.
- “M” stands for metastases. The higher the numbers, the more advanced is the cancer. Combination of T, N and M provides the final stage, for example, T1N0M0, Stage I or T2N1M1, Stage IV. Stage IV is the highest stage and usually represents disease that spread to other parts of the body. Note that cancers which originate in blood cells (lymphomas, leukemias) are either staged in a different way, or not staged at all.
Why is staging important? Together with pathology, stage is a basis for selecting appropriate treatment. In general, very “early” cancers are treated with surgery alone. Larger cancers or cancers that spread to lymph nodes might require additional chemo- and/or radiation therapy before and/or after surgery. In patients with metastatic disease surgery is sometimes used to remove metastases that are threatening vital organs (for example, spinal cord or brain), to decrease the bulk of the disease or, in selected cases, to remove all disease sites, but the majority of patients with widely spread cancer derive more benefit from drug therapy.
It is important to emphasize that cancer stage is only one of several criteria that determines prognosis. Some wide spread indolent cancers may progress very slowly or stay in remission for a long time while earlier stage aggressive cancers may recur.
Treatment Decisions
After cancer is diagnosed and staged, it is time to make therapeutic decisions. Current Oncology already has a wide arsenal of therapies and strategies available (See
Types of Cancer Therapy ). Thousands of new medications and approaches are in the works right now, giving us hope. Unfortunately, medications used for therapy of cancer generally “come with a cost” of toxicity (See
Side Effects of Cancer Therapy ). It is therefore very important to select an approach which will fit you personally. The final choice will depend on the type and spread of your tumor, on the presence or absence of symptoms requiring immediate attention, on how aggressive you want to be with your treatment, on your preference for treatment timing and schedule and on your general state of health.
Patients with resectable cancer will generally undergo surgery, sometimes followed or preceded by chemotherapy and/or radiotherapy. Patients with certain types of disease (for example, leukemias, lymphomas, some types of esophageal or head and neck cancers), and a majority of patients with metastatic disease will be offered drug therapy and/or radiation therapy instead of surgery.
How long you will be receiving therapy will again depend on the type and stage of your disease. After completion of all planned treatments we will continue to watch you closely for any sign of cancer recurrence or progression (see Close Monitoring below)
Monitoring
The goal of monitoring is to watch for cancer recurrence or progression in order to intervene in time. This strategy could be used at any time during your fight with cancer and usually consists of follow up visits, physical exams, laboratory tests and imaging studies. A particular type of imaging study (CT, MRI, PET, PET/CT) will primarily depend on the location and type of the tumor.
All patients on active therapy will be closely monitored for response and/or signs of disease progression with regular physical exams and imaging studies. Tumor markers are also helpful in checking the efficiency of therapy. Because these molecules are produced by tumor cells, their levels will, in general, go down when cancer cells are killed, and surge back up when cancer recurs or stops responding to therapy. It has to be stressed, however, that tumor markers are generally not as reliable as imaging studies.
All patients who have their cancers completely removed and have completed all planned therapy will be monitored for signs of recurrence (Surveillance). Regular evaluations are crucial because they may allow us to catch cancer recurrence early and intervene on time. This strategy is also utilized in patients with advanced disease who received their planned therapy and are on “treatment holiday.”
Close monitoring is sometimes employed up front, when patients with certain slow growing, indolent cancers are watched without therapy until disease progression or symptoms prompt initiation of active treatment (Watchful Waiting).
Depending on the clinical situation, frequency of follow-up visits, laboratory tests and imaging studies vary. For example, a patient with colon cancer which was completely resected three years ago will be seen once in six months, while patient with metastatic disease on treatment holiday will be seen every two to four weeks.