Approach to Staging and Monitoring

Jeffrey W. Clark

Staging and monitoring are essential components of cancer management. Staging is performed to assess the extent of disease, and it is used to help determine prognosis and choice of therapy. Monitoring serves to detect the reappearance or progression of cancer and contributes importantly to updating prognosis and revising treatment plans. Staging and monitoring strategies are determined by tumor type, natural history, response to therapy, and characteristic pattern of spread. The frequency and duration of monitoring depend on the rate of disease recurrence.

The primary physician, in collaboration with the oncologist, is in an ideal position to conduct much of the needed noninvasive staging and monitoring. To do so effectively requires an understanding of the limitations of the many available laboratory tests and radiologic procedures so that important decisions about test and procedure selection can be made effectively and unnecessary expense avoided.

STAGING (1, 2 and 3)

Terminology and Principles of Staging

Cancer stage is primarily defined by the anatomic distribution of disease. The task of staging is to identify the amount and distribution of tumor. Several staging systems are used to express the extent of disease. Most incorporate designations for local disease (confined to a visceral site), regional extension (with or without involvement of contiguous lymph nodes), and distant metastasis. By far, the most commonly used one for solid tumors is the TNM system (developed by the International Union Against Cancer [UICC]; see below for more details). Hematologic malignancies incorporate other factors (e.g., bone marrow involvement) that necessitate different staging systems.

The TNM System

To standardize staging, the TNM system is being used with increasing frequency. The T refers to tumor size, the N to lymph nodes, and the M to metastases. Numbers are added to designate subcategories, reflecting the size of the tumor (Tx [unknown], Tis, T0 to T4), the degree of nodal involvement (N0 to N3), and the absence or presence of distant metastases (Mx [unknown], M0, or M1).

Although the specifics vary among tumors, the various subcategory designations have specific meaning. The T categories are as follows: Tx, unknown; Tis, carcinoma in situ; T0, no detectable primary tumor; T1, the smallest measurable tumor mass or tumor; T2, larger tumor mass or tumor extending
directly to adjacent structures; T3, very large tumor or still further direct extension; and, T4, tumor of any size with local tissue invasion and direct extension into adjacent structures. As regards N categories, N0 designates no nodal metastasis; N1, small number of regional lymph nodes; N2, more extensive regional lymph node involvement; and N3, more numerous or distant regional nodal metastasis. Mx designates unknown metastatic status, M0 no identified metastases, and M1 indicates metastatic disease.

The TNM staging classification is increasingly preferred because of its consistency, comparability, and precision. Other staging systems commonly used for particular cancers have direct correlates in the TNM system and can be expressed in its terms. (The most widely used staging system in the United States is that of the American Joint Committee on Cancer [AJCC].) Most staging systems use numbers to define specific stages. Although the specific numbering can vary significantly between cancers even within a given staging system, in general stage 0 are usually in situ cancers, stage I are small cancers confined to the primary site, stage II are larger cancers but still confined to the primary site, stage III cancers most commonly include involvement of regional lymph nodes but no metastases to distant sites. Stage IV cancers include involvement of distant metastases. For the specifics for any given cancer, it is important to refer to the staging table for that cancer (1).

Staging Principles

A well-designed staging evaluation reflects the characteristic pattern of spread of a malignancy, both locally and distantly. Staging is performed clinically (by means of history, physical examination, imaging procedures, and serum markers), pathologically (by direct sampling of tissue), and for most tumors (except leukemias) with imaging studies. The three are complementary. As specific molecular characteristics of malignancies continue to be defined, these are increasingly being utilized in combination with TNM staging to identify the appropriate management and treatment for each patient.

Staging Procedures

History and Physical Examination

Although much emphasis is placed on laboratory and radiologic procedures in clinical staging, the history and physical examination continue to play central roles in the determination of tumor mass, local spread, and metastasis. In almost every cancer workup, historical and physical data are required for intelligent staging and determination of the need for additional study. The failure to conduct a careful history and physical examination risks subjecting the patient to unnecessary or misguided studies.

Imaging Procedures

For most cancers (except leukemias), it is also necessary to obtain further information noninvasively regarding the anatomic extent of disease using imaging studies. Among the most frequently ordered are computed tomography (CT), magnetic resonance imaging (MRI), ultrasonography, and radionuclide scanning (particularly positron emission tomography [PET] scans). Even the plain film of the chest or bone can sometimes provide diagnostic information, although these are limited by lack of specificity and inability to detect very early lesions. All of these technologies will continue to evolve not only technically but also in terms of cost, convenience, and patient comfort. Ongoing and future studies should help define appropriate use of specific imaging modalities for a given situation.

Computed Tomography and Magnetic Resonance Imaging.

CT and MRI represent important advances over older contrast and radionuclide studies. They provide not only improved detection of tumor but also better quantification of tumor burden. CT is the less expensive and more readily available of the two technologies, but MRI provides enhanced resolution in some areas, particularly the central nervous system. In addition, it avoids the use of radiation.

CT of the chest is particularly useful for staging patients with lung cancer and those with malignancies with high rates of metastasis to the lung and mediastinum (e.g., sarcomas, melanomas, Hodgkin disease, non-Hodgkin lymphoma, and testicular cancers). CT of the abdomen enhances evaluation of many organs including the liver, adrenals, kidneys, pancreas, and retroperitoneum by identifying lesions that are difficult to detect noninvasively. A positive scan result, confirmed by biopsy if appropriate, can obviate the need for surgical exploration in patients who are not surgical candidates. Results of pelvic CT for the detection and staging of early ovarian and prostate cancers have been variable; the test often lacks sensitivity in the detection of early disease or early spread to pelvic nodes. MRI or CT of the head has virtually eliminated invasive and radionuclide staging studies of the central nervous system. Conducting the study with contrast agents (as appropriate, but usually done unless there is a contraindication) can further improve sensitivity of both CT and MRI.

MRI, particularly in the central nervous system, has contributed to the staging and monitoring of cancer. Compared with CT, it is more sensitive and offers a better assessment of the posterior fossa and the spinal cord. Its increased cost is justified when enhanced sensitivity is required. MRI can sometimes be useful in helping to evaluate lesions within an organ (e.g., liver) seen on CT scan that need additional characterization. In addition, MRI continues to be utilized as a means of staging of pelvic malignancies since this can be an area of decreased sensitivity for CT imaging. Ultrasound also continues to be evaluated as a better means of imaging the pelvis (see under ultrasound).

Only gold members can continue reading. Log In or Register to continue