Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Clinical and Pathologic Staging of Prostate Cancer
Introduction
Cancer staging criteria are designed to characterize the extent of a tumor and the burden of disease. Staging criteria serve several purposes, including defining patient prognosis, helping to determine appropriate treatment, facilitating the exchange of information among treatment centers, and serving as a basis for cancer research.
The Whitmore–Jewett classification was the original system used to stage prostate cancer. This system has since been supplanted by the TNM staging system, which has been used to stage prostate cancer since 1975. The TNM system stages cancers by the extent of the primary tumor (T), involvement of regional lymph nodes (N), and the presence or absence of metastatic disease (M).
It is important to differentiate between the clinical and pathological stage of prostate cancers. Clinical staging assigns a stage using data available at the time of diagnosis from physical examination and imaging studies, before definitive treatment is initiated. This differs from the pathological staging, which assigns stage based on pathological examination of the radical prostatectomy specimen and any lymph nodes removed at the time of surgery. Thus, pathological stage is the more accurate of the two staging systems, as limitations in physical exam and imaging modalities can result in a clinical stage assignment that poorly estimates the true extent of disease.
The clinical and pathological staging criteria for prostate cancer, as defined by the American Joint Committee on Cancer (AJCC) Cancer Staging Manual, are shown in Table 39.1 .
Table 39.1
Clinical and Pathologic Staging Criteria for Prostate Cancer
| Primary tumor (T) | Regional lymph nodes (N) | Distant metastasis (M) | |||
|---|---|---|---|---|---|
| Clinical stage | |||||
| cTx | Primary tumor cannot be assessed | Nx | Regional lymph nodes not assessed | M0 | No distant metastasis |
| cT0 | No evidence of primary tumor | N0 | No regional lymph node metastases | M1 | Distant metastasis |
| cT1 | Clinically unapparent tumor neither palpable nor visible by imaging | N1 | Metastasis in regional lymph nodes | M1a | Nonregional lymph node(s) |
| cT1a | Tumor incidental histologic finding in 5% or less of tissue resected | M1b | Bone(s) | ||
| cT1b | Tumor incidental histologic finding in more than 5% of tissue resected | M1c | Other site(s) with or without bone disease | ||
| cT1c | Tumor identified by needle biopsy (e.g., because of elevated PSA | ||||
| cT2 | Tumor confined within the prostate | ||||
| cT2a | Tumor involves one-half of one lobe or less | ||||
| cT2b | Tumor involves more than one-half of one lobe but not both lobes | ||||
| cT2c | Tumor involves both lobes | ||||
| cT3 | Tumor extends through the prostate capsule | ||||
| cT3a | Extracapsular extension (unilateral or bilateral) | ||||
| cT3b | Tumor invades seminal vesicle(s) | ||||
| cT4 | Tumor is fixed or invades adjacent structures other than seminal vesicles such as rectum, bladder, levator muscles, and/or pelvic wall | ||||
| Primary tumor (T) | Regional lymph nodes (N) | Distant metastasis (M) | |||
|---|---|---|---|---|---|
| Pathologic stage | |||||
| pT2 | Organ confined | pNx | Regional nodes not sampled | M0 | No distant metastasis |
| pT2a | Unilateral, one-half of one side or less | pN0 | No positive regional nodes | M1 | Distant metastasis |
| pT2b | Unilateral, involving more than one-half of one side but not both sides | pN1 | Metastases in regional node(s) | M1a | Nonregional lymph node(s) |
| pT2c | Bilateral disease | M1b | Bone(s) | ||
| pT3 | Extraprostatic extension | M1c | Other site(s) with or without bone disease | ||
| pT3a | Extracapsular extension or microscopic invasion of bladder neck | ||||
| pT3b | Seminal vesicle invasion | ||||
| pT4 | Invasion of rectum, levator muscles, and/or pelvic wall | ||||
Clinical staging of prostate cancer
Criteria Used to Assign Clinical Stage and Staging Errors
The AJCC clinical staging criteria for prostate cancer are shown in Table 39.1 . Tumors that are neither palpable nor visible on imaging are assigned clinical stage T1. Those that are either palpable on digital rectal examination (DRE) or visible on either transrectal ultrasound (TRUS) or MRI are deemed to be clinical stage T2. Extraprostatic tumors are assigned to clinical stage T3, and those that invade adjacent organs are classified as clinical stage T4.
Prior research has suggested that errors in assigning clinical stage are common. Many of these staging errors are due to the inappropriate consideration of prostate biopsy results when assigning clinical stage. Per the AJCC, DRE and imaging findings at diagnosis are the criteria that should be considered when assigning clinical stage. Prostate biopsy results are not meant to factor into clinical stage assignment; however, many clinicians consider laterality of positive prostate biopsies when determining clinical stage. For example, a patient with a unilateral nodule on DRE and a bilaterally positive biopsy, should be assigned to clinical stage T2a or T2b. However, many of these patients are incorrectly assigned to clinical stage T2c due to inappropriate consideration of the bilaterally positive biopsy result.
Another common cause of clinical staging errors is the disregard for imaging findings when assigning clinical stage. In fact, positive imaging findings may be ignored in nearly two-thirds of patients when assigning clinical stage. These errors often occur when lesions on TRUS or MRI are disregarded, and patients with these abnormal findings are incorrectly assigned to clinical stage T1c.
Recent data suggest that MRI is a promising imaging modality for the diagnosis and staging of prostate cancer. This is likely to result in increased use of MRI and MRI/ultrasound fusion biopsies in the near future. The improved ability of MRI, compared to ultrasound, to visualize clinically localized prostate tumors should result in a higher prevalence of clinical T2 tumors, with a corresponding decrease in T1 lesions. However, it is unclear whether clinicians will tend to ignore MRI results, as is common with TRUS findings, when assigning clinical stage. A failure to incorporate MRI findings in clinical stage assignment will only increase the prevalence of staging errors. Future staging guidelines will need to reach a consensus regarding how imaging findings should be incorporated into clinical staging parameters.
Staging errors resulting from the misinterpretation of clinical staging criteria clearly lead to heterogeneous patient populations within the same clinical stage group. This heterogeneity can bias clinical research, generate miscommunication among practitioners, and potentially lead to the administration of inadequate or overly aggressive treatment to men with prostate cancer.
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here