Treating Prostate Cancer: Determining Its Severity

“How bad is it, Doc?”

It’s the question most men ask when they get over the shock of learning that their prostate biopsy found cancer. And the very same question is just as important for doctors as for patients. Before doctors can tell a man what therapeutic options are available to him, they must determine the severity of the cancer.

It’s a crucial question, but it can be hard to answer, particularly for prostate cancer. That’s because the disease is so variable, ranging from indolent tumors that are all but harmless to aggressive tumors that are life-threatening. At the extreme ends of the spectrum, predicting the behavior of prostate cancer is fairly accurate, but in the far-more-common middle, it’s a bit dicey. Still, doctors are making progress, and more will follow from new research.

To evaluate the severity of prostate cancer, doctors consider three factors: the anatomic stage of the disease, its microscopic grade, and biologic evidence of its likely behavior.

Anatomic staging

Prostate cancer usually begins in one area of the gland and then spreads, first within the prostate, then through its capsule to the seminal vesicles and neighboring tissues, and then to lymph nodes and bones. Different stages of the disease require different treatments.

Most prostate cancers are diagnosed by means of an ultrasound-guided transrectal core biopsy. Doctors will already have three important pieces of information by the time they perform the biopsy that confirms a diagnosis of prostate cancer: the results of a digital rectal exam (DRE), a blood PSA (prostate-specific antigen) level, and the results of a transrectal ultrasound (TRUS). For most men with PSAs below 10 nanograms per milliliter (ng/mL), bone scans, CTs, and MRIs are rarely positive — but even though they’re not necessary, many doctors order them anyway. It’s a waste of money, and it can produce as much worry as reassurance. On the other hand, men should have imaging tests if they have PSAs above 10, high-grade tumors, or worrisome symptoms such as back pain, weakness, or weight loss. In such cases, magnetic resonance imaging (MRI) or computed tomographic (CT) scanning can be used to look for enlarged lymph nodes in the pelvis and abdomen. In addition, a bone scan can be employed to look for metastatic disease. Some centers also use a nuclear imaging test called the ProstaScint, but it appears less useful than standard imaging techniques.

Unfortunately, however, patients with negative scans may still have microscopic spread of the tumor through the capsule. It is a crucial distinction that determines if a man is a candidate for surgery, but until new MRI techniques prove their mettle, the only way to be sure is to remove the gland surgically and send it to a pathologist for evaluation.

There are two major systems for evaluating prostate cancer based on the location and size of the tumor. The older Whitmore-Jewett classification system assigns a letter from A to D to the cancer, with a number to indicate gradations within each stage. Although it served well for many years, it’s been largely replaced by the TNM system, which evaluates the primary tumor (T stage), the lymph nodes (N stage), and distant metastases (M stage). Before surgery, patients are assigned to a stage based on clinical criteria; clinical staging can be noted by a “c” placed before the T stage. Patients who undergo radical prostatectomy are staged pathologically based on an examination of their tissues; a “p” before the T stage denotes pathological staging.

Anatomic staging is crucial to planning treatment. Tumors that are confined to the prostate (stages T1 and T2) are associated with a better prognosis than more advanced cancers. Men with early, organ-confined disease also have the option of surgical treatment, which does not offer the possibility of cure to men with more extensive disease.