Cancer is a major public health problem, accounting for roughly 25% of all deaths in the United States. Though many treatments have been devised for various cancers, these treatments often vary in severity of side effects. It is useful for clinicians to know how aggressive a patient's cancer is in order to determine how aggressively to treat the cancer.
For example, most patients with early-stage asymptomatic prostate cancer are treated with radical prostatectomy or radiotherapy and optionally adjuvant therapy (e.g., hormone or chemotherapy), all of which have severe side effects. For many of these patients, however, these treatments and their associated side effects and costs are unnecessary because the cancer in these patients is not aggressive (i.e., grows slowly and is unlikely to cause mortality or significant morbidity during the patient's lifetime). In other patients the cancer is virulent (i.e., more likely to recur) and aggressive treatment is necessary to save the patient's life.
Some tools have been devised to help physicians in deciding which patients need aggressive treatment and which do not. In fact, several clinical parameters are currently in use for this purpose in various different cancers. In prostate cancer, for example, such clinical parameters include serum prostate-specific antigen (PSA), Gleason grade, pathologic stage, and surgical margins. In recent years clinical parameters have been made more helpful through their incorporation into continuous multivariable postoperative nomograms that calculate a patient's probability of having cancer progression/recurrence. See, e.g., Kattan et al., J. CLIN. ONCOL. (1999) 17:1499-1507; Stephenson et al., J. CLIN. ONCOL. (2005) 23:7005-7012. Despite these advances, however, many patients are given improper cancer treatments and there is still a serious need for novel and improved tools for predicting cancer recurrence.