Prostate cancer progression in the presence of undetectable or low serum prostate-specific antigen level.

Background: The serum prostate-specific antigen (PSA) level after definitive treatment for prostate cancer (PC) is a powerful predictor of outcome. Occasionally, PC progression can occur despite low or undetectable PSA levels. The authors report on the clinical and pathologic characteristics of patients who experienced PC progression with undetectable or low PSA levels.

Methods: From an electronic database of all patients with PC who were treated at The University of Texas M. D. Anderson Cancer Center between 1999 and 2004, a group of 46 patients was identified who had progression to metastatic PC detected with concomitant PSA levels from 0.1 ng/mL to 2 ng/mL. Patient charts were reviewed for tumor stage, Gleason score, pretreatment PSA level, and the presence of atypical histologic variants (ie, ductal, sarcomatoid, or small cell cancers). The nadir PSA level after treatment and the PSA level at the time metastatic PC was detected were determined. The patients were followed semiannually, and imaging studies were obtained at the discretion of treating physicians. The sites of metastasis and histologic confirmation were reported when available.

Results: Twenty-three of 46 patients underwent radical prostatectomy, 11 patients received radiation therapy, and 12 received hormone treatment as their initial form of therapy. Progression to metastatic disease with concomitant, undetectable PSA levels occurred in 10 patients, including 3 patients who had not received treatment with hormones. The sites of metastasis included bone (n = 35 patients), liver (n = 7 patients), retroperitoneal lymph nodes (n = 5 patients), lungs (n = 4 patients), and brain (n = 1 patient). Aggressive and locally advanced PC were common features in these patients: Eighty-five percent had Gleason scores >or=7, 63% had clinical T3 or T4 tumors, and 41% had pretreatment PSA levels >10 ng/mL. Atypical histologic variants were observed in 21 patients (46%) and in 8 of 10 patients who progressed with undetectable PSA levels. In 10 patients (22%), metastasis were detected in the presence of an undetectable PSA level. Eight of those patients had small cell carcinoma. In 19 patients (41%), progression to metastasis occurred without any increase in their PSA from the nadir level. Thirty-one patients (67%) were asymptomatic at the time metastasis was detected, and the detection of metastasis in these patients occurred only because of routine imaging studies.

Conclusions: Progression of PC may occur despite undetectable or low PSA levels. Complete physical evaluation and imaging studies may be indicated in the surveillance of patients with high-grade, locally advanced tumors, especially when atypical histologic variants are present.