Biochemical Recurrence in Prostate Cancer and Temporal Association to Bone Metastasis

BACKGROUND Prostate cancer is a common cancer in men. Radical prostatectomy, i.e., the surgical removal of the entire prostate, is a frequently used option. Biochemical recurrence (BCR), i.e., detectable prostate specific antigen (PSA), is common in some men following such treatment. The timing of BCR to metastatic spread of disease in bones is usually a few years. If the biochemical failure occurs after a longer duration from the time of curative intent, it is generally believed to lead to local recurrence. CASE REPORT We report on two cases. A 78-year-old male was diagnosed with Gleason 7, prostate cancer in 2001. He subsequently underwent an open radical prostatectomy. Serial post-operative PSA's were undetectable (<0.01 ng/mL) up to 2016. He was diagnosed with a detectable PSA for the first time with a value of 0.3 ng/mL, that year. The PSA continued to rise to a level of 1.1 ng/mL. This rise in the PSA was within a 12-month interval. Subsequent bone scan and bone biopsy detected prostate cancer metastasis in multiple bones. Our second case was a 65-year-old male who underwent a laparoscopic radical prostatectomy in the year 2006 for a biopsy proven prostate cancer with Gleason 3+4=7. Serial post-operative PSA's were undetectable up to 2017. Within a span of 8 months, the PSA rose from 0.3 ng/mL to 1.52 ng/mL. A positron emission tomography scan demonstrated pubic bone lesion indicative of prostate cancer metastasis. CONCLUSIONS BCR can occur a decade after curative intent treatment of prostate cancer. The duration from BCR to detectable metastasis can be shorter. We demonstrated here that the site of recurrence, in such scenarios, can be distant metastasis and not local recurrence alone. Better imaging modalities are needed to identify the spread of prostate cancer at low levels of PSA.