Changes in Cancer Volume in Serial Biopsies of Men on Active Surveillance for Early Stage Prostate Cancer

Abstract

We described changes in tumor volume on serial biopsies during an extended period in men on active surveillance. The study cohort included men diagnosed with prostate cancer between 1998 and 2010 enrolled in active surveillance with 6 or more months of followup. Change in volume over time was assessed as change in percent cores positive, percent cancer in 1 biopsy core and the doubling of total cancer volume (mm). Logistic regression was used to determine the association between grade and volume progression. A total of 399 men met the study inclusion criteria. Mean patient age was 61.8 years old and 313 (78%) had low risk disease. Overall 231 (58%) men had stable disease on repeat biopsies. There were 39 (10%) men with a volume increase, defined by an increase to more than 33% cores involved or an increase in maximum single core positive to more than 50%, and there were 44 (11%) with an increase in volume and grade. Approximately 10% of men experienced a decrease in cancer volume. On multivariate analysis there was a significant association between grade and volume progression on any biopsy (OR 3.07), and a doubling of tumor length (mm) at 5 years (OR 6.30). Prostate cancer volume increases and decreases at a similar rate of 10% per biopsy. An increase in tumor volume is associated with an increase in cancer grade on early repeat biopsies. However, there is a large degree of variation in cancer volume over time.