Changes in cancer volume in serial biopsies of men on active surveillance for early stage prostate cancer

Purpose: We described changes in tumor volume on serial biopsies during an extended period in men on active surveillance. Materials and Methods: 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. Results: 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). Conclusions: 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.