The role of the tumor growth fraction has been investigated poorly in metastatic castration-resistant prostate cancer (mCRPC). The aim of this study was to assess whether some prostate-specific antigen (PSA)-related variables of tumor cell kinetics predict the overall survival in early and late mCRPC, and to explore changes in the tumor growth fraction after chemotherapy.
A retrospective analysis of 3 tumor cell kinetic variables in patients with mCRPC receiving first-line chemotherapy has been performed. The PSA-related tumor growth rate, the log ratio, and the tumor response have been measured at 3 different times. A further analysis has been performed after stratification by the Gleason score and chemotherapy. Finally, tumor growth after progression to chemotherapy has been explored.
G at castration resistance is significantly associated with survival after chemotherapy among patients with a low Gleason score (r=−0.650, P-value=0.022). At the time of first-line chemotherapy, both G and PSA response rates report a significant relationship with survival. At the time of postchemotherapy progression, only the G after 12 weeks of chemotherapy maintains a relationship with survival in patients with a low Gleason score (r=−0.483, P-value=0.023); in particular, a tumor growth rate <−0.5%/day appears to be associated with a poor postprogression survival. Despite the lack of correlation between postprogression G and postprogression survival, the response to chemotherapy defines 2 groups with different growth characteristics.
Among patients with mCRPC, tumor cell kinetics appears to be able to predict the outcome, especially in tumors with a low Gleason score.