PURPOSE: Understanding prostate-specific antigen (PSA) kinetics after radiation therapy plays a large role in the management of patients with prostate cancer (PCa). This is particularly true in establishing expectations regarding PSA nadir (nPSA) and PSA bounces, which can be disconcerting. As increasingly more patients are being treated with stereotactic body radiation therapy (SBRT) for low- and intermediate-risk PCa, it is imperative to understand the PSA response to SBRT. METHODS AND MATERIALS: PSA data from 5 institutions were retrospectively analyzed for patients with localized PCa treated definitively with SBRT alone from 2004 to 2016. Patients received 35 to 40 Gy in 5 fractions, per institutional standards. Patients who had less than 12 months of PSA data or received androgen deprivation therapy were excluded from this study. Linear and logistic multivariable analysis were performed to identify predictors of nPSA, bounce, and biochemical recurrence, and joint latent class models were developed to identify significant predictors of time to biochemical failure. RESULTS: A total of 1062 patients were included in this study. Median follow-up was 66 months (interquartile range [IQR], 36.4-89.9 months). Biochemical failure per the Phoenix criteria occurred in 4% of patients. Median nPSA was 0.2 ng/mL, median time to nPSA was 40 months, 84% of patients had an nPSA ≤0.5 ng/mL, and 54% of patients had an nPSA ≤0.2 ng/mL. On multivariable analysis, nPSA was a significant predictor of biochemical failure. Benign PSA bounce was noted in 26% of patients. The median magnitude of PSA bounce was 0.52 ng/mL (IQR, 0.3-1.0 ng/mL). Median time to PSA bounce was 18.1 months (IQR, 12.0-31.1 months). On multivariable analysis, age and radiation dose were significantly associated with a lower incidence of bounce. Joint latent class models modeling found that nPSA and radiation dose were significantly associated with longer time to biochemical failure. CONCLUSIONS: In this multi-institutional cohort of patients with long-term follow-up, we found that SBRT led to low nPSAs. In turn, lower nPSAs are associated with reduced incidence of, and longer time to, biochemical failure. Benign PSA bounces occurred in a quarter of patients, as late as several years after treatment. Further studies are needed to directly compare the PSA response of patients who receive SBRT versus other treatment modalities.
PURPOSE: Understanding prostate-specific antigen (PSA) kinetics after radiation therapy plays a large role in the management of patients with prostate cancer (PCa). This is particularly true in establishing expectations regarding PSA nadir (nPSA) and PSA bounces, which can be disconcerting. As increasingly more patients are being treated with stereotactic body radiation therapy (SBRT) for low- and intermediate-risk PCa, it is imperative to understand the PSA response to SBRT. METHODS AND MATERIALS: PSA data from 5 institutions were retrospectively analyzed for patients with localized PCa treated definitively with SBRT alone from 2004 to 2016. Patients received 35 to 40 Gy in 5 fractions, per institutional standards. Patients who had less than 12 months of PSA data or received androgen deprivation therapy were excluded from this study. Linear and logistic multivariable analysis were performed to identify predictors of nPSA, bounce, and biochemical recurrence, and joint latent class models were developed to identify significant predictors of time to biochemical failure. RESULTS: A total of 1062 patients were included in this study. Median follow-up was 66 months (interquartile range [IQR], 36.4-89.9 months). Biochemical failure per the Phoenix criteria occurred in 4% of patients. Median nPSA was 0.2 ng/mL, median time to nPSA was 40 months, 84% of patients had an nPSA ≤0.5 ng/mL, and 54% of patients had an nPSA ≤0.2 ng/mL. On multivariable analysis, nPSA was a significant predictor of biochemical failure. Benign PSA bounce was noted in 26% of patients. The median magnitude of PSA bounce was 0.52 ng/mL (IQR, 0.3-1.0 ng/mL). Median time to PSA bounce was 18.1 months (IQR, 12.0-31.1 months). On multivariable analysis, age and radiation dose were significantly associated with a lower incidence of bounce. Joint latent class models modeling found that nPSA and radiation dose were significantly associated with longer time to biochemical failure. CONCLUSIONS: In this multi-institutional cohort of patients with long-term follow-up, we found that SBRT led to low nPSAs. In turn, lower nPSAs are associated with reduced incidence of, and longer time to, biochemical failure. Benign PSA bounces occurred in a quarter of patients, as late as several years after treatment. Further studies are needed to directly compare the PSA response of patients who receive SBRT versus other treatment modalities.
Authors: Rebecca G Levin-Epstein; Naomi Y Jiang; Xiaoyan Wang; Shrinivasa K Upadhyaya; Sean P Collins; Simeng Suy; Nima Aghdam; Constantine Mantz; Alan J Katz; Leszek Miszczyk; Aleksandra Napieralska; Agnieszka Namysl-Kaletka; Nicholas Prionas; Hilary Bagshaw; Mark K Buyyounouski; Minsong Cao; Nzhde Agazaryan; Audrey Dang; Ye Yuan; Patrick A Kupelian; Nicholas G Zaorsky; Daniel E Spratt; Osama Mohamad; Felix Y Feng; Brandon A Mahal; Paul C Boutros; Arun U Kishan; Jesus Juarez; David Shabsovich; Tommy Jiang; Sartajdeep Kahlon; Ankur Patel; Jay Patel; Nicholas G Nickols; Michael L Steinberg; Donald B Fuller; Amar U Kishan Journal: Radiother Oncol Date: 2020-10-07 Impact factor: 6.280
Authors: Juanita M Crook; Chad Tang; Howard Thames; Pierre Blanchard; Jeremiah Sanders; Jay Ciezki; Mira Keyes; W James Morris; Gregory Merrick; Charles Catton; Hamid Raziee; Richard Stock; Frank Sullivan; Mitch Anscher; Jeremy Millar; Steven Frank Journal: Radiother Oncol Date: 2020-04-27 Impact factor: 6.280
Authors: Luca F Valle; Dan Ruan; Audrey Dang; Rebecca G Levin-Epstein; Ankur P Patel; Joanne B Weidhaas; Nicholas G Nickols; Percy P Lee; Daniel A Low; X Sharon Qi; Christopher R King; Michael L Steinberg; Patrick A Kupelian; Minsong Cao; Amar U Kishan Journal: Front Oncol Date: 2020-05-20 Impact factor: 6.244
Authors: Thomas Zilli; Sandra Jorcano; Samuel Bral; Carmen Rubio; Anna M E Bruynzeel; Angelo Oliveira; Ufuk Abacioglu; Heikki Minn; Zvi Symon; Raymond Miralbell Journal: Cancer Med Date: 2020-03-11 Impact factor: 4.452