Genitourinary Cancer

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SU_28_2281 - Prostate Cancer-Specific Mortality Following Salvage Post-Prostatectomy Radiation Therapy: A Competition Between Age and Time to Biochemical Failure

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Prostate Cancer-Specific Mortality Following Salvage Post-Prostatectomy Radiation Therapy: A Competition Between Age and Time to Biochemical Failure
W. C. Jackson1, K. Suresh1, V. Tumati2, R. T. Dess1, P. D. Soni1, S. G. Zhao1, Z. S. Zumsteg3, R. Hannan2, B. Hollenbeck4, A. George4, S. Kaffenberger4, S. Salami4, J. W. D. Hearn1, S. Jolly5, T. M. Morgan4, R. Mehra6, M. Schipper1, F. Y. Feng7, N. B. Desai2, and D. E. Spratt1; 1Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 2Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 3Cedars-Sinai Medical Center, Los Angeles, CA, 4Department of Urology, University of Michigan, Ann Arbor, MI, 5Michigan Medicine, Ann Arbor, MI, 6Department of Pathology, University of Michigan, Ann Arbor, MI, 7Department of Radiation Oncology, University of California San Francisco, San Francisco, CA

Purpose/Objective(s): While biochemical recurrence (BCR) following post-prostatectomy salvage radiation therapy (SRT) is common, the time from SRT to BCR is heterogeneous. Furthermore, disease progression following BCR is variable, and as such, some men with BCR post-SRT are unlikely to die from prostate cancer. We therefore sought to develop a model to estimate a man’s risk for prostate cancer-specific mortality (PCSM) incorporating patient age at BCR and time to BCR post-SRT.

Materials/Methods: We performed an institutional review board approved multi-institutional retrospective analysis on 547 men consecutively treated with SRT following prostatectomy. Men with lymph node involvement at prostatectomy were excluded. BCR was defined as a rise in PSA ≥ 0.2ng/mL above the post-SRT PSA nadir followed by a second equal or higher value. PCSM was defined as any death directly attributable to prostate cancer or death in a man with distant metastases (DM). Cumulative incidence curves were estimated using a Fine and Gray regression model to evaluate the effect of time-to-BCR and patient age on risk of PCSM, while accounting for non-prostate related deaths as competing risks.

Results: Median follow-up post-SRT was 8.4 years. Of the 547 men treated, 274 experienced BCR. Median time to BCR for all patients was 4.9 years. The estimated 10-year cumulative incidence of BCR was 60%. For the subset of men with BCR, median time to BCR was 1.3 years. There was an inverse relationship between the time-to-BCR post-SRT and the risk of developing metastatic disease. Men with BCR ≤ 18 months had an increased incidence of PCSM than men with a later BCR (HR: 12.3, 95%CI: 5.95-25.2, p<0.001). We next created a model to account for age and time to BCR to predict the cumulative incidence of PCSM. Interestingly, age and time to BCR had a complex interaction. The 10-year estimated cumulative incidence of PCSM for a 50-year-old and 70-year-old man with BCR 18 months post-SRT were similar (24.5% and 28.8%, respectively). In contrast, the 10-year estimated cumulative incidence of PCSM for a 50-year-old and 70-year-old man with BCR 5 years post-SRT were lower, and there was a more apparent interaction of age and time to BCR (2.4% and 10.7%, respectively).

Conclusion: Given the frequency of BCR following SRT, we created a simple and clinically useful model to estimate a man’s risk of PCSM based on age at BCR and time-to-BCR post-SRT. Men with BCR within 18 months of SRT are at high risk for PCSM, and this holds true for both younger and older men. In general, older men were at higher risk for PCSM, consistent with literature suggesting that elderly men are more likely to be diagnosed with aggressive prostate cancer. Our data suggests that even with delayed time to BCR, older men still have high rates of PCSM, underscoring the importance of life expectancy estimates to account for competing risks in these men.

Author Disclosure: W.C. Jackson: None. K. Suresh: None. S.G. Zhao: Travel Expenses; GenomeDx. Patent/License Fees/Copyright; GenomeDx, Celgene. B. Hollenbeck: None. S. Kaffenberger: None. J.W. Hearn: None. S. Jolly: None. T.M. Morgan: None. F.Y. Feng: Research Grant; GenomeDx. Advisory Board; GenomeDx, Dendreon, Sanofi. Travel Expenses; GenomeDx. Liaison, GU Translational Research Program; Radiation Therapy Oncology Group. President and Founder; PFS Genomics. N.B. Desai: Employee; Parkland Dallas County Hospital. Uncompensated advisory single meeting; Accuray.

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