Genitourinary Cancer

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SU_28_2285 - PSA Velocity before Biochemical Failure is Associated with Distant Metastasis after Partial Prostate Treatment with Brachytherapy

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

PSA Velocity before Biochemical Failure is Associated with Distant Metastasis after Partial Prostate Treatment with Brachytherapy
M. King1, P. L. Nguyen1, N. Boldbaatar1, D. D. Yang2, R. A. Cormack3, C. J. Beard4, M. D. Hurwitz5, W. W. Suh6, C. M. Tempany7, A. V. DAmico8, and P. F. Orio III7; 1Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 2Harvard Medical School, Boston, MA, 3Department of Radiation Oncology, Brigham and Women’s Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 4Department of Radiation Oncology, Brigham and Women's Hospital, Boston, MA, 5Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, 6Cancer Center of Santa Barbara, Santa Barbara, CA, 7Brigham and Women's Hospital, Boston, MA, 8Dana Farber Cancer Institute and Brigham & Women's Hospital, Boston, MA

Purpose/Objective(s): The prognosis for men who experience biochemical failure (BF) after partial prostate therapy (e.g. brachytherapy (BT), cryotherapy, high frequency ultrasound) has been difficult to define, since residual gland continues to produce prostate specific antigen (PSA). We sought to determine whether PSA velocity prior to BF was associated with time to metastasis for men who underwent partial gland treatment with BT, after adjusting for known prognostic factors and salvage treatments.

Materials/Methods: We conducted a retrospective analysis of all men who experienced BF (nadir + 2) after magnetic resonance imaging-guided prostate BT to the peripheral zone. We excluded men without a PSA value within the 2 years prior to BF or those who developed metastasis within 1 year after BF. Fine and Gray’s competing risks regression was utilized to determine whether PSA velocity was associated with time to metastasis after BF. The model was adjusted for age at BF, National Comprehensive Center Network risk category [very low (reference)/low/intermediate], time to BF, nadir PSA before BF, salvage androgen deprivation therapy (ADT), and salvage BT/radical prostatectomy (RP). Time 0 was the time of BF.

Results: Of the 354 men who underwent partial gland BT, 105 patients experienced BF. The median time to BF after initial therapy was 4.5 (inter-quartile range [IQR]: 2.4-7.7) years. The median follow-up time after BF was 6.0 (IQR: 3.6-9.2) years. Twenty-three patients received salvage BT/RP and 17 received ADT. Twenty patients developed metastases at a median interval of 5.0 (IQR: 3.3-9.2) years after BF. In the multivariate model, PSA velocity was significantly associated with metastasis (adjusted hazard ratio 1.18 [95% confidence interval (CI): 1.05-1.27] per ng/mL/year increase, p < 0.001), whereas salvage ADT (0.43 [0.13-1.44]; p = 0.17) and salvage BT/RP (HR 0.73 [0.23-2.39]; p = 0.61) were not. PSA velocity, dichotomized at 3.0 ng/year (77th percentile) remained significant (6.12 [2.31, 16.26]; p < 0.01). The median PSA velocities for the 5 patients who died from prostate cancer compared with the remaining that did not were 4.2 (IQR: 3.6-8.3) ng/mL/year and 1.5 (IQR: 0.7-2.7) ng/mL/ year, respectively.

Conclusion: PSA velocity > 3.0 ng/mL/ year prior to BF was associated with time to metastasis after partial prostate treatment, whereas salvage ADT and local treatments were not. PSA velocity may be an important prognostic factor for men who experience BF after partial gland treatments, although further clinical validation is warranted.
Multivariate model Adjusted HR p-value
NCCN risk (Very Low as reference)
Low 2.83 [0.47, 16.88] 0.25
Intermediate 2.63 [0.40, 17.43] 0.32
Age at failure 0.97 [0.90, 1.06] 0.53
Time to failure 1.04 [0.86, 1.26] 0.66
Salvage ADT 0.43 [0.13, 1.44] 0.17
Salvage BT/RP 0.73 [0.23, 2.39] 0.61
Nadir PSA prior to failure 0.59 [0.33, 1.05] 0.07
PSA Velocity (continuous) 1.18 [1.05, 1.27] <0.01

Author Disclosure: M. King: None. P.L. Nguyen: Honoraria; Bayer. Consultant; Nanobiotix, Infinity Pharmaceuticals, GI Windows, Astellas, Augmenix. Advisory Board; Ferring, Medivation, Genome DX, Dendreon. Stock Options; Augmenix. Program Committee; Genitourinary Cancers Symposium. N. Boldbaatar: None. D.D. Yang: None. R.A. Cormack: Honoraria; American Association of Physicists in Medicine, American Brachytherapy Society, ASTRO. Travel Expenses; American Association of Physicists in Medicine, American Brachytherapy Society. Board Member; New England Chapter of AAPM. C.J. Beard: None. M.D. Hurwitz: None. W. Suh: CHAIR; ACR. Chair - GI cancers: Member - Breast cancer; ACR. A.V. DAmico: None. P.F. Orio: Honoraria; CR BARD. Advisory Board; Augmenix. President-Elect &Chairman, Socioeconomic Committee; American Brachytherapy Society. President-Elect; American Brachytherapy Society. RUC alternate advisor; ASTRO.

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