Biopsy Grade Group as a reliable prognostic factor for BCR in Afro-Caribbean men with intermediate- and high-risk prostate cancer

208 Background: Treatment of high risk prostate cancer (HRPCa) with external beam radiotherapy (EBRT) plus brachytherapy (BT) boost (EBRT+BT) has been prospectively associated with lower rates of BCR, albeit potentially with increased toxicity, and retrospectively linked to decreased distant metastasis (DM) and PCa-specific mortality (PCSM) compared to EBRT alone. However, it is unclear whether patients who develop BCR following either approach have similar downstream oncologic outcomes. Methods: We identified 706 out of 3820 men with HRPCa treated at 13 institutions from 1998-2015 with EBRT (n=468/2134) or EBRT+BT (n=238/1686) who developed BCR. We compared rates of DM, PCSM, and all-cause mortality (ACM) after BCR between treatment groups using Fine-Gray competing risk regression. Models were adjusted for age, Gleason grade group, initial PSA (iPSA), clinical T stage, time-dependent use of systemic salvage, and interval to BCR using inverse probability of treatment weighting. Results: Median follow-up was 9.9 years from RT and 4.8 years from BCR. Groups were similar in age, iPSA, presence of ≥2 HR features, and median interval to BCR (3.3 years). Most men received neoadjuvant/concurrent androgen deprivation therapy (ADT), 92.5% and 91.0% for EBRT and EBRT+BT, respectively, though for a longer duration with EBRT (median 14.7 vs. 9.0 months, p=0.0012). Local and systemic salvage rates were 2.3% and 36.3% after EBRT, and 2.6% and 43.6% after EBRT+BT, respectively. Initial EBRT+BT was associated with significantly lower rates of DM after BCR (HR 0.48, 95% CI 0.36-0.64, p<0.001). Rates of PCSM and ACM did not significantly differ (HR 0.93, 95% CI 0.67-1.30, p=0.93, and HR 0.8, 95% CI 0.6-1.1, p=0.11, respectively). Conclusions: In this large retrospective series of radiorecurrent HRPCa, initial treatment with EBRT+BT was associated with significantly lower rates of DM after BCR compared with EBRT, despite shorter ADT use and a similar median interval to BCR. Local salvage was widely underutilized in both groups. In the absence of salvage for local failure after EBRT, upfront treatment intensification with BT may reduce DM, though not PCSM or ACM, even after development of BCR.

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The effect of maximum tumor diameter on disease control in intermediate and high-risk prostate cancer patients treated with brachytherapy boost.

Journal of Clinical Oncology ◽

10.1200/jco.2021.39.6_suppl.252 ◽

2021 ◽

Vol 39 (6_suppl) ◽

pp. 252-252

Author(s):

Matthew Parsons ◽

Ryan Hutten ◽

Ashley Khouri ◽

Alexander Tward ◽

Glen Morrell ◽

...

Keyword(s):

Prostate Cancer ◽

High Risk ◽

Prognostic Factor ◽

Interquartile Range ◽

Tumor Diameter ◽

T Stage ◽

High Risk Prostate Cancer ◽

Risk Prostate Cancer ◽

Brachytherapy Boost ◽

Maximum Tumor Diameter

252 Background: Larger maximum tumor diameter (MTD) has been associated with worse prostate cancer outcomes for those undergoing surgery as well as salvage radiation. MTD is also an important consideration for patients weighing active surveillance. However, the impact of MTD in intermediate and high-risk prostate cancer treated with external beam radiotherapy (EBRT) and brachytherapy boost is unknown. We set out to evaluate MTD of the dominant nodule on MRI as a prognostic factor in patients treated with EBRT and brachytherapy boost for localized prostate cancer. Methods: Patients with prostate cancer treated with EBRT and brachytherapy boost were identified from an institutional database. In patients with a pretreatment MRI, data on MTD were retrospectively collected. Clinical data including age, ADT use, pretreatment PSA, International Society of Urologic Pathology (ISUP) group, clinical T-stage, and presence of adverse pathology on imaging (either seminal vesicle invasion or extraprostatic extension) were also collected. Multivariable and univariable cox proportional hazards models for biochemical failure (BF) and distant metastasis (DM) were produced in patients with MTD grouped by receiver operating characteristic (ROC) cutpoint. Cumulative hazard functions for BF and DM were compared with log-rank test and stratified by ISUP group. Results: Of 191 patients treated with EBRT and brachytherapy boost, 113 had pretreatment MRI and available MTD measurement. Median follow up was 40 months (interquartile range 23-66 months) and median MTD was 17 mm (interquartile range 13-22mm). Increasing MTD was associated with higher T stage and increased ADT use. ROC cutpoint optimization identified MTD of 24mm to be the optimal cut-point for both BF and DM. On univariate log-rank analysis, patients with MTD > 24mm had higher 5-year BF (31% vs 4%, p = 0.004) and DM (21% vs 4%, p = 0.002) than those with MTD≤24. Stepwise multivariable cox model for BF (P = 0.130, HR 1.08, 95% CI 0.98-1.21) and DM (P = 0.115, HR 1.09, 95% CI 0.98-1.23), MTD did not demonstrate statistical significance when controlling for clinical t-stage, adverse pathologic features on imaging, ISUP group, and ADT use. However, in patients with ISUP group 4-5 disease, MTD > 24 was independently associated with increased risk of DM (P = 0.032, HR 1.18, 95% CI 1.01-1.37). Conclusions: This is the first study to evaluate MTD on MRI as a prognostic factor in the setting of brachytherapy boost. These results demonstrate that for patients treated with EBRT and brachytherapy boost, MTD is independently associated with risk for metastasis in patients with ISUP grade 4 and 5 disease. Although these results require further validation, this suggests a possible role for MTD as a factor in risk assessment models and clinical decision-making.

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