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Radiotherapy, prostatectomy confer similar outcomes for aggressive prostate cancer

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August 17, 2016

Radiotherapy and radical prostatectomy conferred equivalent survival outcomes among men with aggressive prostate cancer, according to the results of a comparative analysis.

However, extremely dose–escalated radiotherapy prolonged metastasis-free survival with lower use of salvage therapy, results also showed.

“Our study focuses on a particularly aggressive form of prostate cancer, and provides the largest series of outcomes for patients with this diagnosis who were treated in the modern era,” Amar U. Kishan, MD, chief resident in the department of radiation oncology at UCLA Jonsson Comprehensive Cancer Center, said in a press release. “Our conclusions are relevant to both physicians advising patients about the effectiveness of different treatment options, and patients who would like to learn more about these options on their own.”

International treatment guidelines for aggressive prostate cancer — defined by a Gleason score of 9 or 10 — endorse radical prostatectomy and external beam radiotherapy with androgen-deprivation therapy, with or without a brachytherapy boost, as acceptable treatment options.

However, research comparing radiotherapy with radical prostatectomy has produced conflicting efficacy conclusions.

Kishan and colleagues evaluated data from 487 men with aggressive prostate cancer who received treatment between 2000 and 2013.

Treatment options included radical prostatectomy (n = 170); definitive external beam radiotherapy, with or without ADT (n = 230); or extremely dose–escalated radiotherapy (n = 87), defined as external beam radiotherapy with a brachytherapy boost, with or without ADT.

Rates of 5-year and 10-year OS, disease-specific survival and distant metastasis–free survival served as the study’s primary endpoints.

The entire cohort had a median follow-up of 4.6 years (interquartile range, 2.87-7.36).

Men treated with radiotherapy tended to be older at time of treatment and had higher initial PSA levels and clinical stages (P < .05 for all).

A majority of patients treated with radiotherapy (external beam, n = 216; extremely dose–escalated, n = 75) received upfront ADT. Men who underwent external beam radiotherapy received ADT for a significantly longer duration (median, 24 months vs. 8 months; P < .05).

A greater proportion of men treated with radical prostatectomy underwent local salvage therapy (n = 73; 49%) than those treated with external beam radiotherapy (n = 2; 0.9%) or extremely dose–escalated radiotherapy (n = 1; 1.2%; P < .0001).

Similarly, a greater proportion of men treated with radical prostatectomy underwent systemic salvage therapy (30.1%) than those who underwent external beam radiotherapy (19.7%) or extremely dose–escalated radiotherapy (16.1%; P < .001 for both).

Significantly more men who underwent extremely dose–escalated radiotherapy achieved 5-year distant metastasis–free survival (94.6%) than men who underwent external beam radiotherapy (78.7%; P = .0005) and radical prostatectomy (79.1%; P < .0001). This benefit persisted at 10 years (89.8% vs. 66.7% vs. 61.5%).

The researchers observed similar rates of 5-year OS among men who underwent extremely dose–escalated radiotherapy (84.7%), external beam radiotherapy (79.9%) and prostatectomy (90.3%). Rates also were similar for 10-year OS (59.2% vs. 65.3% vs. 72.1%), 5-year disease-specific survival (95.6% vs. 91.6% vs. 91.7%) and 10-year disease-specific survival (88.1% vs. 80.5% vs. 78.5%).

Multivariate analyses showed no significant differences in OS or disease-specific survival across treatment groups.

The researchers acknowledged study limitations, including the retrospective study design and that data were derived from several treating institutions. Further, the overall follow-up duration may have been too short to adequately collect an adequate number of events.

“Our data suggest that the radical prostatectomy and external beam radiotherapy–based treatments provide equivalent [disease-specific survival] and OS for patients with Gleason 9-10 prostate cancer, with extremely dose–escalated radiotherapy providing the best systemic control,” Kishan and colleagues wrote. “These data are hypothesis-generating in suggesting that optimal outcomes ... require a combination of local control and systemic therapy. Alternative strategies, perhaps including some form of systemic therapy with radical prostatectomy, may offer comparable outcomes.” – by Cameron Kelsall

Disclosures: The researchers report no relevant financial disclosures.