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Adjuvant radiotherapy improves outcomes for high-risk prostate cancer

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March 14, 2018

Rahul D. Tendulkar

Adjuvant radiotherapy appeared associated with better outcomes than surveillance followed by early-salvage radiotherapy among patients with prostate cancer with adverse pathological features who underwent prostatectomy, according to study results published in JAMA Oncology.

“It remains very controversial whether patients with high-risk features after a radical prostatectomy for prostate cancer should receive adjuvant radiation therapy to prevent a recurrence of their prostate cancer as measured by a rise in PSA, or whether we should observe patients after surgery and only radiate those who demonstrate a detectable PSA,” Rahul D. Tendulkar, MD, of the department of radiation oncology at Cleveland Clinic, told HemOnc Today.

Tendulkar and colleagues studied 1,566 consecutive propensity score-matched patients who underwent prostatectomy and received adjuvant radiotherapy (PSA, 0.1-0.5 ng/mL; n = 371) or surveillance followed by early-salvage radiotherapy (PSA < 0.1 ng/mL; n = 1,195) between January 1987 and December 2013 at 10 U.S. academic centers.

Median follow-up was 73.3 months for the early-salvage cohort and 65.8 months for the adjuvant cohort.

Adjuvant radiotherapy appeared associated with superiority across all outcomes (12-year actuarial rates):

  • 69% (95% CI, 60-79) had freedom from biochemical failure compared with 43% (95% CI, 35-51) of the early-salvage cohort (effect size, 26%);
  • 95% (95% CI, 90-97) had freedom from distant metastases compared with 85% (95% CI, 76-90) of the early-salvage cohort (effect size, 10%); and
  • OS was 91% (95% CI, 84-95) compared with 79% (95% CI, 69-86) for early-salvage cohort (effect size, 12%).

In a multivariate analysis for biochemical failure, favorable prognosis appeared associated with adjuvant radiotherapy, lower Gleason score and T stage, nodal irradiation and postoperative androgen deprivation therapy.

Results from a sensitivity analysis showed adjuvant radiotherapy’s association with decreased risk for biochemical failure remained significant unless more than 56% of patients in that cohort were cured by surgery alone. This threshold is greater than estimated 12-year freedom from biochemical failure rate of 33% to 52% with prostatectomy alone.

“One of the challenges in interpreting this study is that some patients treated with ‘adjuvant’ radiation may not have benefited from radiation, as some proportion of this group would never have had a PSA recurrence had they been simply observed,” Tendulkar said. “Along the same line, all patients treated with ‘early-salvage’ radiation had already declared themselves as having measurable prostate cancer, so it is not an apples-to-apples comparison.”

Limitations of the study included its retrospective design, selection bias and inconsistencies in PSA levels.

“Atlhough the results of this retrospective study are intriguing, unfortunately only a randomized trial with sufficient sample size and statistical power can settle the question of adjuvant vs. early-salvage radiation after prostatectomy,” Tendulkar said. “Some trials are currently being conducted outside the U.S., but none have been reported yet.” – by Cassie Homer

 

For more information:

Rahul D. Tendulkar, MD, can be reached at Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195.

 

Disclosures: Tendulkar reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.

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