Prostate cancer patients who show signs of disease progression after surgery to remove the prostate may benefit by combining standard therapy with short-term androgen deprivation (STAD) and pelvic lymph node radiation therapy (PLNRT), a clinical trial reports.
The research, “Short Term Androgen Deprivation Therapy Without or With Pelvic Lymph Node Treatment Added to Prostate Bed Only Salvage Radiation Therapy: The NRG Oncology/RTOG 0534 SPPORT Trial,” was recently presented at the American Society for Radiation Oncology (ASTRO) 2018 Annual Meeting, held in San Antonio, Texas.
Patients who undergo prostate removal — called prostatectomy — often show signs of cancer’s return in the form of an increase in blood prostate-specific antigen (PSA) levels. The current standard therapy is prostate bed radiation therapy (PBRT), but even then, 30% to 40% of patients see their PSA levels increase again within 5 to 10 years.
Radiation therapy directed at the prostate lymph nodes and androgen deprivation therapy are thought to be effective complementary therapies, but scientific evidence was lacking without a clinical trial.
The SPPORT Phase 3 trial (NCT00567580) was thus designed to test the benefits of adding STAD, or STAD plus PLNRT, to PBRT in patients with rising levels of PSA after prostatectomy.
This is the first trial to assess the benefits of expanding radiation therapy to the prostate lymph nodes and the second to assess the importance of androgen deprivation in patients who underwent prostatectomy — the GETUG 16 Phase 3 trial (NCT00423475) that concluded in 2015 was the first.
SPPORT enrolled 1,792 men treated at medical centers in the U.S., Canada, and Israel from 2008 to 2015. Eligible patients also showed increasing PSA levels and evidence that some cancer cells were still present after prostatectomy. The men ranged in age from 39 to 84 (median age 64), and most (87%) were Caucasian.
Patients randomly received either PBRT alone, PBRT and STAD, or PBRT, STAD, and PLNRT. Researchers then measured the rates of freedom-from-progression — defined as an increase of PSA levels, clinical failure, or death due to any cause — after five years.
“Adding hormone therapy and pelvic lymph node treatment substantively increased the proportion of patients who remained free from disease progression, to the point that we could report the data after an early interim analysis,” Allan Pollack, MD, PhD, the study’s lead author, said in a press release.
Results of the early analysis correspond to 1,191 patients.
“The level of significance reached at this point was considerable, making it unlikely that the results will change substantively with longer follow-up, although outcomes such as the rates of distant metastasis and survival require much more patient follow-up,” Pollack added.
This early analysis found that while 71% of patients treated with PBRT alone did not show disease progression after five years, the addition of hormone therapy increased this value to 83%, and the addition of PLNRT further increased it to 89%.
After five years, 91.7%, 94.4%, and 95.2% of patients in each treatment group were free of distant metastasis. The three-treatment approach reduced the risk of distant metastasis by 48% compared to PBRT alone.
“To be seeing differences in distant metastasis with relatively short follow-up speaks to the robustness of the impact, suggesting that the results will be sustained with longer follow-up,” Pollack said.
Severe side effects were low across the different treatments. However, PLNRT was associated with blood and bone marrow effects, such as lower red and white cell counts.
As the trial’s primary data collection concludes in December 2020, researchers will further investigate differences between the treatments.
However, “releasing the data at this juncture is important for physicians treating patients with a rising PSA following prostatectomy. The strategy of combining prostate bed and pelvic lymph node radiation therapy with short-term hormone therapy should be much more strongly considered in routine clinical practice than it is currently,” Pollak concluded.
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