SAN ANTONIO -- Adding hormone therapy and radiation therapy (RT) to the pelvic lymph nodes increased the freedom-from-progression (FFP) rate for prostate cancer in the salvage setting, an interim analysis of the SPPORT trial found.
At 5 years, FFP was 89.1% when this approach was added to prostate bed radiation therapy (PBRT) for patients with persistent or rising PSA levels after prostatectomy compared with 82.7% with PBRT plus hormone therapy and 71.7% with PBRT alone (P<0.0001), reported Alan Pollack, MD, PhD, of the Sylvester Comprehensive Cancer Center in Miami.
Action Points
- Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
In a press briefing here at the American Society for Radiation Oncology (ASTRO) meeting, Pollack called the significant difference between the group receiving pelvic lymph node RT plus androgen deprivation therapy (ADT) and the PBRT alone group "striking."
"Pelvic lymph node treatment has major effect that we haven't seen before, and this is the first trial to document that effect in the salvage setting," he said.
The trial compared three treatment approaches:
- PBRT alone 64.8-70.2 Gy
- PBRT plus 4 to 6 months of ADT
- PBRT and ADT plus 45 Gy RT to the pelvic lymph nodes
Among patients followed for up to 8 years, the rate of distant metastases trended toward benefit with the triple therapy compared with PBRT alone (HR 0.52, 95% CI 0.32-0.85, P=0.014) and PBRT plus ADT (HR 0.64, 95% CI 0.39-1.06, P=0.28). There were 108 patients with distant metastases among the nearly 1,800 patients.
But Daniel Spratt, MD, of the University of Michigan, told 番茄社区app that while this potential benefit has never been shown before, the three-arm trial design required a P value of less than 0.0125 to be significant.
Spratt, who was not involved with the study, also cautioned that the early data do not inform whether giving this intensive therapy for low-risk patients would be necessary. "I really think we ought to await longer follow-up to see if these more favorable patients benefit."
Eric Horwitz, MD, of Fox Chase Cancer Center in Philadelphia, told 番茄社区app that SPPORT is a modern well-designed trial that reflects and supports how many patients are treated in clinical practice. "So that's a really big deal," he said.
"We're pretty careful of using the data to support how we treat a person or not, and this now really fills in a piece of the puzzle," said Horwitz, referring to the approach at his institution. "It's actually a big piece of the puzzle."
"There is a group of men who do benefit from adding a short course of hormones," he added. "And this now shows that with well-designed radiation, some men actually benefit from a bigger or wider field."
He too cautioned that while the data are not fully available, it is likely that the benefit is probably not for everybody. For patients with a "super-low" PSA, evidence suggests that recurrence is likely confined to the prostate bed, he said. "So that's probably a person where you can probably get away with treating the prostate bed."
ASTRO moderator Neha Vapiwala, MD, of the University of Pennsylvania in Philadelphia, called the study "paradigm changing," explaining that radiation oncologists who treat prostate cancer patients have struggled with the question of whether to treat the lymph nodes or not. "It's a very divisive sort of question," Vapiwala said. "What was presented here in this data are truly level 1 evidence that clearly show the separation of curves to the point that we look forward to what additional follow-up will reveal."
From 2008 to 2015, the NRG Oncology/RTOG 0534 SPPORT trial randomized 1,792 prostate cancer patients with persistant or rising PSA levels from the U.S., Canada, and Israel to one of three treatment arms. Median patient age was 64 years and 87% were white. Nearly all (93%) had an ECOG performance status of 0.
Gastrointestinal adverse events (AEs) were significantly higher with the three-treatment regimen (grade ≥2: 6.9% versus 2.0% with PBRT alone) as were grade ≥2 (5.1% versus 2.3%, respectively) and grade ≥3 (2.6% versus 0.5%) blood-bone marrow AEs.
Patients were stratified by Gleason score (≤7, 8-9), PSA (≥0.1 to ≤ 1.0 ng/mL, >1.0 to <2.0 ng/mL), and stage (pT2 and margin negative, all others). Over half the patients had pT2 disease (54.3%) and positive margins (50.1%), while most had no seminal vesicle involvement (85.2%). The primary endpoint was FFP at 5 years, with failure defined as an increase in PSA of 2.0 ng/mL, clinical progression, or death due to any cause.
Disclosures
Pollack disclosed relationships with Radiation Therapy Oncology Group (RTOG) and Varian Medical Systems.
Primary Source
American Society for Radiation Oncology
Pollack A, et al 鈥淪hort 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鈥� ASTRO 2018; Abstract LBA-5.