medwireNews: Postprostatectomy salvage radiotherapy guided by 18F-fluciclovine-positron emission tomography (PET)–computed tomography (CT) is associated with improved outcomes relative to that guided by conventional imaging, research suggests.
Reporting in The Lancet, Ashesh Jani and colleagues from Emory University in Atlanta, Georgia, USA, say “integration of novel PET radiotracers into radiotherapy decisions and planning can make a clinical impact and warrants further study.”
They found that, during a median 3.5 years of follow-up in the phase 2/3 EMPIRE-1 trial, 20% of 76 men with prostate cancer randomly assigned to receive postprostatectomy 18F-fluciclovine-PET/CT-guided radiotherapy experienced a treatment failure event, defined as biochemical or clinical recurrence or progression, or the initiation of systemic therapy.
By comparison, the failure rate was 33% among the 81 men randomly assigned to undergo radiotherapy guided by conventional imaging.
Of note, all of the participants had detectable prostate-specific antigen (PSA) levels after prostatectomy but no systemic metastasis on conventional imaging.
The 3- and 4-year event-free survival (EFS) rates were significantly higher in the 18F-fluciclovine-PET/CT group than in the conventional imaging group, at 75.5% versus 63.0% and 75.5% versus 51.2%, respectively.
And multivariate analysis revealed that individuals who received conventional imaging were a significant 2.04 times more likely to experience a failure event than those who received PET/CT-guided imaging.
Jani and co-authors suggest that “likely reasons for the differences observed include better selection of patients likely to benefit from radiotherapy by excluding patients with extrapelvic disease on 18FfluciclovinePET, fieldsize changes […], and integrating PET registration in the treatment planning process so that finalised target volumes can include regions of 18FfluciclovinePET uptake.”
In terms of toxicity, the researchers observed similar outcomes in both the PET/CT and conventional imaging groups, with few grade 3 adverse events (AEs) and none of grade 4 or 5. The most common AEs were late urinary frequency or urgency (41 vs 46%), and acute diarrhea (21 vs 14%).
They therefore conclude: “To the best of our knowledge, our study provides highest-level available evidence that incorporating advanced molecular imaging with PET into therapy planning improves cancer control without increasing toxicity.”
Jani and team also point out that during their 7-year accrual period (2012–2019) other studies compared the diagnostic accuracy of 18Ffluciclovine with that of 68Ga-prostate-specific membrane antigen as a tracer in PET–CT and found “relative benefits in different settings.”
They are now comparing the two tracers in their own EMPIRE-2 trial, which will look at eventfree survival as a primary endpoint and allow for dose escalation to regions of PET uptake, which they note was not permitted in the current trial.
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Lancet 2021; doi: 10.1016/S0140-6736(21)00581-X