Oligometastases in prostate cancer: Metabolic response in follow-up PSMA-PET-CTs after hypofractionated IGRT

René Baumann, Mark Koncz, Ulf Luetzen, Fabian Krause, Juergen Dunst*

*Corresponding author for this work
20 Citations (Scopus)


Background: Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMAPET/CT) is a new and evolving diagnostic method in prostate cancer with special impact on treatment planning in image-guided radiotherapy (IGRT). Initial results of metabolic response in repeated PSMA PET/CTs after hypofractionated IGRT for metastatic lesions are reported here. Materials and methods: Of 280 patients investigated with 68Ga-PSMA PET/CT in the period from 01/2014 through 12/2016 in the authors’ department, patients were selected according to the following criteria: oligometastatic disease at initial PSMA PET/CT defined as not more than five metastatic lesions, hypofractionated IGRT to all lesions, no systemic therapy in the last 6 months and during follow-up, and at least one follow-up PSMA PET after radiotherapy. Radiotherapy was administered to all PSMA PET-detected lesions (CTV = PET-GTV + 1 to 2 mm), mostly with 35 Gy in five fractions (one lesion with four fractions of 7 Gy due to dose constraints, two lymph nodes with 50 Gy in 25 fractions to an extended volume plus a boost of 7 Gy × 2 to the PET-positive volume). Metabolic response of irradiated lesions was evaluated on repeated PSMA PET/CTs according to PERCIST criteria. Five patients with a total number of 12 PSMA PETs matched the criteria. Patients received radiotherapy to all PET-positive lesions and had at least one (in one case three) follow-up PSMA PET examinations after radiotherapy with an interval to the first PET of 2–15 months; the median follow-up for all patients was 11 months. Results: The mean prostate-specific antigen (PSA) values at the time of examination were 8.9 ± 8.5 ng/ml (median 3.3 ng/ml, range 0.17–21.8 ng/ml). A total number of 18 metastatic deposits were detected. The PET-positive tumor volume was 5.9 ± 13.3 cm3 (median 1.25 cm3). The mean standardized uptake value (mean SUVmax) of the 18 metastatic lesions decreased from 19.9 ± 23.3 (mean ± SD) prior to RT to 5.4 ± 4.6 at post-radiotherapy PSMA PET/CT. Using PERCIST criteria, 14 lesions (78%) showed a metabolic response in PSMA PET with a reduction of SUV of at least 30%, as well as a significant decrease in lesion size; in seven of these lesions, no uptake of 68Ga-PSMA was detectable. In follow-up PET scans, only two lesions showed metabolic progression with an increase in SUVmax yielding a local progression-free survival of 88% after 1 year. There was a correlation between the time interval after radiotherapy (median 3 months, range 1–9 months) and response (p = 0.04) with better metabolic response after longer follow-up. Conclusions: Preliminary results of this study show high metabolic response rates of PSMA PET-positive metastatic lesions after hypofractionated radiotherapy in follow-up PSMA PET with promising local control rates. An interval of several months may be required to fully estimate the efficacy of radiotherapy in control PSMA PET.

Translated title of the contributionOligometastasen bei Prostatakarzinom: Metabolisches Ansprechen in Follow-up-PSMA-PET/CT nach hypofraktionierter bildgeführter Strahlentherapie
Original languageEnglish
JournalStrahlentherapie und Onkologie
Issue number4
Pages (from-to)318-324
Number of pages7
Publication statusPublished - 01.04.2018


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