PSMA PET Scans Guide Long-Lasting Radiation Therapy for Prostate Cancer Recurrence

When prostate cancer returns after the prostate has been surgically removed, it most often reappears in the lymph nodes of the pelvis, and until recently doctors could rarely see it coming until the disease had already spread further. A new long-term study from two major European cancer centres now offers some of the strongest real-world evidence yet that a molecular imaging technique called PSMA PET/CT, paired with a carefully shaped form of radiation therapy, can keep the disease at bay for years in a substantial share of these patients. The findings, published in the European Journal of Nuclear Medicine and Molecular Imaging, come from a retrospective analysis of 179 men treated between 2014 and 2024 at the Medical University of Innsbruck in Austria and LMU University Hospital in Munich, Germany, with a median follow-up of just over five years.

The imaging technology at the heart of the study is prostate-specific membrane antigen positron emission tomography, usually abbreviated PSMA PET. Unlike conventional CT or bone scans, which rely on anatomical changes to reveal tumours, PSMA PET exploits the fact that prostate cancer cells overproduce a surface protein called prostate-specific membrane antigen. A radioactive tracer, either gallium-68 labelled PSMA-11 or fluorine-18 labelled PSMA-1007 in this study, is injected into the bloodstream and binds to that protein, making even small clusters of cancer cells glow on the scan. In this cohort, scans were performed roughly an hour after tracer injection and jointly reviewed by an experienced nuclear medicine physician and a radiologist, with lesion locations confirmed on the accompanying CT component. This sensitivity allows detection of nodal recurrence at prostate-specific antigen, or PSA, levels far below those at which older imaging modalities become useful, opening a therapeutic window in which disease is still limited and potentially curable.

Armed with this detailed map of where the cancer had returned, the treating radiation oncologists did something that has become increasingly evidence-supported but had lacked long-term real-world validation: they delivered elective nodal radiotherapy, or ENRT. Rather than irradiating only the few lymph nodes visible on the PET scan, a strategy known as metastasis-directed therapy, ENRT treats the entire lymphatic drainage region at risk, including nodes that may harbour microscopic disease invisible to even the most sensitive scanner. Target volumes followed the Radiation Therapy Oncology Group atlas and, from 2020 onwards, the NRG Oncology consensus guidelines, adjusted according to the PSMA PET findings. In patients with disease extending above the pelvis, the elective field was stretched to include the paraaortic lymphatic pathways up to two centimetres above the highest PET-positive node. The prostate bed was routinely included in the treatment volume for patients who had not previously been irradiated there.

The technical execution reflected modern image-guided practice. In Innsbruck, patients initially received three-dimensional conformal radiotherapy before the centre switched to volumetric modulated arc therapy in 2017, while Munich used intensity-modulated or volumetric modulated arc therapy throughout. Daily or near-daily cone-beam CT verified patient positioning. All plans included a simultaneous integrated boost, meaning PET-positive lymph nodes received a higher radiation dose per fraction than the surrounding elective regions. In dose terms normalised to two-Gy fractions, the elective nodal regions received a median of 47.5 Gy, the prostate bed 66.0 Gy, locally recurrent disease 70.0 Gy, and PET-positive lymph nodes a median of 62.3 Gy, with doses adapted to respect the tolerance of nearby organs such as the bowel and bladder. Androgen deprivation therapy, which suppresses the testosterone that fuels prostate cancer growth, was recommended for all patients for 24 to 36 months and was actually given to 83.8 percent of the cohort.

The headline result is that this approach delivers durable disease control in routine clinical practice, not just in the carefully selected populations of clinical trials. Across the whole cohort, the five-year metastasis-free survival rate was 61.2 percent, meaning nearly two-thirds of these men remained free of distant spread five years after treatment. Biochemical progression-free survival, which tracks whether PSA remains suppressed, stood at 56.4 percent at five years, and overall survival reached 90.6 percent. Only 20 of the 179 patients died during follow-up, and just three of those had documented metastatic prostate cancer before death. For a population with nodal recurrence after prostatectomy, many of whom carried high-risk features such as grade 4 or 5 tumours, positive surgical margins, or disease extending beyond the pelvis, these figures represent a meaningful benchmark.

The most striking numbers emerged when the researchers separated two biologically distinct groups that are often lumped together. Some men experience a true biochemical recurrence, meaning their PSA fell to undetectable levels after surgery and only later began to rise. Others have PSA persistence, in which the marker never cleared after the operation, a sign that occult cancer cells were likely already disseminated at the time of surgery. Among the 104 men with true recurrence, five-year metastasis-free survival reached 74.3 percent and biochemical progression-free survival 62.3 percent, figures that closely approach the results of the randomised PEACE V-STORM trial, which reported four-year metastasis-free survival of 76 percent for elective nodal radiotherapy. By contrast, PSA persistence independently predicted worse outcomes in multivariable analysis, with more than double the risk of metastasis or death and nearly double the risk of biochemical progression, consistent with the idea that persistence marks more advanced, systemic disease.

The role of hormone therapy emerged as the other dominant prognostic factor. Men who received androgen deprivation therapy alongside their radiotherapy had a 64 percent lower risk of distant metastasis or death and a 74 percent lower risk of biochemical progression compared with those who did not, effect sizes that exceed those reported in meta-analyses of postoperative radiotherapy. The authors caution that this observational association cannot prove causation and may partly reflect the higher disease burden in patients with PET-detected nodal metastases, in whom combined modality treatment may simply be necessary. They also deliberately avoided analysing hormone therapy duration, because retrospectively grouping patients by the therapy actually completed rather than the intended duration invites statistical distortions known as immortal-time bias. The optimal duration of androgen suppression in this setting remains an open question for prospective trials.

Perhaps the most instructive finding concerns where the cancer returned when it did return. Among the 54 patients with imaging-confirmed recurrence, only 7.4 percent failed within the irradiated field, while 72.2 percent relapsed exclusively outside it and another 20.4 percent relapsed both inside and outside. This spatial pattern carries a double message. On one hand, it suggests the radiation targets were well designed, since true in-field failure was rare. On the other hand, the overwhelming predominance of out-of-field and distant relapse, including bone metastases in 20.7 percent of the entire cohort, points to microscopic disease lurking below the detection threshold of even PSMA PET, or to an inherently more aggressive systemic biology in these tumours. A negative PSMA PET scan, in other words, does not guarantee the absence of occult metastases, particularly in patients with high PSA levels at recurrence, and the authors argue that this limitation, not inadequate target coverage, is the main enemy to be fought.

The study is not without caveats, and the authors are candid about them. Its retrospective design introduces selection bias and limits causal inference, treatment varied between centres and eras, and the two institutions used different tracers and imaging protocols. Most importantly, toxicity was not systematically assessed and patient-reported quality of life was not collected, so the tolerability of this intensive combined approach cannot be reliably judged from these data. The multivariable models, built on data-driven variable selection, should be treated as exploratory. Nevertheless, the inclusion of higher-risk, less selected patients, including those with PSA persistence and paraaortic disease that the PEACE V-STORM trial excluded, is precisely what makes the results valuable as a real-world benchmark. Two ongoing phase III trials, GETUG-P12-OLIGOPELVIS 2 and POINTER-PC, are now testing whether adding elective nodal radiotherapy to hormone therapy improves survival and whether treating whole nodal regions outperforms targeting only visible nodes. Until those results mature, this bi-institutional analysis provides the strongest long-term signal yet that PSMA PET-guided elective nodal radiotherapy, combined with androgen deprivation, can convert nodal recurrence after prostatectomy from an ominous harbinger of metastatic disease into a controllable, and for many patients durably arrested, chapter of the illness.

Subject of Research: Long-term outcomes of PSMA PET/CT-guided salvage elective nodal radiotherapy for nodal prostate cancer recurrence after radical prostatectomy

Article Title: PSMA PET/CT-guided salvage elective nodal radiotherapy for nodal metastases after radical prostatectomy: a bi-institutional long-term outcome analysis

Article References: Vorbach, S. M., Seppi, T., Santo, G., Virgolini, I., Ganswindt, U., Keilholz, M., Brose, S. F., Casuscelli, J., Klimek, K., Werner, R. A., Schmidt-Hegemann, N.-S., Belka, C., Trapp, C., & Rogowski, P. (2026). PSMA PET/CT-guided salvage elective nodal radiotherapy for nodal metastases after radical prostatectomy: a bi-institutional long-term outcome analysis. European Journal of Nuclear Medicine and Molecular Imaging. https://doi.org/10.1007/s00259-026-08147-z

Image Credits: AI Generated

DOI: 10.1007/s00259-026-08147-z

Keywords: PSMA PET/CT, prostate cancer, elective nodal radiotherapy, radical prostatectomy, nodal metastases, salvage radiotherapy, androgen deprivation therapy, metastasis-free survival, biochemical recurrence, oligorecurrent disease, radiation oncology, molecular imaging