Retreating Neuroendocrine Tumors With Peptide Radiation Therapy: Is a Second Round Effective? | Research

The takeaway

Retreatment with peptide receptor radionuclide therapy (Lu-177 DOTATATE) after initial progression was effective and safe in neuroendocrine tumor patients, with median progression-free survival of 17.5 months.

66-month overall survival
From the start of initial PRRT treatment, patients achieved a median overall survival of 66 months (5.5 years), including a retreatment course that provided an additional 17.5 months of progression-free survival.

What the researchers found

After initial PRRT, all 20 patients eventually progressed, with a median progression-free survival (PFS) of 32 months. Upon retreatment (PRRTR), median PFS was 17.5 months (IQR: 7–39 months). At analysis, 15 of 18 evaluable patients had progressed after retreatment, while 3 had stable disease.

The median overall survival from the first cycle of initial treatment was 66 months (IQR: 65–90). Safety was favorable: no significant kidney or liver toxicity was reported, and hemoglobin levels remained stable. The only notable adverse effect was a statistically significant decrease in platelet count after retreatment (p=0.03). Patients who received two retreatment cycles had significantly longer PFS than those receiving one (p=0.014), and the presence of metastases before retreatment predicted shorter time to progression (p=0.04).

Why it matters

Neuroendocrine tumors are relatively rare cancers with limited treatment options, especially after progression on standard therapies. PRRT with Lu-177 DOTATATE has become a valuable treatment, but what happens when patients progress afterward has been a major unanswered question. This study provides real-world evidence that retreatment is viable — giving oncologists and patients another option rather than having to move to less targeted therapies.

How the study worked

This was a single-center retrospective observational study spanning nine years. Twenty patients with progressive neuroendocrine tumors who had previously received [177Lu]Lu-DOTA-TATE PRRT and subsequently progressed were retreated with the same therapy. Researchers evaluated progression-free survival, overall survival, toxicity (renal, hepatic, hematological), and prognostic factors associated with outcomes.

What this study cannot tell us

This was a small (n=20), single-center, retrospective study — the lowest tier of clinical evidence for treatment efficacy. Two patients were lost to follow-up. There was no control group, so it's impossible to know how much of the benefit was due to retreatment versus natural disease course. The retrospective design is subject to selection bias — patients selected for retreatment may have had more favorable disease characteristics. Specific dosing protocols and patient selection criteria were not detailed in the abstract.

How to read the evidence

This is a small, single-center, retrospective observational study with no control group. While it provides useful real-world evidence, the study design limits the ability to draw definitive conclusions about retreatment efficacy. Larger prospective studies are needed.

When this study was published

Published in 2023 with data spanning nine years, this study reflects contemporary PRRT practice and retreatment protocols. The findings are relevant to current clinical decision-making.

The bigger picture

PRRT represents one of the most successful applications of peptide-based targeted therapy in oncology. The somatostatin analog peptide DOTATATE acts as a guided delivery vehicle for the radioactive isotope lutetium-177, exploiting the fact that neuroendocrine tumors overexpress somatostatin receptors. As more patients live longer with PRRT, the question of retreatment becomes increasingly important. This study adds to growing evidence supporting retreatment and helps identify which patients are most likely to benefit.

Questions still open

Would prospective, multi-center studies confirm that PRRT retreatment provides meaningful clinical benefit over best supportive care?
Can biomarkers or imaging criteria better predict which patients will respond well to a second course of PRRT?
Is there an upper limit to the cumulative dose of Lu-177 DOTATATE that can be safely administered across multiple treatment courses?

Common questions

What is peptide receptor radionuclide therapy (PRRT)?

PRRT is a targeted cancer treatment that uses a radioactive peptide (Lu-177 DOTATATE) to deliver radiation directly to neuroendocrine tumor cells. The peptide is a modified version of somatostatin — a natural hormone — that binds specifically to receptors on the tumor surface, acting as a guided missile to bring the radiation precisely where it's needed.

Is it safe to receive PRRT a second time?

According to this study, yes — retreatment was generally well tolerated. There was no significant kidney or liver damage, though platelet counts did decrease. However, this was a small study, and patients should discuss the risks and benefits of retreatment with their oncology team based on their individual situation.

Read the original research

Efficacy, Toxicity, and Prognostic Factors of Re-treatment With [177Lu]Lu-DOTA-TATE in Patients With Progressing Neuroendocrine Tumors: The Experience of a Single Center.

Cureus, 15(10), e47506

View on PubMed ↗Publisher’s paper ↗

Citation

Silva, Maria Manuel; Canha, Marta; Salazar, Daniela; Neves, João Sergio; Ferreira, Gonçalo; Carvalho, Davide; Duarte, Hugo. (2023). Efficacy, Toxicity, and Prognostic Factors of Re-treatment With [177Lu]Lu-DOTA-TATE in Patients With Progressing Neuroendocrine Tumors: The Experience of a Single Center.. Cureus, 15(10), e47506. https://doi.org/10.7759/cureus.47506