In a review of 37 patients with metastatic Merkel cell carcinoma, peptide receptor radionuclide therapy (PRRT) produced objective responses in about 32% of cases with no severe side effects.
31.6% objective response rateSix of 19 evaluable patients with metastatic Merkel cell carcinoma achieved partial or complete responses to PRRT with no severe adverse events.
What the researchers found
Of 37 patients with metastatic Merkel cell carcinoma who received 1-5 cycles of PRRT using 177Lu- or 90Y-labeled somatostatin analogs (cumulative activity 1.5-30 GBq), radiographic response data was available for 19 who received PRRT alone. Six of these 19 patients (31.6%) achieved objective responses ranging from partial to complete. No severe adverse events were reported across the treated cohort.
Why it matters
Metastatic Merkel cell carcinoma has limited treatment options and a poor prognosis. While immunotherapy has improved outcomes, many patients don't respond or eventually progress. PRRT offers a mechanistically different approach — using peptides to deliver targeted radiation directly to tumor cells — that could fill an important treatment gap for this rare cancer.
How the study worked
The authors performed a comprehensive literature review searching for all published reports of PRRT use in metastatic Merkel cell carcinoma. They compiled data from individual case reports and small series, totaling 37 treated patients. Response was assessed radiographically in patients who received PRRT as a standalone therapy.
What this study cannot tell us
The evidence quality is low — data comes from retrospective case reports and small series rather than controlled trials. The total of 37 patients is very small, and radiographic response data was only available for 19 who received PRRT alone. Publication bias likely favors positive outcomes. Patient selection (requiring somatostatin receptor expression) means results may not apply to all Merkel cell carcinoma cases.
How to read the evidence
This is a comprehensive literature review compiling data from case reports and small retrospective series. While it aggregates all available evidence, the underlying data quality is low — no randomized controlled trials exist yet. Prospective trials are underway.
When this study was published
Published in 2023, this review represents the most current synthesis of PRRT evidence for Merkel cell carcinoma as prospective trials begin enrolling.
The bigger picture
PRRT has already been approved for gastroenteropancreatic neuroendocrine tumors and is being explored for other cancers that express somatostatin receptors. Success in Merkel cell carcinoma would expand the reach of peptide-targeted radionuclide therapy to rare skin cancers. Prospective clinical trials are now underway to generate stronger evidence.
Questions still open
- What proportion of Merkel cell carcinomas express sufficient somatostatin receptors for PRRT to be viable?
- How does PRRT compare or combine with immunotherapy in this cancer type?
- Will the ongoing prospective trials confirm the 32% response rate seen in this retrospective review?
Common questions
What is peptide receptor radionuclide therapy (PRRT)?
Is PRRT effective for Merkel cell carcinoma?
Read the original research
Peptide Receptor Radionuclide Therapy in Merkel Cell Carcinoma: A Comprehensive Review.
Journal of nuclear medicine technology, 51(1), 22-25
Citation
Askari, Emran; Moghadam, Soroush Zarehparvar; Wild, Damian; Delpassand, Ebrahim; Baldari, Sergio; Nilica, Bernhard; Hartrampf, Philipp E; Kong, Grace; Grana, Chiara Maria; Alexander Walter, Martin; Capoccetti, Francesca; Kasi, Pashtoon Murtaza; Strosberg, Jonathan. (2023). Peptide Receptor Radionuclide Therapy in Merkel Cell Carcinoma: A Comprehensive Review.. Journal of nuclear medicine technology, 51(1), 22-25. https://doi.org/10.2967/jnmt.122.264904