Research-informed answers to your most important questions about neuroendocrine cancer.
By Anna C. Greene, PhD, NETRF Chief Scientific Officer
You asked. We’re answering.
Through the Know Your NETs survey, patients and caregivers asked many urgent questions about treatment: What happens after Lutathera? Can peptide receptor radionuclide therapy (PRRT) be repeated? What is alpha PRRT? How do doctors decide what comes next? And why don’t we have clearer answers about treatment sequencing?
This post is part of You Ask, NETRF Answers, a series offering research-informed responses to the questions patients and caregivers ask most often. In each post, we answer as clearly as we can based on what is known today, what current research suggests, and where uncertainty remains. When the field does not yet have a good answer, we will say so.
These posts are educational, not medical advice, and they are not a substitute for guidance from your care team.
A note on scope: This post focuses primarily on well-differentiated neuroendocrine tumors (NETs), especially those that express somatostatin receptors and may be considered for PRRT. Poorly differentiated neuroendocrine carcinomas (NECs) are biologically distinct and are generally treated differently. PRRT is not a standard treatment approach for most NECs.
Why are patients asking?
PRRT has changed the treatment landscape for many people with advanced NETs. For patients whose tumors express somatostatin receptors, Lutathera, also called lutetium-177 DOTATATE or Lu-177 DOTATATE, can slow tumor growth and help control disease.
But PRRT is not the end of the story for every patient. Some tumors eventually grow again. Some patients cannot receive PRRT because their tumors do not express enough somatostatin receptors. Some receive PRRT and then face a period of uncertainty: What now? What should we watch? What happens if the cancer progresses?
That is the question behind many of the survey responses: not only “What comes after PRRT?” but “Will there still be options for me?”
The honest answer is yes, there may be options. But the best next step depends on the tumor type, grade, sites of disease, prior treatments, symptoms, imaging results, somatostatin receptor expression, overall health, and patient goals.
It also depends on research that is still underway.
What PRRT does, in plain language
PRRT is a targeted radiation treatment. Many well-differentiated NETs have somatostatin receptors on their surface. PRRT uses a molecule designed to bind to those receptors and carry radiation directly to tumor cells.
Lutathera uses lutetium-177, a radioisotope that emits beta radiation. In Lutathera, lutetium-177 is attached to dotatate, a molecule that binds to somatostatin receptors on tumor cells. After binding, the receptor-drug complex can be internalized into the tumor cell. Beta radiation damages the tumor cell and, because beta particles travel farther in tissue, nearby cells as well. This is why somatostatin receptor imaging, such as gallium-68 DOTATATE PET/CT, is so important before PRRT. It helps determine whether the tumors express the target that PRRT needs.
PRRT has been a major advance, but it is not a cure for most patients with metastatic NETs. In many cases, the goal is disease control: slowing growth, reducing symptoms, maintaining quality of life, and extending the time before another treatment is needed.
Why can disease grow after PRRT?
Progression after PRRT does not mean the treatment “failed” in a simple way. NETs are biologically diverse, and different tumors in the same patient may behave differently.
Several things may contribute. Some tumor cells may be more resistant to radiation. Some may express fewer somatostatin receptors over time. Some areas of disease may grow faster than others. In some patients, the biology of the tumor changes, including grade or proliferation rate. In others, PRRT may control the disease for a time but not permanently eliminate every cancer cell.
This is one reason post-PRRT care is not one-size-fits-all. Doctors need to know not only whether the disease is growing, but how quickly, where it is growing, whether symptoms are changing, and whether the tumors still express somatostatin receptors.
Can PRRT be repeated?
Sometimes, yes. PRRT retreatment, also called rechallenge, is used in some centers for carefully selected patients who previously benefited from PRRT and later developed progression.
But retreatment is not automatic. PRRT exposes the body to radiation, and doctors pay careful attention to cumulative effects, especially on the bone marrow and kidneys. A patient’s blood counts, kidney function, prior radiation exposure, extent of bone disease, time since prior PRRT, and overall disease behavior all matter.
The research so far suggests that PRRT retreatment may benefit some patients, especially those who had a meaningful period of disease control after their first course. But important questions remain: Which patients benefit most? How long should the first response last before retreatment is considered? How many additional cycles are safe? How should retreatment compare with other options such as everolimus, sunitinib, cabozantinib, chemotherapy, liver-directed therapy, or clinical trials?
These are exactly the kinds of questions prospective trials are designed to answer. One ongoing phase II study, called NET RETREAT, is testing retreatment with ¹⁷⁷Lu-DOTATATE PRRT compared with standard treatment options in people with metastatic or unresectable gastroenteropancreatic NETs who previously received PRRT and later had disease progression.
What is alpha PRRT?
Alpha PRRT is one of the areas patients asked about most often.
Standard Lutathera uses lutetium-177, a radioisotope that emits beta radiation. Alpha PRRT uses different radioactive payloads, such as actinium-225 or lead-212, that produce alpha particles as part of their radioactive decay. These radioactive payloads are attached to molecules that target somatostatin receptors. Compared with beta radiation, alpha particles travel a much shorter distance in tissue but deliver highly concentrated radiation damage over that short range.
In plain language, alpha PRRT may deliver a more powerful hit to nearby tumor cells while limiting radiation spread to surrounding tissue. That is why it is exciting, especially for patients whose disease has progressed after standard PRRT.
But alpha PRRT is still being studied. Researchers need to understand which patients are most likely to benefit, how to dose these treatments safely, how to monitor side effects, how to sequence alpha therapy with beta PRRT, and whether it should be used only after Lutathera or earlier in treatment for some patients.
For now, alpha PRRT for neuroendocrine tumors is still investigational. These treatments are being studied in clinical trials, including studies of RYZ101, which uses actinium-225 DOTATATE, and AlphaMedix, which uses lead-212 DOTAMTATE. None of these alpha PRRT approaches has been approved as a routine treatment option for neuroendocrine tumors. Clinical trials are essential to determine whether alpha PRRT is safe and effective, which patients are most likely to benefit, and how it should be used.
What other treatments may come after PRRT?
The next step after PRRT depends on the individual patient. Options may include continued monitoring, another systemic therapy, liver-directed or local treatment, PRRT retreatment, a clinical trial, or supportive care to manage symptoms and quality of life.
The right choice depends on tumor type, grade, rate of growth, location, symptoms, prior treatments, somatostatin receptor expression, overall health, and patient goals. This is why post-PRRT decisions are individualized. There is no single next treatment that is right for every patient.
Why isn’t there a single treatment sequence?
Patients often want to know the “right order” of treatments. That is understandable. But in NETs, treatment sequencing is still one of the biggest research gaps.
Part of the challenge is that NETs vary widely. A slow-growing small-intestinal NET, a pancreatic NET with liver metastases, a lung NET, a Grade 3 well-differentiated NET, and an SSTR-negative NET may all require different strategies. Even within one tumor type, patients may differ in grade, tumor burden, symptoms, receptor expression, sites of disease, prior treatment response, and overall health.
Another challenge is that many NET treatments were developed and tested in different trials, with different patient populations and different points in the treatment journey. That makes it difficult to know the best order for every patient.
Research is now trying to answer more practical questions: Should some patients receive PRRT earlier? Who should receive retreatment? When should doctors switch to chemotherapy or targeted therapy? Can imaging or biomarkers predict who will respond? How should alpha PRRT fit in? Can combinations improve outcomes without adding too much toxicity?
These are not academic questions. They affect real decisions patients and physicians face every day.
What is NETRF doing in this area?
NETRF funds research to improve how neuroendocrine cancer is detected, treated, and understood. NETRF’s Research Roadmap focuses on three major pillars: early detection, new therapies, and precision medicine. The question of what comes after PRRT sits directly at the intersection of new therapies and precision medicine.
New therapies are needed because not every patient responds to current treatments, and most available treatments do not cure metastatic disease. Precision medicine is needed because the next treatment should not be chosen only by what is available. It should be guided by the biology of the tumor and the needs of the patient.
Through donor-supported research, NETRF invests in projects that aim to understand treatment resistance, improve radionuclide therapies, develop new therapeutic targets, study rational treatment combinations, identify biomarkers of response, and build better evidence for treatment sequencing.
The goal is not simply to add more options. The goal is to help researchers learn which option is right for which patient, at which time.
The bottom line
PRRT has changed the outlook for many patients with somatostatin receptor-positive NETs, but it does not answer every treatment question. What we know is that treatment after PRRT is an active and important area of research. What we do not yet know is the best sequence for every patient. Patients need more than a list of possible treatments. They need evidence that helps determine which treatment is most likely to help, when it should be used, and how to preserve quality of life along the way.
The patients who asked, “What happens after PRRT?” are asking one of the most important questions in NET care.
And it is one the research community must continue to answer.
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Through June 30, 2026, your gift to NETRF can go twice as far through our June Match Campaign. Every eligible gift will be matched dollar-for-dollar, up to $100,000, helping fund research in early detection, new therapies, and more personalized treatment approaches for neuroendocrine cancer. Make your gift today.