The assessment of responses to PRRT for gastroenteropancreatic neuroendocrine tumors (GEP-NETs) continues to be fine-tuned. Multiple presentations at the recent 2026 Society of Nuclear Medicine & Molecular Imaging (SNMMI) Annual Meeting shared data that build on this research that is essential to optimizing the therapeutic index of PRRT.

Following these presentations, featured expert Aman Chauhan, MD, was interviewed by Conference Reporter Editor-in-Chief Tom Iarocci, MD. Clinical perspectives from Dr Chauhan on these findings are presented here.

We have come a long way from having no effective therapy for GEP-NETs to having multiple effective therapies. One game changer in the field has been ¹⁷⁷Lu-dotatate, the only US Food and Drug Administration (FDA)–approved radiotheranostic agent for use in patients with metastatic GEP-NETs right now. However, the next generation of studies is pushing the envelope further, looking at dosimetry, novel radiotherapeutic agents, and novel radiation sensitizers to maintain safety while improving efficacy. And because not all studies can be done prospectively, there is an outpouring of new data from real-world analyses that will help us fine-tune some of our questions.

With respect to dosimetry, there are 2 schools of thought: one accepts the one-size-fits-all standard dosing regimens because of their ease of use, while the other focuses more on individual patients and supports theranostics, a precision medicine approach combining therapy and diagnostics (ie, imaging). I belong to the latter, and I think that the next wave of theranostics research should further explore dosimetry. There is an ongoing clinical trial in Europe that is randomizing patients to standard-dose ¹⁷⁷Lu-dotatate–based therapy or to dosimetry-adjusted therapy. This is the first prospective study seeking to determine whether dosimetry-guided PRRT is superior to standard dosing.

However, I am pragmatic and understand that these treatments are not accessible to most patients. One key resistance to implementing dosimetry is a lack of infrastructure and human resources. Most patients with GEP-NETs are treated in a community setting, where having a dedicated theranostics program with access to a physicist and dosimetry software may not be feasible. We have to simplify it, and I think that this is where we could weave in the use of artificial intelligence down the road. We can democratize theranostics by using a centralized cloud-based service where individualized dosimetry assessments can be provided to treating sites using central resources powered by artificial intelligence.

Another area of active research that is essential to optimizing the therapeutic index of PRRT involves the radiographic assessment of tumors. Currently, we are “married” to Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1)–based responses in oncology, but there are some flaws when it comes to responses to radiation-based therapies. For example, a tumor may not look like it is responding when, in fact, it is just not reflected in the RECIST 1.1–based size criteria. It is also not unusual to see delayed responses with PRRT, as radiation-induced DNA damage and resulting antitumor effects may take months to show their true benefit. Weaving in functional aspects such as SSTR status may be relevant to get a comprehensive assessment of disease status.

So, I do think that there is room to fine-tune our assessment of responses with functional imaging (ie, positron emission tomography/single-photon emission computed tomography [SPECT]) as we acquire more data from ongoing studies. At the 2026 SNMMI Annual Meeting, we saw such data from a study conducted by Shahad Howladar, MD, and colleagues in support of ¹⁷⁷Lu-dotatate–based SPECT/CT scans to quantify the response to PRRT in patients with metastatic NETs, similar to findings from the NETTER-1 clinical trial (abstract 262054).

Also at the 2026 SNMMI Annual Meeting, Andrew Voter, MD, PhD, from The Johns Hopkins Hospital presented data on the role of tumor volume metrics in prognosticating response to PRRT (abstract 261071). The basic conclusion from Dr Voter and colleagues was that prior treatment with cytotoxic chemotherapy, increased SSTR-avid tumor volume at disease onset, and increased tumor volume on posttreatment positron emission tomography/CT were all associated with decreased overall survival.

We already know that patients with bulky disease, patients who have had multiple prior treatments, and patients with more high-volume residual disease often do worse. Where this study adds value is that Dr Voter et al are taking these known clinical assertions and quantifying them objectively with the help of imaging-based data. So, again, I think that in the future, there will be a multimodal assessment that incorporates functional imaging along with the currently FDA-approved RECIST 1.1 standards or a CT/anatomic scan–based assessment.

There are also some updates regarding novel imaging radiotracers. In the past, we used indium-based imaging, which was great for the time. When I started practicing, however, we made a huge leap forward with gallium-based imaging, with significant improvements in sensitivity and specificity. Now copper dotatate is available, and this eases the logistical challenges of gallium-based imaging, which, due to its short half-life, requires us to have access to a cyclotron within driving distance. Copper overcame this issue because it can just be shipped; this really helped percolate this important imaging advancement to all corners of the United States.

Both techniques have a sensitivity and specificity of greater than 95%, so the bar is pretty high, but it is still refreshing to see further innovations in the imaging arena. For example, while all currently FDA-approved radiotracer imaging agents are agonists, [⁶⁸Ga]Ga-NODAGA-LM3 is a copper radiotracer that is linked to a somatostatin antagonist. The advantage of this antagonist is that it binds more tightly, so it may produce more sensitive scans, perhaps even in patients with fewer SSTRs. In the end, anything that refines detection excites me. We will see how these agents are developed further in larger studies.