Why a Pre-Treatment Workup Matters
Getting approved for Lu-177 DOTATATE therapy is not a single yes-or-no moment. It is a process. Before your first infusion, your care team builds a detailed picture of your tumor, your organs, and your overall health. Every test on this list has a job to do: confirm the therapy can reach your tumor, protect your kidneys and bone marrow, and make sure you are strong enough to tolerate treatment.
This guide explains each test in plain language — what it looks for, what a good result looks like, and what happens if a number falls outside the normal range. Take this page to your next appointment and use it as a checklist to ask your oncologist where you stand.
For a broader introduction to how Lu-177 DOTATATE works and what to expect throughout the process, see our guide: What Is Lu-177 Therapy? A Patient-Friendly Guide to How It Works, What to Expect, and Whether It Might Be Right for You.
Step 1: Confirming Your Diagnosis — Pathology and Tumor Grade
Lu-177 DOTATATE is designed for patients with well-differentiated neuroendocrine tumors (NETs). Before anything else, a tissue biopsy or cytology report must confirm this diagnosis. Your pathologist's report will include two key numbers.
The Ki-67 Proliferation Index
The Ki-67 index measures the percentage of tumor cells that are actively dividing, giving your doctor a sense of how aggressive the disease may be. It is measured by staining a tissue sample in the lab.
Under the World Health Organization (WHO) grading system:
- Grade 1 (G1): Ki-67 less than 3% — slow-growing, well-differentiated cells.
- Grade 2 (G2): Ki-67 between 3% and 20% — moderate growth rate.
- Grade 3 (G3): Ki-67 greater than 20% — faster-growing tumor.
Grading plays a central role in managing neuroendocrine tumors because it helps predict behavior and guides treatment choices. Lu-177 DOTATATE has the strongest evidence base for Grade 1 and Grade 2 tumors. In the landmark NETTER-1 phase III trial, all enrolled patients had well-differentiated inoperable midgut NETs at Grade 1 or Grade 2 (Ki-67 index ≤ 20%). Some well-differentiated G3 tumors may also qualify if they show high somatostatin receptor expression on imaging — your care team will review this individually.
Mitotic Count
Along with Ki-67, your pathologist counts how many cells are actively splitting under the microscope. Both numbers together determine your official WHO tumor grade. Ask your oncologist for both figures so you understand your grade fully.
Step 2: The Most Important Scan — Somatostatin Receptor PET/CT
This is the most critical test for Lu-177 DOTATATE eligibility. Lu-177 DOTATATE works by attaching to somatostatin receptors (SSTRs) on the surface of NET cells. If your tumor does not express these receptors strongly enough, the therapy cannot reach it and will not work.
Somatostatin receptor (SSTR) PET has shown a clear improvement over conventional imaging in patients with neuroendocrine tumors and has largely replaced the older OctreoScan (111In-pentetreotide scintigraphy) as the standard test for this purpose.
The most common scans used today are:
- 68Ga-DOTATATE PET/CT (gallium-68 DOTATATE)
- 64Cu-DOTATATE PET/CT (copper-64 DOTATATE)
A large study of 1,192 patients with metastatic GEP-NETs confirmed that approximately 92% of metastatic GEP-NETs showed strong, uniform SSTR expression on this type of scan. Most patients with a confirmed well-differentiated NET will likely show positive uptake, but it must still be verified for each person before treatment starts.
What the Scan Report Actually Means: SUVmax and the Liver Comparison
Your scan report will mention a value called SUVmax (standardized uptake value, maximum). This measures how strongly the radiotracer is absorbed by your tumor. To be considered positive — and therefore eligible — your tumor's uptake must be meaningfully higher than the uptake seen in normal liver tissue.
Most programs require the SUVmax of your tumor lesions to be greater than two times the average liver uptake. Your nuclear medicine specialist or radiologist will compare the brightness of your tumor spots against the background liver. The brighter the DOTATATE uptake in the cancer sites compared to normal liver, the more likely the patient is to benefit from PRRT. If there is little or no uptake, other treatment options should be explored.
Some centers use a scoring system called the Krenning scale (scores 0–4). A score of 3 or 4 — meaning uptake higher than normal liver — is generally required to proceed.
How Recent Must the Scan Be?
Most programs require your DOTATATE PET scan to have been done within the past 3–6 months before starting treatment. If your scan is older than that, you will likely need a new one. Tumor biology can change over time, and an outdated scan may not reflect your disease today.
Step 3: Anatomical Imaging — CT and MRI
Alongside the functional PET scan, your team needs high-resolution anatomical images to measure your tumors precisely. A CT or MRI of the chest, abdomen, and pelvis shows exactly where disease is located, how large each lesion is, and how it compares to prior scans.
This matters for two reasons. First, it creates a measurable baseline so your team can later tell whether treatment is working. Second, it confirms that disease is present and measurable by standard criteria (called RECIST 1.1). Most treatment programs require at least one measurable lesion on CT or MRI before proceeding.
These anatomical scans typically need to be no more than 4–12 weeks old at the time of your first treatment cycle, depending on your center's protocol.
Step 4: Blood Tests — Bone Marrow Function
Lu-177 DOTATATE delivers targeted radiation, but some of that radiation can reach surrounding tissues, including the bone marrow, which produces blood cells. Your team runs a complete blood count (CBC) before every cycle to make sure your marrow can handle treatment.
Here are the key thresholds most programs look for before starting therapy:
- White blood cells (WBC): At least 2,000–2,500 per microliter, reflecting your immune system's ability to fight infection.
- Absolute neutrophil count (ANC): Generally at least 1,500 per microliter. Neutrophils are your frontline infection-fighting cells.
- Platelets: At least 75,000–100,000 per microliter. Low counts raise bruising and bleeding risk.
- Hemoglobin: Usually at least 8.0–10.0 g/dL, reflecting red blood cell level and overall energy.
If any of these values fall short, your team may delay treatment until counts recover, or they may investigate whether the NET itself is affecting the bone marrow. Blood tests to monitor bone marrow, kidney, and liver function are done prior to every cycle, to determine if it is safe to proceed.
Step 5: Blood Tests — Kidney Function
Protecting the kidneys is one of the most important safety priorities in PRRT. After each infusion, the radioactive compound is filtered out through the kidneys, exposing them to radiation. This is why kidney-protective amino acid infusions are given alongside each Lu-177 DOTATATE cycle.
Before treatment, your care team will measure kidney function using one or more of these tests:
- Serum creatinine — a waste product that builds up when kidneys are not filtering efficiently.
- GFR (glomerular filtration rate) — how much blood your kidneys filter per minute. Most programs require a GFR of at least 30–50 mL/min before proceeding. Your center may use a 24-hour urine test or a nuclear medicine clearance scan (such as Tc-DTPA) for greater accuracy.
- Blood urea nitrogen (BUN) — another marker of kidney filtering capacity.
Reduced kidney function does not always mean treatment is off the table, but your team will monitor closely and may adjust the number of cycles. In patients with poor kidney function, Lu-177 is cleared more slowly from the body, potentially leading to prolonged exposure to bone marrow and other tissues.
Step 6: Blood Tests — Liver Function
Because NETs frequently spread to the liver, and because the liver processes the amino acid infusion given alongside treatment, liver function must be assessed before therapy begins. Your doctor will look at:
- AST and ALT (liver enzymes) — elevated levels suggest liver stress or damage. Most programs allow levels up to 3–5 times the upper limit of normal.
- Total bilirubin — a breakdown product processed by the liver. Usually must be no more than 3 times the upper limit of normal.
- Serum albumin — a protein made by the liver that reflects its overall reserve and your nutritional status.
Patients with large liver tumor burdens may have mildly elevated liver enzymes simply from disease involvement. Your care team will read these numbers alongside your imaging and overall clinical picture, not in isolation.
Step 7: Performance Status — How Well Are You Functioning?
Beyond lab values, your doctor will formally assess your overall physical function using one of two standard scales:
- ECOG Performance Status (0–4): 0 = fully active; 1 = restricted but ambulatory; 2 = up and about more than 50% of waking hours. Most programs require a score of 0–2.
- Karnofsky Performance Scale (0–100%): A score of 60% or higher is generally required.
A good performance score suggests your body can handle treatment, recover between cycles, and benefit from the therapy.
Step 8: Additional Tests Your Team May Order
Depending on your history and your center's protocol, your workup may also include:
- Chromogranin A (CgA) — a blood tumor marker elevated in many NETs. A baseline level helps track response over time.
- 24-hour urine 5-HIAA — elevated in carcinoid tumors; useful for monitoring functional tumors.
- Pregnancy test — required for women of childbearing age, as Lu-177 DOTATATE may cause fetal harm.
- Echocardiogram — some patients with carcinoid syndrome develop carcinoid heart disease (Hedinger syndrome); cardiac evaluation may be requested if symptoms suggest this.
- Bone scan or MRI — if bone metastases are suspected but not clearly visible on PET.
- Somatostatin analogue (SSA) timing check — if you are on octreotide or lanreotide, the timing of your last injection relative to DOTATATE infusion matters. Short-acting octreotide is typically held for at least 24 hours before treatment; long-acting formulations are usually paused for at least 4 weeks beforehand, unless your team confirms adequate receptor uptake on imaging despite continued use.
Putting It All Together: What "Eligible" Actually Looks Like
There is no single pass/fail score. Eligibility is a judgment call made by a multidisciplinary team — usually including a nuclear medicine specialist, medical oncologist, and sometimes a hepatologist or nephrologist — who weigh scan results, blood values, tumor grade, performance status, and prior treatments together.
A clear path to eligibility looks like this: a confirmed well-differentiated (G1 or G2) NET on biopsy, strong DOTATATE uptake on PET/CT, a GFR above 50 mL/min, blood counts within acceptable ranges, and an ECOG score of 0 or 1. Many patients with borderline results are still considered, particularly when other treatment options have been exhausted.
To understand what life may be like once treatment begins — including what symptom changes to expect — see our related article: Will Lu-177 DOTATATE Make My Neuroendocrine Tumor Symptoms Better? What Patients with Metastatic NETs Can Expect. For a detailed look at managing side effects during treatment, visit: What Side Effects Should I Expect from Lu-177 DOTATATE for a Gastroenteropancreatic Neuroendocrine Tumor — and How Can I Manage Them?
When to Talk to Your Doctor
If you have a confirmed NET diagnosis and your oncologist has raised the possibility of Lu-177 DOTATATE, ask specifically: "Can we review my Ki-67 index, my most recent DOTATATE PET scan report, and my kidney function together to see where I stand?" Bring a list of all your current medications, especially somatostatin analogues, so your team can advise on timing. If any results are borderline, ask what it would take for those numbers to improve and whether repeat testing in a few weeks is an option.
This article is for general information and is not a substitute for medical advice. Always consult your oncologist or care team about your specific situation.
Frequently asked questions
What is the single most important test for Lu-177 DOTATATE eligibility?
The somatostatin receptor PET/CT scan — usually a 68Ga-DOTATATE or 64Cu-DOTATATE PET/CT — is the most critical eligibility test. It confirms whether your tumor cells express the somatostatin receptors that Lu-177 DOTATATE needs to attach to. If your tumor does not show adequate receptor uptake on this scan (at least twice the uptake seen in normal liver tissue), the therapy cannot effectively reach the tumor and will not be recommended.
My Ki-67 is 18%. Does that disqualify me from Lu-177 DOTATATE?
Not necessarily. A Ki-67 of 18% places your tumor at Grade 2, which is within the range studied in the landmark NETTER-1 clinical trial. That trial enrolled patients with well-differentiated NETs with a Ki-67 index up to 20%. However, eligibility also depends on your somatostatin receptor expression on PET, your kidney and bone marrow function, and your performance status. Your care team will look at all of these together, not the Ki-67 number alone.
My kidney function (GFR) is slightly below the usual cutoff. Can I still be treated?
This depends on your specific center and the degree of impairment. A GFR in the range of 30–50 mL/min may still allow treatment to proceed with careful monitoring and dose considerations. Kidney-protective amino acid infusions are given with each cycle to reduce radiation exposure to the kidneys. Your nephrologist or oncologist may order a formal nuclear medicine kidney clearance test (such as Tc-DTPA) to get a more accurate GFR measurement before making this decision. Impaired kidney function does not automatically disqualify you, but it does affect how your team plans and monitors your treatment.
How long before my first Lu-177 DOTATATE infusion should I stop my somatostatin analogue (octreotide or lanreotide)?
Timing depends on the formulation. Short-acting octreotide is typically held for at least 24 hours before each Lu-177 DOTATATE infusion, because it competes with DOTATATE for the same somatostatin receptors and could reduce how well the therapy is taken up by the tumor. Long-acting formulations (such as octreotide LAR or lanreotide Autogel) are generally paused for at least 4 weeks before treatment unless imaging confirms that receptor uptake remains high enough despite continued use. Always follow your specific oncologist's instructions — do not stop or delay your analogue without guidance, as it also controls your symptoms.
Will I need a biopsy even if I already have an older one on file?
In most cases, an existing biopsy report that confirms a well-differentiated NET with a documented Ki-67 index is sufficient, as long as it is reasonably recent. However, if there has been significant disease progression since the original biopsy, if you have new lesions in different locations, or if your clinical picture has changed substantially, your team may recommend a new biopsy to check whether the tumor grade has evolved. Some centers also request archival tissue for research or molecular analysis as part of certain clinical trial protocols.
How often are these tests repeated during treatment?
Blood tests — including blood counts, kidney function, and liver function — are repeated before every treatment cycle, which typically occur every 8–12 weeks. This is done to confirm it is safe to give the next dose. Imaging (CT or MRI) is usually repeated after every two cycles to assess treatment response. Your care team may also repeat the DOTATATE PET scan after treatment to evaluate how well the therapy has worked. If any blood values fall into the concerning range during treatment, your team may delay a cycle, adjust monitoring frequency, or refer you to a specialist.