Summary (10 sec read)
Dr. Ishita Sen explains - Peptide Receptor Radionuclide Therapy (PRRT) is an advanced, targeted treatment for neuroendocrine tumors (NETs) that express somatostatin receptors. It offers significant benefits over chemotherapy, including better tumor targeting, fewer side effects, symptom relief, and improved survival rates. PRRT is especially effective for advanced-stage, metastatic, or inoperable NETs.
What is PRRT?
Peptide Receptor Radionuclide Therapy (PRRT) is a cutting-edge molecular technique designed to treat neuroendocrine tumors (NETs), which express somatostatin receptors. These tumors can arise in various parts of the body, such as the pancreas, small and large bowel, lungs, and even adrenal glands, known as pheochromocytomas, or along the sympathetic chain, referred to as paragangliomas. PRRT uses a radiolabeled peptide, such as Lutetium-177 (Lu-177) or Yttrium-90 (Y-90), to target and deliver radiation directly to these tumor cells, leaving healthy tissue largely unaffected.
Dr. Ishita Sen explains PRRT as "a molecular technique in which a radioisotope, labeled with a small body that targets a particular receptor known as the somatostatin receptor, is used to treat neuroendocrine tumors." These tumors, according to Dr. Ishita Sen, "can arise from various parts of the body and can cause symptoms depending on the type of hormone secreted by the tumor."
PRRT Versus Conventional Treatment?
Compared to conventional treatments, such as surgery, external beam radiation, and chemotherapy, PRRT offers a more targeted, less invasive approach. Surgery remains the preferred method for early-stage localized NETs, but it is often unsuitable for metastatic or inoperable tumors. Chemotherapy, while effective in aggressive forms of cancer, tends to be less effective in well-differentiated, slow-growing neuroendocrine tumors, which are often refractory to such treatment.
PRRT provides a targeted alternative by focusing on somatostatin receptors overexpressed by the tumor cells. This precision minimizes damage to surrounding healthy tissues, making PRRT particularly effective for patients with advanced or metastatic NETs. Dr. Ishita Sen emphasizes that “chemotherapy does not work for these tumors, and the treatment of choice is a targeted therapy called PRRT.” This underscores the distinct advantage of PRRT in cases where traditional treatments fall short.
PRRT Versus Chemotherapy?
Chemotherapy affects rapidly dividing cells indiscriminately, including healthy cells, leading to systemic toxicity and a host of side effects. PRRT, on the other hand, selectively targets tumor cells that express somatostatin receptors, offering fewer side effects and improved outcomes. In Dr. Ishita Sen’s words, “PRRT reduces tumor burden and improves survival while giving patients significant symptomatic relief.” This specificity makes PRRT superior to chemotherapy for neuroendocrine tumors, especially those that are well-differentiated and slow-growing.
The NETTER-1 trial, a pivotal study on PRRT, demonstrated significantly longer progression-free survival (40 months) in patients receiving Lutetium-177 PRRT compared to those receiving high-dose somatostatin analogs alone (8 months). Additionally, PRRT has been shown to provide partial tumor shrinkage in 20-30% of patients and disease stabilization in 70-80% of cases.
What is the PRRT Success Rate?
The success rate of PRRT is impressive, especially in patients with metastatic or inoperable neuroendocrine tumors. Dr. Ishita Sen explains that PRRT can “reduce tumor burden, improve patient survival, and provide significant symptomatic relief.” This includes managing symptoms such as diarrhea, hypoglycemia, and flushing, which result from the hormone secretion by neuroendocrine tumors. PRRT not only extends survival but also improves the quality of life for patients by reducing the symptoms associated with these tumors.
Studies have shown that overall survival rates for PRRT-treated patients range from 63 to 72 months, depending on the stage and type of the neuroendocrine tumor. PRRT provides long-term disease control for many patients, significantly extending their life expectancy.
What to Expect After PRRT Treatment?
After undergoing PRRT, most patients experience mild side effects, including fatigue, nausea, and abdominal discomfort. These symptoms usually subside within a few days. Blood tests are routinely performed to monitor for potential side effects like low blood cell counts and kidney function changes, as PRRT can cause mild bone marrow suppression. Dr. Ishita Sen notes that PRRT “not only reduces the tumor burden but also provides relief from symptoms like diarrhea, flushing, and hypoglycemia,” which are common in neuroendocrine tumor patients.
Patients are also advised to avoid close physical contact with others for about a week post-treatment due to residual radioactivity. Most patients can resume normal activities shortly after their treatment, although fatigue may persist for some time.
How Long Are You Radioactive After PRRT?
The duration of radioactivity after PRRT depends on the isotope used. Lutetium-177, with a half-life of 6.7 days, is largely eliminated from the body within the first week after treatment. Dr. Ishita Sen explains that the radiopharmaceutical injected into the bloodstream “targets the somatostatin receptors on tumor cells, leaving normal cells unharmed since they do not express these receptors.” After 7 days, the residual radioactivity is minimal, allowing patients to return to their usual routines.
Long-Term Side Effects of PRRT?
The long-term side effects of PRRT are generally mild compared to conventional therapies such as chemotherapy. The most significant long-term concern is bone marrow suppression, which can lead to anemia, leukopenia, and thrombocytopenia. In rare cases, patients may experience nephrotoxicity, particularly with Yttrium-90-based PRRT, although this is mitigated by the use of Lutetium-177, which has a better safety profile for the kidneys.
Dr. Ishita Sen highlights the importance of regular monitoring during and after PRRT to detect any early signs of organ damage, particularly in the liver and kidneys. Routine follow-ups with blood tests and imaging studies help track both tumor response and potential side effects.
PRRT for Neuroendocrine Tumors?
PRRT is particularly effective for neuroendocrine tumors that express somatostatin receptors, making it an ideal treatment for gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs) and other somatostatin receptor-positive tumors. Dr. Ishita Sen explains that the radiopharmaceutical “seeks out somatostatin receptors on the tumor cells, allowing for precise targeting.” This makes PRRT highly suitable for patients with metastatic or inoperable tumors, where surgery is not an option.
Neuroendocrine tumors can secrete hormones, leading to a range of symptoms based on the type of hormone produced. PRRT can alleviate many of these symptoms by reducing tumor size and hormone secretion, improving patients' overall quality of life.