Peptide receptor radioligand therapy (PRRLT) is a type of targeted radiotherapy used to treat certain types of cancer. It involves administering a radiolabeled peptide that binds to specific receptors overexpressed on cancer cells. The radiolabeled peptide delivers radiation directly to the tumor while minimizing damage to surrounding healthy tissues.
PRRLT takes advantage of the fact that certain peptide receptors are overexpressed on the surface of cancer cells compared to normal cells. These receptors bind peptide hormones that regulate cell growth and differentiation. Examples include somatostatin receptors, which bind somatostatin and bombesin receptors, which bind gastrin-releasing peptide.
In PRRLT, a synthetic peptide that binds to the overexpressed receptor is chemically linked to a radioactive isotope such as yttrium-90 or lutetium-177. The most commonly used peptides are analogs of somatostatin, such as octreotide and octreotate. The radiolabeled peptide is injected intravenously and travels through the bloodstream to cancer cells overexpressing the receptor. Receptor binding leads to endocytosis and accumulation of the radiopeptide, delivering targeted radiation to cancer cells while sparing normal tissues.
The high energy beta emissions from the radioisotope damage cancer cell DNA, leading to apoptotic cell death. The short path length of beta particles limits radiation damage to surrounding normal cells. Gamma emissions allow imaging which facilitates dosimetry and response monitoring.
PRRLT provides targeted therapy that is less toxic than conventional external beam radiotherapy. Treatment sessions are repeated for maximum effect. It is mainly used to treat neuroendocrine tumors such as gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and pheochromocytoma/paraganglioma. However, receptors such as somatostatin, bombesin and others are also overexpressed in many common solid tumors like breast, prostate and colon cancers.
Some key advantages of PRRLT include:
- Provides radiation therapy targeted directly to cancer cells while minimizing collateral damage
- Results in high tumor response rates and increased progression-free survival
- Well tolerated with mild side effects compared to conventional radiotherapy
- Can be used as neoadjuvant therapy to shrink tumors before surgery, allow resection of previously inoperable tumors
- Useful for treating metastatic disease when other treatments have failed
The field of PRRLT is rapidly evolving with new peptide analogs, radionuclides, combination therapies, and applications to new cancer types. For example, PSMA-targeted radioligand therapy is an emerging PRRLT approach for treating prostate cancer.
With further research to identify new receptors and optimize treatment regimens, PRRLT has the potential to transform the management of several difficult to treat malignancies. Combining PRRLT with checkpoint inhibitors could augment anti-tumor immunity. Overall, peptide receptor radionuclide therapy is a promising strategic addition to the cancer therapeutic arsenal.
If you are dealing with a neuroendocrine tumor or advanced prostate cancer, be sure to ask your oncologist if peptide receptor radionuclide therapy is a good option for your situation. The specialists at Hormone Harmony Clinic offer cutting-edge PRRLT with a patient-centered approach. Contact us today to find out if you might benefit from this innovative targeted therapy.
