Does Specific Activity Provide a Clinical Advantage in Lu-177 PSMA Therapy? A Comparison of the Clinical Efficacy, Molecular Response, and Safety Profiles of CA and NCA Lu-177
This retrospective study of 71 mCRPC patients found that carrier-added (CA) and non-carrier-added (NCA) [¹⁷⁷Lu]Lu-PSMA therapies offer comparable clinical and molecular efficacy, though the higher specific activity of NCA formulations is associated with a significantly increased risk of mild xerostomia.
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For men with advanced prostate cancer that no longer responds to hormone therapy, a new kind of treatment has emerged that targets the disease with remarkable precision. This approach uses a radioactive substance, a form of lutetium, which is attached to a molecule designed to seek out prostate cancer cells. Once injected into the bloodstream, this radioactive traveler hunts down cancer cells that display a specific protein on their surface, delivering a dose of radiation directly to the tumor while sparing most healthy tissue. This method has become a standard option for patients whose cancer has spread throughout the body, offering a way to slow the disease and ease symptoms when other treatments have failed.
The radioactive element used in this therapy, lutetium-177, can be manufactured in two different ways. One method produces a version that contains a significant amount of stable, non-radioactive lutetium mixed in with the radioactive atoms. The other method creates a version that is almost entirely pure radioactive atoms, with very little of the stable kind mixed in. Scientists have long wondered if this difference in purity matters for the patient. The theory was that the purer version, with its higher concentration of radioactive atoms per molecule, might deliver a stronger punch to the cancer or bind more effectively to the tumor. However, until now, it was unclear whether this theoretical advantage actually translated into better results for people undergoing treatment.
A team of researchers at Yeditepe University School of Medicine in Turkey set out to answer this question by looking back at the records of 71 men who had received this therapy. The study was not a new experiment where patients were assigned to groups, but rather a careful review of real-world data from men who had already been treated between 2022 and 2025. The researchers divided these men into two groups based on which type of lutetium they received: one group got the version with the stable mix, and the other got the purer, more concentrated version. Both groups received the same standard dose of the treatment, and the doctors tracked how well the therapy worked and how the patients felt afterward.
The results showed that, for the most part, the two types of treatment performed exactly the same. When the researchers looked at the levels of prostate-specific antigen, a protein in the blood that indicates how active the cancer is, they found no difference between the two groups. About half of the men in each group saw their cancer markers drop by half, a significant sign that the treatment was working. Similarly, when they examined PET scans, which act like a map showing where the cancer is in the body, the two groups showed similar patterns of improvement. The tumors shrank or stopped growing at comparable rates, and the overall ability of the treatment to control the disease was indistinguishable between the two versions. This suggests that the extra purity of the second method does not provide a clear advantage in stopping the cancer or extending life in this specific setting.
However, the study did uncover a distinct difference in how the patients felt during treatment. While the blood counts and kidney function remained stable and similar for everyone, the men who received the purer version of the treatment reported dry mouth more often. Specifically, half of the men in the purer group experienced mild dry mouth, compared to only one-fifth of the men in the other group. This side effect is caused by the radiation affecting the salivary glands, which also happen to have the same protein on their surface that the cancer cells have. The researchers suggest that because the purer version carries more radioactive atoms per molecule, it may deliver a slightly higher dose of radiation to these glands, leading to more frequent dryness. Despite this, the dryness was generally mild and did not become severe for anyone in the study.
The findings offer a clear picture for doctors and patients making treatment decisions. The study indicates that the more expensive or harder-to-produce version of the drug does not necessarily work better at fighting the cancer than the standard version. Both forms appear to be equally effective at controlling the disease and managing pain. The only notable difference was a higher chance of mild dry mouth with the purer version. This suggests that the choice between the two might depend less on hoping for a stronger cancer-killing effect and more on practical factors like cost, availability, and the specific side effect profile that a patient might prefer to avoid. The research confirms that while the chemistry of the drug is different, the clinical outcome for the patient remains largely the same.
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