Two Different Approaches to Cancer Treatment
Chemotherapy and nuclear medicine therapy (specifically radioligand therapy) are both used to treat cancer, but they work through fundamentally different mechanisms. Understanding these differences can help patients appreciate why their treatment plan may include one or both approaches.
How Chemotherapy Works
Chemotherapy uses drugs that target rapidly dividing cells. These drugs circulate throughout the entire body (which is why chemotherapy is called a systemic treatment) and affect any cells that are dividing quickly. Since cancer cells tend to divide faster than most normal cells, they are more susceptible to these drugs.
However, some normal cells also divide rapidly, including those in the bone marrow, the lining of the digestive tract, and hair follicles. This is why chemotherapy can cause side effects like lowered blood counts, nausea, and hair loss. The drugs do not distinguish between cancer cells and rapidly dividing healthy cells.
How Radioligand Therapy Works
Radioligand therapy takes a targeted approach. Instead of affecting all rapidly dividing cells, it delivers radiation specifically to cancer cells that carry a particular molecular target. A molecule designed to seek out that target is linked to a radioactive isotope. When injected, it travels through the body, binds to cancer cells expressing the target, and delivers radiation locally.
Because the radiation has a limited range (just a few millimetres for beta-emitting isotopes like Lutetium-177), the damage is concentrated around the cells the radioligand has bound to. Surrounding healthy tissue receives a much lower dose.
Key Differences
Targeting mechanism: Chemotherapy affects rapidly dividing cells broadly. Radioligand therapy targets specific molecular markers on cancer cells.
Side effect profile: Chemotherapy side effects (nausea, hair loss, immune suppression) stem from its broad action on dividing cells. Radioligand therapy side effects are generally different and relate to radiation exposure in specific tissues. Dry mouth (in PSMA therapy, because salivary glands express some PSMA), fatigue, and temporary blood count changes are common.
Patient selection: Chemotherapy can be given to most cancer patients as long as they are fit enough. Radioligand therapy requires confirmation that the cancer expresses the molecular target, which is done through a diagnostic scan. Not all cancers qualify.
Administration: Chemotherapy is typically given in multiple cycles over weeks or months, often requiring several hours of infusion per session. Radioligand therapy is also given in cycles, but the infusion itself is usually shorter.
When Each Is Used
Chemotherapy remains a cornerstone of cancer treatment for many cancer types. It is often used as a first-line treatment, sometimes in combination with surgery, radiation, or immunotherapy.
Radioligand therapy is currently approved or available for specific situations, particularly advanced prostate cancer (Lu-177 PSMA) and neuroendocrine tumours (Lu-177 DOTATATE). It is often used after other treatments, including chemotherapy, have been tried. Research is expanding its applications.
In many cases, radioligand therapy is not a replacement for chemotherapy but an additional tool in the treatment sequence. Your oncologist will determine where each treatment fits in your overall care plan based on your cancer type, stage, and treatment history.
Working Together
Cancer treatment is increasingly multimodal, meaning that different types of treatment are used together or in sequence to achieve the intended outcome. A patient might receive surgery, followed by chemotherapy, followed by radioligand therapy at a later stage if the cancer progresses. Each treatment targets the disease through a different mechanism, and the combination can be more effective than any single approach alone.
Discuss with your nuclear oncology team which treatment options are relevant to your specific case and how they fit into your overall plan.