Neoadjuvant therapy is the administration of therapeutic agents before a main treatment. One example is neoadjuvant hormone therapy prior to radical radiotherapy for adenocarcinoma of the prostate. Neoadjuvant therapy aims to reduce the size or extent of the cancer before using radical treatment intervention, thus making procedures easier and more likely to succeed, and reducing the consequences of a more extensive treatment technique that would be required if the tumor wasn't reduced in size or extent.
Another related concept is that neoadjuvant therapy acts on micrometastatic disease. The downstaging is then a surrogate marker of efficacy on undetected dissemination, resulting in improved longtime survival compared to the surgery-alone strategy.
This systemic therapy (chemotherapy, immunotherapy or hormone therapy) or radiation therapy is commonly used in cancers that are locally advanced – where clinicians plan an operation at a later stage. The use of such therapy can effectively reduce the difficulty and morbidity of more extensive procedures.
The use of therapy can turn a tumor from untreatable to treatable by shrinking the volume. Often it can be unclear which surrounding structures are directly involved in the disease and which are just showing signs of inflammation. By administering therapy a distinction can often be made. Some doctors give the therapy in the hope that a response will be seen so that they can then decide what is the best course of action. Unfortunately, not everyone is suitable for therapy in this way because it can be extremely toxic. Some patients react so severely that further treatments, especially surgery, are precluded because the patient is rendered unfit for anesthetic.
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