Adjuvant refers to something that provides support, complementation, reinforcement, or enhancement. In the medical context, it commonly refers to a type of therapy or treatment that is given in addition to the primary treatment to improve its effectiveness or reduce the risk of recurrence.

Adjuvant therapy is administered after the primary treatment, while neoadjuvant therapy is given before the primary treatment. The term is frequently used in relation to cancer treatments such as chemotherapy, radiotherapy, hormone therapy, targeted therapy, and biological therapy. Adjuvant treatments aim to optimize the outcome of the primary treatment and enhance the chances of successful patient outcomes.


The term “adjuvant” originates from the Latin word “adjuvare,” meaning to help or strengthen.


Adjuvant in Medicine

In breast cancer, for instance, adjuvant chemotherapy is chemotherapy administered after surgery (either a mastectomy or breast-conserving surgery). Similarly, breast cancer adjuvant therapies include postoperative radiotherapy, hormone therapy, targeted therapy, and biological therapy.

In breast cancer, neoadjuvant (preoperative) chemotherapy is administered before surgery for locally advanced tumors (stage 3), characterized by a large tumor without metastasis. This approach aims to reduce tumor size and minimize the risk of recurrence following surgery. Adjuvant and neoadjuvant radiotherapy are also employed for the same reasons.

Adjuvant in pharmacology

This term refers to a molecule that is used to augment the primary effect of a drug, either physiologically or chemically, or to reduce treatment side effects. Examples include amifostine, which protects the body from the side effects of chemotherapy for cancer, and aluminum compounds, which enhance the immunological response to vaccines, thereby increasing their efficacy.

Adjuvant in Immunology

Adjuvants are substances added to vaccines to enhance the production of antibodies in response to the antigen. They can take the form of compounds, molecules, or microorganisms with reduced viability.

Some current vaccine adjuvants include MF59, AS03, AS04, alum, Vibrio cholerae toxin (cholera toxin), thermolabile Escherichia coli enterotoxin, and cytokines including IL-6, IL-12, IL-15, IL-18, and IL-21.

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