What Is Adjuvant Therapy?

Medically Reviewed By: Harold J. Burstein, MD, PhD

Adjuvant therapies are treatments that are given after surgery or other frontline therapy to reduce the risk that cancer will come back. Frontline therapy may succeed in removing or eliminating the entire visible mass of a tumor, but tiny, undetectable traces of it may remain in the body. Adjuvant therapy is designed to kill or block those residual cancer cells.

Adjuvant therapy can be used to treat cancer in a variety of organs and tissues and is most often given to patients with breast, colon, or lung cancer.

If adjuvant therapy is recommended, does that mean that cancer cells definitely remain in the body?

Not necessarily. Because the microscopic amounts of cancer left over after surgery can be too small to be seen, doctors cannot be certain that surgery or other frontline therapy has removed every last tumor cell. Adjuvant therapy is recommended as a precaution in case such cells to remain.

Which treatments are used as adjuvant therapies?

  • Chemotherapy – Drugs that kill cancer cells throughout the body
  • Radiation therapy – High-powered energy beams directed against tumor cells
  • Hormone therapy – Agents that block or halt the production of hormones that fuel the growth of some tumors
  • Immunotherapy – Treatments that harness the immune system to attack cancer or supplement the immune system’s cancer-fighting ability
  • Targeted therapy – Drugs that block the action of specific genes or proteins that cancer cells rely on for growth and survival

[Learn more: Which types of cancer can be treated with immunotherapy?]

How effective are these therapies?

The effectiveness of adjuvant therapy depends on a variety of factors, including:

  • Type of cancer – Some forms of cancer respond better to adjuvant treatments than others.
  • Cancer stage – Early-stage cancers, which have not spread beyond their initial site, generally are less likely to recur than those that have spread, or metastasized.  Adjuvant therapy can substantially lower the risk of recurrence in some metastatic cancers.
  • Lymph node involvement – The more lymph nodes containing tumor cells, the more likely tumor cells will remain in the body after surgery.  Adjuvant therapy can be particularly useful in such cancers.

How long is adjuvant therapy given?

The duration of adjuvant therapy treatment depends on numerous factors, including the type and extent of the cancer and the type and intensity of adjuvant therapy used.  In some cases, adjuvant therapy may be given for months or years.

What are the side effects of adjuvant therapies?

Like primary, frontline therapies, nearly all adjuvant therapies cause side effects. These vary depending on the type and amount of adjuvant therapy involved. For example, some chemotherapy agents can cause fatigue, hair loss, nausea, and other complications.

What is the difference between adjuvant and neoadjuvant therapy?

Neoadjuvant therapy is given before the primary treatment. A patient requiring surgery, for example, may be treated with chemotherapy and/or radiation therapy first, to shrink the tumor and make it easier to remove.

About the Medical Reviewer

Harold J. Burstein, MD, PhD

Dr. Burstein graduated from Harvard College before earning his MD at Harvard Medical School. He also received a PhD in cellular immunology and a master's degree in the history of science from Harvard. He trained in internal medicine at Massachusetts General Hospital before his oncology fellowship at DFCI. In 1999, he joined the staff of DFCI and Brigham and Women's Hospital, where he is a clinician and clinical investigator in the Breast Oncology Center.  Dr. Burstein is an internationally renowned breast cancer expert, who has led and participated in multiple clinical trials, and developed national and international breast cancer treatment guidelines.  Recognized as one of the leading breast oncologists, he is a perennial "Top Doctor" in the US for breast cancer care.  He teaches students, residents and fellows at Harvard Medical School and Dana-Farber.