Preventive Chemotherapy: What It Is and How It Works

Kate Middleton recently revealed that she has been undergoing ‘preventive chemotherapy’ for cancer following abdominal surgery in January. What is preventive chemotherapy, and why is it performed even after successful cancer surgery, as in the case of the Princess of Wales?

Preventive chemotherapy is medically called ‘adjuvant chemotherapy,’ which is the term we will use for the remainder of this article.

What is preventive chemotherapy?

Preventive chemotherapy is chemotherapy given to destroy any remaining cancer cells in the body after primary cancer treatment. As the name suggests, its goal is to prevent cancer from coming back. Other preventive modalities also exist, including hormonal therapy, radiation therapy, targeted therapy, and immunotherapy.

Doctors often administer adjuvant chemotherapy after surgical removal of a tumor. Even if surgery is successful, meaning that cancer is no longer detectable after surgery, small numbers of cancer cells are sometimes still left behind. This condition — called ‘minimal residual disease’ — escapes detection except by highly specialized laboratory techniques that are not always available. By eliminating these remaining cancer cells, adjuvant chemotherapy aims to increase the chance that patients can live cancer-free for the rest of their lives.

Understanding different phases of cancer treatment

Adjuvant chemotherapy plays a distinct role alongside other types of chemotherapy as part of a comprehensive cancer treatment plan:

  • Induction (‘first-line’ or ‘primary’) chemotherapy is the main treatment for a person’s cancer. Its purpose is to achieve cancer remission, the state in which all signs and symptoms of cancer are gone. It is frequently used in combination with radiation therapy.
  • Consolidation (‘intensification’) chemotherapy is sometimes given to destroy any leftover cancer cells after remission is achieved with induction therapy. It is similar to adjuvant chemotherapy, except that adjuvant chemotherapy is given after surgery, while consolidation chemotherapy is given after induction chemotherapy.
  • Maintenance chemotherapy is sometimes given after consolidation chemotherapy to keep a patient in remission for as long as possible. It involves a longer period of treatment and lower dosages compared to consolidation chemotherapy.
  • Neoadjuvant chemotherapy is given prior to cancer surgery. It aims to decrease the size of a tumor or to make a tumor operable, giving the surgery a better chance of being successful.
  • Palliative chemotherapy aims to reduce symptoms of cancer rather than to achieve or sustain cancer remission.

What types of cancer is preventive chemotherapy used for?

Adjuvant chemotherapy is often used in the treatment of the following cancer types:

  • Breast cancer. Data collected from 33,177 older women with breast cancer showed that receipt of adjuvant chemotherapy was associated with a 21% reduced risk of death from breast cancer and a 36% reduced risk of death overall.
  • Colorectal cancer. An analysis of 33,069 patients across 34 studies found that adjuvant chemotherapy improved survival in patients with stage II/III colorectal cancer. Compared to patients treated with surgery only, those who underwent both surgery and adjuvant chemotherapy had significantly better median overall survival (118.8 vs. 74.6 months) and median disease-free survival (86.3 vs. 40.8 months).
  • Lung cancer. A study of 1,867 patients with non-small cell lung cancer revealed that those who received adjuvant chemotherapy had improved overall and disease-free survival at 5 years compared to those who did not.

Importantly, how well cancer responds to adjuvant chemotherapy depends on multiple factors, including the cancer type and subtype, cancer stage, and patient characteristics. Not all cancers respond equally to adjuvant chemotherapy.

For instance, in the previously referenced study on breast cancer in older women, adjuvant chemotherapy was more effective for cancers that spread to multiple lymph nodes. Breast cancer molecular subtype also affected how much patients benefited from adjuvant chemotherapy. This supports the results of another study of 1,248 women, which demonstrated that survival improved only among women with more aggressive breast cancers.

Therefore, the presence of the following features more strongly supports the use of adjuvant chemotherapy:

  • Later cancer stage
  • Genetic mutations making cancer recurrence more likely
  • Biomarkers that make a cancer more susceptible to chemotherapy
  • Younger, healthier patients

How does adjuvant chemotherapy work?

If you have been diagnosed with cancer, your doctor will determine whether and how your specific disease is likely to respond to adjuvant chemotherapy. Your doctor will also discuss with you the risks and benefits of adjuvant chemotherapy. You and your doctor should consider your goals for treatment and your desired quality of life.

If you and your doctor decide to proceed with adjuvant chemotherapy, your treatment plan will include a discussion of:

  • Chemotherapy regimen. Over 100 different chemotherapy drugs exist, but a limited number are used in the adjuvant setting. According to one study, 34.8% of drugs used to treat metastatic breast, colon, and non-small cell lung cancers are also applied as adjuvant chemotherapies. Intravenous administration is most common, although pills can also be an option. Adjuvant chemotherapy is usually given in cycles, involving treatment on some days and rest on other days.
  • Duration of treatment. Adjuvant chemotherapy is usually started a few weeks after surgery, and the total treatment duration varies. While 3 to 9 months is fairly standard, treatment can be shorter or longer. The optimal duration for adjuvant chemotherapy is an area of active investigation. For example, while the standard of care for stage III colon cancer was traditionally accepted to involve 6 months of adjuvant chemotherapy, more recent results have shown 3 months to be just as effective in certain cases.
  • Side effects. Chemotherapy is associated with many different side effects because the drugs destroy healthy cells as well as cancer cells. Side effects are more likely to occur among older patients. Some of the most common short-term side effects include hair loss and gastrointestinal symptoms such as nausea, vomiting, and diarrhea. Side effects are usually managed with a combination of medications, lifestyle modifications, and adjustments to chemotherapy dosages.

Considerations and risks

While adjuvant chemotherapy can prolong cancer-free survival among patients undergoing surgery, it does not benefit everyone equally.

Patients who achieve success with adjuvant chemotherapy tend to live longer and regain their quality of life after the side effects of treatment wear off.

Others pay a bigger price. Long-term side effects of adjuvant chemotherapy can include persistent fatigue, weight loss, depression, cognitive changes, peripheral neuropathy, and many others. Some people experience a worsening quality of life up to 4 years post-treatment.

The benefits of adjuvant chemotherapy do not always outweigh the risks. For example, in certain cases, adjuvant chemotherapy might only improve 5-year survival rates by 5%. Research suggests that cancer patients, particularly those who are older or have poorer physical health, often value the quality of life over the length of life.

Making informed decisions

If you have cancer and are eligible to begin adjuvant chemotherapy, it is important to make an informed decision on whether treatment would be best for you. Some questions you may want to ask your doctor include:

  • How much longer can I expect to live if I receive treatment?
  • What is the chance that treatment will allow me to stay cancer-free?
  • How long will I have to be on treatment?
  • What is likely to happen if I choose not to receive treatment?
  • What are the short- and long-term side effects of treatment?
  • What other adjuvant therapy options exist besides chemotherapy?

Engaging in honest conversations with your doctor and loved ones can ensure that you make a decision that is true to your life’s goals and values. While adjuvant chemotherapy can help you enjoy a longer life, there are many factors to consider in determining whether this treatment is right for you.

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