Chemotherapy is a type of treatment commonly used for many types of cancer. It is the use of drugs to kill cancer cells, usually by stopping the cancer cells' ability to grow and divide. Systemic chemotherapy is often delivered through the bloodstream (called intravenously or IV) to reach cancer cells throughout the body. Some chemotherapy is given orally (by mouth) as a pill. A patient may receive one drug at a time or combinations of different drugs at the same time.

Chemotherapy doses are often based on ideal body weight, which is an estimate of a patient's body surface area (the size of the outside of the patient's body), rather than the patient's actual body weight and body surface area. Because of this approach, patients who are obese (determined by using a body mass index or BMI calculator [1]) may be getting less chemotherapy for their actual weight and height than patients who are not obese. This is often because of concerns that higher doses of chemotherapy may cause more side effects. Studies estimate that up to 40% of patients who are obese do not receive doses based on actual body weight, which may affect their survival and risk of the disease worsening. Furthermore, studies show that higher doses do not cause more severe side effects.

Research has shown that patients with cancer who are obese are more likely to die from the disease than those who are not obese. Although the suspected causes of this difference in prognosis (chance of recovery) are complex, doses of chemotherapy that are not based on a patient's actual weight may contribute.