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What Goes into Planning Your Chemotherapy
Planning chemotherapy involves more than just picking a medication. Your cancer care team considers many factors—like cancer type, treatment goals, and your overall health—to decide which type of chemo to use, how much to give, and how often. Understanding how these decisions are made can help you feel more informed and prepared.
How chemo works with other treatments
Sometimes chemo is the only treatment you need (primary treatment). Or, it might be used along with other treatments. For example, chemo may be used:
- To shrink a tumor before surgery or radiation therapy. Chemo used in this way is called neoadjuvant therapy.
- After surgery or radiation therapy to help kill any remaining cancer cells in the body. Chemo used in this way is called adjuvant therapy.
- With other types of medicines, such as targeted therapy that acts on certain targets of cancer cells or immunotherapy that helps the immune system fight cancer.
- With other treatments if cancer comes back or doesn't completely go away.
Choosing the right chemo
Cancer is sometimes treated with a single chemo drug, but often, several drugs are used together. They may be given in a certain order or in certain combinations (called combination chemo). Using 2 or more drugs that work in different ways can kill more cancer cells than using one by itself. It can also help lower the chance that the cancer becomes resistant to any one type of chemo.
In some cases, the best doses and schedules for each drug are well known, based on research studies in people with similar cancers.
In other cases, less may be known about the best way to treat a certain type or stage of cancer. Your overall health, other medical conditions, or medicines you take might also affect your treatment options. In these cases, different doctors might choose different drug combinations or schedules.
Factors a cancer care team considers when recommending treatment options include:
- The type and subtype of cancer
- The stage of the cancer (where it is, how big it is, and whether it’s spread to other parts of the body)
- Results of other tests on the tumor, such as biomarkers
- Your age
- Your overall health and current medications
- Other serious health problems (such as heart, liver, or kidney diseases)
- Goal of treatment
- Types of cancer treatments you have had in the past
If your treatment plan is not clear, or you are given several possible options, ask your cancer care team about getting a second opinion. It’s important to feel confident that you understand your choices and are making the decision that’s right for you.
Choosing the right chemo dose
Doctors must calculate chemo doses very carefully because most chemo drugs are strong medicines with a narrow dose range for safety and effectiveness. Too little may not treat the cancer, and too much can cause life-threatening side effects.
There are different ways to determine chemo dosage (amount), depending on the drug. Most chemo drugs are measured in milligrams (mg).
Chemo dosage by body weight
The overall dose may be based on a person’s body weight in kilograms (1 kilogram is 2.2 pounds).
For example, if 10 milligrams (mg) of a drug is needed for each kilogram (kg) of body weight, a person weighing 50 kilograms (110 pounds) would get 500 milligrams of the drug (50kg x 10mg/kg = 500mg).
Chemo dosage by body surface area
Some chemo doses are determined based on body surface area (BSA), which is calculated using height and weight. BSA is expressed in meters squared (m2).
Chemo dosage for children
Because children’s bodies process medicines differently, dosages for children and adults differ, even after BSA is taken into account. Children may have different levels of sensitivity to the chemo, too.
Other factors that can affect chemo dosage
Dosages of some chemo may also be adjusted for people who:
- Are over age 65
- Have poor nutrition
- Have already taken or are currently taking other medicines
- Have already had or are currently getting radiation therapy
- Have low blood cell counts
- Have liver or kidney diseases
- May otherwise be unable to tolerate full doses
Chemo cycles
Chemo is usually given at regular intervals called cycles. A cycle may be a dose of one or more types of chemo on one or more days, followed by several days or weeks without treatment. This gives normal cells time to recover from the effects of the chemo.
Some drugs are given for several days in a row, or every other day, followed by a rest period. Others work best when given continuously over a set number of days.
Each drug is given on a schedule that makes the most of its anti-cancer actions and minimizes side effects. If more than one type of chemo is used, the treatment plan will say how often and exactly when each should be given.
The number of cycles given may be decided before treatment starts, based on the type and stage of cancer. In some cases, the number is flexible and will take into account how the treatment affects the cancer and the person’s overall health.
When treatment plans change
In most cases, the most effective chemo doses and schedules for specific cancers have been found by testing them in clinical trials. It’s important, when possible, to get the full course of chemo, the full dose, and keep the cycles on schedule. This gives you the best chance of getting the maximum benefit from treatment.
There may be times, though, when serious side effects require adjusting the chemo plan (dose and/or schedule) to allow your body time to recover. Sometimes, you might be given supportive medicines to help you recover more quickly. Or sometimes, the cancer cells develop resistance to the chemo and a different type might be needed.
The goal is always to give enough chemo to treat the cancer effectively, while keeping side effects as manageable as possible. Your cancer care team will work with you to adjust the plan as needed and support you through treatment.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
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Last Revised: May 15, 2025
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