Chemotherapy for Cancer Treatment

Chemotherapy is a major tool in the fight against cancer. This site tries to explain the kinds of chemotherapy, what the medicines do, and how they are administered.

Chemotherapy drugs are also called antineoplastic drugs, meaning they work against neoplasms (tumors) and often are classified as cytotoxic drugs. “Cytotoxic” means they kill cells, which is one reason chemotherapy has such severe side effects.  Many of the targeted chemotherapy drugs introduced in recent years are less toxic than the older medicines are.  Many of the new drugs are given orally, in contrast to the intravenous administration of traditional chemotherapy. The nature of the newer drugs differs from the chemotherapy medicines of decades ago.  Most new NMEs deliver targeted therapy; they would not even be recognizable as chemotherapy to people in the 1960s.  Even today, the public thinks of chemotherapy as a treatment with severe side effects.  While “old-style” chemo treatment do indeed cause serious side effects, targeted therapies tend to be easier on the body.  Of the 117 NMEs for cancer approved from 2015 to 2020:

Monoclonal Antibodies (unconjugated)33 NMEs
Antibody-drug Conjugates10
Small molecule kinase inhibitors40
Other signal induction inhibitors20
Alkylating agents3

Chemotherapy agents are prescription drugs. Any doctor can prescribe them but typically only oncologists do so. Unlike most prescription drugs you might take, oncology drugs are not carried by pharmacies. They are not sold at the retail level. Instead, they are sold wholesale to clinics and hospitals and treatment centers that in turn sell them to the patient (and bill the patient’s insurance company.)

Oncology and Treatment of Patients

Oncology is the branch of medicine concerned with the nature and treatment of cancer. Oncologists are doctors that specialize in treating cancer patients, and some nurses are specially trained in cancer care.

CallaixChemotherapy is one tool in the oncologist’s toolbox. It is the main treatment for some cancers, especially leukemia, lymphoma, and cancer of the bone marrow. It can be an important part of treatment of other malignancies, including solid tumors that form in the lungs, breasts, colon, and pancreas, where surgery and/or radiation is often combined with chemotherapy.  In the US 650,000 patients get cancer chemotherapy in an outpatient facility every year, and observers estimate over 50 percent of cancer patients worldwide receive chemotherapy treatment.

The three classic “modes” of cancer treatment are surgery, radiation, and chemotherapy. Sometimes the terms “surgical oncology” and “radiation oncology” are used to refer to subspecialties devoted to those forms of treatment. “Medical oncology” is the branch concerned with chemotherapy treatment. Most oncologists do not specialize to that extent, and will oversee a treatment regimen involving more than one mode. Multimodality treatment is the use of more than one mode on a patient.  Chemotherapy used with radiation or surgery is sometimes called Combined Modality Chemotherapy.

Each patient gets prescribed a regimen that outlines the type, dosage, and schedule for chemotherapy administration. Most often chemotherapy is given in a “course” of several weeks.

The goals of chemotherapy can differ depending on the type of cancer, how far the cancer has developed, whether surgery or radiation will also be employed, and the overall health of the patient. Sometimes the doctor aims (hopes) to essentially cure the cancer with chemotherapy (or send it to indefinite remission.) Sometimes the chemotherapy is intended mainly to forestall or retard the spread of cancer to other parts of the body (metastasis.) Sometimes the doctor wants to shrink the tumor before surgery (common in neoadjuvant chemotherapy). Sometimes the goal is to reduce the symptoms of the cancer without hope of a cure (palliative chemotherapy). And often chemotherapy is given to a patient after surgery or radiation to prevent the cancer from showing up again (adjuvant chemotherapy.)

Who gets chemotherapy?

Doctors don’t prescribe chemo lightly, or any other systemic therapy for that matter, and one reason we make doctors spend so much time in medical school and other training is so they can learn how to weigh the information about each patient and make a decision.

The stage of the tumor matters; chemotherapy guidelines almost always specify cancer stage with suggested regimens.  The overall physical condition and health of the patient is another big factor as chemo is hard on the body. Which diseases are present is a factor, and the patient has some say, too.

The medical community has developed scoring systems to try to quantify or more precisely evaluate whether a patient is healthy enough for chemo.  These include the Karnofsky score and the WHO/ECOG score.

Cure or No Cure?

Sometimes chemotherapy causes a cancer to go into remission.  Other times it forestalls growth of the cancer and gives the patients additional time.  Other times it fails.

Why does chemotherapy not work?

  • Primary resistance: Tumor not sensitive to treatment with the chemotherapy regimen applied.
  • Secondary resistance: Tumor develops resistance to drug that once worked.  Some cells had a natural resistance and they survived and multiplied while cells that were susceptible to the drug died.

Note: there are no drugs that correct the underlying genetic and/or epigenetic defects responsible for any type of cancer.

Systemic Therapy for Cancer

infusionThere are about 200 different diseases classified as cancer, and although they share some characteristics, they are separate diseases.  They progress at different rates –  this rate difference has implications for survival rates and treatment approaches.  Cancers start in one location or system in the body and have the potential to metastasize – to spread throughout the body.  This is one reason cancer is classified as a systemic disease – it can affect the whole body.

About half of diagnosed cancer patients eventually develop metastasis.  Metastatic cancer is, all other things being equal, more serious and debilitating and life threatening than local cancer.

Traditionally there were three “modalities” of cancer treatment.

  • Surgery
  • Radiation
  • Chemotherapy

Chemotherapy was the only kind of systemic therapy.

In recent decades new types of systemic therapies for cancer have been developed.  Nowadays forms of systemic therapies for cancer include:

    • Traditional chemotherapy drugs
    • Hormonal therapies

Some publications and medical professionals refer to targeted,  biologic, and hormonal therapies as chemotherapy.  The word chemotherapy and what it covers is evolving.

About the Chemotherapy Drug Industry

Evaluation of Chemotherapy Treatment

Other illnesses

Chemotherapy drugs developed for cancer are sometimes used for other diseases. Immune system disorders such as lupus and arthritis are can be addressed with low doses of the drugs with the hope of weakening the innate immune system. And patients undergoing bone marrow transplants are sometimes treated with chemotherapy before the surgery.