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Treatment and the treatment process

Combination chemotherapy

In leukemia treatment, chemotherapy is almost always given as a combination of several drugs. This topic explains why.

Last updated: ~2 min read
Three keys of light approaching a translucent leukemia cell from different sides on a dark navy background.
Figure 1.Several drugs target the cell from different sides.

01Short answer

Combination chemotherapy means using two or more drugs with different mechanisms together. Each drug strikes the leukemia cell from a different side: one disrupts how DNA is built (antimetabolites), one damages DNA (anthracyclines, alkylating agents), one stops cell division (vinca alkaloids), and steroids cause lymphoid cells to die. Combining them serves three goals: to kill more leukemia cells, to prevent resistance, and to "spread" side effects across different organs so that each drug can be given at a safe dose. "7+3" in AML and ALL protocols are classic examples of combination chemotherapy.

02Simple explanation

One key is not enough. A leukemia cell can learn to protect itself from one drug.

Several keys. Different drugs target different weak points.

Safety. Drugs with different side effects are chosen.

The plan. The day and time of each drug are set in advance.

03Scientific explanation

Principles: each drug should work on its own, have a different mechanism and non-overlapping toxicity, and be given at the optimal dose and interval (NCI, ACS).

The cell cycle: cytarabine and methotrexate act in S phase and vincristine in M phase; anthracyclines and alkylating agents work in various phases. Combining them reaches cells in different phases.

Resistance: according to the Goldie–Coldman hypothesis, the chance of resistant cells arising grows with the leukemia burden; combining several drugs early lowers this risk.

04What happens in the body?

Why is one drug not enough?

Leukemia cells are not genetically identical. A cell resistant to one drug may be sensitive to another. So a combination gives a more reliable result.

In a maze of light, every exit for one dim cell is closed by different coloured barriers.
Figure 3.A combination leaves resistant cells no way out.

The cell cycle

Cells are at different stages of division. Drugs acting in different phases together reach more cells.

A glowing ring of four coloured arcs with a dividing cell at its centre.
Figure 2.The drugs act in different phases of the cell cycle.

Side effects

Common side effects are low blood counts, nausea, hair loss and tiredness. Some are specific to one drug (for example numb fingers with vincristine). The team monitors each one separately.

05How is combination chemotherapy built?

A simplified outline.

Choice — Different mechanisms.1ChoiceDifferent mechanisms.
Schedule — Days and order.2ScheduleDays and order.
Giving — Drip, tablet, intrathecal.3GivingDrip, tablet, intrathecal.
Monitoring — Tests and side effects.4MonitoringTests and side effects.
More cellsDestroyed.
ResistanceLess likely.
SafetyToxicity spread out.

06Main drug groups used in combinations

GroupExampleHow it works
AntimetabolitesCytarabine, methotrexate, mercaptopurineDisrupt DNA building
AnthracyclinesDaunorubicin, idarubicin, doxorubicinDamage DNA
Alkylating agentsCyclophosphamide, bendamustineCross-link DNA strands
Vinca alkaloidsVincristineStop cell division
SteroidsPrednisolone, dexamethasoneKill lymphoid cells
EnzymesAsparaginaseDeprive cells of an amino acid

* Each group is explained in detail in the following topics.

07Key terms

Combination chemotherapy
Using several drugs together.
Protocol
The exact drug schedule.
Cell cycle
The stages of cell division.
Resistance
A cell’s ability to withstand a drug.
Toxicity
A drug’s harmful effect.
Course (cycle)
Drugs plus a recovery period.

08Key points

  • Leukemia chemotherapy is usually a combination.
  • The drugs work in different ways.
  • Combinations prevent resistance.
  • Side effects are spread out.
  • The schedule is followed exactly.
  • Each drug’s effects are monitored separately.

09Frequently asked questions

How many drugs will there be?

Usually 2–5, depending on the protocol.

Will I get them all on the same day?

Sometimes; more often they are spread over different days.

Do more drugs mean more side effects?

Not necessarily; drugs are chosen so their side effects do not overlap.

Can I combine it with alternative treatment?

Herbs and supplements can interact with the drugs; talk to your doctor first.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. How many drugs will there be?

  2. Will I get them all on the same day?

  3. Do more drugs mean more side effects?

  4. Can I combine it with alternative treatment?

My questions

12Sources

  1. National Cancer Institute (NCI). Chemotherapy to Treat Cancer
  2. American Cancer Society. How Chemotherapy Drugs Work
  3. Cancer Research UK. Chemotherapy
  4. NHS. Chemotherapy
  5. MedlinePlus. Cancer Chemotherapy
  6. MedlinePlus. Hepatitis B
  7. ICUsteps. Guide to intensive care: when you leave the ICU
  8. ICUsteps. Guide to intensive care: returning home
  9. NICE. Rehabilitation after critical illness in adults (CG83)
  10. Acute Medicine & Surgery, 2019. Post-intensive care syndrome: its pathophysiology, prevention, and future directions
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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