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← How does chemotherapy work? - Hyunsoo Joshua No

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Showing Revision 1 created 12/02/2019 by lauren mcalpine .

  1. During World War I, one of the
    horrors of trench warfare
  2. was a poisonous yellow cloud
    called mustard gas.
  3. For those unlucky enough to be exposed,
  4. it made the air impossible to breathe,
    burned their eyes,
  5. and caused huge blisters on exposed skin.
  6. Scientists tried desperately to develop an
    antidote to this vicious weapon of war.

  7. In the process they discovered the gas
    was irrevocably damaging the bone marrow
  8. of affected soldiers— halting its
    ability to make blood cells.
  9. Despite these awful effects,
    it gave scientists an idea.
  10. Cancer cells share a characteristic with
    bone marrow: both replicate rapidly.
  11. So could one of the atrocities of war
  12. become a champion in the
    fight against cancer?
  13. Researchers in the 1930s
    investigated this idea
  14. by injecting compounds derived
    from mustard gas
  15. into the veins of cancer patients.
  16. It took time and trial and error to find
    treatments that did more good than harm,
  17. but by the end of World War II,
  18. they discovered what became known
    as the first chemotherapy drugs.
  19. Today, there are more than 100.

  20. Chemotherapy drugs are delivered
    through pills and injections
  21. and use "cytotoxic agents," which means
    compounds that are toxic to living cells.
  22. Essentially, these medicines cause some
    level of harm to all cells in the body—
  23. even healthy ones.
  24. But they reserve their most powerful
    effects for rapidly-dividing cells,
  25. which is precisely the hallmark of cancer.
  26. Take, for example, those first
    chemotherapy drugs,

  27. which are still used today and
    are called alkylating agents.
  28. They’re injected into the bloodstream,
  29. which delivers them to
    cells all over the body.
  30. Once inside, when the cell exposes
    its DNA in order to copy it,
  31. they damage the building blocks of
    DNA’s double helix structure,
  32. which can lead to cell death unless
    the damage is repaired.
  33. Because cancer cells multiply rapidly,
  34. they take in a high concentration
    of alkylating agents,
  35. and their DNA is frequently exposed
    and rarely repaired.
  36. So they die off more often
    than most other cells,
  37. which have time to fix damaged DNA
  38. and don’t accumulate the same
    concentrations of alkylating agents.
  39. Another form of chemotherapy involves
    compounds called microtubule stabilizers.

  40. Cells have small tubes that assemble
    to help with cell division
  41. and DNA replication, then break back down.
  42. When microtubule stabilizers
    get inside a cell,
  43. they keep those tiny tubes
    from disassembling.
  44. That prevents the cell from completing
    its replication, leading to its death.
  45. These are just two examples of the six
    classes of chemotherapy drugs

  46. we use to treat cancer today.
  47. But despite its huge benefits,
    chemotherapy has one big disadvantage:
  48. it affects other healthy cells in the body
    that naturally have to renew rapidly.
  49. Hair follicles, the cells of the mouth,
    the gastrointestinal lining,
  50. the reproductive system, and bone marrow
    are hit nearly as hard as cancer.
  51. Similar to cancer cells, the rapid
    production of these normal cells

  52. means that they’re reaching for
    resources more frequently—
  53. and are therefore more exposed to
    the effects of chemo drugs.
  54. That leads to several common side
    effects of chemotherapy,
  55. including hair loss, fatigue, infertility,
    nausea, and vomiting.
  56. Doctors commonly prescribe options
    to help manage these side-effects,
  57. such as strong anti-nausea medications.
  58. For hair loss, devices called cold caps
    can help lower the temperature
  59. around the head and
    constrict blood vessels,
  60. limiting the amount of chemotherapy
    drugs that reach hair follicles.
  61. And once a course of chemo
    treatment is over,
  62. the healthy tissues that’ve been badly
    affected by the drug will recover
  63. and begin to renew as usual.
  64. In 2018 alone, over 17 million people
    world-wide received a cancer diagnosis.

  65. But chemotherapy and other treatments
    have changed the outlook for so many.
  66. Just take the fact that up to 95% of
    individuals with testicular cancer
  67. survive it, thanks to advances
    in treatment.
  68. Even in people with acute myeloid
    leukemia— an aggressive blood cancer—
  69. chemotherapy puts an estimated
    60% of patients under 60
  70. into remission following their
    first phase of treatment.
  71. Researchers are still developing
    more precise interventions

  72. that only target the intended
    cancer cells.
  73. That’ll help improve survival rates
    while leaving healthy tissues
  74. with reduced harm,
  75. making one of the best tools we have
    in the fight against cancer even better.