How Does Chemotherapy Treat Breast Cancer?

It’s October, aka breast cancer awareness
month. There’s so much pink stuff everywhere that
no doubt by now you are aware: breast cancer exists. But that doesn’t tell us about what to actually
expect when someone we love receives what can be a very frightening diagnosis. Breast cancer is the second most commonly
diagnosed cancer in women, after skin cancer — although anyone can get it. Fortunately, the rate at which we’re learning
about this disease, and getting better at treating it, means patients have a lot more
options, and a lot better chances than they did 100 years ago. In fact, we’re making progress SO fast that
there are more options than there were 10 or 20 years ago. And a year from now there will probably be
more options than there are today. So we’re going to tell you how things have
changed and what to expect. Breast cancer was documented by the ancient
Egyptians in a 3600 year old medical papyrus, and for most of history between then and now,
the best option available was to try to cut it out. The first modern breast cancer treatment was
the Halsted radical mastectomy, introduced in the 1880s. It’s even less nice than it sounds, and
involved removing not only the breast, but some of the underlying chest muscle, surrounding
lymph nodes, and skin. These days, surgery is usually more conservative,
and it’s often possible to preserve some of the breast while removing just the lump
or affected region. One reason surgery today isn’t as nasty is
that we’ve developed more tools to fight cancer since the 19th century. Radiation like gamma rays can also be used
to kill cancer cells. This radiation causes physical breaks in DNA,
and cancer cells with badly damaged DNA can’t divide, so those cells die. Early radiation therapy used needles made
of radium placed near the tumor. These days, for breast cancer, radiation will
often come from an external beam, or a doctor may insert a small amount of radioactive material
near the tumor during treatment. Not everyone with breast cancer needs radiation,
but those who do will generally receive it after surgery. Then there’s the topic of chemotherapy. It’s a scary-sounding word, but it literally
just means therapy with chemicals — or as we usually prefer to call them, drugs. If we were naming it today we might be more
likely to call it pharmacotherapy, or just plain drug therapy. But we’re not naming it today, so we have
chemotherapy. The main goal of chemotherapy is to kill cancer
cells, and these drugs employ a broad variety of chemical tricks to do just that. From cisplatin to paclitaxel, almost every
chemo drug has a slightly different way of killing cancer cells. H Chemotherapy reaches the entire body as it’s
taken in pill form or through IV. That’s good to catch all the nasty cells
if the cancer has spread, but not great for healthy cells that get caught by the chemo. Chemo is really toxic to cancer cells but
it’s harmful for healthy cells too. That’s why it tends to have side effects,
though for many patients those aren’t so bad. And chemo isn’t the only chemistry-based
tool we’ve developed. One way breast cancer is different from most
other cancers is that its growth is often driven by our hormones, notably estrogen. Estrogen enters cells and binds to a receptor
in the breast that tells them to grow. Many breast cancers take advantage of this
receptor to snag the estrogen signal and use it to grow bigger. The drug tamoxifen came into use in the 1970s. Tamoxifen blockslatches onto the estrogen
receptor in the breast, so estrogen can’t send its growth signal within the cancer cell. This has been a huge success because so many
breast cancers involve the estrogen receptor. The major disadvantage is that eventually,
cancer becomes resistant to the estrogen receptor That is, it keeps growing even without the
signal, so blocking it is no use. Even with tamoxifen, patients might still
need other chemo treatments. Trastuzumab was introduced in 1998, which
was another big breakthrough. It is a targeted therapy, which is kind of
a buzzword these days, but it’s also a genuinely exciting direction for cancer therapy. Unlike chemo, which is distributed to the
entire body, targeted therapies make a beeline for the tumor, so fewer healthy cells are
killed resulting in fewer sideeffects. Trastuzumab is a kind of antibody, the Y-shaped
molecules our immune systems use to target and bind to harmful invaders like viruses. Trastuzumab, instead, binds to a molecule
on the surface of some breast cancers called HER2. HER2 is another one of those growth receptors,
a bit like the estrogen receptor, and breast tumors in roughly one in five patients have
an abnormal amount too much of it on the surface of their cells. Trastuzumab blocks HER2 a bit like tamoxifen
blocks the estrogen receptor. And it works really well to improve the survival
of the minority of patients whose tumors have abnormal HER2. Other up-and-coming therapies based on our
immune systems are even more promising. Some new options might help the patient’s
immune system spot cancer and destroy it, and there’s even talk of cancer vaccines. But most patients aren’t likely to see those
just yet. Someone being treated for breast cancer in
1917 didn’t have much to look forward to besides a nasty surgery with a relatively
low success rate. In 2017, they can expect much more: a combination
of treatments tailored to the disease they have and its molecular profile. The chemistry of modern treatments is designed
to target the biology of tumor cells with unprecedented precision. By the next time breast cancer awareness month
comes around, there will probably be treatments we didn’t even think of when we were writing
this thing. Hey, if you’re watching this in the future,
what’s it like? Let us know in the comments, and thanks for
stopping by.