It’s October 2020, Breast Cancer awareness month. There is so much pink stuff everywhere that no doubt by now you are aware: breast cancer exists. Breast cancer is the second most commonly diagnosed cancer in women, after skin cancer. But that doesn’t tell us about what to actually expect when someone we love receives what can be a very frightening diagnosis– 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 breasts 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 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 to 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. Tamoxifen locks latch 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.
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.
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 side effects. 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.
