The history of treating cancer goes back thousands of years, literally millennia. Archaeologists have found evidence of a surgery to remove cancer from the skull of an ancient Egyptian, dating back over four thousand years. At the time, surgery may have been the only option available, but cancer therapy has gone through countless advancements since then. Nowadays, our standard of care mostly consists of four main categories: surgery, radiation therapy, chemotherapy, and various biological therapies.

Today, the challenge is knowing what we have at our disposal. In the past, limited options made decision-making easy, but now we have to choose, and to do that, we need to know what they do.

The goal of cancer therapies is clear: kill cancer cells. Surgery, the treatment with the longest history, takes a straightforward approach to this, quite literally removing the affected cells from the body.

Radiation therapy takes a slightly different approach. It can be administered in a few different ways: either from the outside, called external beam radiation therapy, or from the inside, known as brachytherapy. Both use a source of high-energy radiation to damage a cell’s DNA, directly or indirectly.

By damaging the cells’ instruction manual, you can cause them to self-destruct or kill them before they get the chance.

As it turns out, radiation isn’t the only therapy that kills cells by damaging their DNA. Chemotherapy is the use of chemicals to kill cancer, and there are dozens of options to choose from. With that said, almost all chemotherapies kill cells by damaging their DNA.

Lastly, we have biological therapies. This includes any treatment from a living organism, making it a broad category. Some biological approaches are hormone therapy, immunotherapy, or gene therapy. Now, unfortunately, we don’t have time to unpack all of those in a single issue. With that said, what’s fascinating about biological therapy compared to other approaches is that many don’t directly kill cancer.

Regardless of the approach, direct or indirect, the end product is a dead cell, often achieved by damaging its DNA.

Well, plain and simple, cancer treatments kill cells, and although cancer is the primary target, healthy cells rely on many of the same things to stay alive. So, when we treat cancer, we’ve almost guaranteed some damage to healthy cells. That means it’s critical to consider the balance of damage to cancerous versus healthy cells.

Localized therapies, which include surgery and radiation therapy, affect a specific region of the body. On the other hand, systemic treatments, chemotherapies and biological therapies can spread through the whole body. This means the damage done to healthy cells is only in one spot or can spread through the whole body.

With localized therapies, reducing the affected area is an easy way to minimize accidental damage. For surgery, as little tissue as possible is removed to keep the healthy tissue intact. For radiation therapy, there’s incredible work being done to protect healthy cells.

But what happens when the cancer isn’t all in the same spot - what happens when it metastasizes? We can’t exactly remove or irradiate everything. That’s when we have to use systemic therapies that can reach every corner of the body that localized treatments can’t. Chemotherapy isn’t at all selective, which means that it damages virtually every cell it touches, cancerous or not. Biological therapy is more specific to cancer, but even so, there are risks. They can result in the over-activation of the immune system or hormone imbalances, both of which can lead to serious complications. So, as cancer is treated, we have to strike a careful balance between killing cancer and protecting healthy tissue.

The discussion about cancer can be really overwhelming. The biology itself is already deeply complicated. But then we also have to factor in all of the different ways of killing cancer, how they work, and what they do to our bodies. Even our baseline treatments, the ones that are most commonly used, surgery, radiation therapy, chemotherapy, and biological therapies, are deeply nuanced, each in their own way. Today, we’ve only just scratched the surface of how they work and some of the associated risks. At the end of the day, whatever the treatment, the goal is always to balance the killing of cancer cells while preserving healthy cells. If you find this as fascinating as I do, let me know, and maybe we can do an issue on emerging treatments like gamma knives and photon beams!

I hope you learned something today, and if you find yourself getting a little excited about killing cancer, don’t worry, it’s not weird, I do too.

See you next week!

If you missed last week’s letter, you can read “Here, There, Everywhere” to learn a little more about how cancer spreads.