One of the things we learned early on in Dan’s cancer journey was that even if a treatment worked, eventually, it wouldn’t. Cancer cells become drug resistant.
When doctors first diagnosed Dan with stage IV lung cancer in 2012, they perscribed a targeted treatment called, Tarceva. The treatment worked well for 18 months before the cancer in his body became drug resistant and again progressed.
After that, he volleyed back and forth between targeted treatments, immunotherapy, and traditional chemotherapies. He would take each treatment until the cancer again became drug resistant.Then, the doctors would put him on a new drug. This is something that’s often difficult for people to understand.
Once a treatment works, why can’t you use it indefinitely?
There are several reasons for this.
Remember in yesterday’s blog on cancer cells, we learned about the ways that cancer cells are different from healthy cells? As these cells mutate, they act more and more abnormal. One of the ways they differ is that the cells can become drug resistant to the chemotherapy treatments that we rely on the kill the cancer cells.
One form of drug resistance in chemotherapy is similar to the way we become drug resistant to antibiotics after taking antibiotics repeatedly, inappropriately, or for long periods of time, The bacteria which aren’t killed become stronger.
In chemotherapy, some cells survive and mutate. They then continue to multiply and soon there are more cells that don’t respond to the treatment than those that do. This is one theory as to why Dan became resistant to Tarceva. Thankfully, over the years, researchers have been working on this problem. Just in the nick of time, the FDA approved a drug called Tagrisso. This is another targeted treatment that is used when the original EGFR mutation that some lung cancer patients have, becomes drug resistant to the currently targeted treatments that are available such as Tarceva, Iressa, and Afatinib.
A Drug Resistant Protein Molecule
Cancer cells use a molecule called “p-glycoprotein” to protect themselves against cancer drugs. Resistant cells often have high levels of this protein, in the cell walls. The protein acts like a pump which removes toxins from cells. This includes pumping chemotherapy out of the cell faster than it can take the treatment in. Because there isn’t enough of the chemotherapy in the cell, it can’t kill the cell.
An Inactive Gene
In a study done on colon cancer cells, researchers discovered that cells which were initially sensitive to the drug oxaliplatin and later became drug resistant, had inactivated a gene in their DNA. This caused the cells to repair these breaks and they are back in business, growing and spreading. This is known as acquired resistance. Researchers are also studying how the loss of this gene function causes tumors to be drug resistant from the outset, otherwise known as primary resistance.
Lack of Transportation
Cancer cells can become drug resistant because the protein that transports the drug across the cell wall stops working.
Sometimes, a cancer cell can produce hundreds of copies of a particular gene, which triggers an overproduction of protein rendering the treatment ineffective. This is known as gene amplification.
If cancer becomes drug resistant to one drug, it’s more likely that it will be resistant to others. For example, once Dan’s cancer became resistant to Tagrisso, and EGFR targeted treatment, his cancer was resistant to all of the other EGFR targeted treatments. This is known as multidrug resistance. This is why it’s so important to choose the best possible treatment first. Sometimes, doctors give patients multiple drugs in combination, to reduce the chances of becoming drug resistant to any one drug.
We need to adjust our expectations.
Often, our expectations of cancer treatment are too high. The human body is complex on every level and when it breaks down, there is no easy fix. Sometimes the systems which protect us under normal circumstances can be the very problem we encounter when things are no longer working as they were designed to. Thankfully, researchers are continuing to look at ways of preventing drug resistance.
I am an author, writer, and speaker and homeschooling mom of 3. Since my husband, Dan was diagnosed with stage IV lung cancer in 2012, I’ve focused my writing and speaking on helping cancer patients and their families advocate for themselves and live life to the fullest, despite their illness.
My goal is to help people face cancer with grace.
My book Facing Cancer as a Friend: How to Support Someone Who Has Cancer, is available on Amazon.com