HER2 positive and Herceptin

Yesterday was my first solo Herceptin treatment at the cancer center. Some people thought that I was finished 'chemo' and were surprised to hear that I am still going to the cancer center every three weeks until October 2013 for treatments. I decided that this might be a good opportunity to explain HER2, what it means to be HER2 positive, what Herceptin is, how it works and what some of its side effects are.

The information that I am providing has been drawn from a variety of sources, I have put them together in a way that I feel provides an OK description without getting too overly complicated.

I'll start with what HER2 stands for - HER-2 is the acronym that was created to describe the 'human epidermal growth factor receptor 2' gene.

The HER2 gene is responsible for making HER2 protein. When the gene is present in normal amounts, the protein plays an important role in normal cell growth and development. The HER2 protein transmits signals directing cell growth. A healthy breast cell has two copies of the HER2 gene. HER2 positive breast cancer gets started when a breast cell has an overexpression of the HER2 gene. These 'extra' copies start producing too much of the HER2 protein resulting in the affected cells being 'given orders' to grow and divide much too quickly.

A tumor is tested for HER2 status as part of the pathology performed after biopsy, lumpectomy or mastectomy.  

It is estimated that about one in five women diagnosed with breast cancer have HER2 positive tumours. HER2 positive breast cancers tend to be more aggressive than other types of breast cancer and they are more likely to spread to lymph nodes and other organs. Due to this, in the past, women with HER2 positive breast cancer had a poor prognosis (higher rate of recurrence and mortality).

Enter the work of Dr. Dennis Slamon in bringing us Herceptin, first approved for use in advanced breast cancer in 1998, then more widely used for earlier stage HER2 positive breast cancer in 2005. The name herceptin is derived from HER2 and from the words 'intercept' and 'inhibitor'.

Herceptin is a targeted therapy that works by attaching itself to the HER2 receptors on breast cancer cells and blocking them from receiving growth signals. By blocking these signals, Herceptin may slow or even stop the growth of the breast cancer cells. Herceptin may also alert the immune system to destroy cancer cells onto which it is attached.

There is a wonderful movie about Dr. Slamon's work that I have watched recently and would recommend if anyone is interested in what went into getting Herceptin into clinical trials and approved. The movie is titled 'Living Proof' and stars Harry Connick Jr, well done and not too clinical, the focus is more on relationships and on the stories of the women that he worked with in the clinical trials.

For a primary breast cancer, Herceptin is usually given once every three weeks for a year. I had my first three infusions in combination with the chemo drug Taxotere and now I will continue for 14 treatments of Herceptin alone, once every three weeks, given intravenously through my port.

Some of the most common side effects of Herceptin can be low grade fever with chills, weakness, nausea and body pain. Less common side effects include headache, abdominal pain, back pain, infection from decreased white blood cell count, flu-like symptoms, vomiting and diarrhea, sleep problems, skin rash, dizziness, swelling of the feet, ankles or hands and neuropathy (tingling of fingers and toes). It can cause heart problems and congestive heart failure which is one of the reasons they did a baseline MUGA scan on me last summer prior to starting chemo and why I am having another MUGA scan on January 7th.

The list of side effects can seem overwhelming at first look but not every one has every side effect, some people are lucky enough to have none. So far following my first solo Herceptin I did experience a headache last evening, accompanied by a feeling like I have a head cold that started while it was infusing. I'm told that Kleenex will continue to be my best friend during treatment due to the runny nose that is common with treatment. I was already experiencing body pain and neuropathy from the previous chemo so it's hard to tell if it is any worse than it was before, definitely tolerable at the moment anyway. I also have been experiencing some swelling prior to yesterday's treatment, so far it is no worse than it had been before.

Due to the possibility of side effects, my oncologist has scheduled my treatments to occur on a Thursday so that I have a long weekend (if needed) in which to get over the worst of the effects before going back to work on the following Monday.

There you have it, Herceptin and HER2 in a nutshell.

Take care, everyone.