How fast do Her2+ tumors grow?

I was diagnosed triple positive in Aug 2014. My last mammo was in 2011 when nothing was found. No prior history of breast issues or family history. I did not have insurance between 2011-2014. I got insurance in 2014 and immediately got a mammo and there was a 1 cm spiculated lesion. No invadion in lymph nodes. The tumor was standing still and barely dividing, despite being HER2+. No Ki-67 done probably because of very low mitotic rate (I was working in a pathology lab at the time and the resident pathologist did the analysis on my sample. I went on to have Taxol once a week x 12 weeks and Herceotin for a year. 36 radiation treatments. So far, April 2017, bloodwork is good, tumor markers within normal limits. No masses felt but none were felt the first time either.

I hesitate to say that mammography is a surefire method of knowing when a tumor began, or how fast it grew. I had a 2.6cm palpable lump - I could literally roll it between my fingers and it was at the outside edge of the breast, right where the end of the underwire in my bra would sit. It was never seen on a mammogram at any point. Because the lump was palpable, my clear mammo was followed five minutes later by an ultrasound which clearly showed it. It is impossible for me to know when it started and how fast it grew, because I had a clear mammogram a year prior and a clear mammogram with an aggressive tumor in place. Even though I had been surgically menopausal for nine years at the time of diagnosis I still had very dense breast tissue. Mammography is accurate just under 80% of the time - slightly more in older women with less breast density, so it definitely has some limitations.

I had a normal mammogram in June 2016 and found a lump in November 2016. My mammograms reports said dense or extremely dense, but I was never told by any doctor that I saw that I should get a 3D mammogram. I did do BSE's, but not always regularly. I found the lump because I was having some discomfort in that area and trying to figure out why. It was 2.7-2.8 cm on initial US imaging.

No one will confirm for me that it definitely was or was not there on the previous scan. I have not had surgery yet - doing neoadjuvant chemo first - so I have no idea for cell replication rate. The best answer I've gotten is that it probably grew within a couple of months. Scary!

HER2 (which stands for "human epidermal growth factor receptor 2/neu"), sometimes called “HER2neu" is a protein encoded in the proto-oncogene ERBB2 that, if a tumor cell has enough receptors that “amplify" or “overexpress" this gene, is a sign of more rapid cell division & therefore speed of tumor growth. (Overexpression of this gene is also found in other cancers such as glioblastoma, lung, and uterus). If this gene is overexpressed, it suppresses normal cell death, aka “apoptosis." (Cancer happens when a cell refuses to die as Nature intended, and instead divides ad infinitum until it is either removed, killed by medications and/or radiation, or the host dies). The reason why HER2+ bc is treated with not just targeted therapy but also chemo is that chemo kills rapidly-dividing cells and therefore provides a one-two punch against “HER2 type"—ER/PR-/HER2+—and triple-positive bc (in the latter case it's a one-two-three punch, the third punch being long-term anti-hormonal therapy).

As one person on this board did, some HER2+ patients participate in a trial of neoadjuvant targeted therapy without chemo, then surgery once the tumor has shrunk sufficiently, then adjuvant chemo. There is also, at my cancer center, a trial of neoadjuvant endocrine therapy for hormone-receptor-positive Stage II bc patients, in an effort to see if their tumors can shrink enough to facilitate surgery, possibly without being followed by chemo. I am not sure whether HER2+ patients are eligible to participate. One Stage II woman in our support group was getting neoaduvant letrozole, but she didn’t mention her HER2 status. A friend of mine with adenocarcinoma of the lung achieved NED status without additional chemo by participating in a neoadjuvant Herceptin trial; the primary tumor disappeared, and surgery was cancelled. He’s been NED for four years.