The link between thyroid cancer and breast cancer

 Before I quote my two sources to back up the title of this blog, I would like to repeat the definitions of having a recurrence versus having a second primary cancer. A recurrence is when one has cancer after treatment is completed. But it is the SAME type of cancer. Having a second primary cancer is a cancer survivor developing a new unrelated ( or different) type of cancer. 

According to the American Cancer Society, " People who have or had thyroid cancer can get any type of cancer, but they have an increased risk of developing:

*Breast cancer

* Prostate cancer

*Kidney cancer

*Adrenal cancer- which is especially high in people who had the medullary type of thyroid cancer.

Patients treated with radioactive iodine also have an increased risk of acute lymphocytic leukemia ( ALL), stomach cancer and salivary gland cancer."

The second quote is from the article "The Breast-Thyroid Cancer Link: A Systematic Review and Meta-Analysis" This study is published in the Cancer Epidemiol Biomarkers Prev, 2016 Feb: 25(2): 231-238 and can be accessed from HHS Public Access. The study is authored by Sarah Nielsen, Michael White, et.al.

" Rates of thyroid cancer in women with a history of breast cancer are higher than expected. Similarly, rates of breast cancer in those with a history of thyroid cancer are increased. Explanations for these associations include detection bias, shared hormonal risk factors, treatment effect, and genetic susceptibility. With increasing numbers of breast and thyroid cancer survivors, clinicians should be particularly cognizant of this association. "

I had papillary with follicular variant thyroid cancer in 2010, then invasive lobular breast cancer in 2015. I have been interested in the relationship between these two cancers ( I think that this fact has now been established) for some time now. When I woke up from the anesthesia after my bilateral mastectomies for breast cancer, one of the first questions I asked was " were there any thyroid cancer cells present in my breast cancer tissue?" The answer to that was no, of course. At the time I did not know about the difference between having a recurrence and having a second primary cancer. I did suspect that there was some connection, I just had not been able to find one in the literature- until recently. 

I am relaying this information, not to scare anyone, but to emphasize what women with breast cancer or thyroid cancer may want to do. First, make sure that your physician is aware of the link between breast and thyroid cancer. Breast and/or thyroid cancer patients should:

* Get regular checkups and mammograms ( if this applies- in other words, if the woman has not had bilateral mastectomies)

* Eat a well balanced diet and stay at a healthy weight

* Exercise regularly

* Get plenty of sleep

* Limit alcohol consumption

* Stop smoking, and limit exposure to places where tobacco smoke is present

It is important to let your physician know of any unusual symptoms that one is having. Additional testing ( other than scheduled screening exams- colonoscopies, mammograms ( if appropriate),etc) is not recommended if patients do not present with symptoms that could indicate illness. This is a subject that patients feel differently about. On the one hand, a test that MIGHT show an early stage cancer or spread of a previous cancer would seem like a good idea. But testing anxiety, possible over-exposure to radiation from unnecessary imaging are two things that need to be considered before testing. It is important for the patient to have regular follow up by their physician(s) though. Early detection is, of course, important in the successful treatment of any cancer. 

I have seen different percentages in several articles that I have read about the thyroid-breast cancer link. The most startling one is in an article called: A Linkage Between Thyroid and Breast Cancer: A Common Etiology? This article is in Cancer Epidemiol Biomarkers Prev ( 2019) 28(4) 643-649, by Eric Bolf, Brian Sprague and Frances Carr. According to their study: 

" Women with breast cancer are 2-fold more likely to develop future thyroid cancer and women with thyroid cancer have a 67% greater chance of developing breast cancer than the general population. The etiology of these cancers and possible causative factors are at an infancy stage and just beginning to be studied. Further investigation into the genomics and epigenetics underlying both breast and thyroid cancer can yield clues...as to who are at greatest risk. "

The take away from my blog, and my own personal advice here- what I consider important and what pertains to my situation ( we are all different)  is to get regular mammograms and neck checks. And if I was able to do anything over, it would be to get 3D mammograms AND ultrasounds once or twice yearly. It might have taken me a little while to talk my physician into ordering this, and yes, I may have had to pay for some or all of the tests, but to me, it would have been worth it. I had dense breast tissue with calcifications.  I was diagnosed as having stage 2B invasive lobular breast cancer. I had bilateral mastectomies and 3 months of chemotherapy, which I feel saved my life. I would have liked to have been diagnosed  earlier, though. I was unfortunately not aware of the connection between these two cancers or I would have been a better patient advocate for myself. Please do not skip your yearly or bi-yearly mammograms! And please have your physician do a neck check, and even an ultrasound to check for nodules- especially if thyroid disorders or thyroid cancer are common in your family. This is the advice that I give to my daughter and this is the advice that I give to you. 

Total thyroidectomy versus Partial thyroidectomy- some pros and cons

 The debate between getting a total thyroidectomy (TT) and a partial thyroidectomy ( PT) is usually a heated one. Reading posts over the years, from thyroid cancer patients on various thyroid cancer websites, it seems to me that people feel strongly one way or the other ( TT or PT). I believe that this is not a " one solution fits all" but there are several things to consider with both surgeries. I have tried my best to present the arguments for both groups in a non-biased manner, but I need to make a disclosure. For my thyroid cancer ( stage III, papillary with follicular variant) my surgeon and I decided it was best to go with a TT. Before the surgery, I did ask the surgeon for a PT and he said " No way! I have been doing this surgery for many years now, and I have seen too many people who had PTs have to come back to have the other side removed." Well, at the time I was a little upset at his remarks, but as it turned out, I did indeed have a cancerous tumor in the other side ( unknown until final biopsy ) that would have had to be removed with a second surgery. In my case, I was fortunate that my surgeon " recommended" a TT over a PT. In spite of my experience, I will present the pros and cons of both. And as I said, hopefully, in a non-biased manner.

My information for this blog comes from an article that I read on the Thyca.org website. ( wonderful website- every thyroid cancer patient can benefit from frequent visits to this site) The article is titled: ATA Thyroid nodule/DTC guidelines, by Haugen ET AL. This is a long and rather complex article, but with time and a little patience, I think it is worth the read. 

I think that a lot of us, including myself, have had a biopsy or two that came back as inconclusive ( the article refers to this as being a nodule that is " cytologically indeterminate ". ) There are two recommendations for this situation. One suggested recommendation would be a PT. Another recommendation would be the TT. The reasons given for the TT are that the nodule looked suspicious upon further analysis, the nodule looked suspicious when an ultrasound was performed, the nodule was large ( here the author defined this as greater than 4 centimeters) , the BRAF gene was present, there was a family history of thyroid cancer, or the patient had a history of radiation exposure. I really had not heard of the BRAF gene until recently. For those of you who, like me, were not familiar with this gene here is a simple definition: the BRAF gene, when mutated, can cause normal cells to become cancerous. This gene is most common in melanoma, but can also play a role in other types of cancer. 

When there are more than one nodule, every nodule ( this study recommends biopsy on nodules 1 centimeter or greater ) should be biopsied. The risk of cancer is the same as with patients who have only one nodule. The follow up with patients with multiple nodules can be: 1) wait and see- repeat FNA as prescribed by the physician 2) PT or 3) TT. 

The risks of doing a PT are fairly obvious. There may be malignancy in the other lobe that has not been detected or presents with a false negative after FNA. If there is a malignancy in the other lobe, then the patient will have to undergo a second surgery. There could also be spread of the thyroid cancer if cancerous nodes are not detected and removed. 

Now for the pros.  Having a PT, when appropriate, has less impact on the voice ( vocal cord damage). Also, the remaining thyroid lobe may produce enough thyroid hormone that supplementing with thyroid hormone will not be necessary.  When having a PT, there is less chance that the parathyroid glands will be damaged. ( there are four parathyroids; they are near proximity to the thyroid and while do not participate in thyroid hormone production, produce parathyroid hormone (PTH) which regulates the amounts of calcium, phosphorus, and magnesium in bones and blood. A person can get by with only one parathyroid, but may need calcium supplementation. If all four are removed, a person will need calcium supplementation for life.) 

After a TT, thyroid hormone replacement is mandatory. A patient cannot survive without hormone therapy. This means frequent trips to get blood work done so that TSH, free T4, T3 and other blood values remain in the correct range. I think that people who have not had to have their thyroid removed or those that are hypothyroid for other reasons, do not realize that it is not a " one and done" kind of thing. There are changes in the body (ex: weight changes, dietary changes, other medications added) as well as how one takes their medication, drug manufacturer practices - potency and consistency in strength and dosage of the thyroid hormone drugs. Many factors contribute to the necessity of consistent blood work so that thyroid patient's bodies are working correctly and the patients are feeling well. It is also very important that before a TT, a patient needs to be sure that the surgeon has experience in doing this surgery. As stated above, it is extremely important to keep as many parathyroids as possible. To explain why a skilled surgeon is vital, the parathyroid gland is the size of a grain of rice! It is also important for the surgeon to take care with the vocal cords, which are in close proximity to the thyroid gland. 

For the pros of having a TT: well, the cancerous nodules are gone, unless they have spread into the lymph nodes or vascular tissues. A patient may decide, along with their physician, that a TT will prevent a possible second surgery. One can not discount peace of mind, when TT is appropriate. 

In conclusion, having a PT versus a TT should be based on tests ( FNA, ultrasounds, etc) recommendations from a patient's endocrinologist, physician and/or surgeon, and most importantly, what a patient prefers and feels is right for them.  This is a personal decision and there is no one choice that is right for everyone.