Wednesday, March 20, 2024

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. 

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