We have known for a long time that women who get breast cancer in one breast have a higher risk of getting a second one in the other breast. We refer to this as a “contralateral second primary breast cancer.” This knowledge has resulted in a significant increase in prophylactic mastectomies. The real question is whether the risk is the same for everyone. We know that women who have had a lobular cancer have a lifetime risk of developing a second cancer in the opposite breast of about 20%. (This means there is a 20% chance they will develop a second cancer in the opposite breast before they die.) For women who have had a ductal cancer, the lifetime risk is about 15%, or 1% per year. And women who have a genetic mutation that increases breast cancer risk—BRCA1 or BRCA2—are at very high risk of developing cancer in the other breast. But can we parse the risk even further, so that we actually know which women would benefit from more surveillance or from prophylactic surgery?

A Northern California research group has taken the first step in trying to figure this out, and their findings were published July 9 in the Journal of the National Cancer Institute. The investigators used the Surveillance Epidemiology and End Results (SEER) database to identify 4,927 women who had been diagnosed with a first breast cancer between January 1992 and December 2004 in. (SEER collects and publishes cancer incidence and survival data from population-based cancer registries.) Then, they divided the women into two groups: those with hormone-positive tumors (ER/PR+) and those with hormone-negative tumors (ER/PR-). Then they looked at the women’s age, ethnicity, and whether they had developed a second tumor in the other breast. (Unfortunately, they did not have information about whether the women carried a BRCA1 or 2 genetic mutation, were Her2-positive, or had taken tamoxifen or an aromatase inhibitor as part of their cancer treatment.) This means we only get a big picture result, without a lot of nuances. Even so, the data are interesting—and not surprising.

First, all the women who were 30 and under had a higher risk of a developing a cancer in the opposite breast. This would be expected, since they are more likely to be mutation carriers and to have a long life ahead of them—and more years alive means more years in which to get a second tumor.

They also found that women who had ER-negative tumors had a higher risk of developing a tumor in the opposite breast than did women with ER-positive tumors. There are several explanations for this. that the first is that the women with hormone-positive tumors are usually older and often had taken postmenopausal hormone therapy. When diagnosed with breast cancer, they usually stop the hormones and start on tamoxifen or an aromatase inhibitor, both of which decrease the risk of a second cancer in the opposite breast. The second is that the women with hormone-negative tumors are usually younger (which means they have more time to get a second tumor) and more likely to have hereditary cancer and therefore to have both breasts at risk. Although women with BRCA mutations can reduce their risk by having their ovaries removed, it is not clear that this strategy would work for women who are not mutation carriers. This feeds right into one of my current pet hypotheses: there are probably two different big groups of breast cancer that should be thought of as separate diseases. (I will blog more on that later).

So, should you be scared? The study showed that women whose first breast tumors were hormone-positive were at greater risk than the general population of developing a second tumor, but the risk is not that high. The researchers saw 13 more cases per year in this group of women than they would have expected to see if they had followed 10,000 women who had not had breast cancer. Women who had a hormone-negative tumor were more likely than those who had a hormone-positive tumor to develop a second cancer, and it was more likely to be another hormone-negative tumor. The researchers saw 20 more cases of hormone-positive tumors and 24 more cases of hormone-negative tumors per year than they would have expected to see if they were looking at a group of 10,000 women who had not had breast cancer.

More interesting are the young women where risk for a second hormone-negative tumor were high if they had been diagnosed under 50 (34/10,000 person years); and even higher if they had been diagnosed under 30 (77/10,000 person years). The risk of second tumors also varied by ethnicity, with non-Hispanic blacks, Hispanics, and non-Hispanic Asian or Pacific Islander patients having a slight greater risk of second cancers than non-Hispanic whites. This makes sense, since these ethnic groups also had more hormone-negative tumors and were more likely to develop them at a younger age.

Whether these levels of risk are enough for you to consider preventative surgery (prophylactic mastectomy) is obviously an individual choice. For the women who were diagnosed with hormone-negative tumors under age 30 or even under age 50 it might suggest that they would benefit from yearly MRI or other screening, but this has not been studied.

Most importantly, it tells us that we need to figure out the causes of breast cancer. Treating a young woman with chemotherapy, surgery, and radiation without figuring out what caused the cancer in the first place is putting her at risk of having it happen again!

JOIN THE ARMY OF WOMEN and help us sort this out once and for all!

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9 Responses to What is the Risk of Getting a Second Cancer in the Other Breast?

  1. Cynthia Svee says:

    I was diagnosed in 2000, so am almost 8 years cancer free, single mastectomy, 1 node positive,estrogen positive and chemo! Complete hysterectomy in 2001 and still have not bounced back…….foggy headed, moody, no libido, need HELP! Was wondering if a low dosage of estrogen to get back on track would be an okay idea?????

  2. Patti says:

    I was diagnosed Sept 2008 with invasive lobular carcinoma…er/pr positive, no node involvement. Tumor was less than 1 cm, had total mast, no radiation, no chemo. Had uterus removed in 1994. At time of diagnosis, I was taking Premarin for the previous 3 years. Of course, immediately stopped Premarin when diagnosed.
    My question is…..I have had horrible reactions/side effects to aromotase inhibitors. Is there some alternative?? I cannot see living 5 years trying to tolerate those meds. Almost drove me out of my mind.
    Certainly, this situation has come up with someone else. Any help would be most appreciated.

  3. Lorrie says:

    I also has lobular invasive,e/p positive diagnosed in November 2007. 3 tumors, between under 1 centimeter and between 1 ans 2 centimeters, no node involvemnt, no radiation, no chemo, and am on Femara, an aromatase inhibitor. I had a terrible time with ariimidex-mood and weight problems-once switched to another AI (Femara), I have had no side effects. Keep trying. I am also concerned about recurrence in my other healthy breast and how to make sure, I medically do what is needed to protect myself.

  4. Alicia Gray says:

    Well I guess I’m the exception to a lot of things, but I’m 57 years old and in October of 2007 I was diagnosed with Stage 1 Estrogen Positive breast cancer. The following day my 81 year old mother was diagnosed with her 3rd instance of breast cancer – in her early 70’s she had been diagnosed with Stage 1 ER+ breast cancer and 9 years later she was diagnosed with a separate 2nd instance of Stage 1 ER+ breast cancer and had a mastectomy. About a year later she had her 2nd breast removed for cosmetic and fear of cancer in that breast, and when they biopsied it they found HER2+ breast cancer.

    My mother’s mother had breast cancer in the 1970’s when she was in her 70’s and a radical mastectomy and died a year later of unrelated causes. I had a bilateral mastectomy.

    All of us were postmenopausal and I didn’t qualify for BRCA testing based on my genetic counseling. The only thing I can figure is that I and my family just seem to fall in some sort of undiscovered category of genetic predisposition to this dreaded disease.

  5. Lisa G says:

    I was 38 years old when i was diagnosed with Stage 1 triple negative tumor,negative nodes and negative breast cancer gene. No one in my family ever had breast cancer. Had chemo and radiation in 2007. In 2008 had an ovarian tumor scare and had one removed. Was not cancer. Normal periods resumed until 2 mos ago they just stopped. Suffering with hot flashes-personal hell on earth. Effexor doesnt help. Gained 20 lbs too, but happy to be alive and well. We need research on triple negative tumors. thanks

  6. Kathleen Gilfillan says:

    February 09 dx with estrogen+, lobular and ductal ca, invasive involving 3 nodes of 13 and I had a bilateral mastectomy and a sentinel node bx with the unaffected side as well. After surgery and chemo I am said to be Cancer Free..the arimidex is a drag,,i am sore and weak and it is difficult to do exercise without suffering. Any ideas on what I what I can add to my diet or meds to help?

  7. Lori Nava says:

    I was diag. in 2007 with stage 2 breast cancer. I did Chemo and radiation and have been on Tamoxifin since Jan. 2008. Recently I have had severe stomach/abdominal pain, diariah, and keep having to burp? I thought it was food poisening at first but it has been about 5 days now. I don’t want to be a worrier, but does this sound like the cancer could be back somewhere else?
    Lori Nava

  8. I was diagnosed with breast cancer in December of 2007. Had a mastectomy because diagnostic tests found two spots. One tumor was Stage 1, well differentiated, invasive ductal carcinoma and the other was ductal in situ, Stage 0, Grade 0 no nodes, estrogen + No chemo was necessary due to early diagnosis. Oncologist did not recommend oral adjuvant therapy either as he felt in my case the risks would out weigh the benefits. Am 55 years old with no history of breast cancer in family. Any comments? Oncologist highly regarded!!

  9. jeremy says:

    Hi Guys – I am a medic – love the website (excuse the pun) – but I think there is an error in this article = para beginning “So, should you be scared? The study showed that women whose first breast tumors were hormone-positive” shouldn’t that be -ve?

    Also I would like to reproduce part of a diagram from the website in a book with acknowledgement of course – who should I contact for permission?

    Many thanks

    Jeremy Price

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