Should I continue Letrozole after five years (no course of Tamoxifen first)?

Hi Susan and Alison:

Just an update on my visit to the oncology clinic yesterday - it was very rushed as appointments were already running 1.25 hours late at 8:30 a.m. (!!), so the oncologist I was booked with (I seem to see a different one every time I go) had little time to talk. His feeling was that as there is no evidence that continuing Letrozole after 5 years is beneficial, I should stop taking it after December. I have another appt booked at the oncology clinic in early December so I will talk further about it with whomever I see at that time. I will also talk to my family doctor, who used to be an associate at the local oncology clinic, at my annual physicial in October.

Thank you, once again, for your help and encouragement!

Dear Alison and Susan:

Thank you both so much for your speedy replies - the information and references are extremely helpful, and I am feeling less 'hung out to dry' now. I have an appointment tomorrow at the oncology clinic so the timing is great!

I will stay in touch and let you know what I decide to do.

Thanks again for your help and guidance.

Here are some more resources for you:

Sometimes it helps to have the exact terminology correct that the researchers are using regarding the current research for long-term use of letrozole: "extended adjuvant endocrine therapy for breast cancer" (for this one particular study).

Here are all of the researchers and their affiliations (initials are in parenthesis, please verify as I copied and pasted and could have made an error). They may know of other ongoing research and/or clinical trials, also. Please note: the authors listed are usually listed in a hierarchical order (and may be easier to contact someone further down the list??):

- Judith-Anne W. Chapman: National Cancer Institute of Canada Clinical Trials Group, Queen's University, Kingston, ON, Canada (JAWC, DM, LS, WP, MP, CY)
- Daniel Meng: National Cancer Institute of Canada Clinical Trials Group, Queen's University, Kingston, ON, Canada (JAWC, DM, LS, WP, MP, CY)
- Wendy Parulekar: National Cancer Institute of Canada Clinical Trials Group, Queen's University, Kingston, ON, Canada (JAWC, DM, LS, WP, MP, CY)
- James N. Ingle: Department of Oncology, Mayo Clinic, Rochester, MN (JNI)
- Hyman B. Muss: Department of Medicine, Vermont Cancer Center, Burlington, VT (HBM)
- Lois Shepherd: National Cancer Institute of Canada Clinical Trials Group, Queen's University, Kingston, ON, Canada (JAWC, DM, LS, WP, MP, CY)
- Michael Palmer: National Cancer Institute of Canada Clinical Trials Group, Queen's University, Kingston, ON, Canada (JAWC, DM, LS, WP, MP, CY)
- Changhong Yu: National Cancer Institute of Canada Clinical Trials Group, Queen's University, Kingston, ON, Canada (JAWC, DM, LS, WP, MP, CY)
- Paul E. Goss: Department of Hematology and Oncology, Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA (PEG)

Hi,

Your additional information helps, and now I understand your question better..thanks!

I'm sure you already know this (the reason for your question):
According to the NCI (National Cancer Institute), "the long term risks [beyond 5 years] of letrozole have not been fully evaluated."

As Susan mentioned, the research that you/your doctor are referring to (Letrozole as a "new" treatment for breast cancer; the latest findings were reported in 2003) and ongoing research on this subject is still being conducted by the Canadian Cancer Society (CCS).

The newest results (February 2008) are discussed by Dr. Chapman at the CCS. (click on orange link)

Dr. Chapman states (February 2008):
"New findings from a landmark breast cancer clinical trial involving the drug letrozole show that, in this group of patients, women were more likely to die from non-breast cancer-related causes than from breast cancer-related causes."

"The research team found that non-breast cancer related causes accounted for 60% of deaths. The top causes of death included: cardiovascular disease including stroke (15%), other malignancies (15%), infection (6%), multiple causes (5%), and non-cardiovascular organ failure (4%). The results were particularly striking for older women. Among women aged 70 years or older, non-breast cancer-related causes accounted for 72% of deaths. The new results are published in the February 12 issue of the Journal of the National Cancer Institute." You can read the journal article here.

Dr. Chapman's email is listed as a contact: Correspondence to: Judith-Anne W. Chapman, PhD, National Cancer Institute of Canada Clinical Trials Group, Queen's University, 10 Stuart St, Kingston, ON, Canada (e-mail: [email protected]).

You may want to contact the CCS (or ask your physician to), and inquire about any more recent findings regarding long-term use of letrozole).

Also, the NCI journal (JNCI) is available for free online, and you can search by topic to review any new clinical findings. The language is "medical-speak", but the abstracts and conclusions are easily understandable, and at least is some more information from which you can ask your doctor to elaborate on.

Lastly, there are phone numbers and contact information to receive more information about "this study, breast cancer and letrozole" at http://www.cancer.gov/newscenter/letrozoletamoxifenQandA (scroll down to #34). You can read #19 Q&A: How long should these women take letrozole?

"A: For women in the study, the plan was to give letrozole for five years. Because the study was halted early, there are very few women who have completed five years of letrozole. However, there are a large number of women who have safely completed three years. Therefore, the researchers feel able to recommend at least three years at this time. The researchers will continue to follow the women in the study and report on their tolerance of the drug as they complete the full five years of treatment."

To me, this means you can ask the researchers or CCS who have been "continuing to follow the women in the study about their tolerance of the drug", and if they have "completed and/or extended beyond the five years".

I hope this information helps!

Hi,
We are not able to provide medical advice on what medication you should/should not be taking; there are too many factors involved that only you and your doctor are privy to.

Are you having symptoms that are concerning? Did you read any information about Letrozole that you are questioning? What has your doctor told you about these medications?

Letrozole and Tamoxifen both inhibit estrogen in your body. Why are you wondering if you should continue Letrozole? Why are you concerned that you did not use Tamoxifen first?

I assume you were prescribed these, as you diagnosed with breast cancer, and are in menopause? Can you tell us more about this?

While we wait to hear back from you, here is some drug information:
- Letrozole, source: MedlinePlus
- Tamoxifen, source: MedlinePlus