Arimidex and Tamoxifen Both Useful for Early Breast Cancer But with Different Safety Profiles

MedicalResearch.com Interview with:

Professor Jack Cuzick, PhD, FMedSci, FRCP(hon) Director, Wolfson Institute of Preventive Medicine and Head, Centre for Cancer Prevention Queen Mary University of London.

Prof. Jack Cuzick

Professor Jack Cuzick, PhD, FMedSci, FRCP(hon)
Director, Wolfson Institute of Preventive Medicine and
Head, Centre for Cancer Prevention
Queen Mary University of London.

MedicalResearch.com: What is the background for this study? What are the main findings?

Dr. Cuzick: Ductal carcinoma in situ (DCIS) is a very early form of breast cancer, where cancer cells are present in milk ducts, but have not spread to the surrounding breast tissue. It is estimated that approximately a fifth of all screen-detected breast cancers are DCIS, with around 4,800 people diagnosed with DCIS in the UK each year.

Our IBIS-II DCIS trial looked at 2,980 postmenopausal women with DCIS in 14 countries, who were either given anastrozole or tamoxifen for five years after surgery.

The two groups had a similar number of cases of the disease recurring, whether they took tamoxifen or anastrozole. Those who took anastrozole had an 11 per cent lower rate of recurrence of DCIS or invasive cancer than those who took tamoxifen, but this difference was not significant. The similar NSABP B-35  trial found a 29% reduction with anastrozole and the combined analysis of the two trials indicated a significant 21% reduction.

The key difference between the two groups were in the side effects of the medication. Women who took anastrozole experienced fewer womb and ovarian cancers and non melanoma skin cancers, and fewer deep vein thromboses and gynecological issues, compared with those who took tamoxifen. However more fractures and musculoskeletal side effects were seen among those receiving anastrozole.

MedicalResearch.com: What should clinicians and patients take away from your report?

Dr. Cuzick: We found that anastrozole and tamoxifen had similar overall efficacies, with slightly better outcomes for those who took anastrozole. But more importantly, because of their very different side-effects, anastrozole can be offered as an alternative for patients who may not tolerate tamoxifen as well or have previous illnesses making tamoxifen unsuitable.

Now we know that anastrozole is effective for treating hormone sensitive ductal carcinoma in situ, women will have a greater choice of treatments to suit their own previous medical histories and tolerability of medications.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Dr. Cuzick: Breast cancer has a very long natural history with many recurrences five or more years after treatment completion , so long tern follow up is essential to fully evaluate these treatments. Future work on the tumour samples will also be done to see if we can identify individuals more likely to respond better to one of the two treatments

MedicalResearch.com: Is there anything else you would like to add?

Dr. Cuzick: These results indicate that hormone receptor (oestrogen receptor) status should be measured in women with DCIS, to decide if they should receive one of these treatments. This is currently not routinely done. 

MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.

Citation:

Anastrozole versus tamoxifen for the prevention of locoregional and contralateral breast cancer in postmenopausal women with locally excised ductal carcinoma in situ (IBIS-II DCIS): a double-blind, randomised controlled trial

Forbes, John F et al.

The Lancet , Volume 387 , Issue 10021 , 866 – 873

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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