The findings presented at the San Antonio Breast Cancer Symposium (SABCS) offer the prospect of significantly changing the future clinical approach to breast cancer therapy and significantly decreasing the disease’s recurrences. Breast cancer, the most frequently reported cancer in women in terms of incidence, is associated with a high risk of recurrence after primary treatment. However, latest research and recommendations of the ATLAS clinical trial presented in San Antonio symposium may offer a solution to this issue.
Researchers at the symposium debated that extending the adjuvant tamoxifen (Nolvadex) therapy for an additional 5 to 10 years after primary treatment can decrease the risk of recurrence. This was concluded from the results of ATLAS trial, in which almost 7,000 women were enrolled with a positive history of Estrogen receptor positive breast cancer. The trial was conducted from 1996 to 2005, in which patients were randomly enrolled to continue the regime for an additional 5 years or stop it, after primary tamoxifen therapy for 5 years
The results were analyzed and reported by Dr. Richard Gray, lead researcher from Oxford University, UK, who suggested that the overall outcome after 5 to 9 years of treatment with tamoxifen is not associated with a significant reduction in the recurrence (patients remain cancer- free for an additional few years only due to carry-over effect); however, with 10- year tamoxifen therapy, the risk of recurrence in next 10 to 14 years is 25% lower than the women who continued the therapy for 5 years. Additionally, the risk of breast- cancer related mortality is reported to be 30% lower than the control group.
Prolonged tamoxifen therapy is associated with potential side effects like clotting disorder, endometrial cancer, fatigue and hot flashes. The absolute increase in risk of mortality due to endometrial cancer in women with 10 year therapy with tamoxifen is only 0.2% higher than those who consume tamoxifen for 5 years.
Gray emphasized that benefits and risks of the therapy should be considered but extended tamoxifen therapy is a preferable choice since “risks are far smaller than the benefits.”
Although another similar study (with a much smaller sample size of 1200) reported that extended tamoxifen therapy is not associated with additional benefits, but the ATLAS study is definitely more reliable as suggested by Dr. Peter Ravdin of the University of Texas Health Sciences Center at San Antonio (who also moderated the press briefing:
“We can now tell [premenopausal patients] that clinical evidence shows that 10 years [of tamoxifen] is superior to 5 years. And I’m going to be comfortable doing that.”
The American Cancer Society estimates that about 232,340 new cases of invasive breast cancer in women will be diagnosed in 2013, and although the mortality is not very high, the recurrence rate can significantly affect the quality of life. Current standard treatment includes tamoxifen and Aromatase inhibitors in estrogen receptor positive early breast cancers.