ASCO Breast--10 year ATAC results--arimidex still tops tamoxifen & benefits continue

[Lani]

after completion of treatment

Again, this was not a study that evaluated her2+s separately


ASCO Breast: Ten Years On, Anastrazole Still Tops SERM


A NATIONAL HARBOR, Md. -- The aromatase inhibitor anastrozole (Arimidex) extended its disease control advantage over tamoxifen in an analysis of 10-year outcomes in a large randomized clinical trial in breast cancer.
Patients treated with anastrozole had a 4.3% absolute reduction in the hazard ratio for recurrence compared with patients treated with tamoxifen, according to Aman Buzdar, MD, of MD Anderson Cancer Center in Houston.

The difference exceeded the 2.7% absolute gap seen after five years of follow-up. Consistent with previous reports from the study, survival did not differ significantly between treatment groups.

Moreover, the anastrozole arm did not have an excess fracture risk, and no new morbidity or mortality concerns have arisen, Buzdar reported here at the American Society of Clinical Oncology's Breast Cancer Symposium.

"At 10 years of median follow-up, anastrozole is significantly superior to tamoxifen in preventing breast cancer recurrence," said Buzdar. "The absolute difference in recurrence rates continues to increase after treatment completion."

The findings came from the landmark ATAC (Arimidex, Tamoxifen Alone or in Combination) study. The trial began as a three-arm comparison of anastrozole, tamoxifen, and the combination of the two drugs given as adjuvant therapy to women with surgically treated hormone receptor-positive breast cancer. Follow-up of the combination arm ended early after an interim analysis showed the combination had safety and efficacy similar to tamoxifen alone.

The two remaining arms of the trial included 6,241 postmenopausal women with invasive breast cancer. The primary endpoints were disease-free survival, recurrence or a new primary cancer, all-cause mortality, and safety/tolerability.

Reports after median follow-up of 33, 68, and 100 months showed that anastrozole reduced the risk of recurrence compared with tamoxifen.

During active treatment, the anastrozole arm was associated with an increased incidence of fractures and arthralgia. But the excess had disappeared by 100 months.

Overall, anastrozole was associated with fewer adverse effects, and fewer patients in the arm discontinued treatment because of side effects.

The five-year results showed a recurrence rate of 9.8% in the anastrozole arm and 12.5% in the tamoxifen arm. The 10-year report showed a recurrence rate of 19.7% with anastrozole and 24% with tamoxifen, a difference that translated into a hazard ratio of 0.79 in favor of anastrozole (P=0.0002).

Anastrozole-treated patients also had a significantly greater carryover effect of risk reduction during years five through nine, said Buzdar. The analysis showed a 33% carryover in the tamoxifen arm compared with 50% in the anastrozole arm, a difference that translated into a hazard ratio of 0.81 (P=0.03).

Anastrozole's advantage for distant recurrence also continued to increase. The five-year analysis showed an absolute difference of 1.3% (9.2% versus 7.9%), increasing to 2.6% (17.7% versus 15.1%) after 10 years (P=0.02). A similar, but smaller, difference emerged from an analysis of contralateral cancer.

Anastrozole also was associated with a 14% reduction in the hazard ratio for disease-free survival (P=0.003). A difference in the rate of death after recurrence approached statistical significance (P=0.09).

Anastrozole was associated with a 5% lower rate of all-cause mortality, but the difference did not achieve statistical significance (P=0.4).

Serious adverse events were less common in the anastrozole arm during the on-treatment phase (157 versus 294), but the difference narrowed after patients stopped treatment (66 versus 78).

An excess of fractures in the anastrozole arm during the on-treatment phase (375 versus 234) had earlier caused some concern, but the rate decreased more in the anastrozole arm than in the tamoxifen arm after treatment ended (175 versus 188), erasing the difference as time went on.

The frequency of myocardial infarction and stroke was similar in the two arms. The number of cases of endometrial cancer was lower in the anastrozole arm during treatment (four versus 12) and off treatment (three versus 12).

The study was supported by AstraZeneca.

One or more investigators in the study disclosed relationships with AstraZeneca.


Primary source: ASCO Breast Cancer Symposium
Source reference:
Buzdar A, et al "Ten-year analysis of the ATAC trial" ASCO Breast 2010; Abstract 256.

[karen z]

Lani,
Thanks for posting.