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CompletedNCT00814125Updated May 1, 2009

ATAC - Endometrial Sub-Protocol

A Phase 3 interventional study of Anastrozole (Arimidex) and Tamoxifen (Nolvadex) in Breast Cancer, sponsored by AstraZeneca. Completed. Open to female participants aged 45 Years and older. Per ClinicalTrials.gov, last updated 2009-05-01.

Sponsored by AstraZeneca · Phase 3 and Interventional

Phase
Phase 3
Study type
Interventional
Enrollment
285
Allocation
Randomized
Ages
45 Years and older
Sex
Female
01

Study summary

To compare the difference between the ARIMIDEX group and the tamoxifen group in the incidence of abnormal endometrial histological findings arising after treatment has commenced.

02

Conditions studied

  • Breast Cancer

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Keywords

  • Endometrial
  • Endometrial histological findings
03

In context

Breast Neoplasms

12,544 studies on the registry are indexed under Breast Neoplasms; 2,892 are open to participants now.

This study's enrollment of 285 is above the median of 72 across 9,303 interventional studies indexed under Breast Neoplasms.

Browse Breast Neoplasms studies →

Lead sponsor

AstraZeneca is the lead sponsor of 3,429 studies on the registry; 270 are open to participants now.

Of its 357 completed or terminated interventional studies of FDA-regulated products, 173 (48%) have results posted.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
45 Years and older
Sexes eligible
Female
Accepts healthy volunteers
No

Inclusion criteria

  • Patients eligible for entry into the main ATAC trial (1033IL/0029)
  • Not received any previous tamoxifen, for whatever reason
  • Not undergone a hysterectomy and do not have a hysterectomy planned within the next 6 years
  • No previous endometrial ablation

Exclusion criteria

Exclusion Criteria:

  • Excluded from entry into the main ATAC trial (1033IL/0029). As detailed in Section 4.4 of the main ATAC trial (1033IL/0029)
05

Study design

Phase
Phase 3
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Double (Participant, Investigator)
Enrollment
285 participants (actual)

Study arms

  • Active comparator
    1

    Arimidex 1mg + Nolvadex placebo

    Drug: Anastrozole (Arimidex) · Drug: Nolvadex placebo

  • Active comparator
    2

    Arimidex placebo + Nolvadex 20mg

    Drug: Tamoxifen (Nolvadex) · Drug: Arimidex placebo

  • Active comparator
    3

    Arimidex 1mg + Nolvadex 20mg

    Drug: Anastrozole (Arimidex) · Drug: Tamoxifen (Nolvadex)

Interventions

  • DrugAnastrozole (Arimidex)

    1mg, orally, once daily

    Also known as: Arimidex

  • DrugTamoxifen (Nolvadex)

    20mg, orally, once daily

    Also known as: Nolvadex

  • DrugNolvadex placebo
  • DrugArimidex placebo
06

What researchers measure

Primary outcomes

  1. Withdrawl

  2. Death

07

Study locations

No study locations are listed for this record.

08

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on May 1, 2009, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
09

Registry details

Key details

Study ID
NCT00814125
Lead sponsor
AstraZeneca
First posted
Dec 24, 2008
Start date
Jun 1997
Completion
Dec 2005
Last update
May 1, 2009

Oversight

Data monitoring committee
Yes
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is completed, as verified in Apr 2009. You cannot join it, but the record below documents what was studied.

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