Adjuvant aromatase inhibitors and tamoxifen (Guidelines)


The results for oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor-2 (HER2) testing should be available on all patients as soon as possible after surgery and before any decisions are made on the most appropriate adjuvant therapy. For patients already on treatment and reaching the 2 to 3 year and 5 year time frames, it is essential that retrospective testing of PR and HER2 is available in a timely manner to allow provision of recognised best management.

Is the patient postmenopausal?

Postmenopausal at time of diagnosis of breast cancer defined as:

  • Amenorrhoea more than 2 years duration and age over 50 years
    If amenorrhoea less than 2 years duration and/or age less than 55 years check LH/FSH/estradiol before chemotherapy

Chemotherapy-induced amennorhoea does not equal postmenopausal

NB: Ovarian function tests are unreliable post-chemotherapy/hormonal therapy

If premenopausal before chemotherapy with persisting chemo-induced amenorrhoea following chemo then at the time of considering an AI:

  • over 55 years class as postmenopausal
  • 50 to 55 years use assessment of menopausal status before chemotherapy
  • less than 50 years old = premenopausal unless ovarian ablation.

Yes the patient is postmenopausal

Any one of:

  • Grade 3
  • Node +ve1
  • ER poor2
  • HER2 +ve
  • Path size >5cm (T3 & T4)
  • Prev. neoadj AI with response

Aromatase inhibitor* 5 years duration

All of:

  • Grade 1 AND
  • Node -ve1 AND
  • Size <2cm
Tamoxifen 5 years duration

All the rest, ie:

  • Grade 2 node –ve1 size <5cm
  • Grade 1 node –ve1 size 2 to 5cm

Extended adjuvant*

5 years tamoxifen + 3 years AI

Or switch*

2·5 years tamoxifen + 2·5 years AI

 *The individual AI, letrozole, anastrozole or exemestane, will be chosen based on the prevailing licences.

Immediate AI:   Anastrozole 1mg once daily (firstchoice)
or letrozole 2·5mg once daily (second choice) 

Switch AI:         Exemestane 25mg once daily

Extended AI:     Letrozole 2·5mg once daily

It is recommended that:

  • all patients switching from tamoxifen to an AI should have a DXA scan shortly after that switch
  • the patient's GP should check blood lipids around 4 to 6 months after that switch
  • patients receiving tamoxifen should be made aware of the symptoms of thromboembolism and advised to report sudden breathlessness and any pain in the calf in one leg.

1Micrometastases defined as 0·2mm to 2mm = node positive, isolated tumour cells defined as <0·2mm = node negative

2ER poor defined as Allred 3 to 5

No the patient is not postmenopausal

Ineligible for AI, consider tamoxifen


LH/FSHLuteinizing hormone/follicle stimulating hormone
DXADual-energy X-ray absorptiometry
AIAromatase inhibitors

Last reviewed: 09/10/2023

Next review date: 31/10/2025

Author(s): General Surgery.

Version: 3

Approved By: TAM subgroup of ADTC

Reviewer name(s): Mr Ian Daltrey, Consultant Breast Surgeon.

Document Id: TAM112