# Aromatase inhibitor

Source: https://onco.cc/terms/aromatase-inhibitor/  
OnCo record `aromatase-inhibitor` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Pills that stop the body making oestrogen (after the menopause, when it comes from fat and muscle rather than the ovaries), starving hormone receptor-positive breast cancer. Taken for five to ten years after surgery, they halve recurrence.

## Summary

Letrozole, anastrozole and exemestane block the aromatase enzyme; in premenopausal women they only work with ovarian function suppression (GnRH agonist or oophorectomy, SOFT/TEXT). They modestly beat tamoxifen in postmenopausal adjuvant therapy (ATAC, BIG 1-98) and are the partner drug for CDK4/6 inhibitors in metastatic disease. Side effects are joint pain, bone loss (needing bisphosphonates), vaginal dryness and cardiovascular effects, and adherence over 5-10 years is a real problem. Resistance often comes through ESR1 mutations, which favour switching to a SERD.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: aromatase inhibitors; aromatase inhibition; ovarian suppression; ovarian function suppression; OFS; extended endocrine therapy; adjuvant endocrine therapy; endocrine therapy

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Aromatase_inhibitor
- Wikipedia: https://en.wikipedia.org/wiki/Aromatase_inhibitor

## Connected records

- terms: [Endocrine resistance](https://onco.cc/terms/endocrine-resistance/), [Endocrine therapy and endocrine resistance](https://onco.cc/terms/endocrine-therapy-resistance/), [Hormone receptor status (ER / PR)](https://onco.cc/terms/hormone-receptor-status/), [Salpingo-oophorectomy](https://onco.cc/terms/salpingo-oophorectomy/), [Selective oestrogen receptor degrader (SERD)](https://onco.cc/terms/serd/)
- cancers: [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Lobular carcinoma in situ (LCIS)](https://onco.cc/cancers/lobular-carcinoma-in-situ/)
- fronts: [Hormonal Therapy](https://onco.cc/fronts/hormonal/)
- technologies: [Acupuncture for aromatase-inhibitor joint pain](https://onco.cc/technologies/acupuncture-aromatase-inhibitor-arthralgia/), [Acupuncture for hot flushes on endocrine therapy](https://onco.cc/technologies/acupuncture-hot-flushes/), [Bone loss caused by cancer treatment, and what rebuilds it](https://onco.cc/technologies/cancer-treatment-bone-loss/), [CDK4/6 inhibitors](https://onco.cc/technologies/cdk46-inhibitor/), [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/), [Menopause brought on by cancer treatment, and the options for it](https://onco.cc/technologies/menopause-after-cancer-treatment/), [Minoxidil for persistent chemotherapy- and endocrine-therapy hair loss](https://onco.cc/technologies/minoxidil-chemotherapy-alopecia/), [Vaginal oestrogen after breast cancer: what the evidence says, and where it disagrees](https://onco.cc/technologies/vaginal-oestrogen-after-breast-cancer/)
- drugs: [Letrozole (and other aromatase inhibitors)](https://onco.cc/drugs/letrozole/), [Tamoxifen](https://onco.cc/drugs/tamoxifen/)

---
JSON: https://onco.cc/api/v1/entities/aromatase-inhibitor.json