# Low-dose tamoxifen for high-risk women, prescribed by pharmacists and nurses

Source: https://onco.cc/ideas/idea-prev-low-dose-tamoxifen-uptake/  
OnCo record `idea-prev-low-dose-tamoxifen-uptake` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A 5 mg tamoxifen dose halves breast cancer recurrence after precancer with far fewer side effects than the full dose. Almost nobody is prescribed it. Change who can prescribe.

## Summary

TAM-01 showed 5 mg a day reduced recurrence after DCIS, atypical hyperplasia or LCIS by about half with side effects close to placebo, yet uptake of risk-reducing medication is under 10%. Propose nurse and pharmacist prescribing, an automatic offer at diagnosis of high-risk lesions, and inclusion in screening-risk feedback.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: Automatic offer plus non-physician prescribing raises uptake of risk-reducing medication among eligible women from under 10% to at least 40%.
- Rationale: The barriers are prescriber inertia and fear of side effects; low dose addresses the second, delegation the first.
- Proposed test: Run a cluster RCT in breast units.
- Maturity: early-clinical
- Actor: clinic

## Sources

- Bottleneck evidence (Prevention we already have is not deployed): Islami et al., Proportion of cancer attributable to modifiable risk factors (CA 2018): https://doi.org/10.3322/caac.21440

## Connected records

- cancers: [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/)
- fronts: [Hormonal Therapy](https://onco.cc/fronts/hormonal/), [Prevention & Risk](https://onco.cc/fronts/prevention/)
- technologies: [Chemoprevention & risk-reducing surgery](https://onco.cc/technologies/chemoprevention/), [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/)
- targets: [Estrogen receptor (ERα)](https://onco.cc/targets/estrogen-receptor/)
- bottlenecks: [Prevention we already have is not deployed](https://onco.cc/bottlenecks/b-prevention-adoption/)
- key papers: [IBIS-I: five years of tamoxifen keeps preventing breast cancer for at least 20 years](https://onco.cc/key-papers/paper-ibis-i-tamoxifen-lancet-oncol-2015/), [Proportion and number of cancer cases and deaths attributable to potentially modifiable risk factors in the United States](https://onco.cc/key-papers/paper-islami-ca-cancer-j-clin/)
- roadmaps: [Cancer prevention roadmap: tobacco control and vaccines → biomarker-guided chemoprevention → interception in carriers](https://onco.cc/roadmaps/prevention-roadmap/), [Hormonal therapy roadmap: removing the ovaries → tamoxifen → oral degraders switched by a blood test](https://onco.cc/roadmaps/hormonal-therapy-roadmap/)

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