If you’ve been treated for hormone-receptor positive early breast cancer and have completed five years of hormone (endocrine) therapy — such as tamoxifen or an aromatase inhibitor (AI) — you may have heard about continuing treatment longer.
A large international study published in The Lancet (2025) examined whether staying on these medications beyond five years provides extra protection, and how to balance that benefit against quality of life.
🩺 How much does endocrine therapy help in the first five years?
Endocrine therapy has been one of the most successful treatments for hormone-receptor-positive breast cancer.
- Without hormone therapy, around 20 to 25 out of every 100 women with hormone-positive breast cancer will have a recurrence within the first five years after surgery.
- Taking tamoxifen or an aromatase inhibitor for five years roughly halves that risk, lowering recurrences to about 10–12 out of 100 women.
- This first five-year course also reduces breast-cancer deaths by about one-third, based on decades of global research.
In short, the first five years of endocrine therapy provide the greatest survival benefit.
📰 What’s new: findings from the 2025 Lancet study
- The 2025 analysis combined data from 22,000 post-menopausal women who had already completed five years of endocrine therapy.
- Over the next decade, about 15 in 100 women who stopped treatment had a recurrence, compared with about 12 in 100 who continued on an aromatase inhibitor.
- This means that continuing therapy prevented around 3 to 4 extra recurrences per 100 women.
- The benefit was strongest for women with lymph-node-positive disease, who face a higher risk of the cancer returning.
- For distant (metastatic) recurrence, the risk fell from about 9 in 100 to 7 in 100.
- Overall survival was similar between groups, meaning the benefit was mainly in reducing recurrence, not yet in extending life expectancy.
- Bone thinning and fractures were slightly more common with longer therapy (about 5% vs 3%).
⚖️ Balancing benefit and quality of life
1. Understand your personal risk
Your individual risk of recurrence depends on factors such as your age, tumour size, tumour grade, and whether lymph nodes were involved.
- Higher-risk patients (for example, those with larger or lymph-node-positive cancers) tend to benefit more from extended therapy.
- Lower-risk patients may gain little extra advantage and can often stop safely at five years after discussion with their doctor.
2. Recognise and manage side-effects
- Joint or muscle pain: regular exercise, stretching, physiotherapy, or switching to a different medication.
- Hot flushes or night sweats: cooling strategies, light clothing, and non-hormonal medicines.
- Vaginal dryness or low libido: moisturisers, lubricants, or referral to a menopause or sexual health specialist.
- Bone thinning: regular DEXA scans, calcium and vitamin D, weight-bearing exercise, and sometimes bone-strengthening medicine (e.g. bisphosphonates or denosumab).
3. Review annually
It’s important to check in with your oncologist each year and ask:
“Is the benefit still worth it for me, and how am I feeling day to day?”
Some women may benefit from planned treatment breaks to help symptoms settle.
💡 The SOLE Study (Study of Letrozole Extension)
The SOLE trial tested whether taking planned “breaks” from hormone therapy affected outcomes.
- Nearly 5,000 post-menopausal women took part after completing five years of earlier treatment.
- One group took letrozole continuously for five years, while the other took it nine months each year, with a three-month break annually.
- Results showed no difference in recurrence or survival between the two groups.
- Women who took planned breaks reported fewer joint pains, hot flushes, and better overall wellbeing.
This shows that for some women, short, planned “treatment holidays” can improve comfort and quality of life without reducing effectiveness.
🧭 Putting it all together
| Treatment period | Main benefit | Approx. recurrence risk (per 100 women) | Typical trade-offs |
|---|---|---|---|
| No endocrine therapy | — | 20–25 | — |
| First 5 years of therapy | Large reduction in recurrence and deaths (≈ 30% lower mortality) | ↓ to 10–12 | Menopausal symptoms, fatigue |
| Extending therapy to 10 years | Small extra reduction in late recurrence (mainly in higher-risk women) | ↓ to 12 | More joint pain, bone loss, sexual side-effects |
Survival benefit:
Long-term studies (EBCTCG 2011 & 2025) show that the first five years of endocrine therapy significantly improve survival, while extended therapy mainly reduces late recurrences and may provide a small additional survival benefit in higher-risk women.
❓ Questions to discuss with your specialist
- What is my personal risk of the cancer returning later?
- How much extra benefit would I gain from continuing treatment?
- How are my bones, joints, and daily wellbeing?
- What supports can help manage symptoms?
- Would an intermittent approach (as in the SOLE study) or stopping therapy be reasonable for me?
💬 In summary
- The first five years of hormone therapy make the biggest difference — roughly halving the risk of recurrence and reducing deaths by one-third.
- Continuing for another 3–5 years offers modest extra protection (about 3–4% absolute benefit), mainly for women at higher risk.
- The decision should be individualised, balancing small added benefits against side-effects and overall quality of life.
- Regular discussions with your oncologist help you stay protected, informed, and comfortable.
📚 References
- Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). Extending the duration of endocrine treatment for early breast cancer: a collaborative meta-analysis of 12 randomised trials (22,031 women). The Lancet, 2025.
- Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). Tamoxifen for early breast cancer: 15-year outcomes. Lancet, 2011.
- Goss PE et al. MA.17R Trial of Letrozole after 5 Years of Endocrine Therapy. NEJM, 2016.
- Mamounas EP et al. NSABP B-42: 10-Year Update. JNCI, 2023.
- Colleoni M et al. SOLE Trial: Continuous vs Intermittent Letrozole Extension. Ann Oncol, 2018.
- Burstein HJ et al. ASCO Clinical Practice Guideline Update on Endocrine Therapy. JCO, 2019.