Ductal carcinoma in situ (DCIS) is often found through screening before it has a chance to spread. While this sounds reassuring, it leads to a tough question: how much treatment is enough? Most DCIS patients undergo surgery, often followed by radiation and/or hormone (endocrine) therapy. But not all DCIS is aggressive, and over-treating low-risk cases can cause unnecessary side effects.
This new study, published in NPJ Breast Cancer, takes a fresh look at how long endocrine therapy needs to be taken—and whether it might offer similar protection as radiation. Researchers analyzed 1,916 patients from two large California cancer centers, with a median follow-up of 7 years. All had breast-conserving surgery; some received additional treatments—radiation, endocrine therapy (like tamoxifen or aromatase inhibitors), both, or neither. Crucially, the team tracked exactly how long patients stayed on endocrine therapy, a detail often missing in clinical registries.
The study found that taking endocrine therapy for less than 2 years did not significantly lower the risk of recurrence compared to surgery alone. But taking endocrine therapy for 2 years or more significantly reduced the chance of another breast cancer diagnosis—just as much as radiation or a combination of radiation and endocrine therapy. Endocrine therapy of 2+ years also had a unique benefit: it lowered the risk of recurrence not only in the same breast, but also in the opposite breast—something radiation does not do.
Why this Matters for DCIS Patients
This real-world data suggests that completing at least 2 years of endocrine therapy could be a powerful option for some DCIS patients—especially those who are hesitant about radiation. For patients with estrogen receptor-positive (ER+) DCIS, this adds an important piece of information when weighing treatment choices.
Still, endocrine drugs can have side effects (such as hot flashes, fatigue or increased blood clot risk), so any decision must balance benefits and side‑effects. Going forward, tools that assess a patient’s specific risk—using genetics, imaging, or biomarkers—could help personalize treatment, ensuring patients get just enough care: not too little, not too much.
Crucially, this underscores the need for shared decision-making and honest conversations. Not every patient will tolerate endocrine therapy well, and not every case of DCIS needs aggressive treatment. But this study shows that, for those who do choose hormone therapy, duration truly matters—and sticking with it may offer long-term benefits, even without radiation.
Click here to read the full study.