- βA major South Korean study suggests that overall tumor risk profile β not just size β should guide whether small thyroid cancers need immediate surgery, which could spare many patients from operations they may not need.
| Country | South Korea |
| Institution | Seoul National University Bundang Hospital, Seoul National University College of Medicine |
| Journal | Endocrinology and metabolism (Seoul, Korea) |
| Year | 2025 |
| PMID | 39962344 |
South Korean Researchers Challenge the 1 cm Surgery Rule for Thyroid Cancer
A study from South Korea published in Endocrinology and Metabolism (2025) is expanding a landmark research program at Seoul National University Bundang Hospital that could reshape how small, low-risk thyroid cancers are managed β not just in Asia, but potentially in the United States as well.
What Is This Study About?
The research focuses on papillary thyroid microcarcinoma (PTMC) β a small, slow-growing form of thyroid cancer typically measuring 1 centimeter (about 4/10 of an inch) or less. For years, the standard approach in many countries, including the US, has leaned toward surgical removal. But a growing body of evidence, pioneered in Japan and now expanded by South Korean researchers, suggests that many of these cancers can be safely monitored with active surveillance (AS) β meaning regular ultrasound checkups instead of immediate surgery.
The new phase of this program, called MAeSTro-EXP, takes things a step further by asking: What about low-risk thyroid tumors slightly larger than 1 cm β up to 1.5 cm? The researchers hypothesize that a tumor's overall risk profile matters more than its exact size when deciding whether surgery is truly necessary.
What Did the Original Study Find?
The first phase of MAeSTro enrolled 1,177 patients between 2016 and 2020 and produced important data showing that active surveillance was a safe and cost-effective alternative to immediate surgery for low-risk tumors under 1 cm. It also examined quality of life and identified ultrasound-based predictors of cancer progression β helping doctors determine which patients actually need to move forward with surgery.
How Is This Different from US Guidelines?
Current US guidelines from the American Thyroid Association (ATA) do acknowledge active surveillance as an option for very low-risk PTMC under 1 cm, but adoption in clinical practice remains inconsistent. Many American patients are still advised to have surgery. This South Korean study β now conducted in partnership with researchers in Australia β pushes the boundary further by evaluating surveillance for tumors up to 1.5 cm, which falls outside current US guideline recommendations. If the data supports this expanded approach, it could influence future ATA guideline updates.
Why Does Thyroid Cancer Matter for Diabetes Patients?
People with type 2 diabetes have a modestly elevated risk of thyroid dysfunction and certain thyroid conditions, making thyroid health a relevant topic for the diabetes community. Additionally, some diabetes medications and metabolic factors can influence thyroid function, so staying informed about thyroid cancer management is worthwhile.
Why This Matters for US Patients
- Many Americans with small, low-risk thyroid tumors may be undergoing surgery that this growing body of international research suggests could be safely avoided.
- The study introduces a cross-cultural comparison between South Korea and Australia, which could reveal whether race and ethnicity affect how these cancers behave β important data for America's diverse population.
- Active surveillance means fewer surgeries, lower costs, and avoided surgical risks such as voice changes or low calcium levels from parathyroid damage.
- US patients diagnosed with small thyroid nodules or early thyroid cancer should ask their endocrinologist whether active surveillance is appropriate for their specific situation.
At mdsdiabetes.com, our clinical team stays current on international endocrinology research because thyroid and metabolic health are deeply connected. If you have questions about thyroid health in the context of diabetes management, our resources and care team are here to help.
Full Citation
[South Korea] β Moon, Lee, Cha (2025). Study Protocol of Expanded Multicenter Prospective Cohort Study of Active Surveillance on Papillary Thyroid Microcarcinoma (MAeSTro-EXP). Endocrinology and Metabolism (Seoul, Korea). PMID: 39962344. DOI: 10.3803/EnM.2024.2136. Institution: Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.