Editor’s Note: The 2026 National Breast Cancer Conference was held in Beijing from April 10–12, during which major updates to the Chinese Society of Clinical Oncology (CSCO) Breast Cancer Guidelines 2026 (CSCO BC Guidelines 2026) were officially released. At the meeting, Professor Jiayi Chen from Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, reviewed and interpreted the latest updates in the radiotherapy section of the guidelines.These revisions were primarily driven by two landmark clinical trials—SUPREMO and NSABP B-51—which led to important adjustments in recommendations regarding postmastectomy radiotherapy for intermediate-risk patients and regional nodal irradiation in patients achieving ypN0 status after neoadjuvant therapy.
Oncology Frontier invited Professor Chen to provide a deeper interpretation of the updated radiotherapy recommendations, the clinical impact of the SUPREMO and NSABP B-51 trials, and the latest advances in hypofractionated radiotherapy.
01
Oncology Frontier: The 2026 edition of the CSCO BC Guidelines was officially released during this year’s National Breast Cancer Conference. Compared with the 2025 edition, what major updates were introduced in the radiotherapy section?
Professor Jiayi Chen: The most important updates in the radiotherapy section of the 2026 CSCO BC Guidelines are based on two pivotal clinical trials.
The first is the SUPREMO study, which evaluated whether chest wall radiotherapy could be safely omitted in intermediate-risk early breast cancer patients following mastectomy. This population included patients with pT1N1, pT2N1, pT3N0, or high-risk pT2N0 disease.
The second is the NSABP B-51 study, which investigated the safety of omitting regional nodal irradiation in patients with initially node-positive (cN1) disease who converted to axillary ypN0 status after neoadjuvant chemotherapy.
In the 2025 CSCO BC Guidelines, for patients with one to three positive axillary lymph nodes following mastectomy for early breast cancer, the Category I recommendation for postoperative radiotherapy was:
“Postoperative radiotherapy including the chest wall and regional lymph nodes; in patients without axillary dissection, irradiation should include the undissected high-risk axilla [1B].”
The Category II recommendation stated:
“Postoperative radiotherapy may be omitted in patients at low risk of recurrence [2B].”
These recommendations were generally consistent with international guidelines.
However, based on the SUPREMO study results recently published in The New England Journal of Medicine, chest wall radiotherapy did not improve 10-year overall survival in intermediate-risk early breast cancer patients treated with mastectomy and systemic therapy.
Consequently, the 2026 CSCO BC Guidelines revised recommendations for this patient population:
- The Category I recommendation now remains:
“Chest wall plus regional nodal radiotherapy [1A].”
- The previous Category II recommendation has been removed.
For patients with cN1 disease who achieved ypN0 status after neoadjuvant therapy and subsequently underwent breast-conserving surgery, the 2025 guidelines aligned with earlier NCCN recommendations:
- Category I:
“Whole-breast irradiation ± tumor-bed boost plus regional nodal irradiation; in patients without axillary dissection, consideration should be given to including the undissected high-risk axilla [2A].”
- Category II:
“Whole-breast irradiation ± tumor-bed boost.”
Based on the NSABP B-51 findings, the 2026 guidelines revised these recommendations as follows:
- Category I no longer includes regional nodal irradiation, and instead recommends:
“Whole-breast irradiation ± tumor-bed boost [2A].”
- Category II now recommends:
“Whole-breast irradiation + tumor-bed boost + regional nodal irradiation [2B].”
For patients with cN1 disease who achieved ypN0 status after neoadjuvant therapy and underwent mastectomy:
- The Category I recommendation has been removed.
- Category II now recommends:
“Chest wall plus regional nodal irradiation (including undissected axilla) [2B].”
That said, there remain important differences between the patient populations enrolled in the SUPREMO and NSABP B-51 studies and those encountered in routine clinical practice. Therefore, applying these findings in real-world settings still requires careful discussion and individualized judgment.
02
Oncology Frontier: Based on these two studies and the updated 2026 guidelines, what impact do you believe these changes will have on real-world radiotherapy practice?
Professor Jiayi Chen: In my view, the SUPREMO study has not fundamentally changed current clinical practice.
For patients with N1 disease, both postmastectomy radiotherapy (PMRT) and regional nodal irradiation following breast-conserving surgery have always been approached with individualized decision-making. In general, the indications for PMRT and regional nodal irradiation are primarily limited to patients with high-risk features, which is already widely accepted.
These high-risk factors include lymphovascular invasion, young age (particularly <40 years), histologic grade 3 disease, larger tumor burden, and elevated Ki-67 levels—all of which have been consistently recognized across the literature.
When patients possess one or especially multiple high-risk features, we believe they can derive meaningful benefit from postoperative radiotherapy, particularly regional nodal irradiation. Conversely, for patients lacking any high-risk factors, expert consensus has already supported omission of PMRT or regional nodal irradiation in selected cases.
By comparison, I believe the NSABP B-51 study has had a greater and more meaningful impact on my own clinical practice.
Importantly, this is the first study demonstrating that systemic treatment response—specifically pathological complete response after neoadjuvant therapy—can directly alter locoregional treatment decisions in clinical practice.
However, the study also identified three subgroups in which recurrence risk increased after omission of regional nodal irradiation.
First:
Patients who underwent mastectomy rather than breast-conserving surgery.
In these patients, omission of regional nodal irradiation effectively meant omission of all postoperative radiotherapy, resulting in complete loss of regional nodal protection. Their recurrence risk increased by 28%.
Second:
Patients whose axillary lymph nodes achieved pCR but whose primary breast lesion did not achieve pCR.
In this subgroup, omission of regional irradiation increased recurrence risk by 26%.
Third:
Patients whose ypN0 status was assessed using sentinel lymph node biopsy rather than full axillary dissection.
After neoadjuvant chemotherapy, the false-negative rate of sentinel lymph node evaluation is higher than in patients who have not received neoadjuvant therapy. In these patients, omission of both axillary dissection and regional nodal irradiation may slightly increase risk.
Therefore, in real-world practice, we should exercise additional caution when considering omission of regional nodal irradiation in patients with these characteristics.
Before release of the 2026 guidelines, several important studies on hypofractionated radiotherapy were also reported.
One particularly important study was the French UNICANCER HypoG-01 trial, which directly compared 3-week moderate hypofractionated radiotherapy versus conventional 5-week fractionation in early breast cancer patients requiring regional nodal irradiation.
The results demonstrated that the 3-week regimen was non-inferior to the 5-week regimen regarding ipsilateral arm lymphedema—the primary safety endpoint—and also achieved favorable long-term oncologic outcomes.
Regarding hypofractionated radiotherapy more broadly, many important findings have emerged in recent years from institutions including the National Cancer Center/Cancer Hospital of the Chinese Academy of Medical Sciences and our own institution, Ruijin Hospital.
These studies have confirmed that moderate hypofractionation—and even ultra-short-course regimens—can effectively replace conventional 5-week radiotherapy schedules.
Collectively, these findings further encourage us to adopt individualized treatment strategies and confidently implement shorter-course radiotherapy in clinical practice.
This approach not only reduces treatment-related toxicity and improves patient acceptance of radiotherapy, but also allows more patients to benefit from effective treatment.
Professor Jiayi Chen
Ruijin Hospital, Shanghai Jiao Tong University School of Medicine
