Fleur Mauritz, ctRO Young Researcher Award
 

ESTRO 2026 Congress Report

 

Background

Indications are under debate regarding the use of postoperative locoregional radiotherapy in patients with small breast cancer (max. 5cm, cT1-2) with limited involvement of lymph nodes at diagnosis (cN1) and who respond well to the primary systemic therapy (i.e. chemotherapy). The previously published five-year outcomes of the radiotherapy after chemotherapy (RAPCHEM) study and the NSABP-B51 trial showed that excellent locoregional control could be achieved when radiotherapy was tailored to the nodal response after primary chemotherapy. However, there were no long-term results on the use of such a strategy, and therefore we present the 10-year results of the RAPCHEM study.

 

Methods

In this prospective registry study, patients were included who had been referred to one of 17 participating Dutch radiation oncology centres with cT1–2N1 breast cancer (with ≤3 suspicious nodes at imaging) and who had been treated with primary chemotherapy followed by breast and axillary surgery. Three risk groups (low-, intermediate-, and high-risk), with corresponding radiotherapy guidelines, were defined based on the response to the chemotherapy. In the low- and intermediate-risk groups, the radiation therapy was (partially) omitted: the low-risk group received only whole breast radiotherapy after lumpectomy and no radiotherapy after mastectomy; the intermediate-risk group received whole breast or chest wall radiotherapy without regional nodal radiotherapy

 

Results

After ten years, only 24 patients out of the total 838 (2·9%) had a locoregional recurrence. There were 65 locoregional recurrences (representing 7.8% of the 838 patients) when recurrences that occurred simultaneously with distant metastasis were taken into account. No significant differences were seen in locoregional recurrence with or without synchronous distant metastasis among the risk groups, despite the (partial) omission of locoregional radiation therapy in the low- and intermediate-risk groups.

Additional analysis showed that hormone-negative tumours had a higher risk of developing a locoregional recurrence, including synchronous distant metastasis, than did hormone-positive tumours. Moreover, those tumours tended to relapse early, i.e. within five years.

 

Conclusion

Our results show that tailoring the radiotherapy to the nodal response after chemotherapy in patients with cT1-2N1 breast cancer (with ≤3 nodes at imaging) is associated with very low rates of locoregional recurrence 10 years after diagnosis. Application of this strategy could therefore help to prevent unnecessary treatment and thus improve the quality of patients’ lives. Tumour subtypes are a valuable target for further individualisation of treatment.

 

Fleur Mauritz

Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, The Netherlands

 

Fleur Mauritz, receiving the Young Research Award from Constantinos Zamboglou, ctRO Associate Editor