BARCELONA — The chances of breast cancer recurring in the breast, chest wall, or nearby lymph nodes remained low at 10 years when radiotherapy was tailored to patients’ individual risk following chemotherapy and surgery in the Dutch RAPCHEM study.

Among 838 patients with small, node-positive breast cancer that had not spread to distant sites, 24 (2.9%) had locoregional recurrence. Radiotherapy was selected according to how patients’ lymph nodes responded to chemotherapy, with less treatment for those with less residual nodal disease. 

“I think the take-home message of our study is that in certain prespecified women with breast cancer and a good response to the chemotherapy, we can de-escalate or reduce the radiation therapy and thereby the morbidity that goes with that radiation therapy,” said Fleur Mauritz, MD, Maastro, Maastricht University Medical Center+, Netherlands, speaking with Medscape News Europe.

Reporting the findings here at the 15th European Breast Cancer Conference, Mauritz said, “Our risk group stratification seems appropriate with omission of the regional radiation in the low-risk group, and [no] chest wall radiation in this group as well after mastectomy, and [no] regional radiation therapy of the axilla [at] levels 3 and 4 in the intermediate-risk group.”

Charlotte Coles, MD, professor of breast clinical oncology at the University of Cambridge, UK, was the invited discussant for the trial. She said the results were “very reassuring” and called RAPCHEM “an innovative trial many years ahead of its time.” 

RAPCHEM shows that response to neoadjuvant chemotherapy can act as a prognostic biomarker, enabling tailoring of radiotherapy following axillary lymph node dissection, Coles observed. 

Later, speaking with Medscape News Europe, Coles said, “This has really got the potential to change how we look at things and to give much kinder radiotherapy.”

Separately, on X, Icro Meattini, MD, associate professor and clinical oncologist at the University of Florence, Italy, noted that the RAPCHEM findings were a “strong signal that risk-adapted [radiotherapy] can reduce overtreatment without compromising outcomes.”

The RAPCHEM Study 

RAPCHEM was a prospective registry study designed to evaluate long-term locoregional recurrence in patients with cT1-2N+M0 breast cancer with fewer than four suspicious nodes on imaging. The patients received radiotherapy based on pathology findings after neoadjuvant chemotherapy and definitive surgery. Participants were treated at 17 centers across Netherlands between 2011 and 2015. Follow-up at 5 years has already been reported. 

Patients were categorized into risk groups based on their post-chemotherapy nodal status: low-risk (ypN0; n = 291), intermediate-risk (ypN1; n = 370), and high-risk (ypN2 or higher; n = 177). The majority (around 70% in each group) were aged between 40 and 59 years. 

Patients in the low-risk group received whole-breast radiotherapy after lumpectomy and no radiotherapy after mastectomy. Patients in the intermediate-risk group received whole-breast or chest-wall radiotherapy and, if they had not undergone axillary lymph node dissection, radiotherapy to axillary levels 1-2. Patients in the high-risk group received whole-breast or chest-wall radiotherapy plus radiotherapy to the nonresected part of the axilla — levels 3-4 after axillary lymph node dissection and levels 1-4 if no axillary dissection had been performed — with or without internal mammary node radiotherapy.

Secondary endpoints were overall survival and recurrence-free interval at 10 years, which were 83.0% and 79.2%, respectively.

Coles noted several caveats when interpreting the findings. She said the study included a carefully selected group of patients: All had T1 or T2 disease and one to three involved lymph nodes, some had undergone preoperative sentinel lymph node biopsy, and all had received some form of preoperative imaging. She also noted that most patients in the study underwent axillary lymph node dissection, whereas current practice is increasingly focused on reducing the extent of axillary surgery, when possible, to limit treatment-related toxicity. 

As for next steps, Mauritz said the data were still being investigated. “We are trying to zoom in on the risk factors and biology of the tumor so we can say something more about that.”

RAPCHEM was supported by Maastricht Radiation Oncology in Netherlands. Mauritz and Coles reported no relevant financial relationships. 

Sara Freeman is a medical journalist based in London, UK.