No radiotherapy after breast-conserving surgery is safe in selected younger patients

Avoiding radiotherapy after breast-conserving surgery in selected younger (50–69) post-menopausal patients appears not to increase the risk of recurrence nor to decrease survival, as is suggested by results of the single-arm IDEA trial.

Radiotherapy is recommended after lumpectomy to improve local control of invasive breast cancer and a modest survival benefit. However, the absolute benefit of radiotherapy is not the same for all subgroups of patients, and survival benefit appears restricted to those with a large absolute reduction in recurrence (>10–20%). Multiple studies have shown a low risk of ipsilateral breast events or other recurrences for selected patients: those aged 65–70 or older, with stage I breast cancers, and treated with breast-conserving surgery and endocrine therapy without adjuvant radiotherapy.

The prospective, single-arm IDEA trial (NCT02400190) aimed to evaluate if younger post-menopausal patients could also be successfully treated without radiotherapy, adding a genomic assay (Oncotype DX) to the classic selection factors. IDEA enrolled 200 post-menopausal patients aged 50–69 years, with pT1N0 unifocal invasive breast cancer, with margins 2 mm or wider after breast-conserving surgery, whose tumours were oestrogen receptor (ER)-positive, progesterone receptor (PR)-positive, and HER2-negative, with Oncotype DX 21-gene recurrence risk score ≤18, who were willing to avoid radiotherapy and to take at least 5 years of endocrine therapy and surveillance on study. Primary endpoint was the rate of breast cancer recurrence at 5 years of follow-up after breast-conserving surgery. Dr Reshma Jagsi (Emory University School of Medicine, MI, USA) presented the results [1].

Among the 186 participants with clinical follow-up of at least 56 months, overall and breast cancer-specific survival rates at 5 years were both 100%; 2 deaths occurred beyond 5 years. Recurrence-free survival rate at 5 years was 99%. There were 2 recurrences: 1 isolated ipsilateral axillary recurrence at 21 months and 1 ipsilateral breast event at 49 months; 6 additional patients recurred beyond 5 years.

“These results show a very low risk of relapse for post-menopausal patients with stage I cancers, avoiding radiotherapy using a genomic assay in combination with classic clinical and biological features for treatment selection, including patients younger than 60 years,” Dr Jagsi concluded. “However, long-term follow-up beyond the 5-year required period of endocrine therapy will be important to determine if the risk of recurrence increases, particularly after discontinuation of endocrine therapy. In addition, results from ongoing randomised trials are needed to determine whether the option of avoiding initial radiotherapy can be offered to a broader group of women than current guidelines recommend.”

1. Jagsi R, et al. Five-year outcomes of the IDEA trial of endocrine therapy without radiotherapy after breast-conserving surgery for postmenopausal patients age 50-69 with genomically-selected favorable stage I breast cancer. Abstract GS02-08, SABCS 2023, 5–9 December, San Antonio, TX, USA.

 

Copyright ©2024 Medicom Medical Publishers



Posted on 11 January 202411 January 2024