Abstract 161P
Background
Over 60% of the women who are diagnosed with breast cancer in the Netherlands are treated with systemic treatment, which may be administered before (neoadjuvant systemic therapy, NST) or after (adjuvant) locoregional treatment. Depending on the subtype, 10-75% of patients will have a pathologic complete response (pCR) after NST. In this patient group, risk of local recurrence is extremely low, with reported 5-year rates of 0-3.5%. The administration of adjuvant radiotherapy in these patients is not expected to contribute significantly to local recurrence and overall survival, but may cause considerable morbidity. Our aim is to show that omission of radiotherapy after breast conserving therapy in patients treated with NST who achieve a pCR is safe and will result in good quality of life.
Methods
The DESCARTES trial is a national, multicenter, single arm prospective cohort study. Radiotherapy is omitted in cT1-2N0 patients who achieve a pCR of the breast and lymph nodes after NST and breast conserving therapy. A pCR is defined as ypT0N0 (i.e. absence of invasive carcinoma and in-situ carcinoma in the breast). Primary endpoint is the 5-year local recurrence rate, which is expected to be <4%. In total, 595 patients are needed to achieve a power of >80% (one-side alpha of 0.05). Quality of life is measured using EORTC-QLQ-C30, EORTC-QLQ-BR23 and Cancer Worry Scale questionnaires at baseline, 1 and 4 years after surgery. Projected accrual is 5 years.
Results
Local recurrence rate at 5 years is expected to be less than 4%. Secondary determinants are local non-salvageable recurrence free survival, quality of life, regional recurrence rate, distant recurrence free survival, disease-specific free survival and overall survival.
Conclusions
This trial will fill the lack of information on local recurrence rates when radiotherapy is omitted in selected patients. When the trial results are positive, the de-escalation of radiotherapy can be immediately offered to selected breast cancer patients with pCR after NST.
Clinical trial identification
NCT05416164.
Legal entity responsible for the study
The authors.
Funding
The Dutch Cancer Society (KWF, project 13761).
Disclosure
All authors have declared no conflicts of interest.