ESTRO 2022

Session Item

Saturday

May 07

10:30 - 11:30

Room D3

Late-breaking

Chair: , United Kingdom;

Chair: , The Netherlands

Session Code: 1220

Session Type: Proffered Papers

Track: Clinical

10:50 - 11:00

DBCG phase III randomized trial of hypo- vs standard fractionated RT in 2879 pN+ breast cancer pts

Birgitte Offersen, Denmark

Presentation Number: OC-0102

Abstract

Abstract Title:

DBCG phase III randomized trial of hypo- vs standard fractionated RT in 2879 pN+ breast cancer pts

Authors:

Birgitte Offersen¹, Jan Alsner¹, Hanne M Nielsen², Troels Bechmann³, Mette H Nielsen⁴, Ingvil Mjaaland⁵, Claus Kamby⁶, Carine Krkove⁷, Tamaz Lorincz⁸, Sami Al-Rawi⁹, Egil B Stoere¹⁰, Andreas Schreiber¹¹, Mechthild Krause¹², Unn-Miriam Kasti¹³, Louise W Matthiessen¹⁴, Piotr Kedzierawski¹⁵, Tanja Marinko¹⁶, Marjaana Luukkaa¹⁷, Tanja Skyttä¹⁸, Maj-Britt Jensen¹⁹, Jens Overgaard¹

¹Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; ²Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; ³Lillebaelt Hospital, Department of Oncology, Vejle, Denmark; ⁴Odense University Hospital, Department of Oncology, Odense, Denmark; ⁵Stavanger University Hospital, Department of Oncology, Stavanger, Norway; ⁶Rigshospitalet, Copenhagen University Hospital, Department of Oncology, Copenhagen, Denmark; ⁷Université Catholique de Louvain, Cliniques Universitaires St-Luc, Radiotherapy Department, Bruxelles, Belgium; ⁸Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; ⁹Zeeland University Hospital, Department of Oncology, Naestved, Denmark; ¹⁰UiT, The Arctic University of Norway, Department of Clinical Medicine, Tromsoe, Norway; ¹¹Academic Teaching Hospital Dresden-Friedrichstadt, Department of Oncology, Dresden, Germany; ¹²University Hospital Carl Gustav Carus, Technische Universität Dresden, Clinic for Radiotherapy and Oncology, Dresden, Germany; ¹³Hospital of Kristiansand, Department of Oncology, Kristiansand, Norway; ¹⁴Herlev and Gentofte University Hospital, Department of Oncology, Herlev, Denmark; ¹⁵Holycross Cancer Center, Department of Oncology, Kielce, Poland; ¹⁶Institute of Oncology Ljubljana, Department of Oncology, Ljubljana, Slovenia; ¹⁷Turku University Hospital, Department of Oncology, Turku, Finland; ¹⁸Tampere University Hospital, Department of Oncology, Tampere, Finland; ¹⁹Rigshospitalet, Copenhagen University Hospital, DBCG, Copenhagen, Denmark

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Purpose or Objective

Adjuvant radiation therapy (RT) for node-positive early breast cancer using 50 Gy/25 fr has been Danish Breast Cancer Group (DBCG) standard since 1982. Over the last decade moderately hypofractionated breast cancer RT based on 40Gy/15fr has been increasingly used, however, not for loco-regional therapy due to concern over a higher risk of morbidity. In that scenario, the non-inferiority DBCG Skagen trial 1 was designed the hypothesis being that 40 Gy/15 fr (2.67 Gy/fr) did not result in more arm lymphedema than 50 Gy/25 fr (2.0 Gy/fr) 3 years after RT.

Material and Methods

A total of 2879 patients ≥18 years operated for node-positive breast cancer were enrolled during 2015-21 and randomized 50 Gy/25 fr vs. 40 Gy/15 fr. All tumour-bed boosts were simultaneous integrated (SIB). The primary endpoint was ipsilateral arm lymphedema at 3 years (≥10% increase in arm circumference 15 cm proximal and/or 10 cm distal to the olecranon on the treated side compared to the contralateral arm). All target volume delineations were according to the ESTRO consensus on target volume delineation of early breast cancer. Accrual was to stop, when 3-year estimates of arm lymphedema had been reported in 1012 patients. The trial was registered with ClinicalTrials.gov, number NCT02384733.

Results

The 50 Gy group comprised 1442 patients (50%) and the 40 Gy group 1437 patients (50%). Median age was 58 years (range 20-86 years). Mastectomy was used in 1372 patients (48%), 1507 patients (52%) had lumpectomy, and a SIB was used in 16% of the patients.

At median follow-up of 2.0 years (IQR 0.0-3.1) the 3-year rates of ipsilateral arm lymphedema were 11.7% in the whole group, whilst in the 50 Gy versus 40 Gy group it was 11.6% versus 11.8%, absolute difference 0.1% (95% CI -0.4% to 0.4%), p=0.96. Range of shoulder motion was not impaired (<20% different) in 97.5%, the frequencies being 96.3% (50Gy) versus 98.7% (40Gy), no difference. Breast induration in post-lumpectomy patients was 26.0% (22.9% (50Gy) vs 29.1% (40Gy), p=0.11. In patients treated with/without SIB, induration was 22.0% versus 29.5%, difference 7.4% (p=0.12).

Overall, the 3-year risk of loco-regional recurrence was 1.8% (1.2-2.7) (50Gy) and 1.8% (1.1-2.7) (40Gy), risk of distant failure was 5.6% (4.3-7.1) (50Gy) and 6.9% (5.5-8.6) (40Gy), and risk of death was 3.7% (2.6-5.0) (50Gy) and 4.8% (3.6-6.2) (40Gy).

Conclusion

Moderately hypofractionated loco-regional breast cancer irradiation of node-positive breast cancer does not result in more arm lymphedema compared to standard fractionated therapy. The 3-year loco-regional recurrence risk was very low. Moderately hypofractionated RT did not influence the risk of distant recurrence or death.

Funding: The Danish Cancer Society and DCCC RT (Danish Comprehensive Cancer Centre RadioTherapy Group)