Simultaneous integrated boost within the lymphatic drainage system in breast cancer: A single center study on toxicity and oncologic outcome

Sophie T Klusen; Antonia Peiler; Georg P Schmidt; Marion E Kiechle; Stefan Muench; Rebecca Asadpour; Stephanie E Combs; Kai J Borm

doi:10.3389/fonc.2023.989466

Simultaneous integrated boost within the lymphatic drainage system in breast cancer: A single center study on toxicity and oncologic outcome

Front Oncol. 2023 Apr 6:13:989466. doi: 10.3389/fonc.2023.989466. eCollection 2023.

Authors

Sophie T Klusen¹, Antonia Peiler¹, Georg P Schmidt², Marion E Kiechle², Stefan Muench¹, Rebecca Asadpour¹, Stephanie E Combs^{1

3

4}, Kai J Borm¹

Affiliations

¹ Department of Radiation Oncology, Technical University Munich, Medical School, Klinikum rechts der Isar, Munich, Germany.
² Department of Gynecology and Obstetrics, Technical University Munich, Medical School, Klinikum rechts der Isar, Munich, Germany.
³ Deutsches Konsortium für translationale Krebsforschung (DKTK) - Partner Site Munich, Munich, Germany.
⁴ Institute of Radiation Medicine, Helmholtzzentrum München, Munich, Germany.

Abstract

Background and purpose: In breast cancer patients, the increasing de-escalation of axillary surgery and the improving resolution of diagnostic imaging results in a more frequent detection of residual, radiographically suspect lymph nodes (sLN) after surgery. If resection of the remaining suspect lymph nodes is not feasible, a simultaneous boost to the lymph node metastases (LN-SIB) can be applied. However, literature lacks data regarding the outcome and safety of this technique.

Materials and methods: We included 48 patients with breast cancer and sLN in this retrospective study. All patients received a LN-SIB. The median dose to the breast or chest wall and the lymph node system was 50.4 Gy in 28 fractions. The median dose of the LN-SIB was 58.8 Gy / 2.1 Gy (56-63 Gy / 2-2.25 Gy). The brachial plexus was contoured in every case and the dose within the plexus PRV (+0.3-0.5mm) was limited to an EQD2 of 59 Gy. All patients received structured radiooncological and gynecological follow-up by clinically experienced physicians. Radiooncological follow-ups were at baseline, 6 weeks, 3 months, 6 months and subsequent annually after irradiation.

Results: The median follow-up time was 557 days and ranged from 41 to 3373 days. Overall, 28 patients developed I°, 18 patients II° and 2 patients III° acute toxicity. There were no severe late side effects (≥ III°) observed during the follow-up period. The most frequent chronic side effect was fatigue. One patient (2.1 %) developed pain and mild paresthesia in the ipsilateral arm after radiotherapy. After a follow-up of 557 days (41 to 3373 days), in 8 patients a recurrence was observed (16.7%). In 4 patients the recurrence involved the regional lymph node system. Hence, local control in the lymph node drainage system after a median follow-up of 557 days was 91.6 %.

Conclusion: If surgical re-dissection of residual lymph nodes is not feasible or refused by the patient, LN-SIB-irradiation can be considered as a potential treatment option. However, patients need to be informed about a higher risk of regional recurrence compared to surgery and an additional risk of acute and late toxicity compared to adjuvant radiotherapy without regional dose escalation.

Keywords: axillary therapy; breast cancer; lymph nodes; nodal positivity; simultaneous integrated boost; toxicity.