ESTRO 2023 - Abstract Book

S1017

Digital Posters

ESTRO 2023

PO-1272 Targeted axillary sampling postprimary chemotherapy data analysis from a single unit in South Africa

C. Benn 1 , D. van Loggerenberg 2 , M. Hugo 3

1 Milpark Breast Care Centre of Excellence, Breast , Johannesburg, South Africa; 2 Milpark Breast Care Centre of Excellence, Research, Johannesburg, South Africa; 3 Milpark Breast Care Centre of Excellence, Radiation Oncology, Johanensburg, South Africa Purpose or Objective The Netcare Milpark Breastcare Centre of Excellence is an internationally accredited breast unit based in South Africa. Global breast cancer management trends have changed from a less structured approach to a more biological approach, with increase in neoadjuvant chemotherapy (NAC) and a decrease in axillary lymph node dissection. In keeping with this, a total of 2558 newly diagnosed cancer patients were seen at our unit from 2016-2020, of which between 36 and 42% per year receive primary/neoadjuvant chemotherapy as their initial treatment for breast cancer. Standard of care post-NAC has traditionally required an axillary dissection. Recently, targeted axillary dissection has been postulated and studied in many academic units. Thus, in this paper, we analyze the data from patients who underwent targeted axillary node sampling post-NAC over a four year period at our unit. Materials and Methods The study is a retrospective review. 953 patients who underwent NAC and subsequent targeted axillary node sampling between January 2016 to December 2020 were included. Data was anonymised and a secondary record analysis was performed. The following data points were collected for each patient:

•Response post-chemotherapy •Pathological nodal staging at biopsy •Number of nodes sampled post-NAC •Type of surgical intervention (mastectomy vs breast-conserving surgery) •Follow-up status post

Patients were followed up with serial mammograms and/or ultrasounds for a period of 1 to 5 years.

Results *Table(s) to show the results found on analysis of patients who underwent NAC and axillary node sampling from 2016-2020

Cancer sub-type % at diagnosis Luminal A: 21.5-22 Luminal B 33.5-34 Triple Neg: 21 Her 2: 23

Pathological nodal (Pn) staging at surgery: Pn0: 59% Pn1: 21%

Pn1: 4% Pnx: 4% Pn2: 2% Pn1a: 6%

On average, 3 nodes were retrieved per patient

Response post-chemotherapy 60% of patients in our setting had a full pathological response.

Conclusion No patients presented with recurrence following targeted axillary sampling after having received neoadjuvant chemotherapy, surgery and radiation. Thus, targeted axillary node sampling is shown to be safe in this cohort of patients with no nodal recurrences documented thus far on routine radiological follow-up.

PO-1273 Anatomic predictor of contralateral breast exposure in breast cancer radiotherapy

Z. Naimi 1 , M. El Bessi 1 , M. Bohli 1 , R. Ben Amor 1 , A. Hamdoun 1 , R. Haddad 1 , L. Kochbati 1

1 Abderrahmen Mami Hospital, Radiation Oncology Department, Ariana, Tunisia

Purpose or Objective This study aimed to analyse the correlation between contralateral breast (CLB) exposure and patient’s specific anatomic parameters in breast cancer radiotherapy and to investigate whether these parameters could reliably predict doses to CLB. Materials and Methods Data of 150 patients planned for adjuvant 3D conformal breast cancer radiotherapy were evaluated. Radiotherapy was delivered by tangential fields +/- supraclavicular field, using a mono-isocentric technique and a hypofractionated schedule (40 Gy delivered in 15 daily fractions +/- an additional boost of 13.35 Gy). The CLB was contoured based on the ESTRO