ESTRO 2023 - Abstract Book

S421

Sunday 14 May 2023

ESTRO 2023

We first confirmed in 2D cultures the ability of the reporter to specifically label cells in hypoxia. In 3D cultures of H1299 UnaG spheroids, UnaG-positive cells are located in the central part of the spheroids, and do not proliferate in untreated spheroids. Irradiation of H1299-UnaG spheroids leads to a significant enrichment of UnaG-positive cells, indicating that the hypoxic cells are the main surviving population that drives spheroid regrowth. Upon IR they retain the integrity of the inner spheroid core while increased cell death is observed in the UnaG-negative cells. The surviving UnaG-positive cells despite being reoxygenated remain arrested for a prolonged period before they start to proliferate and give rise to regrowing spheroids. Lastly, we generated H1299-UnaG xenograft tumors and found that UnaG-positive-cells coincide with pimonidazole-positive tumour areas and show absence of active cell cycle marker Ki-67 in untreated tumours. Upon IR, regrowing tumours show significantly higher percentage of UnaG-positive cells which are almost exclusively Ki67-positive compared to untreated controls revealed with cell-by-cell analysis of whole tumour cross-sections.

Conclusion Collectively, our data demonstrate the feasibility to track individual tumour cells that were hypoxic at the time of irradiation and provide proof that the hypoxic tumour cells drive tumour relapse after irradiation. OC-0512 Randomized trial of person-centered versus standard RTT care for breast cancer patients NCT04507568 M. Velec 1 , V. Hoang 1 , A. Cashell 1 , K. Bryant 1 , S. Chen 1 , R. Hyvarinen 1 , S. Kim 1 , G. Lee 1 , S. Lofgren 1 , S. Moledina 1 , D. Powell 1 , A. Vloet 1 , O. Wong 1 , A. Liu 1 , A. Santiago 1 , J. Nachman 1 , J. Croke 1 , A. Fyles 1 , R. Glicksman 2 , E. Hahn 1 , K. Han 1 , J. Helou 1 , F. Liu 1 , D. Rodin 1 , C.A. Koch 1 1 Princess Margaret Cancer Centre, Radiation Medicine Program, Toronto, Canada; 2 Princess Margaret Cancer Centre, Princess Margaret Cancer Centre, Toronto, Canada Purpose or Objective Patients with breast cancer have unmet informational needs and anxiety during radiotherapy. To address this gap, a person centered service was designed through Radiation Therapist (RTT)-led education and continuity-of-care over the whole radiotherapy pathway. The aim of this study was to determine if the person-centered model was more effective at reducing anxiety compared to standard care. Materials and Methods Breast cancer patients requiring locoregional radiotherapy were prospectively accrued and randomized (1:1) to the intervention or standard care arm. The intervention was a 1-on-1 pre-CT education session led in-person by an RTT with expertise in breast radiotherapy who subsequently performed CT, planning, treatment delivery and support for the same patient. Standard care had no dedicated RTT-led education session and was usually delivered by many different RTTs over the care pathway. Patient-reported endpoints collected using validated questionnaires were changes relative to baseline in anxiety (HADS-A) as the primary endpoint, and self-efficacy (PROMIS), treatment concerns (CaTS) and health engagement (PHE) as secondary endpoints. Changes over time and between arms were evaluated using linear mixed-effects models. Post-treatment satisfaction items (EORTC PATSAT) were compared using unadjusted Wilcoxon rank sum tests. Optional semi-structured interviews were conducted post-treatment to thematically analyze patients’ experiences using qualitative methods. Results Patients (109 total) were randomized to the intervention (54) or standard care (55). Median age overall was 51 (28-81), and the majority were treated with 40 Gy/15 fractions (94%) using a 4-field technique (93%) in active breath-hold (57%). Anxiety was significantly reduced post-treatment (Figure) although the magnitude was similar between arms (p=0.682). Procedural concerns were significantly reduced prior to the 1st fraction in the intervention arm (p=0.001). Other secondary outcomes were similar between arms (Table). Satisfaction improved with the intervention for provision of information (p=0.042), identifying care team roles (p=0.042) and overall hospital care (p=0.024). Thematic interview analysis (20 intervention, 21 standard care) demonstrated that patients highly valued pre-treatment RTT-led education, and appreciated having one consistent RTT (or a small, consistent team of RTTs) particularly at the start of treatment course, when intimidated by the breath-hold technique or for especially vulnerable individuals.