ESTRO 2024 - Abstract Book
S611
Clinical - Breast
ESTRO 2024
Patients’ characteristics are shown in Table 1. Group A median age was 69 years (range: 46 – 87) VS 71 years (range: 46 – 84) for Group B (p = 0.16); five PBI (5.6%) and 4 (4.5%) WBI patients had diabetes (p = 0.73); T-stage was 1 for every patient. The most striking difference was the median follow-up: 37 (5 – 109) VS 67 (53 – 155) months for Groups A and B, respectively (p < 0.0001). Radiologically detected fat necrosis occurred in 29 (33.0%) PBI patients, with a median time interval from RT end to fat necrosis diagnosis of 8 months (range: 3 – 31). In the WBI group, fat necrosis rate was 28/88 (31.8%), with a median time of insurgence of 24 months (range: 5 – 66) after the end of RT. Kaplan-Meyers curves for the actuarial rates of fat necrosis after PBI vs WBI are shown in Fig.1. The chi-squared test proved no significant difference between the two groups regarding crude rates of fat necrosis (p = 0.87). The Cox regression resulted in a Hazard Ratio (HR) of 1.5 [95% Confidence Interval: 0.86 to 2.5, p = 0.16] for the fat necrosis rate for PBI vs WBI. The present population of 176 patients does not have the statistical power to detect HRs<2.6 as significant. The results from Cox regression remain inconclusive and a larger population size is needed to clarify the issue ( ∼ 800 patients).
Table 1. Patients Characteristics PBI
WBI
p-value
Total patients
88
88
Age
69 (46 – 87)
71 (46 – 84)
0.16 0.73 0.36
Diabetes
5 (5.6%)
4 (4.5%)
Hypertension
43 (48.9%)
37 (42.0%)
T-stage = 1
88 (100%)
88 (100%)
Hormonal Therapy
66 (75.0%)
77 (87.5%)
0.03
Median Follow-up
37 (5 – 109) months
67 (53 – 155) months
< 0.0001
RT technique
VMAT (100%)
3D (100%)
Fat Necrosis 0.87 PBI: Partial Breast Irradiation; WBI: Whole Breast Irradiation; RT: Radiation Therapy; VMAT: Volumetric Modulated Arc Therapy. 29 (33.0%) 28 (31.8%)
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