ESTRO 2024 - Abstract Book

S604

Clinical - Breast

ESTRO 2024

29.4 days, with a single dose (SD) of 2.66 Gy and a total dose (TD) of 42.56 Gy. The biologically effective dose (BED) was 99.2 Gy. The biological equivalent dose for the standard regimen at 2.0 Gy (EQD2) was 49.6 Gy. In the standard RT (SRT) group, 69 patients (50.4%) underwent 25 sessions over an average of 42.3 days with SD of 2.0 Gy, TD of 50.0 Gy, BED of 100.0 Gy, and EQD2 of 50.0 Gy. All patients received RT of the anterior chest and regional lymph nodes including supraclavicular 3DCRT and IGRT. The mean SR was 47.3 Gy in the experimental group, and 54.8 Gy – in the standard group. Monitoring median was 29.3 months.

Results:

Tonsillitis was detected at follow-up CT in 32 (23.4%) of 137 patients, with a detection period of 22.2 months after the end of RT (6.2 to 40.9 months). Moreover, tonsillitis developed in 15 patients (22.1%) of the HFRT group, and in 17 patients (24.6%) of the SRT group. The maximum thyroid dose was an average of 39.8 Gy for HFRT group patients, and an average of 44.2 Gy for SRT group patients. The mean thyroid dose was an average of 17.6 Gy for HFRT group patients, and an average of 22.6 Gy for SRT group patients. The maximum thyroid dose was an average of 43.0 Gy for patients who developed tonsillitis, and an average of 41.7 Gy for those who did not (p = 0.56). The mean thyroid dose was 22.3 Gy for patients who developed tonsillitis, and 19.5 Gy for those who did not (p = 0.037). Threshold level In the HFRT group, when tonsillitis developed, the maximum dose was on average 44.8 Gy, the mean thyroid dose was 22.7 Gy. In the SRT group, when tonsillitis developed, the maximum dose was an average of 41.4 Gy, the mean thyroid dose was 21.9 Gy. That said, the average received TD in HFRT group when tonsillitis developed was 45.2 Gy, in SRT group – 56.6 Gy, while the average received TR in HFRT group when tonsillitis did not develop was 47.9 Gy, in SRT group – 54.2 Gy. A pattern was found, that development of tonsillitis was most common among thinner women, whose body mass index (BMI) was up to 25; 17 of 41 of them (41.5%) developed tonsillitis, by contrast with only 15 of 96 women (15.6%) with BMI greater than 25, χ2 = 10.7, df = 1, p = 0.001. Tonsillitis was also most likely to develop among breast left side RT (22 of 77 (28.6%) women developed tonsillitis), by contrast with only 10 of 60 women (15.6%) with breast right side RT, χ2 = 2.67, df = 1, p = 0.102. With tonsillitis development, only 15.6% of patients were detected to have COVID-19, although among patients who did not develop tonsillitis, COVID-19 was detected in 25.7% of patients.

Conclusion:

Tonsillitis happens at average mean thyroid dose above 22 Gy, in women with left side breast cancer with BMI up to 25 in 22.2 months on average.

Keywords: breast cancer, tonsillitis, hypofractionated RT