Abstract 3736
Background
For decades, conventionally fractionated whole breast irradiation (CF-WBI) was used after breast conserving surgery (BCS). Pivotal phase 3 trials on hypofractionated-WBI (HF-WBI) showed its non-inferiority as compared to CF-WBI. However, younger patients (<60 years) are not currently worldwide treated with HF-WBI. The aim of this multi-center comparative study is to confirm the safety of HF-WBI in a real-life series of younger patients.
Methods
Between 2010 and 2016, a total of 786 patients aged less than 60 years old with early stage breast cancer were treated with postoperative WBI after BCS in three breast cancer centers: 340 underwent HF-WBI while 446 were treated with CF-WBI. Acute toxicity was evaluated at the end of WBI. Late toxicity was evaluated at 6, 12, 24, and 36 months.
Results
At univariate logistic analysis, hypofractionation showed a significant protective effect in terms of acute edema (p = 0.0001), acute wet desquamation (p = 0.009), chronic edema (p = 0.0001), chronic erythema/pigmentation (p = 0.0001), and breast fibrosis (p = 0.0002). At multivariate logistic analysis, hypofractionation was independent significant factor for acute edema (OR 0.09, 95% CI 0.02 to 0.48; p = 0.005), acute wet desquamation (OR 0.07, 95% CI 0.009 to 0.59; p = 0.014), and chronic edema (OR 0.18, 95% CI 0.04 to 0.75; p = 0.018). Significant association between individual characteristics and toxicity (grade 2 or more) are summarized in Table.Table:
215P
| Toxicity | N | Protective factor | p-value | OR (95%CI) | Risk factor | p-value | OR (95%CI) |
|---|---|---|---|---|---|---|---|
| Acute edema | 43 | Hypofractionation Dmax/Prescribed dose° <107% | 0.0001 0.001 | 0.09 (0.03-0.30) 0.16 (0.06-0.46) | Chemotherapy | 0.002 | 2.63 (1.42-4.90) |
| Chronic edema | 50 | Hypofractionation Dmax/Prescribed dose° <107% | 0.0001 0.003 | 0.20 (0.09-0.44) 0.31 (0.14-0.66) | EIC presence Boost dose >10 Gy Breast size >492 cc | 0.0001 0.032 0.003 | 3.0 (1.66-5.46) 9.02 (1.21-67.45) 2.67 (1.41-5.05) |
| Acute erythema/ pigmentation | 163 | HER2 positive status Trastuzumab | 0.002 0.022 | 0.30 (0.14-0.63) 0.39 (0.18-0.87) | Smoking habits Boost dose >10 Gy Breast size >492 cc | 0.001 0.038 0.002 | 2.14 (1.37-3.32) 2.60 (1.06-6.41) 1.78 (1.24-2.54) |
| Chronic erythema/ pigmentation | 110 | Hypofractionation Dmax/Prescribed dose° <107% | 0.0001 0.001 | 0.40 (0.25-0.63) 0.45 (0.28-0.73) | EIC presence Positive FSM Boost dose >10 Gy Breast size >492 cc | 0.0001 0.002 0.007 0.034 | 2.39 (1.54-3.71) 3.47 (1.56-7.71) 15.43 (2.08-114.3) 1.58 (1.04-2.41) |
| Acute wet desquamation | 20 | Hypofractionation Dmax/Prescribed dose° <107% | 0.009 0.047 | 0.14 (0.03-0.61) 0.29 (0.08-0.99) | - | - | - |
| Breast fibrosis | 117 | Hypofractionation Tumor grade Ki67 index Dmax/Prescribed dose° <107% | 0.0002 0.022 0.023 0.017 | 0.44 (0.29-0.68) 0.53 (0.31-0.92) 0.60 (0.38-0.93) 0.58 (0.37-0.91) | EIC presence Boost dose >10 Gy Breast size >492 cc | 0.0001 0.022 0.0001 | 3.03 (1.99-4.62) 6.76 (2.04-22.45) 2.84 (1.83-4.41) |
Conclusions
HF-WBI showed significantly improved toxicity outcomes in terms of both acute skin edema and wet desquamation, and chronic skin edema. HF-WBI after BCS should replace CF-WBI independently of age.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.
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