[Acute skin toxicity in breast intensity modulated radiotherapy using field in field technique]

The optimization with presegmentation irradiation technique (Dosisoft™), used in treatment of breast carcinomas, facilitates the treatment delivery and improves radioprotection. The objective of our study was to evaluate the potential impact of this innovative technique on the acute skin toxicity especially on the rate of moist desquamation during irradiation of the whole breast after conservative surgery.

The scores of acute skin toxicity observed at 50 Gy in 103 patients treated with the presegmentation technique were compared to those of 101 patients with similar breast size treated with a classic 3D technique. All patients received 50 Gy/2 Gy per fraction, 5 days a week using 4 MV photon beam. The boost on the tumoural bed was realized according to conventional technique. Using the NCI-CTCAE V4, the skin toxicity was recorded every week during the medical visit. Moreover, the following factors that could induce skin toxicity have been studied: breast size, body mass index, age, prior chemotherapy, concurrent administration of trastuzumab, hypertension, diabetes, smoking habits and statin uptake.

The incidence of moist desquamation observed in all sites, has been decreased to only 9.8% in the presegmentation group versus 16.8% in the test group, the difference being not statistically significant OR=0.53 [0.23; 1.22] (P=0.13). In univariate analysis the presegmentation technique enabled a significant decrease of 4.4 Gy in mean, of the value of maximum dose (P=0.001). The other risk factors of skin toxicity are the increase of breast size (P<0.001), a high body mass index (P<0.001), hypertension (P=0.03) and concurrent administration of trastuzumab (P=0.07). In multivariate analysis, the two remaining significant factors are breast size (OR=1.004 [1.002; 1.006]) and trastuzumab administration (OR=4.95 [1.17; 20.79]).

The comparison of the skin toxicity induced by the presegmentation or the reference technique shows a trend regarding the improvement of the skin tolerance when using the presegmentation technique, thus pleading in favour of its use considering its dosimetric interest and the improvement of radioprotection of the patient. The next step will consist to experiment the simultaneous boost on tumoural bed using this technique.