Session Item

Helical tomotherapy (HT) is a rotational intensity modulated radiation therapy (IMRT) technique, which allows conformal target irradiation and efficient cardiac sparing in case of complex target volumes and of specific anatomic considerations. However, HT increases low-dose bath to non-target volumes (such as the lungs, the contralateral breast or the liver), which late consequences are still poorly known. The aim of this study was to analyze late hepatic toxicities after irradiation of non-metastatic breast cancer with HT.

This single center retrospective study included all non-metastatic breast cancer patients treated with tomotherapy between 01/10 and 01/21 at the IC (Paris, France), with a biological hepatic function considered as normal before irradiation and re-assessed after more than 1 year without metastatic disease at this reevaluation time point, and for whom the dosimetric parameters to the whole liver were assessable. Biological hepatic function evaluation included γGT, ALT, AST, total bilirubin and LDH. Mean and maximum dose to the liver were retrieved from DVH.

A logistic regression analysis was carried out with cancer laterality, obesity, chemotherapy, hormonotherapy, trastuzumab, mean and maximum dose as explanatory variables for late biological hepatic toxicity perturbation. The selected covariates for the multivariate analysis were those with a p-value less or equal to 0.20 in the univariate analysis. Significance level was 0.05.

Forty-nine patients were included in this study; 15 patients (31%) received neoadjuvant chemotherapy, 28 patients (57%) adjuvant chemotherapy, 11 patients (22%) Trastuzumab for 1 year for HER2-expression tumors, and 38 patients (78%) hormonotherapy; 27 patients (55%) were irradiated for a right breast cancer; 43 patients (88%) received lymph node irradiation and 41 patients (84%) a tumor bed boost. Median total prescription dose was 63.8 Gy [40-66]. Median mean and maximum dose to the liver were 2.8 Gy [0.3-16.6] and 26.9 Gy [0.7-51.7], respectively.

At a median follow-up of 56 months, 11 patients (22%) developed low grade late biological hepatic perturbation: all patients had late grade 1 hepatic toxicities predominating on γGT (5 patients) and ALT (3 patients); 3 patients (6%) had additional late grade 2 hepatic toxicities (γGT, ALT and total bilirubin increase). There was no grade ≥3 toxicity.

Univariate and multivariate analysis, Trastuzumab was a significant predictor variable of late biological hepatic toxicity (OR=4.4 [1.01-20.18], p=0.04). No other variable was significant.

Late hepatic toxicity was negligible after multimodal management of non-metastatic breast cancer including tomotherapy irradiation and was not influenced by irradiation side or radiation doses delivered to the liver, which were usually low. Consequently, liver may not be a relevant organ-at-risk when planning breast cancer tomotherapy.