The toxicity of hybrid techniques combining hypofractionated whole breast radiotherapy with concomitant tumor bed boost in patients with breast cancer.

BACKGROUND

We examined the acute toxicity of hypofractionated breast radiotherapy (HFRT) with hybrid techniques combining field-in-field intensity-modulated RT (FIF-IMRT) to the whole breast (WB) with inverse-IMRT for concomitant boost (CB) to the tumor bed.

METHODS

This prospective exploratory study enrolled patients with early-stage breast cancer (EBC) or breast ductal carcinoma in situ (DCIS) from January 2020 after breast-conserving surgery. All patients consistently received a 16-fraction hybrid 40 Gy FIF-IMRT plans for WB, CB 8 Gy inverse-IMRT to the tumor bed (hybrid-CB group). Identical contours and planning target volume coverage were replanned with conventional tangential FIF-IMRT for WB (50 Gy in 25 fractions), followed by electron beams to the tumor bed (10 Gy in 5 fractions) (sequential group).

RESULTS

We enrolled 25 patients with EBC and 9 with breast DCIS; 2 (5.9 %) patients had grade 2 acute radiation dermatitis, and 5 (14.7 %) patients had grade 1 skin fibrosis. No recurrence was observed during the median follow-up of 44 months. Mean homogeneity index in the hybrid-CB and sequential groups were 8.9 and 18.6, respectively (p < 0.01). Considering left-sided disease, we found no significant differences in mean, maximal dose, and V5 of heart between groups (p = 0.09, 0.80, and 0.06). V20 values of the ipsilateral lung dose were 13.0 % and 12.9 % (p = 0.47) in the hybrid-CB and sequential groups, respectively, while normal tissue complication probability parameters for breast fibrosis were 20.02 % and 22.13 %, respectively (p < 0.01).

CONCLUSION

HFRT combined with FIF-IMRT for WB with inverse-IMRT CB to the tumor bed causes rare acute radiation dermatitis and decreases moderate-to-severe breast fibrosis without compromising disease control.