Post-op hypofractionated RT noninferior to conventional RT for early-stage breast cancer

Hypofractionated radiotherapy (HFRT) followed by HF tumour bed-boost may have similar tumour control without an increase in toxicities compared with conventional fractionated radiotherapy (CFRT) in patients with breast cancer after breast-conserving surgery (BCS), results of a multicentre, randomized, controlled trial have shown.

“The findings provide additional evidence supporting the clinical practice of hypofractionated radiotherapy [HFRT] in early-stage breast cancer patients,” suggested the researchers.

At a median follow-up of 73.5 months, the primary endpoint, 5-year cumulative incidence of local recurrence (LR), was 2.0 percent and 1.2 percent for CFRT group and HFRT group, respectively. Non-inferiority was confirmed for HFRT group. (hazard ratio [HR], 0.62; 95 percent confidence interval [CI], 0.20 to 1.88; p=0.017) [J Clin Oncol 2020, doi: 10.1200/JCO.20.01024]

The 5-year cumulative incidence of locoregional recurrence (LRR) for all patients was 3.0 percent, with the rate similar between HFRT group and CFRT group (3.1 percent vs 3.8 percent; HR, 1.15; 95 percent CI, 0.53 to 2.48; p=0.725).

Subgroup analysis showed comparable treatment effect, in terms of LR and LRR, between HFRT group and CFRT group regardless of prognostic factors, such as tumour stage, grade and lymphovascular invasion, or adjuvant chemotherapy (p>0.05).

The 5-year disease-free survival (DFS) and overall survival (OS) rates for all patients were 93.6 percent and 97.7 percent, respectively, was no significant difference in survival rates between CFRT group vs HFRT group (p>0.05).

Similar rates of acute and late toxicities were reported in CFRT group vs HFRT group, apart from a significantly greater number of grade 2–3 skin toxicities in the CFRT group (7.5 percent vs 3.0 percent; p=0.019). No grade 4–5 toxicity was observed in either groups.

With vs without regional nodal irradiation (RNI) led to 0 percent vs 2 percent of grade 2 pulmonary toxicity, 50.8 percent vs 9.5 percent of lymphedema, 11.8 percent vs 2.2 percent of shoulder mobility and 30 percent vs 7.8 percent of lung fibrosis.

Incidence of excellent/ good breast cosmesis was 88.5 percent for CFRT group vs 89.9 percent for HFRT group at baseline. Among 688 patients with cosmetic assessment at 3 years, incidences of excellent, good, fair and poor breast cosmesis as well as breast pain and breast induration were comparable between CFRT group and HFRT group. Incidence of excellent/ good breast cosmesis and breast pain was 88.7 percent vs 89 percent and 5.8 percent vs 5.5 percent for CFRT vs HFRT groups, respectively.

The trial included 734 patients (median age, 46 years) from 4 Chinese institutions with T1–2N0–3 invasive breast cancer who had undergone BCS. Patients were randomized (1:1) to receive WBI with or without regional RNI, followed by tumour bed-boost, either at a dose of 50 Gray (Gy) in 25 fractions over 5 weeks with a standard tumour-bed boost at 10 Gy in 5 fractions over 1 week (CFRT; n=366) or 43.5 Gy in 15 fractions over 3 weeks with an HF tumour-bed boost at 8.7 Gy in 3 daily fractions (HFRT; n=368).

At baseline, a total of 477 patients (65.4 percent) received chemotherapy (median, 6 cycles), mostly with taxane-based (76.1 percent) or anthracycline-based (21.0 percent) regimens.

The median time between surgery and the start of radiotherapy was 2.3 months. Tumour-bed boost was given to all, expect two patients, following WBI. Supra/infraclavicular NI and axillary NI was given to 26 patients (3.6 percent) and 2 patients (0.3 percent), respectively.

Almost all (97.4 percent) patients received radiotherapy in the form of intensity-modulated radiotherapy (IMRT) with remaining 2.6 percent of patients received 3-dimensional conformal radiotherapy.