One versus three weeks hypofractionated whole breast radiotherapy for early breast cancer treatment: the FAST-Forward phase III RCT.

Background

FAST-Forward aimed to identify a 5-fraction schedule of adjuvant radiotherapy delivered in 1 week that was non-inferior in terms of local cancer control and as safe as the standard 15-fraction regimen after primary surgery for early breast cancer. Published acute toxicity and 5-year results are presented here with other aspects of the trial.

Design

Multicentre phase III non-inferiority trial. Patients with invasive carcinoma of the breast (pT1-3pN0-1M0) after breast conservation surgery or mastectomy randomised (1 : 1 : 1) to 40 Gy in 15 fractions (3 weeks), 27 Gy or 26 Gy in 5 fractions (1 week) whole breast/chest wall (Main Trial). Primary endpoint was ipsilateral breast tumour relapse; assuming 2% 5-year incidence for 40 Gy, non-inferiority pre-defined as < 1.6% excess for 5-fraction schedules (critical hazard ratio = 1.81). Normal tissue effects were assessed independently by clinicians, patients and photographs.

Sub-studies

Two acute skin toxicity sub-studies were undertaken to confirm safety of the test schedules. Primary endpoint was proportion of patients with grade ≥ 3 acute breast skin toxicity at any time from the start of radiotherapy to 4 weeks after completion. Nodal Sub-Study patients had breast/chest wall plus axillary radiotherapy testing the same three schedules, reduced to the 40 and 26 Gy groups on amendment, with the primary endpoint of 5-year patient-reported arm/hand swelling.

Limitations

A sequential hypofractionated or simultaneous integrated boost has not been studied.

Participants

Ninety-seven UK centres recruited 4096 patients (1361:40 Gy, 1367:27 Gy, 1368:26 Gy) into the Main Trial from November 2011 to June 2014. The Nodal Sub-Study recruited an additional 469 patients from 50 UK centres. One hundred and ninety and 162 Main Trial patients were included in the acute toxicity sub-studies.

Results

Acute toxicity sub-studies evaluable patients: (1) acute grade 3 Radiation Therapy Oncology Group toxicity reported in 40 Gy/15 fractions 6/44 (13.6%); 27 Gy/5 fractions 5/51 (9.8%); 26 Gy/5 fractions 3/52 (5.8%). (2) Grade 3 common toxicity criteria for adverse effects toxicity reported for one patient. At 71-month median follow-up in the Main Trial, 79 ipsilateral breast tumour relapse events (40 Gy: 31, 27 Gy: 27, 26 Gy: 21); hazard ratios (95% confidence interval) versus 40 Gy were 27 Gy: 0.86 (0.51 to 1.44), 26 Gy: 0.67 (0.38 to 1.16). With 2.1% (1.4 to 3.1) 5-year incidence ipsilateral breast tumour relapse after 40 Gy, estimated absolute differences versus 40 Gy (non-inferiority test) were -0.3% (-1.0-0.9) for 27 Gy (

Interpretation

Five-year local tumour incidence and normal tissue effects prevalence show 26 Gy in 5 fractions in 1 week is a safe and effective alternative to 40 Gy in 15 fractions for patients prescribed adjuvant local radiotherapy after primary surgery for early-stage breast cancer.

Future work

Ten-year Main Trial follow-up is essential. Inclusion in hypofractionation meta-analysis ongoing. A future hypofractionated boost trial is strongly supported.

Trial registration

FAST-Forward was sponsored by The Institute of Cancer Research and was registered as ISRCTN19906132.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 09/01/47) and is published in full in

Patients diagnosed with early breast cancer are often recommended to have radiotherapy after surgery because research has shown that it lowers the risk of the cancer returning. However, it may cause some short- and long-term side effects. Previous clinical trials showed that the same, or even better, outcomes with a lower total dose of radiotherapy given in fewer, larger daily doses compared with older historical treatment schedules. The National Institute for Health and Care Research Health Technology Assessment Programme-funded FAST-Forward Trial aimed to see whether the number of doses could be reduced further without reducing the beneficial effects of radiotherapy. Between November 2011 and June 2014, 4096 patients agreed to take part in the FAST-Forward Main Trial testing three schedules of radiotherapy to the breast. Standard treatment given on 15 days over 3 weeks (Control Group) was compared with two different lower dose schedules where treatment was given on 5 days over 1 week (lower dose Test Groups). An additional 469 patients entered a sub-study where the gland area under the arm also received radiotherapy (Nodal Sub-Study). Main Trial 5-year results reported in April 2020 showed that the number of patients whose cancer had returned in the treated breast was low in all groups: around 2 in 100 (2.1%) for the Control Group, and 1.7% in the higher dose and 1.4% in the lower dose Test Groups. The majority of reported side effects assessed by patients and doctors up to 5 years after radiotherapy were mild for all treatment groups. Patients in the Control Group and in the lower dose Test Group experienced similar levels of side effects. More side effects were reported in the higher dose Test Group, although differences were small. Overall, the FAST-Forward findings suggest that the lower dose 1-week schedule gave similar results in terms of the cancer returning and side effects to the standard 3-week treatment and this schedule can now be used to help treat future patients.