Interventions
Explanation for the choice of comparators
{6b}
One week hypofractionated radiotherapy is likely to become the standard
for delivery of breast adjuvant radiotherapy if the results of the FAST
Forward trial support the primary objective. Hence the current trial
will also test a one-week regimen. The three-week course of radiotherapy
used in the control arm has already demonstrated non-inferiority in
terms of oncological outcomes in the START trials. Currently, this is
the standard radiotherapy schedule used for most breast cancer patients
in the participating centers.
Intervention Description
{11a}
Overview
Patients will be randomized into two arms equally:
- Control Arm: 40 Gy in 15 fractions over 3 weeks to the whole
breast or chest wall. Patients undergoing breast conservation therapy
will receive additional boost radiotherapy to the tumour bed. The
supraclavicular fossa will be treated in patients with node-positive
disease or those receiving neoadjuvant chemotherapy. IMC and Axillary
radiotherapy will be given as per the institutional policy. Boost
radiotherapy will be delivered using SIB of 8 Gy in 15 fractions (or
alternatively using a sequential boost of 12 Gy in 4 fractions)
- Test Arm: 26 Gy in 5 fractions over 1 week to the whole
breast or chest wall. Treatment volumes will be the same as the
control arm. Additional boost will be delivered to patients who have
undergone breast conservation. Boost radiotherapy will be delivered
using SIB of 6 Gy in 5 fractions (or alternatively using a sequential
boost of 12 Gy in 4 fractions)
Radiotherapy
Radiotherapy should be started within 12 weeks of the last date of
surgery or last cycle of planned adjuvant chemotherapy. All patients
would be treated on linear accelerators (6 - 15 MV energies).
Radiotherapy planning would be performed on volumetric planning CT scans
with a pre-defined simulation protocol. Patients with left sided breast
cancers should preferably receive cardiac sparing radiotherapy. Field
based planning for the breast and chest wall is allowed in the protocol
where anatomical landmarks are identified and coverage ensured. This is
the current practice in most of the centers in this trial.
The organs at risk to be delineated include the ipsilateral and
contralateral lung, heart, and the contralateral breast. In patients
undergoing radiotherapy for left sided breast, the left anterior
descending artery may also be delineated
(31). The brachial plexus
may be delineated in patients undergoing regional nodal radiation
(32).
Tangential beams would be utilized for irradiating the breast or chest
wall, while regional nodal radiation should be delivered using a
technique that ensures no overlap of the field - in most patients, this
would imply a enface field to cover the supraclavicular fossa (SCF) with
a half beam block or a collimator-couch rotation based technique. Dose
will be prescribed at a point in the midplane for the breast and chest
wall for tangents. For patients receiving SCF radiation, the dose will
be prescribed at the depth of maximum dose (Dmax). In patients who have
undergone breast conservation, boost will be delivered using the
technique used in the institute. Use of a volumetric modulated arc
therapy (VMAT) based Simultaneous Integrated Boost (SIB) for tumor bed
irradiation is allowed. Inverse planned radiation is allowed for
patients receiving radiation to the internal mammary nodal chain.
Dose in the target volume should be homogenous and use of a forward
planned field in field IMRT technique is allowed. Alternatively centers
can specify the technique to be used for ensuring dose homogeneity.
Individualized treatment planning will be done with a target to ensure
that the breast/chest wall is covered with 95% of the prescribed dose
and that the maximum dose does not exceed 107% of the prescribed dose.
In patients undergoing VMAT simultaneous tumour bed boost (SIB), the
dose to the boost target volume will be restricted to < 107%
of the total dose.
Table 2 shows the dose constraints to be used for plan evaluation.