Managing supraclavicular disease from breast cancer with brachial plexus-sparing techniques using helical tomotherapy

Managing supraclavicular fossa (SCF) disease in patients with breast cancer can be challenging, with brachial plexopathy recognised as a complication of high-dose radiotherapy to the SCF. Local control of SCF disease is an important end point. Intensity-modulated radiotherapy (IMRT) techniques provide a steep dose gradient and improve the therapeutic index, making it possible to escalate dose to planning target volumes (PTVs), while reducing the dose to organs at risk (OAR). We explored image-guided IMRT techniques using helical tomotherapy to dose escalate SCF lymph nodes with a view to restrict the dose to the brachial plexus.

Three cases with SCF nodal disease in varying clinical stages of breast cancer were planned and treated using helical tomotherapy-IMRT to assess the feasibility and safety of radiotherapy dose escalation to improve the chances of local control in SCF while restricting the dose to the brachial plexus. Consultant clinical oncologists were asked to define the PTVs and OARs as per agreed inhouse policy. The brachial plexus was outlined as a separate OAR in all three cases. In case 1 the left breast and SCF were treated with adjuvant radiotherapy (40 Gy in 15 fractions) with a sequential boost (10 Gy in five fractions) to the SCF PTV. In case 2, local recurrence was salvaged using a simultaneous integrated boost to the gross tumour plus a 3 mm margin to 63 Gy and 54 Gy to the entire SCF. Case 3 was to control nodal disease with re-irradiation of the SCF to a median dose of 44 Gy, while maintaining a low dose to the brachial plexus. Inverse planning constraints (helical tomotherapy) were applied to the PTV and OARs with the brachial plexus allowed a maximum biologically effective dose (BED) of 120 Gy.

It was possible to treat the SCF to a higher dose using helical tomotherapy-IMRT. The treatment was successful in controlling disease in the SCF. No patients reported symptoms suggestive of brachial plexopathy.

Sequential or simultaneous integrated boost to the SCF was safe and feasible. This is the first publication of dose escalation to the SCF when treating breast cancer with brachial plexus-sparing IMRT techniques. The feasibility of such techniques warrants a multicentre phase II study of dose escalation with IMRT to improve local control in isolated SCF disease.