Impact of radiotherapy on loco-regional control

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Published: 28 Sep 2013
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Prof Ian Kunkler - University of Edinburgh, UK

Prof Ian Kunkler talks to ecancer at the 2013 European Cancer Conference (ECC 2013) in Amsterdam about technical and biological developments in breast radiotherapy; specifically the impact of radiotherapy on locoregional control.

The Oxford overview established that postoperative radiotherapy (RT) improves loco-regional control and survival in early breast cancer both after mastectomy and breast conserving surgery (BCS).

After BCS adjuvant RT roughly halves the risk of first recurrence. For patients at low risk of local recurrence, it is still uncertain whether there is a subset from whom RT may be safely omitted. Selection based on molecular subtype might provide a more reliable way of identifying benefit from RT.

There is limited literature on such correlations. To date molecular classification cannot reliably differentiate those at higher or lower risk of local recurrence after RT. After mastectomy in the DBCG 82b and 82c trials (Kyndi et al, 2008) adjuvant RT significantly reduces LRR in luminal hormone receptor (HR) positive/HER2 negative tumours (3% RT , 32% RT-), HR positive, HER2 positive (3% RT , 48% RT-) and triple negative cancer (15% RT , 32% RT-). No reduction in LRR was seen from PMRT in HER negative, HER2 positive patients, perhaps reflecting the impact of Trastuzumab on local control. Analysis of TRANS SUPREMO in the BIG 2–04 MRC/EORTC SUPREMO trial should provide prospective data on molecular subtypes and risk of LRR /− RT. The role of axillary RT in patients with a positive sentinel node biopsy (SNB) remains controversial.

Interpretation of the ACOSOG Z11 trial which showed no statistically significant difference in regional recurrence or DFS from axillary dissection vs no additional treatment is difficult due to the lack of adequate RT QA and failure to meet its target accrual. There is limited literature on the role of loco-regional radiotherapy in the context of neoadjuvant systemic therapy. Potentially the response to neoadjuvant chemotherapy measured at definitive surgery as residual tumour burden might individualise the need for locoregional therapy to the breast/chest wall and axilla (Smith, 2012). The role of axillary RT in this setting is under study in the recently launched NSABP-RTOG 9353 trial. The Alliance Cooperative Group trial is comparing axillary clearance and axillary RT in patients with residual nodal disease on SNB after neoadjuvant chemotherapy in T1–3, NI patients.