Postmastectomy radiation in breast cancer with one to three involved lymph nodes: ending the debate
Menée à partir des données de 22 essais cliniques portant au total sur 8 135 patientes atteintes d'un cancer du sein traité entre 1964 et 1986, cette méta-analyse évalue l'intérêt d'une radiothérapie, après mastectomie et curage ganglionnaire, pour réduire le taux de récidive à 10 ans et la mortalité à 20 ans
Many trials in breast cancer have investigated various aspects of locoregional and systemic treatments. Combination of the results of these trials in a meticulous meta-analysis, as has been done several times by the Early Breast Cancer Trialists' Collaborative Group (EBCTCG), fills the gaps in evidence and knowledge by conclusively showing significant trends and differences.
Following publication of the effect of radiotherapy after breast-conserving therapy,1 the EBCTCG now presents results for postmastectomy radiotherapy in The Lancet.2 The central issue is the role of postmastectomy radiotherapy in patients with one to three involved axillary lymph nodes, which is currently a matter of debate in many countries.3 Whereas the earlier results were essentially confirmed in this report,1, 4 we get more insight into the effect of the extent of lymph-node involvement, the number of examined axillary lymph nodes, and the use of adjuvant systemic therapy. Overall, postmastectomy radiotherapy improves locoregional disease-free survival, overall disease-free survival, and breast-cancer-specific survival for all patients with involvement of axillary lymph nodes, irrespective of the number of involved lymph nodes and of administration of adjuvant systemic therapy. This improvement is not only statistically significant, but also clinically relevant.
The proportional reductions in rates of recurrence and mortality were independent of the administration of systemic therapy. Whether this finding also applies to patients treated with more contemporary regimens remains to be seen. We need to continue evaluating results of the contemporary multidisciplinary approach in breast cancer to better understand the complex interaction between respective contributions of systemic and locoregional treatments to the final outcome, including survival and toxic effects. As Punglia and colleagues5 pointed out, the contribution of improved locoregional control to survival depends on the effectiveness of systemic treatment. Punglia and colleagues' bell-shaped curve,5 however, misses the component of metastatic risk of the primary tumour. Combining both, the influence of both the effectiveness of systemic therapy and metastatic risk of the primary tumour can be used to estimate the contribution of improved locoregional treatment to the final outcome (figure). For many patients, improvement of systemic therapy will decrease the risk of death due to distant metastasis, after which the importance of optimised locoregional control—which will already be better after systemic treatment—will, relatively, contribute more to survival.
The Lancet , commentaire, 2013