Critical volume

This secondary analysis of the above DBCG PBI trial begs the question of whether it is breast volume or the volume of irradiated breast that is the true predictor of chronic induration after radiation. The breast CTV was contoured in both arms of DBCG-PBI. The authors evaluated dose-volume statistics from patient treatment plans from the trial. While it’s not surprising that the volume of irradiated breast predicted the risk of induration, irradiated breast volume (i.e. V40) was a better predictor than absolute breast volume. Breast volume and irradiated volume are related, but this means that those with large breasts benefit most from techniques such as IMRT or PBI that improve dose homogeneity. Furthermore, the use of >2 beam angles may further reduce the risk of induration when delivering PBI.