Boost dosage to the excision site following conservative surgery for breast cancer: it's easy to miss!

Surgical haemoclips have been left in situ in 27 consecutive patients conservatively operated on for early breast cancer by two surgeons in Newcastle, New South Wales, to demarcate the limits of the excision cavity for accurate postoperative irradiation. As anticipated, the position of these clips varied widely in relation to the patient's recollection of the position of the original lump, the surgical notes, and the surgical scar. In addition the dimensions of the clipped area also varied considerably. So great was the variation in position of the clips that incomplete coverage of the excision cavity in the 'coronal' (en face) plane using an electron field could have occurred in an estimated 10/24 (42%) evaluable cases had surgical clips not been left in situ. Depth of the surgical clips below the skin surface also varied markedly between patients. In 19/26 (73%) evaluable cases the clips were observed to be sited 3 cm or more below the skin surface, while in only 5/26 (19.2%) were the clips found to be 2 cm or less deep to the surface. Had a 9 MeV beam from our Clinac 1800 been used to treat all the cases, a major underdose of the excision cavity would have been likely in 21/26 (81%) evaluable cases. This figure would be improved to 11/26 (42%) had a 12 MeV beam been used--still a very high figure. Neither of these points have received much attention in the literature. This small study sounds a distinct warning and needs to be repeated on a larger scale.