Current perception for negative and close margins in breast conserving therapy: results from the MGH international survey

Abstract

Purpose/Objective: A large number of studies have demonstrated increased local recurrence rates when margins remained positive after local excision as compared to negative ones, especially with longer follow-up times. Therefore, it is imperative to obtain clear negative margins. However the definition for negative margins remains controversial. The purpose of this study is to survey how radiation oncologists in the US and Europe define negative or close margins and to evaluate the decision for re-excision based on margin status in the USA. Materials/Methods: A questionnaire was sent to active members of ESTRO (431) and ASTRO (667 responses) who completed training and see at least 5 breast cancer patients weekly. Negative or close margins were categorized into no tumor cells at the ink, <1mm, <2mm, <3mm, <5mm & <10mm from the inked margins. European results were divided into 7 groups: East=Eastern Europe; UK=Great Britain & Ireland; France=France & Belgium; Germ=Germany, Austria, & Switzerland; ItGr=Italy & Greece; Scan=Netherlands, Sweden, Finland, Denmark; Spain=Spain & Portugal. To evaluate re-excision recommendations based on margins for invasive, DCIS grade 3 and grade 1/2, a second survey was sent to 500 random radiation oncologists in the US with 130 respondents. Results: Negative Margins after local excision: The results are in the table below. Nearly half of Americans defined negative margins if no tumor cells were seen on the ink compared to a quarter of Europeans (44.7 vs 27.6%, p=0.001). Europeans were more likely to choose larger distances of <5mm or <10mm from the ink. Within the USA, there was no difference between academic vs non-academic institutions, unlike Europe (p=0.038). Within Europe, the East and Scan favored at the margin. Most of UK defined negative margins at <1mm, Germ and ItGr <5mm, and Spain and the East <5mm and <10mm from the ink. Close Margins after local excision: Americans were more likely to consider a close margin as no cells <2mm to the ink (36.9% vs 20.6%, p<0.001). Europeans were more evenly divided, most often choosing <5mm (30.1% vs 13.6%, p<0.001). 67.6% of Americans chose close margins as either <1 or <2 mm. In Europe, the definition of close margins differed significantly between the different countries. Scan and France most often defined close margins as <1mm (46.8%,30%). Spain, ItGr, and Germ used <5mm (44%,37%,30.5%). UK was evenly divided for all margin categories. Academic institutions between Europe and the US differed significantly in definitions of negative and close margins, with Europe favoring a wider negative margin. In contrast, non-academic institutions in both continents did not differ. Re-excision for invasive tumor and DCIS based on margin status: Recommendations were fairly consistent. ALWAYS scores for tumor cells on the ink were 93.7%, 92.9%, and 84.1%, and at <1mm, 38.9%, 46.8%, 28.6% for invasive, gr3 DCIS, and gr1/2 DCIS groups, respectively. The SOMETIMES responses clustered fairly evenly on average between the <1mm (47%), <2mm (40%) and <3mm (33%) categories for the three groups. Few re-excisions were recommended for cells <10mm from the inked margin. Conclusions: There are significant differences in the perception of negative and close margins among radiation oncologists in the US and Europe. Overall, the Europeans favor a larger margin width (<5 mm). Only 45% of respondents in the US considered no tumor cells seen at the ink margins as negative margins as defined by the NSABP. The recommendation for re-excision by Americans was made most often for cells at or <1mm from the margin. Given these large differences, a universal definition of negative margins and the recommendations for re-excision are needed.