A Randomized, Controlled Trial of Cavity Shave Margins in Breast Cancer

Amanda Breakey, Mercer University College of Pharmacy

According to the Society of Surgical Oncology (SSO) and the American Society for Radiation Oncology (ASTRO), multiple studies have demonstrated that survival following breast-conserving therapy (BCT) followed by whole-breast radiation therapy (WBRT) is equivalent to mastectomy for the treatment of stages I and II invasive breast cancer. However, as stated by SSO and ASTRO, a lack in consensus on what constitutes an optimal margin width has lead to approximately 25% of women requiring re-excision following BCT. It was also noted that nearly half of these procedures were performed with the rationale of obtaining larger clear margins in women whose margins were negative. According to a consensus guideline set forth by SSO and ASTRO, obtaining wider margin widths than negative margin widths does not significantly reduce the risk of ipsilateral breast tumor recurrence (IBTR), and is not indicated in routine practice.1

Title: A Randomized, Controlled Trial of Cavity Shave Margins in Breast Cancer2
Design Prospective, randomized, controlled; N= 235
Objective To determine the effect of routine excision of circumferential cavity shave margins versus standard partial mastectomy, including excision of selective margins, on outcomes after breast-conserving surgery
Study Groups Shave group (n= 119) and no-shave group (n= 116)
Methods Sealed randomization envelopes were opened intra-operatively after surgeons completed the partial mastectomy. For patients in the shave group, surgeons were instructed to resect additional tissue such that cavity shave margins encompassing the entire cavity were removed.
Duration October 21, 2011 to November 25, 2013
Primary Outcome Measure The rate of positive margins on final pathological testing
Baseline Characteristics The median age of the patients was 61 years (range, 33 to 94). The groups were well matched with respect to demographic and clinicopathological characteristics at baseline (p> 0.05 for all comparisons).
Results After randomization, patients who had been assigned to the shave group had a significantly lower rate of positive margins than did those randomly assigned to the no-shave group (19% vs. 34%, p= 0.01).
Adverse Events Common Adverse Events: N/A
Serious Adverse Events: N/A
Percentage that Discontinued due to Adverse Events: N/A
Study Author Conclusions Cavity shaving halved the rates of positive margins and re-excision among patients with partial mastectomy.

This study focused on optimal tissue removal in partial mastectomy in women undergoing breast-conserving surgery. Patients that underwent cavity shave margins (CSM) were half as likely to have positive margins and require re-excision compared to patients who did not undergo CSM. Further research needs to be conducted to better determine how accurately margins are able to predict residual disease and whether the presence of residual disease found in excised tissue warrants additional surgery, despite the use of systemic and radiation therapy.

References

  1. Moran MS, Schnitt SJ, Giuliano AE, et al. Society of Surgical Oncology-American Society for Radiation Oncology consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in stages I and II invasive breast cancer. Int J Radiat Oncol Biol Phys. 2014;88(3):553-64.
  2. Chagpar AB, Killelea BK, Tsangaris TN, et al. A Randomized, Controlled Trial of Cavity Shave Margins in Breast Cancer. N Engl J Med. 2015; 373:503-510.

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