A study co-authored by Dr David Dodwell from Oxford Population Health has recommended that surgeons should aim to remove a 1mm wide margin of healthy tissue around a breast tumour to try to reduce the risk of cancer returning and improve breast cancer survival rates worldwide.
The findings indicate that inadequate margin widths may result in higher risks of distant recurrence (cancer returning in a different part of the body) and death as a result of breast cancer, as well as increased local recurrence (cancer returning at the same site).
After surgery, a pathologist measures the distance between the outer edge of cancer cells and the edge of the tissue that was removed to establish the width of the margin. Cancer guidelines suggest that allowing for a wider margin of healthy tissue when removing a tumour reduces local recurrence of breast cancer, but no data exist for distant recurrence.
To address this knowledge gap, an international team of researchers searched for published studies reporting on patients undergoing breast conserving surgery for early-stage invasive breast cancer who were monitored for a minimum of five years.
A total of 68 observational studies published between 1980 and 2021 involving 112,140 patients with breast cancer (average age 56 years) were included in the analysis.
Tumour specimen margins were split into three categories based on the degree of healthy tissue removed: involved, meaning that little or no healthy tissue was removed from around the tumour; close, meaning that the healthy tissue measured 2mm or less; and negative, meaning that the healthy tissue measured 2mm or more.
- Across all studies, the rate of distant recurrence was 25.4% in patients with involved margin tumours, 8.4% in patients with involved or close margins, and 7.4% in patients with negative margins;
- Compared with negative margins, involved margins were associated with around a two-fold increased risk of distant recurrence and local recurrence;
- Close margins were associated with a 38% increased risk of distant recurrence and a two-fold increased risk of local recurrence compared with negative margins, after adjusting for chemotherapy and radiotherapy treatment after surgery;
- In five studies published since 2010, involved margins were associated with a 2.4-fold increased distant recurrence as were involved and close margins (1.4-fold increased risk) compared with negative margins.
Recognising that the removal of wider margins require further surgery, the researchers suggest that decisions about re-excision ‘should be the product of an informed discussion between clinicians and patients with full disclosure of the risks of increased distant recurrence associated with close margins.’
Dr David Dodwell, Senior Clinical Research Fellow at Oxford Population Health, said ‘Caution is always required in inferring causality from observational data but given the inevitable lack of randomised evidence we recommend that guidelines relating to margin proximity are reviewed to reflect these findings.’