Intersurgeon agreement in determining 3 cm surgical margins of subcutaneous tumors in dogs.

Abstract

To evaluate intersurgeon agreement in performing a 3cm wide surgical excision for subcutaneous malignancies in dogs. Prospective, blinded, randomized, clinical study. Client-owned dogs with subcutaneous tumors undergoing curative-intent, wide surgical excision between April 2019 to March 2020. Four surgeons, instructed to perform a 3cm wide excision, each sequentially indicated their proposed skin incision locations around subcutaneous tumors, without knowledge of the other surgeons' proposed incisions. A tripod-mounted camera and laser positioning system were used to photograph each surgeon's proposed margin length. A random-effects model was used to estimate the standard deviation of margin lengths that would be expected from a random sample of surgeons. Each of the four surgeons provided 33 independent radial measurements from 11 tumors (six soft tissue sarcomas and five mast cell tumors), for a total of 132 radial measurements. No individual surgeon consistently proposed longer or shorter margin incision locations. The prediction interval for a future margin measurement was 6 mm, implying that the 95% confidence interval of an individual surgeon's margin length would be within ±6 mm of the mean margin length from a random sample of surgeons. Ninety-five percent of surgeons would be expected to deliver a surgical dose between 2.4-3.6cm, for a theoretically uniform surgical dose of 3cm wide margins. Surgical doses are likely to vary at clinically relevant levels among surgeons, complicating design and interpretation of studies attempting to identify an ideal surgical dose.