(P 522) FLUORESCENCE GUIDED SURGERY WITH INDOCYANINE GREEN FOR SURGICAL RESECTION OF METASTATIC BONE AND SOFT TISSUE TUMOURS: A CASE SERIES

Objective: Bone and soft tissue are common metastatic sites of primary cancers resulting in a considerable workload for orthopaedic oncologists, often requiring operative intervention with the goal usually being the removal of the tumour in its entirety. Intraoperative differentiation between malignant tissue and normal tissue remains a challenge in oncological surgery. Indocyanine green (ICG) is a water-soluble, tricarbocyanine dye with enhanced uptake and retention in malignant tumour cells which fluoresces in the near-infrared (NIR) spectrum; this can be imaged intra-operatively using handheld NIR cameras. Fluorescence-guided surgery (FGS) with ICG has shown potential as a novel approach in the resection of both lung metastases and solid cancers, including sarcoma in which a reduction in the unexpected positive margin rate has been demonstrated. This study aims to assess the feasibility of FGS using ICG for the resection of metastatic bone and soft tissue tumours.

Methods: Patients undergoing resection of bone and soft tissue metastases from any primary tumour type were eligible and a total of 17 patients were recruited. ICG was administered intravenously pre-operatively at a dose of 50-100mg. This was then imaged intra-operatively using the Stryker SPY-PHI camera; any alteration to the operative procedure due to fluorescence was at the discretion of the operating surgeon. Following the procedure, it was recorded whether the tumour had fluoresced and surgeons were asked whether they felt this had guided the procedure. The margin status was assessed by expert pathologists.

Results: Patients with metastatic disease from 12 different primary cancers were enrolled, including lung, breast, renal, colorectal, oesophageal, skin, bone, oropharyngeal and endometrial primaries . All 17 tumours fluoresced intra-operatively, and it was felt to provide intra-operative guidance to the surgeon in 12/17 cases. It was felt to be particularly useful in the identification of residual disease during intralesional surgery and for demarcating the extent of disease during bone resections intraoperatively. Of the 17 patients, 4 surgeries were intralesional procedures and 2 had positive margins due to pathological fractures. Of the remaining 11 patients, 9/11 had negative margins on histopathological assessment. There were no adverse events recorded during this study.

Conclusion: This study demonstrates that FGS using ICG is a promising technology in the management of bone and soft tissue metastases and is feasible across a broad range of cancer types. It is not clear yet however whether this translates into improved patient outcomes and should be investigated further in the form of a prospective randomised control trial.