Optimization of near infrared fluorescence tumor localization during robotic partial nephrectomy.

PURPOSE

Near infrared fluorescence allows the differentiation of tumors and normal parenchyma during robotic partial nephrectomy. This may facilitate tumor excision but requires proper dosing of indocyanine green. Under dosing causes inadequate fluorescence of peritumor parenchyma. Overdosing causes tumors to fluoresce inappropriately. Currently there are no described dosing strategies to our knowledge to optimize near infrared fluorescence and reported doses vary widely. We devised a dosing strategy and assessed the reliability of near infrared fluorescence for differential fluorescence.

MATERIALS AND METHODS

Robotic partial nephrectomy with near infrared fluorescence was performed for 79 tumors. Dosing strategy involved at minimum 2 indocyanine green doses, including the test dose and the calibrated dose before resection. The test dose was deliberately low to avoid confounding over-fluorescence. The second dose was calibrated depending on the extent of differential fluorescence achieved with the test doses. Intraoperative assessment of tumor fluorescence was recorded before pathological assessment.

RESULTS

Mean tumor size was 3.5 cm (range 1.1 to 9.8) with a mean R.E.N.A.L. score of 8 (range 4 to 12). Median indocyanine green test dose and re-dose before clamping were 1.25 mg (range 0.625 to 2.5) and 1.875 mg (range 0.625 to 5), respectively. Differential fluorescence was achieved in 65 of 79 tumors (82%) that did not fluoresce. After 3 exclusions for the inability to assess fluorescence or indeterminate histology, 60 of 76 tumors were renal cell carcinoma. Of 60 renal cell carcinomas 55 behaved appropriately and did not fluoresce (92%). Overall 65 of 76 tumors behaved appropriately for an 86% agreement between histology and near infrared fluorescence behavior.

CONCLUSIONS

With our dosing regimen near infrared fluorescence was highly reliable in achieving differential fluorescence of kidney and renal cell carcinomas. Standardized dosing is needed before deciding whether near infrared fluorescence improves robotic partial nephrectomy outcomes and additional studies may further improve reliability.