Page 110 - Fluorescence-guided cancer surgery

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Chapter 7
Interestingly, we identi ed normal parathyroid glands, as small as 1 mm, during surgical exploration of the neck. These glands were not detected by the surgeon by visual inspection or palpation. Normal parathyroid glands can be di cult to distinguish during surgery because of their small size, their variability in location, and similar appearance to lymph nodes. Detection of these normal glands can be of great added value during subtotal parathyroid glands resection in the case of MEN1 syndrome, where 3.5 glands are removed and a portion of the most normal appearing gland is left in site or is auto-transplanted17. Also when normal glands are suppressed by hyperfunctional parathyroid glands, as in patient #9 of the current study, imaging can be useful. These glands were very small, and located in the thymus on both sides, and would not have been auto-transplanted if not detected in the thymectomy specimens by NIR uorescence imaging. Improved identi cation of both parathyroid adenoma and normal glands can limit the extent of neck exploration. Especially small normal glands are at risk of iatrogenic injury when not identi ed in time during neck exploration. The identi cation of normal glands using NIR uorescence imaging and MB was described by Antika et al.18 in rabbits. They used escalating dosages from 0.025 mg/kg to 3 mg/kg (human equivalent dose 0.008 mg/kg to 0.97 mg/kg calculated by using allometric dose translation based on body surface area19) for identi cation of thyroid and parathyroid glands. However, to the best of our knowledge, this is the rst clinical trial to demonstrate the intraoperative identi cation of normal glands using NIR uorescence imaging and MB.
When early administration of MB is compared to late administration (after visual identi cation of the adenoma), a mean SBR of the adenoma of 3.1 in the early administration group versus 6.1 in the late administration group is seen. Although this di erence was not signi cant (P = 0.08), it shows that MB follows the kinetics of a perfusion tracer, and don’t show clear (active) accumulation in parathyroid adenomas. Nevertheless, a mean SBR of 3.1 is suitable for intraoperative identi cation of parathyroid adenoma’s and normal glands as clearly shown in the current study.
Developing probes that speci cally accumulate in parathyroid glands could enhance SBR and the time window of which optimal SBRs are achieved. A recent published study of our research group showed the high-sensitivity identi cation of parathyroid and thyroid glands in several animal models using novel tissue-speci c NIR uorophores20. However, probes such as these are not