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Primary hyperparathyroidism is usually cured by removing the single over-active parathyroid adenoma. During surgery, however, surgeons often see a thin rim of normal parathyroid tissue that still "glows" under a near-infrared parathyroid tissue sensor (PTS). It is unclear whether keeping this tissue in place helps preserve hormone function or whether it leaves behind cells that could become over-active again.
The WHITE CAP study will compare two common surgical choices:
Preservation strategy - the surgeon removes only the adenoma and leaves the glowing rim of normal tissue untouched.
En-bloc strategy - the surgeon removes the adenoma together with the glowing rim; if too little parathyroid tissue remains, a small fragment is transplanted into the forearm muscle.
About 120 adult patients who have a single parathyroid adenoma will be randomly assigned (like tossing a coin) to one of the two strategies. All operations will use the same FDA-cleared PTS camera that shows the glands in real time without dye or radiation.
The main question is whether preserving the normal rim lowers the rate of temporary low blood-calcium (numbness, tingling) during the first two days after surgery. The study will also check long-term results-blood calcium and parathyroid hormone (PTH) levels, symptoms, and any return of the disease-over two years.
The PTS imaging itself is painless and adds only a few minutes to the operation. Risks are the same as for standard parathyroid surgery, and participants can withdraw at any time without affecting their usual care.
Full description
Background and Rationale Near-infrared autofluorescence (NIRAF) highlights parathyroid tissue at a wavelength of 820 nm. Several devices, including Fluobeam LX and PTeye®, have FDA 510(k) clearance for intra-operative identification of parathyroid glands. In ~70 % of single-gland disease, NIRAF shows a viable rim of normal tissue partially encasing the adenoma. Retrospective data conflict on whether rim preservation reduces transient hypocalcaemia or increases recurrence. No prospective randomized evidence exists.
Objectives Primary: Compare the incidence of transient hypocalcaemia (albumin-corrected Ca < 2.00 mmol·L-¹ or need for calcium/vit-D supplementation) within 48 h post-operative between preservation and en-bloc strategies.
Secondary: (i) Permanent hypocalcaemia at 6 months; (ii) PTH ≥ 15 pg·mL-¹ at 24 h; (iii) operative time and blood loss; (iv) biochemical or clinical recurrence up to 24 months; (v) correlation of quantitative NIRAF intensity with gland viability.
Study Design Multicentre, parallel-group, 1:1 randomized controlled trial (RCT). Block randomisation (size 4) stratified by centre and baseline vitamin-D status. Total sample 120 participants (60 per arm, includes 10 % attrition). Single-blind: outcome assessors and laboratory staff remain unaware of allocation.
Interventions Preservation arm: After adenoma excision, surgeon confirms NIRAF-positive rim and leaves it in situ; only minimal defatting to ensure vascularity.
En-bloc arm: Adenoma plus NIRAF-positive rim excised en bloc. If fewer than two normal glands remain in the neck, a 30 mg fragment is minced and autotransplanted into the non-dominant brachioradialis.
Eligibility Inclusion: age 18-75 y; biochemically confirmed primary hyperparathyroidism; imaging (MIBI or 4D-CT) concordant with a solitary adenoma; written informed consent.
Exclusion: multiple endocrine neoplasia, >1 enlarged gland on imaging, eGFR < 30, pregnancy, neck re-exploration, planned concomitant total thyroidectomy.
Outcome Assessments Serum Ca, phosphate, Mg, PTH measured pre-op; 6 h, 24 h, 48 h; Day 7; Months 1, 6, 12, 24. Laryngoscopy if voice change occurs. Recurrence defined as Ca above upper limit plus PTH > 65 pg·mL-¹ after Month 12. NIRAF intensity recorded (arbitrary units) using standard ROI software.
Statistical Plan Transient hypocalcaemia expected 30 % in en-bloc vs 10 % in preservation. With α = 0.05, 1-β = 0.80, needs 54 per arm; rounded to 60. Intent-to-treat analysis. Risk ratios with 95 % CI; secondary continuous outcomes by mixed-effects ANCOVA. Interim safety review at 50 % recruitment (O'Brien-Fleming boundary).
Regulatory and Ethics PTS devices are FDA-cleared; study classified as non-significant-risk device research exempt from IDE (21 CFR 812.2(b)). All centres have IRB approval. Data stored in REDCap, anonymised, GDPR-compliant. A three-member DSMB (endocrine surgeon, endocrinologist, biostatistician) will monitor AEs; trial pause if permanent hypocalcaemia exceeds 15 %.
Data Sharing De-identified participant data and analytic code will be available upon reasonable request 6 months after primary publication.
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120 participants in 2 patient groups
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Bo Wang Professor, MD
Data sourced from clinicaltrials.gov
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