Systematic Review: Efficacy of Medical Therapy on Outcomes Important to Adult Patients with X-Linked Hypophosphatemia.

Objective: To examine the highest certainty evidence addressing the management of X-linked hypophosphatemia (XLH) in adults to inform treatment recommendations.

Methods: We searched Embase, MEDLINE, Web of Science, and Cochrane Central up to May 2023. Eligible studies included RCTs and observational studies of individuals 18+ with clinically or genetically confirmed XLH. Manuscripts comparing burosumab to no treatment or conventional therapy (phosphate and active vitamin D) and conventional therapy to no treatment were included. Two reviewers independently determined eligibility, extracted data, and assessed risk of bias (RoB). GRADE methodology was used to assess evidence certainty.

Results: We screened 4,114 records, after removing duplicates, and assessed 254 full texts. One RCT and two observational studies were eligible. The RCT of burosumab versus no treatment had low RoB. Burosumab probably improves pain from fracture/pseudofracture healing (moderate certainty) but has little or no impact on direct pain measures (moderate certainty). Burosumab may reduce the need for parathyroidectomy (low certainty) but has little or no impact on fatigue (high certainty), stiffness (moderate certainty), and mobility (low certainty) over 24 weeks. Burosumab may increase dental abscess risk (low certainty). Indirect evidence comparing burosumab to conventional therapy provided low certainty regarding burosumab versus conventional therapy. Two observational studies on conventional therapy versus no treatment had high RoB and very low certainty regarding the impact of conventional therapy on patient-important outcomes.

Conclusion: No formal comparisons between burosumab and conventional therapy in adults exist. Evidence for conventional therapy versus no treatment is very uncertain. Our review highlights the need for more data on the long-term effects of burosumab and conventional therapy on patient-important outcomes in adult patients with XLH.