Postoperative outcome and clinical management of tumor-induced osteomalacia: a single-center retrospective cohort study on 117 patients

We reported a single-center retrospective cohort study on 117 patients of Tumor-induced osteomalacia (TIO) to summarize our experience with TIO over the past decade. The clinical characteristics, diagnosis, treatment and postoperative outcomes were analyzed. Together, our data demonstrate the characteristics and prognosis of TIO and unveil a possible TIO management process. TIO is a rare paraneoplastic syndrome that ultimately results in debilitating musculoskeletal deficits and regressive activity obstacles due to hypophosphatemia. The diagnosis and treatment of TIO are challenging owing to nonspecific symptoms, occult tumors and the lack of awareness. We aimed to summarize our experience with TIO over the past decade and to optimize its clinical management. A retrospective analysis was conducted of all patients with TIO admitted to our department and underwent surgical treatment at our hospital between 2012 and 2023. Clinical characteristics and postoperative outcomes were evaluated. A total of 117 patients with typical clinical characteristics were enrolled, manifesting diffuse bone pain, decreased serum phosphate and elevated serum intact fibroblast growth factor-23 (iFGF23). All the patients were managed using a stepwise pathway detailing diagnosis, identification of the causative tumors, operations and postoperative surveillance. The causative tumors were equally located in bone and soft tissues, and the main sites were the lower extremities and pelvis (63.2%). 117 cases were caused by phosphaturic mesenchymal tumors (PMTs), which were usually small and benign, with a median volume of 1.45cm3 (IQR 0.70-4.17 cm3) and low Ki67 labeling indices (< 10%, 91.7%). After surgery, the serum P became normal within 7 days in 82.7% of the cured patients; serum iFGF23 decreased rapidly in one day and then gradually increased to normal with other laboratory indices and bone mineral density. The median follow-up period was 12 months (range, 1-144), during which 19 patients remained uncured. Among them, 5 patients experienced local recurrence and 2 suffered distant metastases. Younger age, bone-derived tumors and malignant tumors were risk factors for adverse outcomes. Tumors located in the femoral head, acetabulum, and spine showed a higher risk of obstinacy among bone-derived tumors. TIO patients were able to benefit from the management including early recognition and diagnosis of the disease, identification and complete removal of the causative tumors, followed by regular postoperative surveillance. Of particular concern were patients with bone-derived tumors, who had high non-remission and recurrence rates. This study was registered with CHICTR.ORG.CN (ChiCTR2100042796).