Elevated levels of circulating fibroblast growth factor 23 with hypercalcemia following discontinuation of denosumab

Inhibition of RANKL Expression in Osteocyte-like Differentiated Tumor Cells in Giant Cell Tumor of Bone After Denosumab Treatment

Giant cell tumors of bone (GCTBs) are locally aggressive tumors with the histological features of giant cells and stromal cells. Denosumab is a human monoclonal antibody that binds to the cytokine receptor activator of nuclear factor-kappa B ligand (RANKL). RANKL inhibition blocks tumor-induced osteoclastogenesis, and survival, and is used to treat unresectable GCTBs. Denosumab treatment induces osteogenic differentiation of GCTB cells. In this study, the expression of RANKL, special AT-rich sequence-binding protein 2 (SATB2, a marker of osteoblast differentiation), and sclerostin/SOST (a marker of mature osteocytes) was analyzed before and after treatment with denosumab in six cases of GCTB. Denosumab therapy was administered a mean of five times over a mean 93.5-day period. Before denosumab treatment, RANKL expression was observed in one of six cases. After denosumab therapy, spindle-like cells devoid of giant cell aggregation were RANKL-positive in four of six cases. Bone matrix-embedded osteocyte markers were observed, although RANKL was not expressed. Osteocyte-like cells were confirmed to have mutations, as identified using mutation-specific antibodies. Our study results suggest that treatment of GCTBs with denosumab results in osteoblast-osteocyte differentiation. Denosumab played a role in the suppression of tumor activity via inhibition of the RANK-RANKL pathway, which triggers osteoclast precursors to differentiate into osteoclasts.

Rebound hypercalcemia post-denosumab cessation in metastatic breast cancer

Denosumab delays and prevents skeletal related events in patients with malignancy-related bony metastases. Rarely, denosumab discontinuation can lead to rebound hypercalcemia in the setting of increased bone resorption. We describe the case of a 49-year-old breast cancer survivor who developed rebound hypercalcemia after cessation of long-term denosumab. She had been treated with 42 doses of denosumab between August 2013 and March 2020 and 8 months after her last dose of denosumab developed symptomatic hypercalcemia. Parathyroid hormone levels were suppressed, and active malignancy was excluded based on biochemical and radiological testing. She required treatment with intravenous bisphosphonates on three separate occasions in order to achieve long-term normalization of her hypercalcemia. Rebound hypercalcemia post-denosumab cessation is a rare but serious complication that clinicians should be aware of.

Longitude Variation of the microRNA-497/FGF-23 Axis during Treatment and Its Linkage with Neoadjuvant/Adjuvant Trastuzumab-Induced Cardiotoxicity in HER2-Positive Breast Cancer Patients

Purpose

MicroRNA-497 (miR-497) is previously reported to target fibroblast growth factor 23 (FGF-23) and regulates cardiac injury, while their value in predicting drug-induced cardiotoxicity is not reported. Thus, the current study aimed to investigate the correlation of miR-497/FGF-23 with neoadjuvant/adjuvant trastuzumab-induced cardiotoxicity in human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients.

Methods

A total of 97 HER2-positive surgical breast cancer patients who received neoadjuvant/adjuvant trastuzumab contained regimens were enrolled; then, their peripheral blood mononuclear cells (PBMC) and serum were collected at baseline, after neoadjuvant treatment, at 3 months (M3), 6 months (M6), 9 months (M9), and 12 months (M12) after surgery. The PBMC was used for miR-497 measurements, and the serum was used for FGF-23 measurements. The cardiotoxicity events and incidence were recorded.

Results

A total of 24 (24.7%) patients occurred cardiotoxicity during the treatment period. MiR-497 decreased from baseline (median: 0.955) to M12 after surgery (median: 0.602) (p < 0.001), while FGF-23 increased from baseline (median: 0.390 ng/mL) to M12 after surgery (median: 0.566 ng/mL) (p < 0.001); besides, the miR-497/FGF-23 axis greatly reduced from baseline (median: 2.545) to M12 after surgery (median: 1.222) (p < 0.001). At most time points, miR-497 was negatively related to FGF-23 (all p < 0.05). Notably, the miR-497/FGF-23 axis at all time points (including baseline, postneoadjuvant treatment, M3, M6, M9, and M12) was related to a lower risk of cardiotoxicity (all p < 0.05). Furthermore, the miR-497/FGF-23 axis was also positively correlated with the left ventricular ejection fraction (LVEF) at all time points (all p < 0.01).

Conclusion

The MiR-497/FGF-23 axis serves as a potential indicator predicting trastuzumab-induced cardiotoxicity in HER2-positive breast cancer patients.

Rare Causes of Hypercalcemia: 2021 Update

CONTEXT

Primary hyperparathyroidism and malignancy are the etiologies in 90% of cases of hypercalcemia. When these entities are not the etiology of hypercalcemia, uncommon conditions need to be considered. In 2005, Jacobs and Bilezikian published a clinical review of rare causes of hypercalcemia, focusing on mechanisms and pathophysiology. This review is an updated synopsis of rare causes of hypercalcemia, extending the observations of the original article.

EVIDENCE ACQUISITION

Articles reporting rare associations between hypercalcemia and unusual conditions were identified through a comprehensive extensive PubMed-based search using the search terms "hypercalcemia" and "etiology," as well as examining the references in the identified case reports. We categorized the reports by adults vs pediatric and further categorized the adult reports based on etiology. Some included reports lacked definitive assessment of etiology and are reported as unknown mechanism with discussion of likely etiology.

EVIDENCE SYNTHESIS

There is a growing understanding of the breadth of unusual causes of hypercalcemia. When the cause of hypercalcemia is elusive, a focus on mechanism and review of prior reported cases is key to successful determination of the etiology.

CONCLUSIONS

The ever-expanding reports of patients with rare and even unknown mechanisms of hypercalcemia illustrate the need for continued investigation into the complexities of human calcium metabolism.

Hypercalcemia upon denosumab withdrawal in primary hyperparathyroidism: a case report and literature review

Denosumab discontinuation is associated with a rapid increase in bone resorption and a decrease in bone mineral density. Spontaneous vertebral fractures may occur as a side effect of the rebound of bone resorption. Cases of rebound-linked hypercalcemia have also been described, moderate in women with osteoporosis and breast cancer and severe in children receiving oncological doses of denosumab. We report the case of an adult woman with primary hyperparathyroidism and moderate hypercalcemia, treated with denosumab for osteoporosis, who developed severe hypercalcemia and spontaneous vertebral fractures (SVFs) after denosumab discontinuation. An 86-year-old woman with densitometric osteoporosis was treated for 3 years with 60 mg of subcutaneous denosumab every 6 months. She was known to have primary hyperparathyroidism, with a serum albumin-corrected calcium of 2.82 mmol/l (NV 2.15-2.5) at the end of denosumab effect. Nine months after the last denosumab injection, she was hospitalized due to worsening overall health. Clinical evaluation revealed severe hypercalcemia (calcium 3.35 mmol/l). Very high values of bone turnover markers (BTMs) suggested a rebound effect due to denosumab discontinuation. An X-ray showed multiple new SVFs. After injection of denosumab 60 mg, serum calcium rapidly decreased and BTMs were dramatically reduced. A surgical approach by minimally invasive parathyroidectomy allowed for definite resolution of hyperparathyroidism and hypercalcemia. This case suggests that hypercalcemia can be a side consequence of denosumab discontinuation, which can become severe when other causes of hypercalcemia, such as primary hyperparathyroidism, are present.

Fracture risk and management of discontinuation of denosumab therapy: a systematic review and position statement by ECTS

CONTEXT

Denosumab discontinuation is characterized by an increase in bone turnover overriding pre-treatment status, a rapid bone loss in the majority and multiple vertebral fractures (VFx) in some patients.

METHODS

A working group of the European Calcified Tissue Society (ECTS) performed an updated systematic review of existing literature on changes of bone turnover, bone mineral density (BMD), and fracture risk after denosumab discontinuation and provided advice on management based on expert opinion.

RESULTS

Important risk factors for multiple VFx following denosumab cessation are prevalent VFx, longer duration off therapy, greater gain in hip BMD during therapy, and greater loss of hip BMD after therapy according to a retrospective analysis of the FREEDOM Extension Study. Case series indicate that prior bisphosphonate therapy mitigates the biochemical rebound phenomenon after denosumab discontinuation, but it is uncertain whether this attenuation prevents BMD loss and fractures. Current evidence indicates partial efficacy of subsequent antiresorptive treatment with results seemingly dependent on duration of denosumab treatment.

CONCLUSIONS

A careful assessment of indications to start denosumab treatment is advised, especially for younger patients. A case for long-term treatment with denosumab can be made for patients at high fracture risk already on denosumab treatment given the favorable efficacy and safety profile. In case of denosumab discontinuation, alternative antiresorptive treatment should be initiated 6 months after the final denosumab injection. Assessment of bone turnover markers may help define the optimal regimen, pending results of ongoing RCTs. Patients having sustained VFx should be offered prompt treatment to reduce high bone turnover.