Rebound hypercalcemia post-denosumab cessation in metastatic breast cancer

[Electrolyte disorders in oncological patients]

Electrolyte disorders (ED) are common in patients with cancer and in most cases, the etiologies do not differ from the general population. They may also be induced by the cancer, its therapy or paraneoplastic syndromes. ED are associated with poor outcomes, increased morbidity and mortality in this population. Hyponatremia is the most common disorder, often multifactorial, iatrogenic or secondary to the syndrome of inappropriate antidiuretic hormone secretion, usually due to small cell lung cancer. More rarely, hyponatremia may reveal adrenal insufficiency. Hypokalemia is generally multifactorial and associated with other ED. Cisplatin and ifosfamide induce proximal tubulopathies with hypokalemia and/or hypophosphatemia. Hypomagnesemia is often iatrogenic, related to cisplatin or cetuximab, but can be prevented by supplementation. Hypercalcemia can impair life quality and be life-threatening in the most severe cases. Hypocalcemia is less common and often of iatrogenic origin. Finally, the tumor lysis syndrome is a diagnostic and therapeutic emergency that affects the prognosis of patients. Its incidence tends to increase in solid oncology, related to the improvement of therapies. Prevention and early diagnosis of ED are essential to optimize the overall management of patients with underlying cancer and cancer therapy. The aim of this review is to synthesize most frequent ED and their management.

Treatment of Hypercalcemia of Malignancy in Adults: An Endocrine Society Clinical Practice Guideline

BACKGROUND

Hypercalcemia of malignancy (HCM) is the most common metabolic complication of malignancies, but its incidence may be declining due to potent chemotherapeutic agents. The high mortality associated with HCM has declined markedly due to the introduction of increasingly effective chemotherapeutic drugs. Despite the widespread availability of efficacious medications to treat HCM, evidence-based recommendations to manage this debilitating condition are lacking.

OBJECTIVE

To develop guidelines for the treatment of adults with HCM.

METHODS

A multidisciplinary panel of clinical experts, together with experts in systematic literature review, identified and prioritized 8 clinical questions related to the treatment of HCM in adult patients. The systematic reviews (SRs) queried electronic databases for studies relevant to the selected questions. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology was used to assess the certainty of evidence and make recommendations. An independent SR was conducted in parallel to assess patients' and physicians' values and preferences, costs, resources needed, acceptability, feasibility, equity, and other domains relevant to the Evidence-to-Decision framework as well as to enable judgements and recommendations.

RESULTS

The panel recommends (strong recommendation) in adults with HCM treatment with denosumab (Dmab) or an intravenous (IV) bisphosphonate (BP). The following recommendations were based on low certainty of the evidence. The panel suggests (conditional recommendation) (1) in adults with HCM, the use of Dmab rather than an IV BP; (2) in adults with severe HCM, a combination of calcitonin and an IV BP or Dmab therapy as initial treatment; and (3) in adults with refractory/recurrent HCM despite treatment with BP, the use of Dmab. The panel suggests (conditional recommendation) the addition of an IV BP or Dmab in adult patients with hypercalcemia due to tumors associated with high calcitriol levels who are already receiving glucocorticoid therapy but continue to have severe or symptomatic HCM. The panel suggests (conditional recommendation) in adult patients with hypercalcemia due to parathyroid carcinoma, treatment with either a calcimimetic or an antiresorptive (IV BP or Dmab). The panel judges the treatments as probably accessible and feasible for most recommendations but noted variability in costs, resources required, and their impact on equity.

CONCLUSIONS

The panel's recommendations are based on currently available evidence considering the most important outcomes in HCM to patients and key stakeholders. Treatment of the primary malignancy is instrumental for controlling hypercalcemia and preventing its recurrence. The recommendations provide a framework for the medical management of adults with HCM and incorporate important decisional and contextual factors. The guidelines underscore current knowledge gaps that can be used to establish future research agendas.

Incidence of Post-denosumab Rebound Hypercalcaemia in Bony-Metastatic Breast Cancer

Denosumab reduces incidence of skeletal related events in patients with bony-metastatic breast cancer, however cessation is associated with a rebound phenomenon which, rarely, has been associated with hypercalcaemia. We aimed to identify the incidence of post-denosumab cessation rebound hypercalcaemia amongst patients with breast cancer-related bony metastases. We performed a single-centre retrospective cohort analysis to determine the incident of rebound hypercalcaemia amongst patients treated with antiresorptive agents for bony metastatic breast cancer between 2016-2020. 22,320 outpatient encounters were reviewed, which identified 97 patients with bonymetastatic disease treated with antiresorptive therapy. Of the 21 patients who had denosumab ceased, six (28.6%) developed hypercalcaemia. Interval between last denosumab dose and onset of hypercalcaemia was a median 7.5 (range 2-13) months. There was a significant difference in both denosumab treatment duration as well as total treatment dose exposure between patients who developed hypercalcaemia post-denosumab cessation (median 41 months, 40 doses) and those who remained normocalcaemic (median 10 months, 5 doses), p = 0.009. In our study, hypercalcaemia occurred between two and thirteen months after denosumab cessation. Greater denosumab treatment duration as well as total denosumab dose exposure was associated with higher risk of hypercalcaemia after denosumab cessation. Hormonal therapy or previous bisphosphonate treatment was not seen to impact upon development of hypercalcaemia. Rebound hypercalcaemia is a rare but important diagnosis to consider in patients experiencing hypercalcaemia after denosumab cessation.