Development of a Practice Standard for Monitoring Adult Patients Receiving Bone-Modifying Agents at a Community Cancer Center

Abstract

The purpose of this study is to develop a standard for monitoring outpatients starting bone-modifying agents (BMAs) at a community cancer center. The National Comprehensive Cancer Network (NCCN) and American Society of Clinical Oncology (ASCO) guidelines recommend the monitoring of serum magnesium and phosphorus during BMA therapy but do not define a standard interval. The risk of hypomagnesemia and hypophosphatemia was assessed for the BMAs denosumab, pamidronate, and zoledronic acid. Compliance with dental clearance was also evaluated. Adult cancer outpatients newly started on BMAs between January 1, 2016, to December 31, 2016, were evaluated. Patients with hypercalcemia of malignancy were excluded. Primary endpoints were the composite rates of grade 3 and 4 hypomagnesemia and hypophosphatemia. Secondary endpoints included all-grade hypomagnesemia, all-grade hypophosphatemia, charges for laboratory draws, rate of dental clearance, and rate of osteonecrosis of the jaw (ONJ). Among 61 patients, 4.3% experienced grade 3 and 4 hypophosphatemia. No cases of grade 3 and 4 hypomagnesemia occurred. The annual cost for serum magnesium and phosphorus lab draws totaled $9,144.80. Dental clearance was obtained in 100% of patients, with 67% of clearances obtained from a dentist. No patients developed ONJ. Composite rates of grade 3 and 4 hypomagnesemia and hypophosphatemia were lower than reported in the literature. We propose to monitor magnesium and phosphorus levels at baseline, and then every 6 months. More frequent laboratory draws may be indicated based on clinical judgment. This recommendation will reduce laboratory draws and provide cost savings for patients. Compliance with dental clearance was fully achieved.

Table 1

Definitions of Grade 3 and 4 Hypomagnesemia and Hypophosphatemia Based on CTCAE Version 4.0

Table 2

Reported Incidences of Grade 3 and 4 Hypomagnesemia and Hypophosphatemia for Each Injectable Bone-Modifying Agent From the Literature

Figure 1

Screening, inclusion, and exclusion of patients by treatment group. HCM = hypercalcemia of malignancy.

Table 3

Baseline Patient Characteristics

Table 4

Cancer Diagnoses

Table 5

Primary and Secondary Outcomes Related to Hypomagnesemia and Hypophosphatemia

Table 6

Bone-Modifying Agent Cycles and Patients’ Charges for Magnesium and Phosphorus Levels

Table 7

Dental Clearance by a Dentist and Incidence of Osteonecrosis of the Jaw