Continuous glucose monitoring and rates of hyperglycemia during chemotherapy for early-stage breast cancer.
Authors: Ulene Sophie , Wang Shikun , Cook Joshua , McAuley Fiona , Wooster Margaux , Faheem Khadija , McGuinness Julia Elizabeth , Vasan Neil , Trivedi Meghna S. , Crew Katherine D. , Harden Erik , Law Cynthia , Hershman Dawn L. , Accordino Melissa Kate 
Published: July 2024

e24134

Background: Diabetes (DM) and hyperglycemia (HG) during chemotherapy increase the risk of treatment-related toxicities. The prevalence of HG and daily patterns of HG over the course of chemotherapy in patients with early-stage breast cancer (ESBC) are currently unknown. Methods: We conducted a prospective single-arm pilot study of continuous glucose monitoring in patients with ESBC receiving chemotherapy from 12/2020 – 2/2022. Eligibility criteria included: diagnosis of Stage I-III BC, age ≥18, and planned chemotherapy with concurrent corticosteroid supportive care use. Patients were excluded if they were receiving other systemic corticosteroids or insulin. Patients wore FreeStyle Libre Pro continuous glucose monitoring sensors from the time of chemotherapy initiation (± 7 days) through completion. The sensors detected interstitial glucose levels every 15 minutes and were reapplied by the study team every 2-3 weeks. Primary endpoints were: (1) prevalence of HG, defined as number of patients with ≥1 glucose reading ≥140 mg/dL and (2) among those who developed HG, the proportion of time spent hyperglycemic, defined as number of readings ≥140 mg/dL divided by total number of readings. Key secondary endpoints included prevalence of prediabetes (pre-DM) and diabetes (DM) at baseline and changes in A1c from baseline to weeks 12 and 24. The analysis was stratified by baseline A1c (euglycemia [A1c < 5.7%], pre-DM [A1c 5.7%-6.4%], or DM [A1c ≥6.5% and clinical diagnosis of DM prior to study enrollment]). Results: Among 20 evaluable patients, the median age at baseline was 59 (range 34-78) and median body mass index (BMI) was 29.5 kg/m2 (range 19.5-41.6). The most common chemotherapy regimens included docetaxel/cyclophosphamide (25%), weekly paclitaxel ± trastuzumab (20%), paclitaxel followed by doxorubicin/cyclophosphamide (15%), docetaxel/carboplatin/trastuzumab/pertuzumab (15%), and cyclophosphamide/methotrexate/fluorouracil (15%). All 20 patients developed HG. Of 124,165 total readings, 17% were ≥140 mg/dL and mean glucose was 112.7 mg/dL. At baseline, n = 10 were euglycemic, n = 7 had pre-DM, and n = 3 had DM. By cohort, the proportion of time spent hyperglycemic was 3.9% (euglycemia group), 10% (pre-DM group), and 73.3% (DM group) (p < .0001). Mean glucose values were 95.5 mg/dL (euglycemia group), 104.5 mg/dL (pre-DM group), and 183.0 mg/dL (DM group) (p < .0001). Change in mean A1c from baseline to weeks 12 and 24 varied significantly across groups. Conclusions: Among patients receiving chemotherapy for ESBC, we found evidence of HG in all patients, and the proportion of time spent hyperglycemic during chemotherapy varied significantly by baseline A1c. Further interventions should evaluate the benefits of improved glucose control among patients with baseline A1c > 5.7%. Clinical trial information: NCT04473378 .