Abstract P2-13-15: Factors associated with triggering events on the PREVENT trial at 2 years post-operatively
Authors: Ridner Sheila Hedden , Dietrich Mary S , Shah Chirag , Vicini Frank 
Published: March 2020

Abstract
Purpose: An interim analysis of 508 patients who completed 12 months of prospective surveillance in the lymphedema PREVENT study found a significant difference in the time to preventive intervention trigger between those measured with Bioelectrical Impedance Spectroscopy (BIS) (9.5 months) vs. Tape Measure (TM) (2.8 months). However, questions emerged as to the reason for the difference and associated factors. Therefore, a study was performed to determine the factors that influenced the time to intervention trigger in patients randomized to either BIS or TM during the first 2 years post-operatively. Methods: Post-randomization to BIS or TM groups patients were assessed with the assigned measurement method at intervals of at least 3, 6, 12, 18, and 24 months post-operatively. A lymphedema prevention intervention consisting of wearing a compression sleeve and a gauntlet for 12 hours a day for 28 days was triggered when subclinical lymphedema was indicated. A change from baseline measures in the BIS group ≥ 6.5 L-DEX units and in TM ≥ 5% but &lt;10% triggered the intervention. Cox and linear regressions were used to compare the hazard ratios between groups and test for associations with length of time to trigger after treatment within the subsample of patients who triggered. Results: Of the 508 patients evaluated, 6 progressed to clinical lymphedema without moving through a subclinical state, and as such, 502 patients were included in the analysis. Patients in the TM arm were more likely to trigger (n=73 of 239, 30.5%) as compared to those in the BIS arm (n=48 of 263, 18.3%, OR=1.97, 95% C.I. =1.29-2.99, p = .001). Of those who triggered, the median time to their respective trigger threshold within the study arm was considerably less for those in the TM group than those in the BIS group (median=6.9 months, IQR=4-13 vs. 14.3 months IQR=7-19, log likelihood for differences between hazard ratios, p = .001). Age, BMI, regional nodal irradiation, taxane receipt, and extent of axillary surgery were not associated with time to intervention trigger. Conclusions: At 24 months, the median time to intervention trigger lengthened from 12 month findings in both groups, BIS 9.5 months to 14.5 months, TM 2.8 months to 6.9 months. This suggests that prospective surveillance must continue beyond one year post-surgery. After controlling for the strong effect of measurement methods used to assess the triggering threshold, none of the variables was statistically significantly associated with time to trigger within the sample of triggering patients. Additional research in a larger sample is needed to better understand factors related to this time to trigger difference and to explore factors that are related to progression to clinical lymphedema in those who underwent the prevention intervention. These will be further examined at the conclusion of the PREVENT study.
Citation Format: Sheila Hedden Ridner, Mary S Dietrich, Chirag Shah, Frank Vicini. Factors associated with triggering events on the PREVENT trial at 2 years post-operatively [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-13-15.