Accuracy of a mobile sensor-based system for the detection of chemotherapy toxicity in older adults with cancer.
Authors: Soto Pérez de Celis Enrique , Atenafu Eshetu , Torres Ana Cristina , de la O Murillo Andrea , Morales Alfaro Andrea , Jiménez Sotomayor María Reneé , Hernandez Favela Celia Gabriela , Monroy Chargoy Javier , Aguilar-Velazco Jose , Medina Mildred , Moreno-García María Luisa , Pérez de Celis Maria de la Concepción , Contreras Sergio , Chávez Tania , Cardenas-Reyes Paula , Alibhai Shabbir M.H. 
Published: June 2024

1515 Background: Older adults receiving chemotherapy (CT) are at a high risk of toxicity (Tox) and of functional decline. Promptly acting upon CT Tox in older adults is difficult, particularly in developing countries where triage systems and personnel are limited. We previously showed that monitoring older patients using an accelerometer-equipped smartphone is feasible, and that a decline in the number of steps/day may represent a marker of Tox. We aimed to evaluate the diagnostic accuracy of an objective patient-centered measure of physical function (steps/day) for the remote detection of Tox in older adults receiving CT. Methods: We included consecutive patients aged ≥65 years starting first line CT for solid tumors at a single center in Mexico City. Patients underwent a geriatric assessment and were provided with an accelerometer-equipped smartphone. Daily steps were recorded for ≥7 days pre-CT initiation, and median number of pre-CT steps/day was calculated. Patients with ≤600 median pre-CT steps/day, and those using walking aids, were excluded (16% of recruited patients). Steps were monitored daily, compared with median pre-CT steps/day, and % decline was calculated. Patients were called daily, and Tox was assessed using PRO-CTCAE questionnaires. The % decline in steps/day from pre-CT was considered as the index test for Tox, while patient report was considered the reference standard. The association between % step decline and moderate/severe Tox was examined using generalized linear-mixed models. AUC was calculated and Youden’s index used to choose cutoff points for Tox detection. Results: 116 patients were included (96 development cohort, 20 validation cohort). Median age was 73y (range 65-91), 55% were female, and 65% had ≤high school education. The most common tumors were colon (21.5%), pancreas (17.5%), and gastric (12%). 28% of participants had never used a smartphone. The median number of pre-CT steps/day was 2979. Patients were followed for 6764 days, with Tox detected on 64.4% of days. Moderate/severe self-reported toxicity was detected on 1245 days (22.1%), while mild/no toxicity was detected on 4378 days (77.9%). AUC analysis for the development cohort demonstrated that a 32% decrease in steps/day from pre-CT median showed a sensitivity of 77.6% and a specificity of 67.3% for detecting moderate/severe Tox. Sensitivity and specificity of the cutoff in the validation cohort were 75.8% and 69.6%, respectively. Tox associated with a decline in steps/day included fatigue, pain, and nausea. Conclusions: A decline in the number of steps/day measured using an accelerometer-equipped smartphone was useful for the remote detection of moderate/severe Tox in older adults with cancer receiving CT, with a high sensitivity and specificity. This patient-centric measure could be used in clinical practice and research to detect and act promptly on Tox and, potentially, improve outcomes.