Frailty and functional decline strongly influence treatment tolerance and outcomes in older patients with cancer, yet assessment is typically limited to infrequent clinic visits. We propose a multimodal wearable framework to estimate frailty-related functional change between visits in elderly breast cancer patients enrolled in the multicenter CARDIOCARE study. Free-living smartwatch physical activity and sleep features are combined with ECG-derived heart rate variability (HRV) features from a chest strap and organized into patient-horizon bags aligned to month 3 (M3) and month 6 (M6) follow-ups. Our innovation is an attention-based multiple instance learning (MIL) formulation that fuses irregular, multimodal wearable instances under real-world missingness and weak supervision. An attention-based MIL model with modality-specific multilayer perceptron (MLP) encoders with embedding dimension 128 aggregates variable-length and partially missing longitudinal instances to predict discretized change-from-baseline classes (worsened, stable, improved) for FACIT-F and handgrip strength. Under subject-independent leave-one-subject-out (LOSO) evaluation, the full multimodal model achieved balanced accuracy/F1 of 0.68 +/- 0.08/0.67 +/- 0.09 at M3 and 0.70 +/- 0.10/0.69 +/- 0.08 at M6 for handgrip, and 0.59 +/- 0.04/0.58 +/- 0.06 at M3 and 0.64 +/- 0.05/0.63 +/- 0.07 at M6 for FACIT-F. Ablation results indicated that smartwatch activity and sleep provide the strongest predictive information for frailty-related functional changes, while HRV contributes complementary information when fused with smartwatch streams.
Figures & tables
Task
0
1
2
Total
FACIT Δ M3
132
252
78
462
FACIT Δ M6
120
243
99
462
Handgrip Δ M3
75
124
34
233
Handgrip Δ M6
77
98
58
233
TABLE I: Class counts (0=worsened, 1=stable, 2=improved).
Modality
Stable
Worsened
Improved
M3
M6
M3
M6
M3
M6
Garmin Handgrip
20.8k
17.6k
11.5k
15.3k
8.1k
11.2k
Polar Belt Handgrip
5.5k
3.8k
7.6k
4.1k
1.9k
3.3k
Garmin FACIT
40.4k
41.9k
21.7k
18.6k
13.9k
17.6k
Polar FACIT
16.6k
7.9k
9.7k
4.5k
2.9k
4.0k
TABLE II: Number of available instances (in thousands, “k”) by modality, endpoint, follow-up horizon, and delta class (stable/worsened/improved).
Fig. 1: A graphical illustration of the proposed pipeline; the initial two images (human icons) were generated using Google Gemini [ 30 ] (synthetic images).
Endpoint
Metric
M3
M6
Hg
Balanced Accuracy
0.68±0.08
0.70±0.10
F1 score
0.67±0.09
0.69±0.08
FACIT
Balanced Accuracy
0.59±0.04
0.64±0.05
F1 score
0.58±0.06
0.63±0.07
TABLE III: Overall results (mean ± std across LOSO iterations) for the full multimodal MIL model.
Split
Endpoint
BalAcc M3
F1 M3
BalAcc M6
F1 M6
P+S
Hg
0.65 ± 0.04
0.63 ± 0.02
0.67 ± 0.05
0.65 ± 0.03
FACIT
0.52 ± 0.07
0.50 ± 0.08
0.57 ± 0.06
0.55 ± 0.04
P+E
Hg
0.60 ± 0.04
0.61 ± 0.03
0.62 ± 0.05
0.62 ± 0.04
FACIT
0.50 ± 0.02
0.49 ± 0.01
0.51 ± 0.03
0.51 ± 0.04
S+E
Hg
0.50 ± 0.03
0.49 ± 0.05
0.54 ± 0.05
0.55 ± 0.03
FACIT
0.46 ± 0.05
0.46 ± 0.01
0.48 ± 0.06
0.49 ± 0.05
TABLE IV: Ablation results (mean ± std across LOSO iterations) using modality pairs.
Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA. · Division of Geriatrics and Gerontology Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA. · Department of Computer Science, Johns Hopkins University, Baltimore, MD, USA. +3