Dynamic DeepHit: A Deep Learning Approach for Dynamic Survival Analysis With Competing Risks Based on Longitudinal Data - Songwooseok123/Study_Space GitHub Wiki

[๋…ผ๋ฌธ๋งํฌ] (https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8681104)

์š”์•ฝ

The first to investigate a deep learning approach for dynamic survival analysis with competing risks on longitudinal data

  • Dynamic-DeepHit๋Š” longitudinal data๋กœ๋ถ€ํ„ฐ time-to-event distribution์„ ํ•™์Šตํ•˜์—ฌ, dynamicํ•œ survival prediction์„ ํ•  ์ˆ˜ ์žˆ๋‹ค.
    (dynamic์ด๋ž€ ์ƒˆ๋กœ์šด measurement๊ฐ€ ๋“ค์–ด์™”์„ ๋•Œ prediction์ด ๊ฐ€๋Šฅํ•˜๋‹ค๋Š” ๋ง์ธ๋“ฏ)
  • ๊ฐ covariate(feature)๊ฐ€ ๊ฐ event(risk)์— ์–ผ๋งˆ๋‚˜ ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š”์ง€ interpretation๋„ ๊ฐ€๋Šฅํ•˜๋‹ค.
  • longitudinal measurements์˜ temporal importance๋„ ์•Œ ์ˆ˜ ์žˆ๋‹ค.

1. Introduction & Motivation

Survival analysis(์ƒ์กด๋ถ„์„)๋ž€

  • ์–ด๋–ค ์‚ฌ๊ฑด์˜ ๋ฐœ์ƒ ํ™•๋ฅ ์„ ์‹œ๊ฐ„์ด๋ž€ ๋ณ€์ˆ˜์™€ ํ•จ๊ป˜ ์ƒ๊ฐํ•˜๋Š” ํ†ต๊ณ„ ๋ถ„์„ ๋ฐ ์˜ˆ์ธก ๊ธฐ๋ฒ•
    -> ๋ฐ์ดํ„ฐ๋กœ๋ถ€ํ„ฐ ์ƒ์กดํ•จ์ˆ˜,์œ„ํ—˜ํ•จ์ˆ˜๋ฅผ ์ถ”์ •ํ•˜๊ณ  ํ•ด์„ํ•˜๋Š” ๊ฒƒ
    -> ๊ด€์‹ฌ์žˆ๋Š” event์˜ ๋ฐœ์ƒ์‹œ๊ฐ„๊ณผ covariate(feature)์™€์˜ ๊ด€๊ณ„๋ฅผ ์•Œ๋ ค์ค„ ์ˆ˜ ์žˆ์Œ.
  • ex) ์‹ ๊ทœ ๊ฐ€์ž… ๊ณ ๊ฐ์ด ์„œ๋น„์Šค๋ฅผ ์–ธ์ œ(time)๊นŒ์ง€ ์ด์šฉํ• ์ง€(์ƒ์กด),์–ธ์ œ ๊ณ ๊ฐ์ด ์ดํƒˆํ• ์ง€(event = risk) ,์–ด๋–ค ํ™œ๋™(covariate = feature)์ด ๊ณ ๊ฐ ์œ ์ง€(์ƒ์กด)์— ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š”์ง€ ๋ถ„์„,
    • survival function(์ƒ์กดํ•จ์ˆ˜) : ์‹œ๊ฐ„ t ์ดํ›„์— ์ƒ์กดํ•  ํ™•๋ฅ 
    • hazard function(์œ„ํ—˜ํ•จ์ˆ˜) : ํŠน์ •์‹œ๊ฐ„ t์— event๊ฐ€ ๋ฐœ์ƒํ•  ํ™•๋ฅ  -> ์˜ˆ๋ฅผ ๋“ค์–ด event๊ฐ€ ๊ณ ๊ฐ์˜ ์ดํƒˆ์ผ ๋•Œ ์œ„ํ—˜ํ•จ์ˆ˜ ๋ชจ์–‘์„ ๋ณด๊ณ  ๊ณ ๊ฐ์—๊ฒŒ ์ด๋ฒคํŠธ๋‚˜ ํ˜œํƒ์„ ์ œ๊ณตํ•  ํƒ€์ด๋ฐ์„ ๊ฒฐ์ •ํ•  ์ˆ˜ ์žˆ์Œ.
    • Survival analysis(์ƒ์กด๋ถ„์„)with competing risks(event) :
      • event๊ฐ€ ์—ฌ๋Ÿฌ๊ฐœ์ธ๋ฐ, ๋™์‹œ์— ์ผ์–ด๋‚˜์ง€๋Š” ๋ชปํ•จ. ์˜ˆ๋ฅผ ๋“ค์–ด ์‚ฌ๋ง์›์ธ.-> categoricalํ•œ ์ปฌ๋Ÿผ์€ ๋ชจ๋‘ ์ด๋ฒคํŠธ๊ฐ€ ๋  ์ˆ˜ ์žˆ์„ ๋“ฏ
    • CIF(๋ˆ„์ ์œ„ํ—˜ํ•จ์ˆ˜) : t ์‹œ์  ์ „๊นŒ์ง€ ๊ณ ๊ฐ์ด ์ดํƒˆํ•  ํ™•๋ฅ ์„ ๋ชจ๋‘ ๋”ํ•œ ๊ฒƒ.
      image

๊ธฐ์กด Survival analysis model์˜ ๋ฌธ์ œ์ 

  • ๋งค๋…„ ๋ฐ์ดํ„ฐ๊ฐ€ ์ธก์ • ๋˜๋”๋ผ๋„, ๋ณดํ†ต last available measurement๋ฅผ ๊ธฐ๋ฐ˜์œผ๋กœ ๋ถ„์„๋จ.
    -> it is essential to incorporate longitudinal measurements rather than discarding valuable information recorded over time, this allows us to make better risk assessments on the clinical events.

(1)Joint model

  • still maintain a propotional hazard assumption -> ์‹œ๊ฐ„๊ณผ ๊ด€๊ณ„์—†์ด ์œ„ํ—˜ํ•จ์ˆ˜๊ฐ€ ์ผ์ •ํ•˜๋‹ค๋Š” ๊ฐ€์ •

(2)Landmarking

  • not fully dynamic; survival predictions are only available at the predefined landmarking times, not at times at which new measurements are obtained.
  • it makes assumptions about the underlying stochastic process for the survival model, which may not be true in practice -> limiting the model in terms of learning the relationships between the covariates and events of interest.
  • only incorporates a subset of the longitudinal history up to the landmarking time, which may result in information loss when making predictions

(3)๊ธฐ์กดdeep network

  • provide only static survival analysis: use only current information to perform the survival predictions and most of theworks focus on a single risk rather than multiple risks.

Dynamic- Deephit

DynamicDeepHit learns, on the basis of the available longitudinal measurements, a data-driven distribution of first hitting times.

2. Problem Formulation

A. Time-to-Event Data

image

image

  • observed covariates

    • static (time-invariant) and time-varying covariates that are recorded for a period of time image

image

  • time-to-event(s) : ๋ถˆ์—ฐ์†์ ์ด๊ณ , irregulargํ•˜๊ณ  t_max ์ฆ‰ limit์ด ์žˆ๋Š” ๋ฐ์ดํ„ฐ
  • a label indicating the type of event (e.g., death or adverse clinical event) including right-censoring.

B. Cumulative Incidence Function(CIF)

  • probability that a particular event kโˆ— โˆˆ K occurs on or before time ฯ„ โˆ— (conditioned on the history of longitudinal measurements X โˆ—)
  • longitudinal measurements have been recorded up to tโˆ—_J
  • x ํŠน์„ฑ์„ ๊ฐ€์ง„ ์ƒ˜ํ”Œ์ด, t์‹œ์  ๋‚ด์— ์ด๋ฒคํŠธ k๊ฐ€ ๋ฐœ์ƒํ•  ํ™•๋ฅ ์„ ๊ตฌํ•˜๋Š” ๊ฒƒ image image
  • CIF true๊ฐ’ ๋ชฐ๋ผ์„œ ์ถ”์ •๊ฐ’ ์“ธ๊ฑฐ์ž„.

3.DynamicDeepHit

  • learns, on the basis of the available longitudinal measurements, a data-driven distribution of first hitting times of competing events.
  • learns the complex relationships between trajectories and survival probabilities
    • Competing risks are not independent and must be treated jointly

Network Architecture

image

1. shared subnetwork

  • handles the history of longitudinal measurements and predicts the next measurements of time-varying covariates
  • encodes the information in longitudinal measurements into a fixed-length vector (context vector) using RNN
  • We employ a temporal attention mechanism [18] in the hidden states of the RNN structure when constructing the context vector
    • access the necessary information, which has progressed along with the trajectory of the past longitudinal measurements, by paying attention to relevant hidden states across different time stamps

1.1 RNN(GRU)

  • GRU
    • image image image
  • For each time stamp j = 1,...J โˆ’ 1, the RNN structure takes a tuple of $(x_j , m_j , ฮด_j )$ as an input and outputs $(y_j , h_j )$ , where y_j is the estimate of time-varying covariates after time $ฮด_j$ has elapsed, i.e., $x_j+1$ and $h_j$ is the hiddenstate at time stamp j

1.2 Temporal Attention

  • to unravel temporal importance of the history of measurements in making risk predictions image image

2. cause-specific subnetwork

  • Input : shared Sub-network๋ฅผ ํ†ต๊ณผํ•˜๊ณ  ๋‚˜์˜จ context vector์™€ the last measurements
  • ๋Œ€์ƒ์ด ๋˜๋Š” Event์˜ ๊ฐœ์ˆ˜๋งŒํผ Cause-Specific Sub-network๋ฅผ ๊ตฌ์„ฑ(๊ธฐ์กด์˜ ์ƒ์กด๋ถ„์„ ๋ฐฉ๋ฒ•๋“ค๊ณผ๋Š” ๋‹ฌ๋ฆฌ ์—ฌ๋Ÿฌ ์ด๋ฒคํŠธ์— ๋Œ€ํ•ด์„œ ๋ถ„์„ํ•  ์ˆ˜ ์žˆ๋‹ค๋Š” ์ ์ด DeepHit์˜ ๊ฐ•์ ์ด์—ˆ์Œ)
  • ๊ฐ Event๋ณ„ Cause-Specific Sub-network๋ฅผ ํ†ต๊ณผ
  • estimate the joint distribution of the first hitting time and competing events that is further used for risk predictions.

image (= probability of the first hitting time of a specific cause k)

3. Output layer

image

  • Event ๋ณ„ Output Layer ๋ฒกํ„ฐ๋“ค์„ ๋ชจ๋‘ ์ด์–ด๋ถ™์ด๊ณ , Softmax ํ•จ์ˆ˜๋ฅผ ํ†ต๊ณผ
  • ์ด๊ฑธ๋กœ CIF ์ถ”์ •๊ฐ’ ๊ตฌํ•ด

Training Dynamic-Deephit

1.Log-Likelihood Loss

image

  • ์ด๋ฒคํŠธ ๋ฐœ์ƒ ์‹œ๊ฐ„์— ๋Œ€ํ•œ Loss ํ•จ์ˆ˜
  • the negative log-likelihood of the joint distribution of the first hitting time and events, which is necessary to capture the first hitting time in the right-censored data
    • (not censored; i๋ฒˆ์งธ ์ƒ˜ํ”Œ์ด ์ด๋ฒคํŠธ๊ฐ€ ๋ฐœ์ƒํ•œ ๊ฒฝ์šฐ): captures both the โ€œeventโ€ & โ€œtimeโ€ at which the event occurs -> ์ด๋ฒคํŠธ๊ฐ€ ๋ฐœ์ƒํ•˜๋Š” ์‹œ๊ฐ„์„ ์ž˜ ๋งž์ถœ์ˆ˜๋ก Loss ํ•จ์ˆ˜๊ฐ€ ๊ฐ์†Œ
    • (censored ; i๋ฒˆ์งธ ์ƒ˜ํ”Œ์ด ์ด๋ฒคํŠธ๊ฐ€ ๋ฐœ์ƒํ•˜์ง€ ์•Š์€ ๊ฒฝ์šฐ): captures โ€œtimeโ€ censored -> ์ด๊ฒƒ์€ Censoring ๋ฐ์ดํ„ฐ(์ด๋ฒคํŠธ ๋ฐœ์ƒ ์—ฌ๋ถ€๋ฅผ ๋ชจ๋ฅด๋Š” ๋ฐ์ดํ„ฐ)์— ๋Œ€ํ•˜์—ฌ, ๊ด€์ธก ์‹œ์  ์ด์ „๊นŒ์ง€ ์•„๋ฌด ์ด๋ฒคํŠธ๋„ ๋ฐœ์ƒํ•˜๋ฉด ์•ˆ๋˜๊ฒŒ ํ•˜๋Š” Loss ํ•จ์ˆ˜

2.Ranking Loss

image

  • ์ด๋ฒคํŠธ๊ฐ€ ๋ฐœ์ƒํ•œ ์‹œ์ ์ด ๋‹ค๋ฅธ ๋‘ ์ƒ˜ํ”Œ๋กœ๋ถ€ํ„ฐ ์ด๋ฒคํŠธ ๋ฐœ์ƒ ์ˆœ์„œ๋ฅผ ๋งžํžˆ๋Š” Loss ํ•จ์ˆ˜
  • i๋ฒˆ ์งธ ์ƒ˜ํ”Œ์ด j๋ฒˆ ์งธ ์ƒ˜ํ”Œ๋ณด๋‹ค ์ด๋ฒคํŠธ k๊ฐ€ ๋จผ์ € ๋ฐœ์ƒํ–ˆ์„ ๋•Œ์— A๋Š” 1์„ ๋ฐ˜ํ™˜ํ•˜๊ณ , ๋‘ ์ƒ˜ํ”Œ์˜ CIF ์ถ”์ •์น˜์˜ ์ฐจ์ด๊ฐ€ ํด์ˆ˜๋ก L2๊ฐ€ ์ž‘์•„์ง. ์ฆ‰, ๋ชจ๋“  ์ƒ˜ํ”Œ ์Œ๋“ค์˜ ์ˆœ์„œ๋ฅผ ๋งžํžˆ๋Š”๋ฐ, CIF ์ถ”์ •์น˜์˜ ์ฐจ์ด๊ฐ€ ์ตœ๋Œ€ํ•œ ์ปค์ง€๋„๋ก Loss ํ•จ์ˆ˜๊ฐ€ ์„ค๊ณ„
  • concentrate on discriminating estimated individual risks for each cause
  • estimated CIFs calculated at different times
  • to fine-tune network to each โ€œcause-specific estimated CIFโ€
  • penalizes incorrect ordering of pairs
  • adapts the idea of concordance ( = patient who dies at s should have higher risk at time s , than a patient who survived longer than s )
    • coefficients ฮฑk : chosen to trade off ranking losses of the k-th competing event
      • assume here that the coefficients ฮฑk are all equal (i.e. ฮฑk=ฮฑ )
    • ฮท(x,y) : convex loss function
      • use the loss function ฮท(x,y)=exp(โˆ’(xโˆ’y)ฯƒ. ).

3.Prediction Loss

image

  • incorporates the prediction error on trajectories of timevarying covariates to capture the hidden representations of the longitudinal history and to regularize the network.

4. Experiment

data

  • UK Cystic Fibrosis Registry
  • 5,883 patients
  • between ์—ฐ๊ฐ„ 2009-2015.
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