# Estimating optimally tailored active surveillance strategy under interval censoring

## TL;DR

This paper introduces a new method to tailor active surveillance strategies in cancer care, reducing invasive biopsies while accounting for complex data challenges.

## Contribution

A non-parametric kernel-based method is proposed to estimate tailored active surveillance strategies under interval censoring and dropout.

## Key findings

- The proposed method provides accurate estimates of true positive and negative rates under interval censoring.
- Simulation and real-world prostate cancer data demonstrate the method's superiority over existing approaches.
- The framework incorporates cost-benefit analysis for optimal medical decision-making.

## Abstract

Active surveillance (AS) using repeated biopsies to monitor disease progression has been a popular alternative to immediate surgical intervention in cancer care. However, a biopsy procedure is invasive and sometimes leads to severe side effects of infection and bleeding. To reduce the burden of repeated surveillance biopsies, biomarker-assistant decision rules are sought to replace the fix-for-all regimen with tailored biopsy intensity for individual patients. Constructing or evaluating such decision rules is challenging. The key AS outcome is often ascertained subject to interval censoring. Furthermore, patients will discontinue participation in the AS study once they receive a positive surveillance biopsy. Thus, patient dropout is affected by the outcomes of these biopsies. This work proposes a non-parametric kernel-based method to estimate a tailored AS strategy’s true positive rates (TPRs) and true negative rates (TNRs), accounting for interval censoring and immediate dropouts. We develop a weighted classification framework based on these estimates to estimate the optimally tailored AS strategy and further incorporate the cost-benefit ratio for cost-effectiveness in medical decision-making. Theoretically, we provide a uniform generalization error bound of the derived AS strategy, accommodating all possible trade-offs between TPRs and TNRs. Simulation and application to a prostate cancer surveillance study show the superiority of the proposed method.