Delta radiomics for rectal cancer response prediction with hybrid 0.35\xa0T magnetic resonance-guided radiotherapy (MRgRT): a hypothesis-generating study for an innovative personalized medicine approach

Luca Boldrini,Carlotta Masciocchi,Nicola Dinapoli,Marco De Spirito,Calogero Casà,Davide Cusumano,Stefania Teodoli,Giuditta Chiloiro,Francesco Cellini,Jacopo Lenkowicz,Vincenzo Valentini,Maria Antonietta Gambacorta,Luigi Azario

doi:10.1007/s11547-018-0951-y

Abstract

The aim of this study was to evaluate the variation of radiomics features, defined as “delta radiomics”, in patients undergoing neoadjuvant radiochemotherapy (RCT) for rectal cancer treated with hybrid magnetic resonance (MR)-guided radiotherapy (MRgRT). The delta radiomics features were then correlated with clinical complete response (cCR) outcome, to investigate their predictive power. A total of 16 patients were enrolled, and 5 patients (31%) showed cCR at restaging examinations. T2*/T1 MR images acquired with a hybrid 0.35 T MRgRT unit were considered for this analysis. An imaging acquisition protocol of 6 MR scans per patient was performed: the first MR was acquired at first simulation (t0) and the remaining ones at fractions 5, 10, 15, 20 and 25. Radiomics features were extracted from the gross tumour volume (GTV), and each feature was correlated with the corresponding delivered dose. The variations of each feature during treatment were quantified, and the ratio between the values calculated at different dose levels and the one extracted at t0 was calculated too. The Wilcoxon–Mann–Whitney test was performed to identify the features whose variation can be predictive of cCR, assessed with a MR acquired 6 weeks after RCT and digital examination. The most predictive feature ratios in cCR prediction were the L_least and glnu ones, calculated at the second week of treatment (22 Gy) with a p value = 0.001. Delta radiomics approach showed promising results and the quantitative analysis of images throughout MRgRT treatment can successfully predict cCR offering an innovative personalized medicine approach to rectal cancer treatment.

Highlights

Significant improvements in locally advanced rectal cancer (LARC) treatment have been met in the past two decades, and to date the typical therapeutic workflow is represented by neoadjuvant long-course radiochemotherapy (RCT), followed by total mesorectal excision (TME) [1,2,3,4].Regardless of the initial disease stage, approximately 11–42% of these patients achieve a pathological complete response after long-course RCT
Conservative surgical approaches have recently been investigated in patients showing clinical complete response after neoadjuvant treatments: both local excision (LE) and “watch and wait” (W&W) approaches represent to date feasible options in order to reduce morbidities and toxicities related to unnecessary TME procedures [7,8,9]
The usual workflow of radiomics-based radiotherapy studies generally considers imaging acquired in standard staging procedures and assumes that the prescribed radiotherapy dose will be effectively delivered to the patient, without taking advantage of any information coming from IGRT imaging protocols during treatment delivery and limiting the models learning to a single image set [20, 34]

Summary

Introduction

Significant improvements in locally advanced rectal cancer (LARC) treatment have been met in the past two decades, and to date the typical therapeutic workflow is represented by neoadjuvant long-course radiochemotherapy (RCT), followed by total mesorectal excision (TME) [1,2,3,4].Regardless of the initial disease stage, approximately 11–42% of these patients achieve a pathological complete response (pCR) after long-course RCT. Conservative surgical approaches have recently been investigated in patients showing clinical complete response (cCR) after neoadjuvant treatments: both local excision (LE) and “watch and wait” (W&W) approaches represent to date feasible options in order to reduce morbidities and toxicities related to unnecessary TME procedures [7,8,9]. In a very recent systematic review and pooled analysis, patients undergoing W&W approach showed a 3-year overall survival of 93.5% (against a 90.1% rate for patients with pCR) and a non-regrowth free survival rate was of 89.2% at 3 years, supporting the favourable prognostic value of cCR already supposed by the first conservative experiences of HabrGama et al [15, 16]

Objectives

Methods

Findings

Discussion

Conclusion