Propensity score analysis of radical proctectomy versus organ preservation using contact X-ray brachytherapy for rectal cancer

Jean-Pierre Gerard; Lucile Montagne; Brice Thamphya; Jerôme Doyen; Renaud Schiappa; Karene Benezery; Sophie Gourgou; Catherine Dejean; Jean-Michel Hannoun-Levi

doi:10.1016/j.ctro.2021.12.007

Propensity score analysis of radical proctectomy versus organ preservation using contact X-ray brachytherapy for rectal cancer

Clin Transl Radiat Oncol. 2022 Jan 6:33:70-76. doi: 10.1016/j.ctro.2021.12.007. eCollection 2022 Mar.

Authors

Jean-Pierre Gerard¹, Lucile Montagne¹, Brice Thamphya², Jerôme Doyen¹, Renaud Schiappa², Karene Benezery¹, Sophie Gourgou³, Catherine Dejean⁴, Jean-Michel Hannoun-Levi¹

Affiliations

¹ Department of Radiation Oncology, Centre Antoine Lacassagne, Nice, Côte d'Azur University, Nice, France.
² Department of Clinical Research Statistics, Centre Antoine Lacassagne, Nice, Côte d'Azur University, Nice, France.
³ Department of Biometry, Institut de Cancérologie de Montpellier, France.
⁴ Department of Medical Physics, Centre Antoine Lacassagne, Nice, Côte d'Azur University, Nice, France.

Abstract

Introduction: Radical proctectomy (RP-TME) with neo adjuvant chemoradiotherapy (nCRT) remains the standard treatment for T2-T3 rectal cancer. Organ preservation (OP) using CRT and a "watch and wait" strategy (W&W) is a field of research. Planned organ preservation can be proposed for early T1-T3 using contact X-ray brachytherapy (CXB). We compared the oncological outcomes of both approaches using a propensity score matched-cohort analysis.

Material and methods: For comparative analyses between patients with nCRT + RP-TME and patients with CXB + CRT, propensity scores were calculated with logistic regression and multiple imputations for missing data. The variables included in the propensity score model were PS status, T-N stage and rectal circumference extension. Patients were matched 1:1 using the nearest neighbor method with a 0.1 caliper restriction. The 5-year Cancer Specific survival was the primary end point.

Results: The Accord 12 phase III trial included 584 patients who treated with nCRT + RP-TME. The CXB cohort included 71 patients with a planned OP. To select OP patient candidate, T4, tumor with extension >66% circumference were eliminated and only patients treated with CXB + CRT were analyzed in the CXB cohort resulting in a total of 374 patients. A one to one paired cohort with 36 patients in each group was derived. These two cohorts were well matched for all confounding factors except for age. The 5-year cancer specific rate showed no significant difference between the two groups (89% in Accord 12 vs 82% in CXB; p = 0.84). At 5 years, rate of metastasis (15% vs 22%, p = 0.54) showed no significant difference. In the CXB group 33/36 patients preserved their rectum.

Conclusion: The organ preservation strategy using CXB boost yielded a 5-year cancer specific survival rate similar to patients treated with RP-TME. In selected early T2-3 rectal adenocarcinoma an organ preservation strategy could be offered as a reasonable option.

Keywords: Contact X-ray brachytherapy; Organ preservation; Propensity score; Rectal cancer.