ESTRO 2024 - Abstract Book

S1490

Clinical - Lower GI

ESTRO 2024

Apoorva Nayak 1 , David K Simson 1 , Varghese Antony 1 , Anjali K Pahuja 1 , Sauharda Lohani 1 , Shilpa Pati 1 , Sumit Goyal 2 , Shivendra Singh 3 , Munish Gairola 1 , Jaskaran Singh Sethi 1 1 Rajiv Gandhi Cancer Institute and Research Centre, Radiation Oncology, Delhi, India. 2 Rajiv Gandhi Cancer Institute and Research Centre, Medical Oncology, Delhi, India. 3 Rajiv Gandhi Cancer Institute and Research Centre, Surgical Oncology, Delhi, India

Purpose/Objective:

To evaluate the robustness of Immunoscore biopsy (IB) based wait-and-watch strategy (WWS) in patients receiving short-course radiotherapy (SCRT) and chemotherapy. 1

Material/Methods:

This study is a prospective observational study which has included 13 patients who were diagnosed with locally advanced rectal cancer (LARC). After the institutional review board approval, the study was conducted in a tertiary cancer care centre between April 2021 and May 2022. The selection criteria included patients above the age of 18 years with adenocarcinoma and not desirous of surgery. IB evaluated intratumoral CD3+ and CD8+ T cells on an Artificial Intelligence platform and divided patients into high, intermediate and low. Patients with high IB (good outcome) were offered WWS after completing SCRT and 8-12 cycles of 5-FU and oxaliplatin based chemotherapy (CT). They were kept under active surveillance every three months with MRI, sigmoidoscopy and a biopsy if needed. The censor date was on October 10, 2023. The median follow-up was 22 months (range:12 to 29 months). All the statistical analysis was done using Statistical Package for Social Sciences (version 28.0, Armonk, NY: IBM Corp).

Results:

Thirteen consenting patients with a median age of 48 years (range: 28 to 68) were included in the study. Twelve had a lower-rectal disease, and 1 had mid-rectal disease. Of the 13 patients, 7 had high IB score, five intermediate, and one low. Among the seven patients with high IB, six remained under WWS. Out of the six patients under WWS, 1 developed local recurrence after eight months, for which he underwent surgery and is presently disease-free. Five patients with intermediate IB, 4 underwent surgery, and only one opted for WWS. Amongst four patients with intermediate IB who underwent surgery, 1 developed distant metastasis (solitary lung metastasis, underwent wedge resection, and is disease-free). The one patient with intermediate who remained in the WWS group is disease-free. The patient with a low IB, underwent surgery and developed distant metastasis followed by death. At the time of analysis, 12 out of 13 patients were alive and disease-free.

Conclusion:

In this short interim analysis, IB emerges as a promising prognostic and predictive marker in cases of LARC, especially those who opt for WWS and organ preservation. Longer follow-up, randomized trials / real-world evidence should be done to validate the use of IB in clinical practice.