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Mini Oral session 2

67MO - Node-sparing modified short-course radiotherapy combined with CAPOX and tislelizumab in patients with MSS/pMMR locally advanced rectal cancer: A multicentre phase II trial (mRCAT)

Date

12 Dec 2024

Session

Mini Oral session 2

Topics

Clinical Research;  Immunotherapy

Tumour Site

Colon and Rectal Cancer

Presenters

Zhangfa Song

Citation

Annals of Oncology (2024) 24 (suppl_1): 1-20. 10.1016/iotech/iotech100744

Authors

Z. Song1, C. Cai2, X. Sun1, W. Lao3, D. Wang4, X. Wang5, H. Liu6, W. Cui7, J. du8, M. Chen3, H. Wang9

Author affiliations

  • 1 Sir Run Run Shaw Hospital, Zhejiang University, School of Medicine, Hangzhou/CN
  • 2 Jinhua Municipal Central Hospital, Jinhua/CN
  • 3 Sir Run Run Shaw Hospital, Zhejiang University School Of Medicine, Hangzhou/CN
  • 4 Sir Run Run Shaw Hospital Zhejiang University,School of Medicine, Hangzhou/CN
  • 5 Sir Run Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou/CN
  • 6 Department of biostatistics and clinical trail office, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, hangzhou/CN
  • 7 Ningbo Medical Treatment Center Lihuili Hospital - Eastern Campus, Ningbo/CN
  • 8 Central Hospital of Jinhua, JInhua/CN
  • 9 Sir Run Run Shaw Hospital - Zhejiang University School of Medicine - Xiasha Campus, Hangzhou/CN

Resources

This content is available to ESMO members and event participants.

Abstract 67MO

Background

Almost 90% of rectal cancers are microsatellite stable (MSS) or mismatch repair proficient (pMMR) subtypes for which PD-1 blockade is ineffective. The effectiveness is still limited although the radiation can enhance the responses of MSS/pMMR rectal cancer to PD-1 blockade. Our study aims to investigate whether node-sparing modified short-course irradiation combined with chemotherapy and PD-1 blockade could be more effective in patients with MSS/pMMR Locally advanced rectal cancer (LARC).

Methods

We conducted a open-label, prospective, multicentre, phase II trial using Simon's two-stage design. Eligible MSS/pMMR LARC patients(cT3-4N0/+M0/cT2N+M0) were received node-sparing modified short-course radiotherapy (the irradiated planned target volume included only the primary tumour bed but not the tumour-draining lymph nodes, 25 Gy/5f, 5 Gy/f) followed by 4 cycles of CAPOX and tislelizumab. Total mesorectal excision (TME) will be performed at weeks 14-15. The primary endpoint is the rate of pathological complete response (pCR), with a hypothesis of an increased pCR of 30% compared with historical data of 10% after conventional CRT.

Results

Between Aug 18, 2023 to Apr 20, 2024, a total of 46 patients were screened for eligibility. 33 patients ultimately proceeded to surgery, all achieved R0 resection. pCR (TRG 0) and MPR (TRG0+1) were achieved in 78.8% (26/33) and 90.9% (30/33) patients, respectively.3 (9.1%) patients reached TRG 2, no patients had TRG 3. Treatment-related adverse events (TRAEs) of any grade occurred in 29/34 (85.3%) patients. The most common TRAEs of grade 1 or 2 included proctitis (17/34, 50%), leukopenia (14/34, 41.2%), thrombocytopenia (11/34, 32.4%) and anemia (8/34, 23.5%). Grade 3 TRAEs occurred in 5.9% (2/34) of patients, and Grade 4 TRAEs occurred in 8.8% (3/34) of patients. No grade 5 adverse events and treatment-related deaths were recorded.

Conclusions

The node-sparing radiation combined with chemo-immunotherapy regimens dramatically increased pCR rates in MSS/pMMR LARC with tolerable toxicity, which is a promising modality for the treatment of MSS/pMMR LARC patients.

Clinical trial identification

NCT05972655. Release date: August 2, 2023.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.

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