Real-world Efficacy and Safety of Neoadjuvant Dostarlimab in Patients With dMMR/MSI-H Locally Advanced Rectal Cancer

Real-world Efficacy and Safety of Neoadjuvant Dostarlimab in Patients With dMMR/MSI-H Locally Advanced Rectal Cancer

This is an observational, retrospective-prospective, multicentre trial enrolling all patients included in the AIFA monitoring registry of Dostarlimab for the indication in rectal cancer. The aims of the study are to describe the clinical outcomes and safety of patients with dMMR/MSI-H locally advanced rectal cancer (LARC) receiving neoadjuvant dostarlimab in the real-world setting.

The primary objective is to describe the activity of neoadjuvant dostarlimab in terms of objective response rate (RECIST 1.1).

Secondary objectives are:

1. To describe the activity of neoadjuvant dostarlimab in terms of:

   • complete clinical response rate at 6 and 12 months
   • time to clinical complete response
   • duration of clinical complete response
   • near-complete clinical response rate at 6 and 12 months
   • duration of near-complete clinical response
   • duration of objective response
   • rate of surgery (total mesorectal excision or local excision)
   • pathological complete response rate
   • objective response rate (RECIST 1.1) assessed by central radiological review.

2. To describe the safety of neoadjuvant dostarlimab in terms of: Adverse events/SAE incidence and outcome, time and duration of toxicity according to CTCAE v5.0.

3. To descrive the efficacy of neoadjuvant dostarlimab in terms of: event free-survival (EFS), organ preservation at 3 years, time to ditance recurrence and overall survival (OS)

Inclusion Criteria:

• Signed informed consent form
• Age > 18 years
• Histologically confirmed stage II-III rectal cancer
• dMMR/MSI status assessed locally by Immunohistochemistry, next-generation sequencing or PCR

For the retrospective part of the study:

• At least one dose of neoadjuvant dostarlimab from November 2023 (i.e. within the period of AIFA dostarlimab monitoring registry activation for the indication in rectal cancer, which is reimbursed according to the Italian law 648/1996, GU n.252 as of 27/10/2023)
• Eligible deceased or unreachable patients will also be included to avoid selection biases, in respect of the article 110 bis, paragraph 4 of the Italian Privacy Code (a Data Protection Impact Assessment will be produced and published on the Sponsor website before study initiation, and patients explicitly unwilling before death will be not included).

For the prospective part of the study:

- Inclusion in the AIFA dostarlimab monitoring registry for the indication in rectal cancer, to receive dostarlimab according to the Italian law 648/1996, GU n.252 as of 27/10/2023

Exclusion Criteria:

• - Distant metastasis
• Major cognitive dysfunction or psychiatric disorders
• Any previous systemic or local treatment for rectal cancer
• Dostarlimab received within an interventional clinical trial