1. To assess and describe independently in each arm the biological activity (increase in sTILs) of CMP-001 combined with SBRT and of SBRT alone in patients with early stage TNBC in a preoperative setting (Time Frame - Evaluated between baseline and surgery (up to 7 weeks)): A 10% increase in the presence of TILs (between baseline and surgery) is the defined threshold for efficacy.
Percentage of sTILs will be quantified using hematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) as per current consensus.
Secondary outcome:
1. Toxicity of CMP-001 combined with SBRT and of SBRT alone (Time Frame - (S)AEs collected continuously from the time of informed consent signature until end of treatment visit, which correspond to Day 51 to 60.): Assessement of the incidence and severity of AEs and SAEs
2. Tumor response: pCR and pPR (Time Frame - evaluation at surgery (between day 21 and day 30 post-SBRT) or change from baseline to surgery (up to 7 weeks)): Percentage of patients with a pathological complete response (pCR) and pathological Partial Response (pPR) at surgery in the breast tumoral lesion(s) (lymph node tumoral lesion(s) not included)
3. Tumor response: minimal residual cancer (Time Frame - evaluation at surgery (between day 21 and day 30 post-SBRT) or change from baseline to surgery (up to 7 weeks)): Percentage of patients with minimal residual cancer as assessed by the residual cancer burden index (RCB) at surgery in the breast tumoral lesion(s) (lymph node tumoral lesion(s) not included)
4. Tumor response: Ki-67 (Time Frame - evaluation at surgery (between day 21 and day 30 post-SBRT) or change from baseline to surgery (up to 7 weeks)): Mean change of proliferation index Ki-67 from baseline at surgery.
5. Tumor response: change in tumor characteristics (Time Frame - evaluation at surgery (between day 21 and day 30 post-SBRT) or change from baseline to surgery (up to 7 weeks)): Mean change in tumor characteristics and peritumoral tissues as assessed by breast MRI and/or ultrasound (US) from baseline at surgery. Data will also be compared to previously reported findings.
6. Time-to-event (TTE) (Time Frame - time from the date of randomization to the date of earliest objective tumor recurrence (up to 2 years from randomization)): defined as time from the date of randomization to the date of earliest objective tumor recurrence, including progression that precludes surgery, or local or distant disease recurrence (deaths are censored)
7. Event-free survival (EFS) rate (Time Frame - at 24 months): EFS rate is defined as the percentage of patients who are alive and without event (protocol-defined progression prior to surgery; local, regional, or distant recurrence of breast cancer following curative surgery; a new breast cancer; another new onset malignancy; or death as a result of any cause) at month 24, per the Kaplan-Meier estimate of recurrence-free survival at 24 months.
8. Distant disease-free survival (DDFS) rate (Time Frame - at 24 months): DDFS rate is defined as the percentage of patients without objective distant tumor recurrence (outside of the ipsilateral locoregional region) at month 24, per the Kaplan-Meier estimate of distant tumor recurrence-free survival at 24 months.
9. Overall survival (OS) rate (Time Frame - at 24 months): OS rate is defined as the percentage of patients who are alive at month 24, per the Kaplan-Meier estimate of overall survival at 24 months (as event is considered the death from any cause).
10. Biological activity (difference between the 2 arms) (Time Frame - Evaluated between baseline and surgery for both arms (up to 7 weeks)): sTILs increase will be compared between the two arms