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Radiation therapy given before surgery of soft tissue sarcoma decreases the size of the tumor mass and the presence of malignant cells in its peripheral region. NBTXR3 and radiation therapy may kill more cancer cells and increase the tumor shrinkage rendering surgery more feasible or easier and achieve better local control of the tumor.

The study is a multi-center randomized, open-label, two-arm Phase II/III trial in patients with locally advanced soft tissue sarcoma of the extremity and trunk wall. Patients in the experimental treatment arm (Arm A) will receive an intratumoral injection of NBTXR3 followed by radiotherapy and surgery. Patients in the control arm (Arm B) will be treated with radiotherapy alone followed by surgery only. It is expected to enroll approximately 180 patients to have 78 evaluable patients in each arm.


Patients with locally advanced soft tissue sarcoma of the extremities and trunk wall may participate the study. The duration of each patient will include up to 21 days screening phase, an app. 78 days of study treatment (with or without NBTXR3) and a post-surgery safety period (14 days). The end of treatment visit will happen at app. 94 to 101 days, followed by a follow-up period.

Patients will be randomized in a 1:1 ratio, stratified by histologic subtype (mixoid liposarcoma versus others) to one of the treatment arms.

Increase the pathological complete response rate (pCR) of intratumoral injection of NBTXR3 activated by external beam radiation therapy (EBRT), versus EBRT alone in patients with locally advanced STS of the extremity and trunk wall.

Assess the safety profile of NBTXR3 activated by radiotherapy (incidence of early and late adverse events), to compare the objective response rate (ORR), tumor volume changes after NBTXR3 and carcinological resection rates, and to evaluate limb amputation rates.

Assess the tumor response, to evaluate the time-to-local recurrence, Local Recurrence Rate (LRR) at 12 months and to evaluate the time-to-distant recurrence and Distant-Recurrence Rate (DRR) at 12 months.

The interim evaluation was based on an analysis of the results of two-thirds of the patients included in the Phase II/III study – 104 patients were analyzed out of a total of 156. Based on the safety and available efficacy data, the IDMC has recommended the continuation of the Phase II/III trial of NBTXR3 in soft tissue sarcoma.


Patients will be randomized to receive either NBTXR3 as intratumor injection, activated by external beam radiation therapy or external beam radiation therapy alone, as preoperative treatment. Once the radiotherapy treatment is completed, tumor surgery will be performed in all patients. Focus on the study objectives and outcome measures.


NBTXR3 enhances the effects of radiotherapy by increasing the effective dose of a standard X-ray. This approach builds on a standard cancer treatment and a well-established physical mechanism of action. Radiotherapy treatment is currently limited by toxicity or adverse events resulting from damage to healthy tissue and the difference between therapeutic effect and adverse events is referred to as the therapeutic window. NBTXR3 aims to open the therapeutic by increasing the radiotherapy dose in the tumor without increasing damage to healthy tissue. Focus on radiotherapy comparisons.


A Phase I clinical study in 22 patients with different types of Soft Tissue Sarcoma established that intratumoral injection of NBTXR3 followed by radiotherapy has a good safety profile in patients with locally advanced soft tissue sarcoma (STS), a patient population with an important risk of relapse and few treatment options. Focus on the key findings of this study and more detailed results.