Summary

Objectives: A subset of locally advanced soft tissue sarcoma (STS) patients achieve significant therapeutic benefit from preoperative radiation therapy (RT) as shown by Pisters JCO 1996 and Yang JCO 2018. However, the impact of RT on pathological response (pR) and R0 resection is limited, highlighting the need for novel multimodal therapies aimed at local control. NBTXR3 (hafnium oxide nanoparticles), injected intratumorally may represent such an option. Otherwise inert, NBTXR3 augments the effective RT dose deposited within tumor cells when activated by ionizing radiation to increase cancer cell death compared to RT alone. We report here on the results of a phase II/III randomized clinical trial evaluating the preoperative efficacy and safety of NBTXR3 activated by RT in patients with locally advanced STS of the extremity and trunk wall [NCT02379845].

Methods: This is a multi-national phase II/III randomized, open-label clinical trial. Adults with locally advanced STS of the extremity or trunk wall, of any histologic grade, eligible for preoperative RT were randomly assigned 1:1 to receive NBTXR3 as a single intratumoral injection (volume corresponding to 10% of baseline tumor volume at 53.3g/L) followed by external beam RT (EBRT; 50 Gy as 25 fractions of 2 Gy, over 5 weeks) (arm A) or EBRT alone (arm B). Both arms had the chance to go on to receive post-RT surgical resection. The primary objective was to compare the proportion of patients with pathological complete response (pCR; defined as <5% of residual viable cancer cells after surgery), as assessed by a Central Pathology Review Board based on the EORTC guidelines. Key secondary endpoints included negative surgical margin (R0), limb amputation rate and safety. Safety was evaluated in all subjects who received at least one puncture of NBTXR3 or at least one fraction of RT. Subjects are in continued long-term follow-up, focused on safety.

Results: Between March 3rd, 2015 and November 21st, 2017, 180 patients were randomized and 179 received treatment: n=89; arm A and n=90; arm B. The proportion of patients with pCR was 16.1% (14/87) compared with 7.9% (7/89) in arms A and B, respectively (p=0.044). The R0 resection rate was 77.0% (67/87) in arm A versus 64.0% (57/89) in arm B (p=0.0424). The most common grade 3-4 treatment emergent adverse event (AE) was post-operative wound complication, which occurred at a similar rate in each arm (8/89 and 8/90 in arm A and B, respectively). The most common grade 3-4 AE related to NBTXR3 administration was injection site pain (4/89, 4.5%) and hypotension (4/90, 4.4%). Skin injury was the most common grade 3-4 RT-related AE, which was shared between both arms (5/89, 5.6% and 4/90, 4.4% in arm A and B, respectively). Serious AEs were observed in 35 (39.3%) of 89 patients in arm A and 27 (30.0%) of 90 patients in arm B. There were no treatment-related deaths. Follow-up was conducted on 153 patients with a current median follow-up of 18.5 months. Currently 87 patients are still in long-term follow-up.

Conclusion: This registration trial of NBTXR3 combined with EBRT significantly achieved its primary and secondary endpoints of improving pCR, and increasing R0 resection versus EBRT alone. NBTXR3 together with EBRT was well tolerated with a safety profile consistent with EBRT alone. Taken together, these results led to the EU approval (CE Mark) of NBTXR3 + RT for patients with locally advanced STS of the extremity and trunk wall.

Summary

Purpose/Objective(s): Local interventional treatments of cancers include interventional radiology and radiotherapy (RT). NBTXR3, hafnium oxide nanoparticles, is deeply associated to both. Given as a single local administration it increases energy dose deposit inside tumor cells only when activated by ionizing radiation. Various interventional treatments have been used to treat cancers such as liver, lung, bone. Because entirely new therapies such as NBTXR3 are being introduced, implementation of interventional approaches is continuously growing.

Materials/Methods: NBTXR3 is being evaluated in soft tissue sarcoma (STS, extremity, trunk wall) [NCT02379845], head and neck (HN) [NCT01946867, NCT02901483], prostate [NCT02805894], liver [NCT02721056] and rectal cancers [NCT02465593]. NBTXR3 injected volume is a percentage of baseline tumor volume, and therefore heterogeneous. Image guidance allowed for accurate injection. Standard catheters, needles, and syringes were used for preparation and injection. Importantly, percutaneous needle positioning was done within the region to be irradiated to control potential seeding of cancer cells. NBTXR3 was then activated by IMRT (STS, HN), EBRT or combination brachytherapy/EBRT boost (prostate), SBRT (liver), IMRT or IMAT (rectum).

Results: Thus far, NBTXR3 has been administered to 171 patients by intratumoral/lesional, and intraprostate injections depending on indication. NBTXR3 injections have been demonstrated safe and very well tolerated. Local infection, ulceration or massive tumor necrosis were never observed. This has been confirmed by adequate application of treatment schedules, fitting planned irradiation onset 1 to 5 days post-injection. Importantly, grade 1 ecchymosis and hematoma at puncture site (needle entry) observed in few cases always resolved spontaneously and did not impact dosimetry. Indeed, change of tumor/lesion/prostate volume resolved when water (NBTXR3 vehicle) was drained via lymphatic system. So far, inflammatory response to injection procedure itself was mild. Concerning AEs, grade 3 pain was observed in conscious patients under local anesthesia with STS close to joints (limited extensibility), and in needle shift in injection within a subcapsular liver tumor.

Conclusion: Across 7 clinical trials involving tumors in extremity, trunk wall, liver, rectum, prostate and HN, NBTXR3 injection was well tolerated and demonstrated a very good safety profile. The savoir faire of interventional radiology for local treatment of cancers supported implementation of injection procedures with specific parameters according to anatomy. Intratumoral/lesional or intraprostate injection ensures optimum bioavailability at site of irradiation, protecting patients from systemic toxicity. Future clinical research will involve other anatomical sites such as lymph nodes and lung lesions [NCT03589339].

Summary

With recent advances in radiation delivery techniques, an increasing number of cancer patients undergo radiotherapy. However, due to the non-targeted nature of radiotherapy, doses are limited by potential toxicity to surrounding normal tissue. Thus, a major challenge remains to develop new strategies to improve the tumor selectivity of radiation therapy. Nanobiotix has developed NBTXR3 – a hafnium oxide nanoparticle that can enter tumor cells and deposit high levels of energy in cells when exposed to ionizing radiation thereby increasing tumor-specific physical killing through DNA damage/cell destruction and enhancing the intratumoral immune profile.

At 2018 ESTRO, an overview of NBTXR3 was presented, describing its role in current 7 clinical trials.