Modular prosthesis, intramedullary nailing and plate fixation are surgical options for humeral metastasis, but the optimal treatment for pathological or impending fractures remains controversial. This study evaluated complications, reoperations, and revisions in patients with humeral metastases treated with these surgical techniques. We retrospectively analyzed 115 patients with humeral metastases treated with modular prosthesis (n = 33), intramedullary nailing (n = 69) or plate fixation (n = 13). We evaluated complications, reoperations without implant removal and revisions requiring implant removal. Cumulative incidence of complications and death was estimated using competing risk analysis. In modular prosthesis group, 5/33 patients had complications (15.1

ABSTRACT Background Management of pseudotumors following hip arthroplasty remains a subject of debate. This study aims to assess implant survival in relation to clinical variables and compares the outcomes of one‐stage and two‐stage revision surgeries. Methods We retrospectively analyzed 55 cases of pseudotumor surgically treated between 2004 and 2023 at a single tertiary care center. Patients underwent either one‐stage (44%) or two‐stage (29%) revision procedures. The following clinical and demographical information were collected: gender, age at diagnosis, body mass index (BMI) (calculated by dividing the patients' weight by their height squared solid mass), the American Society of Anaesthesiologist values (ASA), a diagnosis of pseudotumor identified by radiology and histological examination, time of diagnosis, surgery treatment, and follow‐up. Implant and patient survival were estimated using the Kaplan–Meier method. Results The mean follow‐up was up to 67 months (95% CI 43.43–95.29), and the mean age at diagnosis was 56 years (95% CI 53–59). Revision strategy correlated with CRP levels ( p = 0.013) and tumor size ( p = 0.003). Ten complications (18%) occurred at a mean of 10 months, including wound issues (1), dislocations (4), abductor dysfunctions (4), and deep infection (1). Implant failure occurred in 3 cases (5%). Implant survival was 92% at 5 years (95% CI 0.68–0.97) and 80% at 10 years (95% CI 0.44–0.94). Fourteen patients died by final follow‐up; 2 deaths (14%) were surgery related. Overall patient survival was 83% at 5 years (95% CI 0.68–0.92) and 67% at 10 years (95% CI 0.48–0.80). Postoperative Harris Hip Score ( n = 34) averaged 73.2 (95% CI 68.6–77.8). Conclusions Surgery is recommended for pseudotumor, although the optimal approach remains argued. Our data support a two‐stage revision for large pseudotumors with elevated inflammatory markers. Revision surgery provides good function and low implant failure risk, but patient mortality remains significant due to fragility.

PURPOSE:The distal femur is the most common site for bone sarcoma in children. Expandable prostheses may be used to overcome the resultant limb length discrepancy due to the sacrifice of the growth plate in children who undergo resection of primary bone tumors in the distal femur. Few studies analyzed the complications in children treated with expandable prostheses. Furthermore, to date, no studies evaluated the association between medial tibial plateau deformity and the use of constrained versus rotating hinges expandable prostheses in children who underwent primary bone resection of the distal femur. This study aimed to evaluate the complications and reconstruction survival rates associated with expandable prostheses for the distal femur in children with primary bone tumours, with a particular focus on the risk of tibial plateau deformity related to the use of constrained versus rotating hinge expandable prostheses. METHODS:We performed a retrospective single-centre study of 25 children who underwent distal femur reconstruction with expandable prostheses after resection of primary bone tumours between 2001 and 2024. Eleven children had rotating hinge expandable prosthesis, 14 children had constrained hinge expandable prosthesis, nine children had mechanical expandable prosthesis, and 16 children had magnetic expandable prosthesis. Eight out of 25 children had expandable prosthesis with uncemented femoral stem, and 17 out of 25 children had cemented femoral stem. All 25 children had expandable prosthesis with uncemented tibial smooth stem. The median age of children was nine years (range, 5-14 years). The median follow-up was 9.4 years (range, 1.1-16.5 years). RESULTS:Twelve out of 25 children (48%) presented complications. The mean number of complications per child was 1.0 (range, 0-2). Aseptic loosening of the femoral stem was observed in four out of 25 children (16%). Periprosthetic fracture occurred in one out of 25 children (4%). Breakage of the hinge component of the prosthesis occurred in one out of 25 children (4%). Infection occurred in two out of 25 children (8%). None of the 14 children with constrained hinged prosthesis presented medial tibial plateau deformity. In contrast, seven out of 11 children (63%) who underwent reconstruction with rotating hinge expandable prostheses presented medial tibial plateau deformity. Overall, nine of the 25 children (36%) had to replace their temporary expandable prosthesis with a definitive standard prosthesis. Reconstruction survival was 79.3% at five years (95% confidence interval 53.7 to 91.7%) and 59.5% at ten years (95% confidence interval 28.3% to 80.1%). CONCLUSION:Rotating hinge prosthesis showed a high risk of medial tibial plateau deformity compared to constrained hinged prosthesis. We may recommend the preferential use of constrained hinge expandable prosthesis in children who undergo primary bone tumour resection of the distal femur to reduce the risk of tibial deformity.

PURPOSE:Femoral bone metastases represent a frequent and severe complication in patients with advanced solid tumours. Although fracture risk assessment commonly relies on Mirels' score, its limited specificity often leads to unnecessary surgical interventions. Patient-specific finite element (FE) models have shown improved accuracy; however, current approaches vary widely in methodology and rarely capture the full fracture process. This study investigates for the first time the application of a linear FE approach based on an incremental element deletion technique to simulate both fracture initiation and propagation in femurs with lytic metastases. METHODS:Twenty-four patients with femoral lytic lesions were retrospectively analyzed, and model outcomes were compared with clinical results. The proposed approach was evaluated for its ability to stratify patients according to pathological fracture risk, in comparison with conventional simulation methods and the clinically accepted Mirels' score. In addition, a new failure threshold parameter derived from the work required to fracture the femur was investigated. RESULTS:The simulations successfully replicated clinically observed fracture paths and demonstrated strong capability in differentiating high- and low-risk patients. The failure criterion based on the last applied load during simulated crack propagation provided the highest diagnostic performance, achieving excellent sensitivity and specificity. The fracture initiation parameter showed comparable performance, while the work-based parameter appeared more affected by variability in femur visibility. CONCLUSION:The proposed modeling framework offers the advantage of predicting fracture paths, providing clinically valuable insight, and represents a further step toward improved stratification methods for the clinical management of femoral metastases.

The distal femoral and proximal tibial physes contribute to more than two-thirds of the total longitudinal growth of the lower limb. Reconstruction with expandable prosthesis after primary bone tumor resection of the distal femur in children aims to restore limb length of the femur due to the sacrifice of the distal femur physis. However, distal femur expandable prosthesis may also lead to disturbance in the proximal tibial physeal growth due to the potential impact of the tibial stem on the proximal tibial physis. Few studies investigated whether an uncemented press-fit tibial smooth stem can preserve proximal tibial physeal growth, but their findings are controversial and limited. Therefore, we analyzed if a press-fit tibial smooth stem may preserve proximal tibial physeal growth after expandable prosthesis reconstruction following primary bone tumor resection of the distal femur in children. We retrospectively analyzed 14 children with distal femur sarcoma who underwent reconstruction with an expandable prosthesis and a press-fit tibial smooth stem: 7 males and 7 females, with a median age of 9 years (range, 5 to 15 years). Proximal tibial physeal growth was measured on immediate postoperative and standing panoramic radiographs of both lower limbs, comparing the treated tibia with the contralateral tibia. Outcomes included absolute growth of the proximal tibial physis (mm), relative growth (

To develop a predictive model for estimating the histological response to preoperative chemotherapy based on imaging data in patients with Ewing sarcoma. We included 133 patients with Enneking stage IIB or IIIB Ewing sarcoma who underwent chemotherapy and definitive surgery between 2003 and 2020. We analyzed various radiological parameters before and after preoperative chemotherapy. The necrotic area was evaluated using gadolinium-contrasted magnetic resonance imaging (radiological necrotic grade). Patients were classified as good histological responders if > 95

Surgical treatments for proximal humerus metastasis include modular prosthesis, intramedullary nailing, plate fixation, and hemiarthroplasty. However, it is controversial which surgical treatment could offer less complications and implant failure. The purpose of our study was to report the risk of complications, reoperations and revisions in patients with proximal humerus metastasis treated with modular prosthesis, intramedullary nailing, plate fixation, or hemiarthroplasty. We performed research in the PubMed and Scopus libraries, obtaining 2247 studies. We analyzed studies reporting the risk of complications, reoperations and removal of the implant in patients with proximal humerus metastasis treated with intramedullary nailing, plate fixation, hemiarthroplasty, or megaprosthesis. We included 11 studies (357 patients) reporting patients treated with modular prosthesis (n = 181), intramedullary nailing (n = 101), plate fixation (n = 51) and hemiarthroplasty (n = 24). The risk of complications in patients with proximal humerus metastasis treated with modular prosthesis was 0–40

PURPOSE:This study aimed to compare the histological response, a surrogate preoperative treatment efficacy marker, of patients treated with preoperative chemotherapy with or without preoperative radiotherapy. Moreover, local recurrence in both groups was investigated. METHODS:Surgical specimens from 210 patients with Ewing sarcoma were assessed between 2003 and 2020 to evaluate their histological response to preoperative treatment; 181 patients received preoperative chemotherapy, while 29 received both preoperative chemotherapy and radiotherapy. The histological response rate in the surgical section was assessed based on tumour necrosis and reparative fibrous tissue. RESULTS:The median histological response rates were 100% (interquartile range = 83-100%) for the preoperative chemotherapy and radiotherapy group and 90% (interquartile range = 60-100%) for the preoperative chemotherapy group (P = 0.004). Multivariate logistic regression analysis indicated that the administration of the preoperative radiotherapy (Odds ratio = 3.36 [95% confidence interval, CI 1.32-8.54]; P = 0.011) and small tumour volume (< 200 mL) were associated with the achievement of > 95% histological response (Odds ratio = 0.52 [95% CI 0.27-0.99]; P = 0.047). Local recurrence occurred in 9.9% (18/181) of patients who received preoperative chemotherapy and in 2.4% (1/29) of patients who received both preoperative chemotherapy and radiotherapy (P = 0.258). CONCLUSION:Preoperative radiotherapy might enhance histological response, potentially reducing local recurrence. Therefore, it should be considered for patients with Ewing sarcoma who are at high risk of local recurrence or may have inadequate surgical margins.

The goal of surgery for pelvic metastasis is pain-free reconstruction that enables daily activity without complications for the patient’s remaining life. The purpose of our study was to assess complications, reoperations, functional outcomes, and survival in patients with pelvic metastasis treated with standard or dual mobility total hip arthroplasty (THA) and antiprotrusio cage. We prospectively analyzed 36 patients with pelvic metastasis who underwent reconstruction with standard (n = 20) or dual mobility (n = 16) bearing THA and antiprotrusio cage between 2015 and 2024 at a single institution. We evaluated complications, reoperations, functional outcomes and survival. Infection occurred in five of 36 patients (14

To depict histological and imaging features of myoepithelial carcinoma of the bone and soft tissue. We retrospectively examined histological features in 22 patients with myoepithelial carcinoma of the bone (4 patients) and soft tissue (18 patients) at a single institution. Imaging analysis of 15 patients (bone, 3 patients; soft tissue, 12 patients;) with preoperative images involved classifying lytic bone lesions via the modified Lodwick–Madewell classification; the growth patterns of soft tissue lesions were classified as well-defined, focally invasive, or diffusely invasive. Local recurrence occurred in eight out of 22 patients (36.3

The aim of this article is to determine the safety and efficacy of core decompression (CD) combined with injection of autologous bone marrow concentrate (BMC), demineralized bone matrix (DBM), and platelet-rich fibrin (PRF) for treating femoral head osteonecrosis. Seventy-seven patients (53 males and 24 females) for a total of 87 hips were treated for hip osteonecrosis with CD combined with injection of autologous BMC, DBM, and PRF at Rizzoli Orthopedic Institute from September 2008 to December 2019. Patients were assessed at baseline, at 45 days, and at 3, 6, 12, 24, and 36 months postoperatively. The primary outcome was the survival rate of hips not converted to total hip arthroplasty (THA). The secondary outcomes were (I) radiographic positive evolution assessed by X-ray films and magnetic resonance imaging and (II) the clinical symptoms evaluated with the Harris Hip Score (HHS). Eighty-seven hips from 77 patients with femoral head osteonecrosis (FHON), 60 males and 27 females, with a median age of 34 years (range 15-55) were included. The cause of necrosis was steroid treatment in 30 patients (17 of these for hematological malignancies, 2 for lupus, 1 for Churg-Strauss syndrome, and the remaining for other causes), 1 was alcohol-related, 4 followed hip injury, while 15 patients had idiopathic causes. THA was carried out in 20 hips (40%). These patients had lesions classified as IIa on the Ficat stage in four cases, six were IIb, nine were III, and one was 4. No CD-related complications were found during THA surgery or at the last follow-up in these cohorts of patients. Radiographic progression of the FHON was found in 14 hips (28%), with a higher percentage on Ficat's stage IIb. There were procedure-related complications in two hips, including one femoral neck fracture and one deep infection. Nineteen hips with successful treatment had good to excellent functional results at a 3-year follow-up or more (HHS >= 80). The long-term outcomes of treatment with CD and injection with BMC combined with DBM and PRF are promising to prevent femoral head collapse in patients with FHON. Moreover, CD does not influence the outcome in cases of THA.

No consensus exists for tumor volume response criteria in patients with Ewing sarcoma. This study aimed to identify an optimal cutoff for predicting a good histological response by analyzing tumor volume changes and tumor necrosis after neoadjuvant chemotherapy. We performed a retrospective analysis of 184 Ewing sarcoma patients, analyzing tumor volume changes before and after neoadjuvant chemotherapy. Patients were divided into two groups based on histological response: good (tumor necrosis ≥ 95

A promising approach enhancing osteosarcoma (OS) prognosis involves the combination of various techniques, such as chemo- and photodynamic therapy, delivered through nanocarriers for synergistic cell death. Among the potential candidates for improving drug accumulation at the tumor site, mesenchymal stromal cells (MSCs) exhibit a significant advantage due to their tumor-homing ability and intracellular drug retention. This study evaluates the efficacy of chemo-releasing and photoactive bimodal nanoparticles, kPCe6 NPs, delivered via MSCs. In vitro analyses show that cells internalize and retain kPCe6 NPs in a dose-dependent manner and that kPCe6-loaded cells induce massive tumor cell death in a tridimensional tumor model. Results from an in vivo orthotopic OS murine model show negligible tumor cell death upon peritumoral administration of two doses containing 10(6) loaded cells. To gain insight into this observation, this work investigates the role of cell dose in treatment efficacy. The results indicate that achieving a tumor reduction higher than 90% requires a substantial number of loaded cells, approximately 35% of the entire tumor mass, highlighting the criticality of the cell dose for the success of this therapeutic approach and its potential impact on clinical translation in OS patients, particularly when the number of tumor cells is limited.

BACKGROUND:Myxofibrosarcoma is a rare malignant soft tissue sarcoma characterised by multiple local recurrence and can become of higher grade with each recurrence. Consequently, myxofibrosarcoma represents a burden for patients, a challenge for clinicians, and an interesting disease to study tumour progression. Currently, few myxofibrosarcoma preclinical models are available.METHODS:In this paper, we present a spontaneously immortalised myxofibrosarcoma patient-derived cell line (MF-R 3). We performed phenotypic characterization through multiple biological assays and analyses: proliferation, clonogenic potential, anchorage-independent growth and colony formation, migration, invasion, AgNOR staining, and ultrastructural evaluation.RESULTS:MF-R 3 cells match morphologic and phenotypic characteristics of the original tumour as 2D cultures, 3D aggregates, and on the chorioallantoic membrane of chick embryos. Overall results show a clear neoplastic potential of this cell line. Finally, we tested MF-R 3 sensitivity to anthracyclines in 2D and 3D conditions finding a good response to these drugs.CONCLUSIONS:In conclusion, we established a novel patient-derived myxofibrosarcoma cell line that, together with the few others available, could serve as an important model for studying the molecular pathogenesis of myxofibrosarcoma and for testing new drugs and therapeutic strategies in diverse experimental settings.

INTRODUCTION:Aneurysmal bone cyst (ABC) is a lytic benign bone lesion representing about 1% of all primary bone tumors. Method to treat ABC's have developed over time. The standard of care cure for ABC has been curettage with or without bone grafting of the defect but is burdened by recurrence rates of approximately 25%-31%. Based on the assumption that ABCs usually supplied by one or more pathological feeding arteries, selective arterial embolization has been described as an adjuvant preoperative procedure to reduce intra-operative hemorrhage, and as primary treatment for lesions in difficult surgical access. In the current study, we therefore asked whether (1) a single or a repeat selective arterial embolization (SAE) for treating ABCs would produce comparable healing rates compared with curettage and bone grafting; (2) evaluated the relationship of recurrence in relation to the site of the cyst, the age, and gender of the patients; and (3) the two techniques differ in term of long-term complication.MATERIAL AND METHODS:We retrospectively reviewed 265 patients who underwent curettage and bone grafting or SAE performed at our institute from 1994 to 2018. The diagnosis of ABC was always established with percutaneous CT-guided biopsy or open biopsy. Patients were followed clinically with plain radiographs or CT scan at 3, 6, 9, and 12 months then annually in the absence of symptoms. Treatment success was determined evaluating pre- and postprocedural imaging according to Chang classification.RESULTS:Two hundred and nineteen were treated with curettage and bone grafting (curettage group), and 46 with SAE Group. Of the 219 patients treated with Curettage and bone grafting (curettage group), 165 out of 219 (75.3%) experienced bone healing, while local recurrence was observed in 54 cases (24.7%) after 12 months on average (range: 3-120 months) from surgery. After the first SAE, bone ossification was seen in 27 (58.7%), without needing any further treatment. Eleven recurred patients were treated with SAE (four patients need two while seven need three SAE to heal), and eight patients with curettage and bone grafting. Thirty-eight out of 46 (82%) patients experienced bone ossification regardless the number of SAE. The overall rate of local recurrence for all patients was 26.7%. SAE group presented a lower complication rate (6%) where two patients experienced skin necrosis, and one limb-length discrepancies (2% of all cohort).DISCUSSION:The use of SAE is an attractive option to treat ABC as it combines on one hand a lower complication rate than curettage and bone grafting, on the other it can be carried out in case of nonresectable ABCs, significantly reducing the size of viable ABC lesions, fostering bone remodeling and mineralization, and most importantly, significantly improving the patient's quality of life.

The objective of this study was to determine the efficacy of the PRECICE 2® nail in the treatment of lower limb length discrepancy in patients with a history of bone tumors. This study reports on outcomes, complications, and the safety of the PRECICE 2 limb lengthening nail in a cohort of pediatric patients with limb length discrepancy after surgery for bone tumors. Seventeen patients were treated with intramedullary magnetic nails. The average patient age at the time of surgery was 19 (range 11–32). The PRECICE 2 nail was used on 14 femurs (6 retrograde and 8 anterograde) and 3 tibias. The average consolidation time was 141 days (range 50–360) with a mean CI of 31 ± 12 days/cm. The ASAMI bone score showed 14 (82%) excellent results, 1 (6%) good result, and 2 (12%) poor results. The ASAMI functional score showed 13 (84.6%) excellent results, 3 (11.5%) good results, and 1 (3.8%) fair result. Patients treated with chemotherapy for bone cancer did not show any increase in distraction time or consolidation time. A total of 3 (17%) problems, 1 obstacle (5.5%), and 1 complication (5.5%) were encountered in our case series. The PRECICE 2 nail allows for effective and accurate lengthening preserving the range of motion in patients treated for bone tumors.

Bone metastases are frequent in patients with cancer. Electrochemotherapy (ECT) is a minimally invasive treatment based on a high‐voltage electric pulse combined with an anticancer drug. Preclinical and clinical studies supported the use of ECT in patients with metastatic bone disease, demonstrating that it does not damage the mineral structure of the bone and its regenerative capacity, and that is feasible and efficient for the treatment of bone metastases. Year 2014 saw the start of a registry of patients with bone metastases treated with ECT, whose data are recorded in a shared database.

Osteosarcoma treatment is moving towards more effective combination therapies. Nevertheless, these approaches present distinctive challenges that can complicate the clinical translation, such as increased toxicity and multi-drug resistance. Drug co-encapsulation within a nanoparticle formulation can overcome these challenges and improve the therapeutic index. We previously synthetized keratin nanoparticles functionalized with Chlorin-e6 (Ce6) and paclitaxel (PTX) to combine photo (PDT) and chemotherapy (PTX) regimens, and the inhibition of osteosarcoma cells growth in vitro was demonstrated. In the current study, we generated an orthotopic osteosarcoma murine model for the preclinical evaluation of our combination therapy. To achieve maximum reproducibility, we systematically established key parameters, such as the number of cells to generate the tumor, the nanoparticles dose, the design of the light-delivery device, the treatment schedule, and the irradiation settings. A 60% engrafting rate was obtained using 10 million OS cells inoculated intratibial, with the tumor model recapitulating the histological hallmarks of the human counterpart. By scheduling the treatment as two cycles of injections, a 32% tumor reduction was obtained with PTX mono-therapy and a 78% reduction with the combined PTX-PDT therapy. Our findings provide the in vivo proof of concept for the subsequent clinical development of a combination therapy to fight osteosarcoma.

The aim of this study was to investigate the chemical and physical surface properties of a hybrid nanohydroxyapatite/collagen/polycaprolactone (nHA/Coll/PCL) material, and to test its in vitro biocompatibility and in vivo osteointegration. Mineralized collagen fibers with nHA were admixed with PCL at a weight proportion of 50:50. The material was characterized by transmission X-ray diffraction (XRD), electron microscopy (TEM), atomic force microscopy (AFM), force spectroscopy, X-ray Photoemission Spectroscopy (XPS), and biocompatibility testing using human mesenchymal stem cells (MSCs), and Hepatocyte carcinoma (HePG2) and primary osteogenic sarcoma (SAOS-2) cells as complementary tests. In addition, the ability of this material to fill three- wall bony defects was tested in the mandible of a sheep. The material had confirmed the relative low crystallinity of the HA having a nano-sized dimension, which was composed of only oxygen, carbon, calcium and phosphorus, without no residual cytotoxic element. Human MSCs on the surface scaffold showed high metabolic activity and a high rate of viability. Biocompatibility complementary testing using HePG2 and SAOS-2 cells showed good metabolic activity, and the lactate dehydrogenase assay using HePG2 cells demonstrated no significant cytotoxicity. Histological analysis of the in-vivo experimentation showed osteointegration of the material and the absence of inflammatory cells at the bone-scaffold interface. Some areas showed bone-cell seeding and isolated agglomerates of bone cells were evident in the inner scaffold.

Background Osteosarcoma (OS) is an aggressive malignant neoplasm that still suffers from poor prognosis in the case of distal metastases or occurrence of multi-drug resistance. It is therefore crucial to find novel therapeutic options able to go beyond these limitations and improve patients’ survival. The objective of this study is to exploit the intrinsic properties of mesenchymal stromal cells (MSCs) to migrate and infiltrate the tumor stroma to specifically deliver therapeutic agents directly to cancer cells. In particular, we aimed to test the efficacy of the photoactivation of MSCs loaded with nanoparticles in vitro and in a murine in vivo ectopic osteosarcoma model. Methods AlPcS 4 @FNPs were produced by adding tetra-sulfonated aluminum phthalocyanine (AlPcS 4 ) to an aqueous solution of positively charged poly-methyl methacrylate core-shell fluorescent nanoparticles (FNPs). The photodynamic therapy (PDT) effect is achieved by activation of the photosensitizer AlPcS 4 in the near-infrared light with an LED source. Human MSCs were isolated from the bone marrow of five donors to account for inter-patients variability and used in this study after being evaluated for their clonogenicity, multipotency and immunophenotypic profile. MSC lines were then tested for the ability to internalize and retain the nanoparticles, along with their migratory properties in vitro. Photoactivation effect was evaluated both in a monolayer (2D) co-culture of AlPcS 4 @FNPs loaded MSCs with human OS cells (SaOS-2) and in tridimensional (3D) multicellular spheroids (AlPcS 4 @FNPs loaded MSCs with human OS cells, MG-63). Cell death was assessed by AnnexinV/PI and Live&Dead CalceinAM/EthD staining in 2D, while in the 3D co-culture, the cell killing effect was measured through ATP content, CalceinAM/EthD staining and TEM imaging. We also evaluated the effectiveness of AlPcS 4 @FNPs loaded MSCs as delivery systems and the ability of the photodynamic treatment to kill cancer cells in a subcutaneous mouse model of OS by bioluminescence imaging (BLI) and histology. Results MSCs internalized AlPcS 4 @FNPs without losing or altering their motility and viability in vitro. Photoactivation of AlPcS 4 @FNPs loaded MSCs induced high level of OS cells death in the 2D co-culture. Similarly, in the 3D co-culture (MSCs:OS ratios 1:1 or 1:3), a substantial decrease of both MSCs and OS cells viability was observed. Notably, when increasing the MSCs:OS ratio to 1:7, photoactivation still caused more than 40% cells death. When tested in an in vivo ectopic OS model, AlPcS4@FNPs loaded MSCs were able to decrease OS growth by 68% after two cycles of photoactivation. Conclusions Our findings demonstrate that MSCs can deliver functional photosensitizer-decorated nanoparticles in vitro and in vivo and inhibit OS tumor growth. MSCs may be an effective platform for the targeted delivery of therapeutic nanodrugs in a clinical scenario, alone or in combination with other osteosarcoma treatment modalities.