Epidemiology and prognosis of osteosarcoma

Osteosarcoma is the most common primary malignant bone tumour with a peak incidence in adolescents and young adults (AYA). However, in France, this rare disease represents less than 10% of all AYA cancers with 150 new cases/year, including adults. Osteosarcoma treatment relies on preoperative chemotherapy, tumour surgical resection and postoperative chemotherapy. With this multidisciplinary approach, the 3-year event-free survival (EFS) rate reaches 70% in patients with non-metastatic osteosarcoma. In France, the chemotherapy regimen used for treatment depends on age: children/adolescents are treated with the combination of methotrexate, etoposide and ifosfamide (M-EI),1 while adults receive a combination of doxorubicin, cisplatin and ifosfamide (API-AI).2 These regimens formed the backbone preoperative chemotherapy of the recent Sarcome-09/OS2006 trial.3 Postoperative chemotherapy is adapted to the metastatic status at diagnosis and, for patients with a localised disease, to the histological response to neoadjuvant chemotherapy according to Huvos' grading.

The main risk factors of relapse are the presence of metastases at diagnosis, a non-operable disease and poor histological response to preoperative chemotherapy, usually defined by ≥10% residual tumour cells. In the Sarcome-09/OS2006 trial, patients with skip metastasis had a poorer outcome than patients with localised disease, close to patients with metastatic disease, and we considered them as metastatic even if the skip metastasis is the unique metastatic lesion. The 3-year EFS in these high-risk patients is around 40%, which has not improved in the last 20 years despite several clinical trials.3 4 To address this issue, new treatment strategies for patients with high-risk osteosarcoma are needed.

Mifamurtide (L-MTP-PE, MEPACT) in osteosarcoma

Mifamurtide is a fully synthetic lipophilic derivative of the muramyl dipeptide (MDP), encapsulated into liposomes. It binds to extracellular Toll-like receptor-4, activating monocytes and macrophages, and promotes antitumour activity. However, mifamurtide also activates antitumour function of macrophages by intracellular nucleotide-binding oligomerisation domain-2 (NOD) receptor. Mifamurtide enters into macrophages, is degraded into MDP and binds to NOD-2 receptors. It induces NF-κB release through activation of receptor-interacting serine/threonine protein kinases (RICK) signaling pathway and secretion of inflammatory cytokines such as TNFa, IL-6, IL-8 and IL-1.5 6 Preclinical studies showed mifamurtide has similar immunostimulatory effects on these cells as the natural MDP, with the additional advantage of a longer half-life in plasma, lower toxicity and better efficacy. The activation of the monocytes/macrophages and dendritic cells may also activate other innate immune cells such as natural killer cells, and may generate an adaptive immune response by T cells. Human monocytes/macrophages, after in vitro activation with mifamurtide, specifically recognised tumour cells and were not cytotoxic to normal cells.7 In vivo administration of mifamurtide resulted in the inhibition of tumour growth in mouse and rat models of lung metastasis, skin and hepatic cancer, and fibrosarcoma.8 9 Interest in mifamurtide for the treatment of osteosarcoma arises from the remarkable results achieved in dogs, in which spontaneous osteosarcoma is common, and similar to the human disease. Randomised studies in dogs of either mifamurtide alone, or in combination with chemotherapy, showed a significantly improved survival in dogs treated with mifamurtide.10 11 Results in animal tumour models do not support a significant interaction of most chemotherapeutic drugs on macrophage activation by mifamurtide.12

Trial rationale

From 1993 to 1997, the randomised, phase III INT-0133 trial, considering patients with newly diagnosed osteosarcoma, and younger than 30, addressed two questions in a factorial design: efficacy of ifosfamide in addition to MAP chemotherapy (methotrexate–doxorubicin–cisplatin); and efficacy of mifamurtide in addition to postoperative chemotherapy. In the 662 patients enrolled with a localised resectable osteosarcoma, the first analysis showed mifamurtide might improve EFS, but a potential interaction between ifosfamide and mifamurtide hampered the results interpretation.13 A second publication on the same population with a longer follow-up reported a significant benefit of mifamurtide on overall survival (OS) (HR 0.71, 95% CI0.52 to 0.96, p=0.03) and a 6-year survival improvement rate from 70% to 78%, with no significant ifosfamide/mifamurtide interaction.14 In addition, 91 patients with synchronous metastatic osteosarcoma recruited in this trial were analysed separately: mifamurtide effect size on OS was similar in this group (HR 0.72, 95% CI 0.40 to 1.30), but not significant (p=0.27).15

A retrospective study on metastatic/relapsed osteosarcoma confirmed mifamurtide safety.16 The most frequent side effects of mifamurtide are chills, fever, fatigue, nausea, tachycardia and headache with mild to moderate grade. Mifamurtide combined with nephrotoxic (cisplatin, ifosfamide) and hepatotoxic (high-dose methotrexate) chemotherapies in the INT-0133 trial did not increase these toxicities.13–15

Based on these results, the European Medicines Agency granted a centralised marketing authorisation on 6 March 2009 for mifamurtide combined with postoperative chemotherapy for patients between 2 and 30 years old and presenting a high-grade non-metastatic osteosarcoma with complete macroscopic resection (EU/1/08/502/001). However, in the USA, no approval has been obtained. In France, the French Transparency Commission required additional investigation before considering mifamurtide as a standard in front-line therapy of osteosarcoma. In several European countries, mifamurtide use is still limited as the results of the INT-0133 trial have been a matter of debate between key-opinion leaders.17 In addition, European Union authorisation does not include patients over 30, as well as patients with primary metastatic disease for whom outcome improvement is still challenging.

Aim of the study

In this context, further investigations of first-line treatment with mifamurtide in osteosarcoma are necessary, especially for patients with a high risk of relapse (metastases at diagnosis or poor histological response to neoadjuvant chemotherapy). As the current postoperative chemotherapy regimens used for the treatment of osteosarcoma in France contain ifosfamide, the possible interaction with mifamurtide would not jeopardise the evaluation of the benefit associated with mifamurtide. Sarcome-13/OS2016 trial intends to evaluate the survival benefit of mifamurtide combined with postoperative chemotherapy for treating patients with high-risk osteosarcoma.

EFS will be used as a primary endpoint. We will also study the impact of mifamurtide on OS, and the feasibility of the planned treatment with calculation of cumulative dose and dose intensity of mifamurtide and chemotherapy. Acute and long-term toxicity will be evaluated, as well as biomarkers that could be surrogate markers of mifamurtide pharmacological effect, or predictive factors of efficacy and/or toxicity of mifamurtide. If the efficacy of mifamurtide is confirmed, this may allow the use of a currently promising, original drug, in patients with osteosarcoma with the highest risk of failure.

This article reports the Sarcome-13/OS2016 trial protocol V.2.0 of the 28  May 2018.

Study design

Sarcome-13/OS2016 is a French, multicentre, randomised, open-label, phase II trial, with two parallel groups in first-line treatment of high-risk patients with osteosarcoma. This trial is part of a study recruiting all patients aged 2–50 years old with a newly diagnosed high-grade osteosarcoma. Enrolment in the randomised trial will take place after neoadjuvant chemotherapy and surgery. After check of eligibility criteria for the randomised part of the trial, and after informed written consent is signed, the investigator will proceed with the randomisation through an online electronic case report form (e-CRF). A password non-disclosure certificate is signed by the principal investigator engaging his responsibility regarding the confidentiality of the access codes for all users of the e-CRF in his centre. Participation to biological ancillary studies is optional, and subject to a separate consent form. The biological samples will be shipped and centralised at different ‘Centre des Ressources Biologiques’ depending on the samples, under the responsibility of a designated person. Postoperative treatment will be allocated by randomisation (1:1) between: arm-A (control arm: postoperative chemotherapy alone) and arm-B (experimental arm: postoperative chemotherapy + mifamurtide). A dynamic allocation process (minimisation) will be used to obtain a balanced distribution of treatment groups according to planned postoperative chemotherapy aged-based regimens and risk groups: (1) localised disease at diagnosis and poor histological response, (2) metastatic disease at diagnosis (skip or distant metastases) and complete removal of lesions before randomisation and good histological response of the primary tumour, (3) metastatic disease at diagnosis (skip or distant metastases) and planned complete removal of lesions, and good histological response of the primary tumour, (4) metastatic disease at diagnosis and complete removal of lesions before randomisation and poor histological response of the primary tumour, (5) metastatic disease at diagnosis and planned complete removal of lesions and poor histological response of the primary tumour.

Since osteosarcoma is a rare disease, a large phase III trial with standard alpha level cannot be performed within a reasonable time frame. A randomised phase II trial evaluating the efficacy of mifamurtide at a relaxed alpha level in high-risk patients will produce new independent data, which may be combined with results from the previous INT-0133 trial.

Patient selection criteria

Study description

Intervention

After preoperative chemotherapy and surgery of the primary tumour, patients presenting high-risk osteosarcoma will be randomised to receive the treatment allocated, either:

• Arm-A: Postoperative chemotherapy alone, according to age group.

• Arm-B: Postoperative chemotherapy, according to age group + mifamurtide.

Postoperative chemotherapy is part of standard of care for high-risk osteosarcoma. Chemotherapy should be administered as per local practice at each investigator site. The choice of the chemotherapy regimen is based on experience from Sarcome-09/OS2006 trial, and treatments are determined according to patient’s age (figure 1):

• Download figure
• Open in new tab
• Download powerpoint

Figure 1

Treatment scheme according to age.

• Patients ≤25 years old, (M)-API regimen: one course of high-dose methotrexate followed by five API courses, every 21 days.

• Patients 26–50 years old, EI-regimen: five EI courses, every 21 days.

Postoperative treatment will have to start as soon as possible after randomisation and within a maximum of 7 days postrandomisation.

Patients allocated to the experimental arm will receive mifamurtide 2 mg/m² intravenously two times weekly for 12 weeks, at least 3 days apart, then weekly for 24 weeks, starting at the same time of postoperative chemotherapy.

Surgery of the metastatic sites will be performed 1–2 weeks after the surgery of the primary site and before randomisation, if possible. If a surgery of both lungs is indicated, one side should be operated before randomisation while the second side will be operated 6 weeks after the start of postoperative treatment. This will allow a sequential biological/immune study in the experimental arm. If the disease burden remains to be operated, the second surgery can be delayed. In that case, an optional biopsy will be proposed to the patients included in the experimental arm. During the postoperative chemotherapy period, patients will have a physical examination and biological tests before each treatment course, every 3 weeks. Radiological, and echocardiography or cardiac MUGA scintigraphy, and audiogram will also be performed. During the mifamurtide period without chemotherapy, patients will be seen in clinic every week by the physician (before each mifamurtide infusion) and will have standard clinical assessment. They will also have a formal visit every 3 months. Follow-up assessment of the disease will be performed (from last treatment administration) every 3 months for 3 years, then every 6 months for 2 years, then every year up to 10 years for all patients. Follow-up assessment of late treatment effects will be performed 1 and 3 years after the end of postoperative chemotherapy.

All medications for the treatment of symptoms are authorised, and their type, posology and duration of administration will be recorded. Patients should receive full supportive care during the study, including transfusions and analgesics, as appropriate.

As mifamurtide has a lipophilic formulation, it is recommended to separate the times of administration of mifamurtide and doxorubicin, or other lipophilic drugs.

Prohibited concomitant treatments are:

• Immunodepressive treatment.

• High-dose non-steroidal anti-inflammatory drugs.

• Chronic use of steroid treatment.

• Systematic use of steroids as antiemetic prophylaxis.

Premature treatment discontinuation may be due to the following reasons: disease progression, unacceptable toxicity, intercurrent conditions that preclude the continuation of treatment, patient choice or physician decision. Except in case of consent withdrawal for the participation in the study, patient follow-up will continue in compliance with the protocol and follow-up data will be collected until the end of the trial.

Outcome measures

Statistical considerations

Statistical analysis

EFS curves will be estimated using the Kaplan-Meier method. Difference between EFS curves will be tested using a log-rank test at a one-sided alpha=10%. As a first step of the analysis, the relative treatment effect of mifamurtide in terms of EFS and its CI will be estimated using a Cox model with adjustment or stratification on stratification variables (chemotherapy regimen and risk group). The proportional hazards assumption will be evaluated using graphical methods and by extension of the Cox model including treatment-time interaction. As an exploratory analysis, the interaction between mifamurtide and the stratification factors (chemotherapy strata and risk group) will be investigated by adding an interaction term between treatment and each factor separately in the multivariable Cox model, in order to evaluate the heterogeneity of treatment effect across the different subgroups. Treatment effect will be estimated by subgroup (first (M)-API vs EI chemotherapy regimens; then the five risk groups) in the multivariable analysis, and reported in a forest plot. A similar approach will be used to evaluate the predictive value of some clinical and biological factors (exploratory analyses). The main analysis will be based on all patients included in the trial, regardless of protocol compliance (intention-to-treat analysis). Sensitivity analyses of EFS will be performed (1) on the per-protocol population, after exclusion of patients who have switched from one arm to the other as well as patients who could not undergo removal of all initially identified metastatic sites; (2) on the intention-to-treat population with adjustment or stratification on stratification variables and also other possible confounders. Absolute gain in EFS time will also be estimated using the restricted mean survival time difference18 19 which remains valid if the PH assumption appears violated or questionable.

Similar statistical analyses will be used for the OS analysis. No interim analysis of efficacy is planned.

As some historical information is available (table 1), the usual hypothesis-driven approach (frequentist approach) will be completed with a Bayesian analysis incorporating the aggregate treatment effect estimated from a fixed-effect meta-analysis from the previous INT-0133 trial (in patients with localised osteosarcoma14; and metastatic disease15) leading to an overall HR=0.786 (SE=0.110). We also plan to incorporate individual historical data, from Sarcome-09/OS2006 subgroup of patients who fulfilled the planned Sarcome-13/OS2016 eligibility criteria, on the control arm of the current trial (See figure 2).

• Download figure
• Open in new tab
• Download powerpoint

Figure 2

Individual historical data, from Sarcome-09/OS2006 subgroup of patients who fulfilled the planned Sarcome-13/OS2016 eligibility criteria, on the control arm of the current trial.

We will use the approach proposed by Brard et al (BMC Medical Research Methodology—BMRM, in press) combining a mixture prior20 to incorporate the aggregate treatment effect from the INT-0133 trial, and a power prior21 to incorporate the individual historical data from Sarcome-09/OS2006 subgroup of patients. The weights allocated to historical data ( ω  and for historical aggregate treatment effect and individual control data, respectively) have been calibrated based on a simulation study (see online supplementary materials). The trial will be considered successful if the posterior probability of (HR<1) is ≥90% (prespecified decision rule). Considering the chosen set of parameters resulting of the simulation study ( and  , the power is increased from 80% (frequentist approach) to 98% (Bayesian approach) if the true treatment effect is HR=0.55. It increases from 34% to 65% if the true treatment effect is consistent with the published INT-0133 data (HR=0.786) (table 2). The posterior distribution of the HR will be described including the probability of HR<1 or HR below different thresholds. Given the higher probability of positive conclusion of the planned Bayesian approach compared with the frequentist approach, it is possible the Bayesian success criteria will be met while the frequentist analysis is non-significant. In this case, we will claim a positive outcome for the trial based on the results of the Bayesian analysis. The ‘power’ of the proposed Bayesian approach is the probability of a positive conclusion considering the prespecified decision rule.

At the end of the trial, we may consider incorporating data from other relevant trials evaluating mifamurtide, which are currently in progress. A non-informative prior will also be considered to describe the distribution of the treatment effect when considering current trial data only. The Bayesian analysis will allow the description of the probability distribution of the treatment effect, such as the probability that HR is lower than various thresholds, not only HR <1. The statistical analytical plan will be amended before data base lock to prespecify all sources of historical data.

For each type of AE, the worst grade observed across the safety observational period (4 weeks after last treatment administration, and up to 24 weeks after last chemotherapy for control arm), will be tabulated by treatment arm, and the percentages of severe AE (grade ≥4 haematological AE and grade ≥3 extrahaematological AE) will be provided. A butterfly plot will be used to illustrate the difference in proportion of patients experiencing AE and severe AE between treatment groups. Relative risks of severe AE associated with mifamurtide will be estimated.

The Standard Protocol Items: Recommendations for Interventional Trials reporting guidelines have been used to report this trial protocol.22

Patient and public involvement

The protocol was designed and developed by paediatricians and medical oncologists who work in the InterSARC network that includes patients and parents, such as the ‘Info Sarcomes’ organisation. Patients were not directly involved in the design of the study; however, the protocol was discussed and approved by ‘Info Sarcomes’ organisation. The protocol has also been examined by the Patient Committee of the National League against Cancer who assessed the burden of the proposed intervention. Patients will be involved in recruitment to the study as the trial will be advertised on various websites (Info Sarcomes, Unicancer, hospitals’ websites) promoting clinical studies to patients. Study results will be made available to study participants by being posted on ClinicalTrials.gov website.

Dissemination

The trial results, even if they are inconclusive, as well as biological ancillary studies, will be presented at appropriate international congresses and published in international peer review journals.

Trial financing

This study is sponsored by UNICANCER. It is mainly funded by the French Ministry of Health through the Hospital Clinical Research Program (PHRC-K-2016–130 grant). The study drug will be provided by Takeda to the sponsor.