The response and survival of children with recurrent diffuse intrinsic pontine glioma based on phase II study of antineoplastons A10 and AS2-1 in patients with brainstem glioma

Sample size

The sample size was calculated based upon the previously used method described by Chang et al. [27]. A response rate to ANP of ≥10 % was considered “of interest,” and the primary endpoint was to determine the overall response rate which was confirmed CR or partial response (PR) to ANP therapy. Objective response (OR) and progression-free survival (PFS) were measured from the first day of ANP administration. The distributions of survival and treatment failure were estimated by Kaplan-Meier analysis. As mentioned before, this paper described 17 RPDIPG patients out of the total of 40 brainstem glioma patients.

Treatment

The median maximum dose of ANP A10 was 8.14 g/kg/day (5.69–15.87) and for AS2-1 0.42 g/kg/day (0.21–0.58). The duration of IV ANP therapy ranged from 5 to 178 weeks with a median of 61 weeks.

ANP A10 and AS2-1 were delivered via a dual-channel infusion pump and single-lumen subclavian catheter (Broviac or Groshong) every 4 h. On the first day of administration of ANP, the flow rate of the pump was maintained at 25 mL/h. Beginning from the second day, individual injections were given at 100 to 250 mL/h depending on the patient’s age and tolerance.

On the first day of treatment, the pump was loaded with 60 mL of A10 (0.3 g/mL) and 60 mL of AS2-1 (0.08 g/mL). The volume of each injection was 10 mL administered every 4 h, six times a day. Beginning from the second day of treatment in children younger than 12 years of age, the dose of each injection was increased on a daily basis in increments of 10 mL until the highest tolerable dose or effective dose was reached. For children 12 years of age or older, the dose of A10 was escalated in increments of 20 mL daily, and over 16 years of age, in increments of 40 mL. When the study subject reached the highest tolerated dose, the “escalation phase” of the treatment stopped.

In summary, there were three different volumes of daily dosage increments of ANP depending on the patient’s age: 10 mL daily dose increase per injection for children younger than 12 years of age, 20 mL for children between 12 and 15 years of age, and 40 mL for patients over 16 years of age. The complicated part of the regimen, which is escalation of dosage, was finished during the patient’s treatment at BC under careful supervision of the sub-investigator assigned to the case. Upon returning home, the patient is given a regimen that consisted of administration of the fixed dose (volume) of ANP through an automatic pump six times a day. The pump was typically loaded with ANP once a day and the rest of the administration was done automatically. It was possible to disconnect the pump in between IV boluses given every 4 h to permit patient’s physical activities. The single dosing could be completed within 1 h which would leave 3 h until the next dose, and during this time, the pump could be disconnected. Long-term observation of the patients confirmed that the regimen created a limited burden on the quality of life. After symptomatic improvement, the children were able to attend school and graduate from it. The subject continued the daily administration of six doses of A10 and AS2-1 (every 4 h via an automated pump) until a response to the treatment was determined.

The rationale for using two formulations of ANP was based on prior clinical trials, pharmacokinetic studies, and laboratory research [5]. The escalation of the dosage of ANP was recommended based on the positive results of previous studies carried out to determine whether patients were able to tolerate large volume infusions of intravenous fluids associated with higher doses of ANP [5]. As a safety precaution, it was recommended that the escalation of the dosages would continue through phase II and phase III trial programs.

Medications that were considered necessary for the patients’ welfare and that did not interfere with the evaluation of treatment were given at the discretion of the investigator. The use of corticosteroids was carefully monitored. Treatment with other antineoplastic or immunomodulatory agents was not permitted during the study. Subjects received full supportive care, including transfusions of blood products and antibiotics when appropriate.

The initial 3 weeks of therapy was administered by BC staff on an outpatient basis, in Houston, TX. The treatment did not require hospitalization. Subjects and/or their legal guardians were trained by clinic staff to self-administer ANP therapy during this time. Starting on week 4, ANP therapy was administered at home with 24-h support available via phone. Treatment and monitoring of the subject’s condition, once released to self-administered therapy, continued under the supervision of the subject’s local attending physician (physician who signed the FDA form 1572).

Evaluation and follow-up

Prior to the start of treatment, a gadolinium-enhanced MRI measured all contrast-enhancing lesions. The products of the two greatest perpendicular diameters of all lesions were calculated and totaled, providing a baseline evaluation for each study subject. The tumor measurements were based on contrast-enhanced lesions, but the nonenhancing lesion and overall tumor size were also measured including T2 and FLAIR images [26, 28]. CR required the disappearance of all enhancing lesions sustained for at least 4 weeks, with only physiologic replacement doses of steroids acceptable. Positron emission tomography (PET) shows resolution of hypermetabolic lesions. PR required 25 % or higher decrease of the sum of the products of the two largest perpendicular diameters of enhancing lesions and stable or reduced corticosteroid doses. PD was determined when there was over 25 % increase of enhancing lesions or new lesions, and stable disease (SD) was the status between PR and PD. In the case of SD, the duration was measured from the time therapy commenced. The results of all MRI and PET scans were verified by radiologists not affiliated with BRI or BC, and their determination of response was accepted. Complete and partial responses were verified by central radiology review.

Blood and urine tests (complete blood count with differential, platelet count, reticulocyte count, and serum chemistry), anticonvulsant serum levels, prothrombin time, and partial thromboplastin time were carried out on all subjects prior to the start of treatment to establish baseline values. The additional pretreatment measurements included KPS, vital signs, clinical disease status, demographics, medical history and current medications, physical examination with neurologic emphasis, chest X-rays, and EKG. Toxicity was evaluated in all patients enrolled in the study. Data on adverse drug experiences (ADEs) were collected during the initial 3 weeks of ANP therapy by clinic staff at the BC. MRIs were repeated at least every 8 weeks during the first 2 years unless the patient’s condition or confirmation of response required an MRI within 4 weeks. PET scans were performed as necessary. When study subjects transitioned to home-based therapy administration under the care of a local physician, clinic staff made daily telephone contact for the first 2 months to ensure protocol compliance, to resolve any issues with therapy administration, and to continue assessing ADEs. Weekly contact was made starting in the third month. Continued patient treatment with ANP was determined on at least a weekly basis and based upon the trial protocol, patient health status, and the response to treatment.

The records of daily administration of ANP were maintained and carefully checked for drug accountability. The ADEs were graded according to the Common Terminology Criteria for Adverse Events (CTCAE v.3). Pharmacokinetic studies have been previously carried out and were not included in this study. Based on a prior study, there was no indication of interference with essential supportive medications, in particular, antiseizure drugs.