Tandem ASCT for neuroblastoma comes with caveat

“In 2009, results of that study were released and the dinutuximab arm was superior,” she noted, so patients were no longer randomized to isotretinoin only.

Prior studies indicated that 40% of patients went off trial at the end of induction therapy, so the investigators enrolled 665 patients to ensure a randomization of at least 332 patients. 

Data cut-off for the presentation was March 31, 2016.

Patient demographics

Of the 665 patients accrued, 13 were ineligible. Twenty-seven patients with favorable prognosis were non-randomly assigned to single ASCT.

Forty percent (229 patients) went off protocol therapy prior to randomization. The main reasons for this were death (8 patients), progressive disease (48 patients), and physician and patient discretion (206 patients).

Investigators randomized 355 patients, 179 to single ASCT and 176 to tandem ASCT.

Patients were a median age of 37.2 months, 38.2% had MYCN amplification, and 88% were INSS stage 4.

The randomized cohorts of patients were similar to the overall patient cohort in terms of age, MYCN amplification, and stage 4 disease.

The randomizations were also well balanced in terms of MYCN amplifications, stage 4 disease, and response to induction chemotherapy.

The investigators retrospectively reviewed the patient characteristics, including age at diagnosis, early response to induction, and assignment to receive immunotherapy, “and there was no statistically significant difference between the randomized cohorts for these characteristics,” Dr Park said.

Safety

The most commonly observed grade 3 or greater non-hematologic toxicities in the single and tandem arms included infection (18.3% and 17.9%, respectively), mucosal toxicities (17.2% and 13.6%, respectively), and hepatic toxicities, including sinusoidal obstructive disorder (6.5% and 6.2%, respectively). 

The investigators observed no significant differences between the arms in regard to the rate of these toxicities. In addition, they observed no difference between the arms in the rate of regimen-related mortality, 4.1% in the single arm, and 1.2% in the tandem arm.

Efficacy

For all patients (n=652) from time of enrollment, the 3-year EFS was 51.0% and the 3-year OS was 68.3%.

In randomized patients (n=355), from the time of randomization, the 3-year EFS was 54.8% and the 3-year OS, 71.5%, with a median survival time of 4.6 years.

There was a statistically significant improvement in EFS for those patients assigned to tandem transplant, with a 3-year EFS of 61.4% as compared to those assigned to single transplant, who had a 3-year EFS of 48.4% (P=0.0081).

There was not a statistically significant difference in OS. However, Dr Park pointed out that the trial was not powered to detect a difference in overall survival. 

When looking at the cohort of stage 4 patients who were older than 18 months, investigators again saw a statistically significant improvement in EFS. The 3-year EFS was 59%.1 for tandem transplants vs 45.5% for single transplants, P=0.0083.

Again, there was no difference in OS in the INSS stage 4 patients older than 18 months.

“And finally, when we analyzed the outcome for children who were assigned to receive immunotherapy,” Dr Park pointed out, “from the time of start of immunotherapy, there was a statistically significant improvement in both event-free survival and overall survival for those children who received tandem transplants.”

The 3-year EFS for patients who received a tandem transplant and immunotherapy was 73.7% compared to the 3-year EFS of 56.0% for patients who received a single transplant and immunotherapy (P=0.0033). 

The 3-year overall survival was also significantly improved for patients who received tandem transplants and immunotherapy (83.7%) compared to those who received a single transplant and immunotherapy (74.4%) (P=0.0322).