Immunotherapy approaches for rare pediatric solid tumors: advances and future directions

PURPOSE OF REVIEW

Immunotherapy for pediatric tumors is rapidly evolving. From major successes in pediatric hematologic malignancies, immunotherapy utility increased in the pediatric solid tumor landscape. Numerous pediatric solid tumors are defined as rare with limitations in diagnosis and treatment. This review will describe four major immunotherapies used in pediatrics and discuss results seen in rare pediatric tumors. We will also briefly review the challenges of immunotherapy in solid tumors and opportunities to drive this therapy forward.

RECENT FINDINGS

Despite rare success employing immunotherapy for pediatric solid tumors, recently there have been several successes in pediatric rare solid tumors. After describing the evolving landscape of rare pediatric tumors, we will demonstrate the successes or disappointments of immunotherapy. We will describe the mechanism of four immunotherapies used in the pediatrics, followed by the published results. Finally, we will discuss the challenges and opportunities for immunotherapies in pediatric rare tumors.

SUMMARY

Pediatric rare tumors are lacking in treatment options. Despite numerous disappointments utilizing immunotherapies in the more common pediatric solid tumors, there have been several successes within the pediatric rare tumor landscape. Much work is still needed to enhance our understanding and knowledge on utilizing these immunotherapies for pediatric rare solid tumors.

Immunotherapy as a Promising Option for the Treatment of Advanced Chordoma: A Systemic Review

OBJECTIVE

To summarize the function and efficacy of immunotherapy as an adjunctive therapy in the treatment of advanced chordoma.

METHODS

Literature search was conducted by two reviewers independently. Case reports, case series and clinical trials of immunotherapy for chordoma were retrieved systematically from Pubmed, Web of Science, Scoupus and Cochrane Library. Clinical outcome data extracted from the literature included median progression-free survival (PFS), median overall survival (OS), clinical responses and adverse events (AEs).

RESULTS

All studies were published between 2015 and 2022. Twenty-two eligible studies were selected for systemic review. PD-1/PD-L1 immune checkpoint inhibitors (ICIs) were the most common used immunotherapy agents in chordoma, among which Pembrolizumab was the most frequently prescribed. CTLA-4 antibody was only used as combination therapy in chordoma. Dose Limiting Toxicity (DLT) was not observed in any vaccine targeting brachyury, and injection site response was the most frequent AV. The response evaluation criteria in solid tumors (RECIST) were the most generally used evaluation standard in chordoma immunotherapy, and none of the included studies employed the Choi criteria.

CONCLUSIONS

No clinical data have demonstrated that CTLA-4 ICIs combined with PD-1/PD-L1 ICIs is more effective than ICIs monotherapy in treating chordoma, and ICIs in combination with other therapies exhibit more toxicity than monotherapy. PD-1/PD-L1 ICIs monotherapy is recommended as an immunotherapy in patients with advanced chordoma, which may even benefit PD-L1-negative patients. The brachyury vaccine has shown good safety in chordoma patients, and future clinical trials should focus on how to improve its therapeutic efficacy. The use of immunomodulatory agents is a promising therapeutic option, though additional clinical trials are required to evaluate their safety and effectiveness. RECIST does not seem to be an appropriate standard for assessing medications of intratumoral immunotherapy.

Trends in clinical development of pediatric cancer for PD-1 and PD-L1 inhibitors: an analysis of ClinicalTrials.gov

Compared with cytotoxic chemotherapy, radiotherapy, and surgery, positive findings have been acquired through the approach of blocking the programmed cell death protein 1 (PD-1) pathway with antibodies that exert inhibitory effects on PD-1 or cell death protein ligand 1 (PD-L1). Results from clinical trials showed great potential in adult patients with cancers, such as melanoma, non-small cell carcinoma, and nasopharyngeal carcinoma. However, studies of checkpoint inhibitors specifically targeting PD-1/PD-L1 in pediatric patients are limited. We evaluated ongoing clinical trials using PD-1 or PD-L1 inhibitors alone or in combination with other therapies to treat pediatric cancer. The proportion of PD-1/PD-L1 combination clinical trials has increased since 2018; the three most common trials over the past 2 years used CTLA-4 monoclonal antibodies, chemotherapy, and therapies that target the vascular endothelial growth factor axis. This commentary aimed to provide trends and specific insights into methods for conducting clinical trials of immunotherapy in the pediatric population.