Pembrolizumab Achieves a Complete Response in an NF-1 Mutated, PD-L1 Positive Malignant Peripheral Nerve Sheath Tumor: A Case Report and Review of the Benchmarks

Rare primary intrapulmonary malignant peripheral nerve sheath tumor showing significant response to sintilimab: A case report and literature review

Primary pulmonary malignant peripheral nerve sheath tumor (MPNST) is a rare soft tissue sarcoma with a low incidence, poor prognosis and limited treatment options. The present study reported a case of lung MPNST in a 63-year-old male patient without any pulmonary symptoms. Immunohistochemical analysis of the tumor indicated a programmed death-ligand 1 (PD-L1) expression tumor proportion score of 60%. A total of six courses of sintilimab were used in this patient and a remarkable response was achieved. In summary, sintilimab single-agent immunotherapy may be a novel treatment for pulmonary MPNST. When encountering analogous cases in the future, oncologists can test for the expression of PD-L1 in patients to guide the therapy's design.

Past, Present, and Future Therapeutic Strategies for NF-1-Associated Tumors

PURPOSE OF REVIEW

Neurofibromatosis type 1 (NF-1) is a cancer predisposition syndrome caused by mutations in the NF1 tumor suppressor gene that encodes the neurofibromin protein, which functions as a negative regulator of Ras signaling. We review the past, current, and future state of therapeutic strategies for tumors associated with NF-1.

RECENT FINDINGS

Therapeutic efforts for NF-1-associated tumors have centered around inhibiting Ras output, leading to the clinical success of downstream MEK inhibition for plexiform neurofibromas and low-grade gliomas. However, MEK inhibition and similar molecular monotherapy approaches that block Ras signaling do not work for all patients and show limited efficacy for more aggressive cancers such as malignant peripheral nerve sheath tumors and high-grade gliomas, motivating novel treatment approaches. We highlight the current therapeutic landscape for NF-1-associated tumors, broadly categorizing treatment into past strategies for serial Ras pathway blockade, current approaches targeting parallel oncogenic and tumor suppressor pathways, and future avenues of investigation leveraging biologic and technical innovations in immunotherapy, pharmacology, and gene delivery.

The NF1+/- Immune Microenvironment: Dueling Roles in Neurofibroma Development and Malignant Transformation

Neurofibromatosis type 1 (NF1) is a common genetic disorder resulting in the development of both benign and malignant tumors of the peripheral nervous system. NF1 is caused by germline pathogenic variants or deletions of the NF1 tumor suppressor gene, which encodes the protein neurofibromin that functions as negative regulator of p21 RAS. Loss of NF1 heterozygosity in Schwann cells (SCs), the cells of origin for these nerve sheath-derived tumors, leads to the formation of plexiform neurofibromas (PNF)-benign yet complex neoplasms involving multiple nerve fascicles and comprised of a myriad of infiltrating stromal and immune cells. PNF development and progression are shaped by dynamic interactions between SCs and immune cells, including mast cells, macrophages, and T cells. In this review, we explore the current state of the field and critical knowledge gaps regarding the role of NF1(Nf1) haploinsufficiency on immune cell function, as well as the putative impact of Schwann cell lineage states on immune cell recruitment and function within the tumor field. Furthermore, we review emerging evidence suggesting a dueling role of Nf1+/- immune cells along the neurofibroma to MPNST continuum, on one hand propitiating PNF initiation, while on the other, potentially impeding the malignant transformation of plexiform and atypical neurofibroma precursor lesions. Finally, we underscore the potential implications of these discoveries and advocate for further research directed at illuminating the contributions of various immune cells subsets in discrete stages of tumor initiation, progression, and malignant transformation to facilitate the discovery and translation of innovative diagnostic and therapeutic approaches to transform risk-adapted care.

The quest for effective immunotherapies against malignant peripheral nerve sheath tumors: Is there hope?

Immune-based therapies represent a new paradigm in the treatment of multiple cancers, where they have helped achieve durable and safe clinical responses in a growing subset of patients. While a wealth of information is available concerning the use of these agents in treating the more common malignancies, little has been reported about the use of immunotherapies against malignant peripheral nerve sheath tumors (MPNSTs), a rare form of soft tissue sarcoma that arises from the myelin sheaths that protect peripheral nerves. Surgical resection has been the mainstay of therapy in MPNSTs, but the recurrence rate is as high as 65%, and chemotherapy is generally ineffective. The immune contexture of MPNSTs, replete with macrophages and a varying degree of T cell infiltration, presents multiple opportunities to design meaningful therapeutic interventions. While preliminary results with macrophage-targeting strategies and oncolytic viruses are promising, identifying the subset of patients that respond to immune-based strategies will be a milestone. As part of our effort to help advance the use of immunotherapy for MPNSTs, here we describe recent insights regarding the immune contexture of MPNSTs, discuss emerging immune-based strategies, and provide a brief overview of potential biomarkers of response.

CDK4/6-MEK Inhibition in MPNSTs Causes Plasma Cell Infiltration, Sensitization to PD-L1 Blockade, and Tumor Regression

PURPOSE

Malignant peripheral nerve sheath tumors (MPNST) are lethal, Ras-driven sarcomas that lack effective therapies. We investigated effects of targeting cyclin-dependent kinases 4 and 6 (CDK4/6), MEK, and/or programmed death-ligand 1 (PD-L1) in preclinical MPNST models.

EXPERIMENTAL DESIGN

Patient-matched MPNSTs and precursor lesions were examined by FISH, RNA sequencing, IHC, and Connectivity-Map analyses. Antitumor activity of CDK4/6 and MEK inhibitors was measured in MPNST cell lines, patient-derived xenografts (PDX), and de novo mouse MPNSTs, with the latter used to determine anti-PD-L1 response.

RESULTS

Patient tumor analyses identified CDK4/6 and MEK as actionable targets for MPNST therapy. Low-dose combinations of CDK4/6 and MEK inhibitors synergistically reactivated the retinoblastoma (RB1) tumor suppressor, induced cell death, and decreased clonogenic survival of MPNST cells. In immune-deficient mice, dual CDK4/6-MEK inhibition slowed tumor growth in 4 of 5 MPNST PDXs. In immunocompetent mice, combination therapy of de novo MPNSTs caused tumor regression, delayed resistant tumor outgrowth, and improved survival relative to monotherapies. Drug-sensitive tumors that regressed contained plasma cells and increased cytotoxic T cells, whereas drug-resistant tumors adopted an immunosuppressive microenvironment with elevated MHC II-low macrophages and increased tumor cell PD-L1 expression. Excitingly, CDK4/6-MEK inhibition sensitized MPNSTs to anti-PD-L1 immune checkpoint blockade (ICB) with some mice showing complete tumor regression.

CONCLUSIONS

CDK4/6-MEK inhibition induces a novel plasma cell-associated immune response and extended antitumor activity in MPNSTs, which dramatically enhances anti-PD-L1 therapy. These preclinical findings provide strong rationale for clinical translation of CDK4/6-MEK-ICB targeted therapies in MPNST as they may yield sustained antitumor responses and improved patient outcomes.

Characterizing T-cell dysfunction and exclusion signatures in malignant peripheral nerve sheath tumors reveals susceptibilities to immunotherapy

PURPOSE

Malignant peripheral nerve sheath tumors (MPNSTs) are malignant tumors that arise from peripheral nerves and are the leading cause of mortality in Neurofibromatosis Type 1 (NF1). In this study, we characterized whether transcriptomic signatures of T-cell dysfunction (TCD) and exclusion (TCE) that inversely correlate with response to immune checkpoint blockade (ICB) immunotherapy exist in MPNSTs.

METHODS

MPNST transcriptomes were pooled from Gene Expression Omnibus (GEO). For each sample, a tumor immune dysfunction and exclusion (TIDE) score, TCD and TCE subscores, and cytotoxic T-cell(CTL) level were calculated. In the TIDE predictive algorithm, tumors are predicted to have an ICB response if they are either immunologically hot (CTL-high) without TCD or immunologically cold (CTL-low) without TCE. TIDE scores greater than zero correspond with ICB nonresponse.

RESULTS

73 MPNST samples met inclusion criteria, including 50 NF1-associated MPNSTs (68.5%). The average TIDE score was + 0.41 (SD = 1.16) with 22 (30.1%) predicted ICB responders. 11 samples were CTL-high (15.1%) with an average TCD score of + 0.99 (SD = 0.63). Among 62 CTL-low tumors, 21 were predicted to have ICB response with an average TCE score of + 0.31(SD = 1.20). Age(p = 0.18), sex(p = 0.41), NF1 diagnosis (p = 0.17), and PRC2 loss(p = 0.29) were not associated with ICB responder status.

CONCLUSIONS

Transcriptomic analysis of TCD and TCE signatures in MPNST samples reveals that a select subset of patients with MPNSTs may benefit from ICB immunotherapy.

Role of perioperative chemotherapy and radiotherapy for localized high-grade malignant peripheral nerve sheath tumor at the extremities and trunk wall: a population-based cohort study

BACKGROUND

Primary tumor resection is the mainstay of treatment for malignant peripheral nerve sheath tumors. However, the efficacy of perioperative chemotherapy and radiotherapy for malignant peripheral nerve sheath tumors has not been elucidated.

METHODS

This retrospective analysis based on a Japanese registry included patients with localized malignant peripheral nerve sheath tumors arising at the extremities and trunk wall. Disease-specific overall survival and local recurrence-free survival were estimated using the Kaplan-Meier method. A Cox regression model was used to identify prognostic factors. Characteristics of groups with or without chemotherapy were adjusted using propensity score matching.

RESULTS

In total, 291 patients were included. The 5-year disease-specific overall survival rate was 70.6%. Multivariate analysis of disease-specific overall survival revealed that deep-seated tumors were a poor prognostic factor, but perioperative chemotherapy was not associated with disease-specific overall survival (hazard ratio, 0.81; 95% confidence interval, 0.45-1.43, P = 0.46). Local recurrence was observed in 55 patients (19.0%), and surgical margins (R1 and R2) were significant risk factors. Overall, perioperative chemotherapy did not prolong disease-specific overall survival (5-year disease-specific overall survival: 74.1% vs. 69.3%, P = 0.75) and had limited efficacy in the group with tumor size ≥ 5 cm, although the difference was not statistically significant (5-year disease-specific overall survival: 77.2% vs. 68.6%, respectively, P = 0.13). After adjustment by propensity score matching, perioperative chemotherapy significantly prolonged disease-specific overall survival (5-year disease-specific overall survival: 74.9% vs. 57.1%, P = 0.03), but this effect was not observed in local recurrence-free survival. In all patients, perioperative radiotherapy did not correlate with local recurrence-free survival (hazard ratio, 1.43; 95% confidence interval 0.78-2.62, P = 0.25).

CONCLUSIONS

Perioperative chemotherapy had limited efficacy for disease-specific overall survival in patients with localized malignant peripheral nerve sheath tumors.

Case Report: Successful Immunotherapy Improved the Prognosis of the Unfavorable Subset of Cancer of Unknown Primary

Background

Cancer of unknown primary (CUP) is heterogeneous and has a wide variety of clinical presentations and a poor prognosis in most patients, with a median overall survival of only 6 months. The development of molecular profiling contributes to precision therapy, and targeted drugs and immune checkpoint inhibitors (ICIs) greatly promote individualized treatment.

Case presentation

Here, we reported a case of an unfavorable subset of CUP who had a long time of survival after the immunotherapy-prominent comprehensive treatment. A 48-year-old man presented with back pain and a cough. A diagnostic work-up showed bone marrow, multiple bones, and lymph node metastasis. Lymph node pathology implies metastatic poorly differentiated cancer. Next-generation sequencing (NGS) showed no special targets, but the tumor proportion score (TPS) of programmed death-ligand 1 (PD-L1) was 80% and the tumor mutation burden (TMB) was 16.7 per million bases. After two cycles of pembrolizumab 200 mg D1 plus nanoparticle albumin-bound (nab)-paclitaxel 200 mg D1&8 (q3w), PET-CT and bone marrow aspiration cytology showed a complete response (CR). Subsequently, pembrolizumab alone was used for three months. The left inguinal lymph nodes showed new metastasis. After two cycles of the combination treatment of pembrolizumab and (nab)-paclitaxel, a partial response (PR) was achieved. After seven months, retroperitoneal lymph nodes showed new metastasis, and the sequential treatment with radiotherapy and pembrolizumab exhibited encouraging efficacy. To date, the patient has survived nearly 40 months with the combination therapy.

Conclusions

The ICI-prominent comprehensive treatment provided clinical benefit for the reported case of CUP. Thus, CUP patients with markers of benefiting from immunotherapy should be actively treated with immunotherapy to improve their prognosis.