Long-Term Outcomes of Radiation Therapy (RT) in the Management of Malignant Peripheral Nerve Sheath Tumors (MPNST) in Patients with Neurofibromatosis Type 1 (NF1)

Low-Grade Malignant Peripheral Nerve Sheath Tumor: A Case Report of Exceptional Parapatellar Location in the Knee

Malignant tumors of the peripheral nerve sheaths are uncommon, constituting a small percentage, typically ranging from 2% to 5% of soft tissue sarcomas. Etiological diagnosis is often difficult but is guided by imaging and confirmed by histopathological and immunohistochemical examination. We report a case of a 46-year-old woman admitted for management of a mass in the medial parapatellar region of the right knee. Her medical history included a burn to the right leg five years ago and a previously undocumented resection of a medial parapatellar tissue mass in the right knee. Radiological examination showed a deep and superficial soft tissue mass in the medial soft tissue of the right knee opposite the patella, with no hemorrhagic components and heterogeneous enhancement after injection of gadolinium. Histopathology confirmed the diagnosis of a low-grade peripheral nerve sheath tumor, and a thoracic-abdominal-pelvic CT scan was performed, which was normal. Treatment consisted of a simple carcinological resection and local radiotherapy. No local recurrence was noted after one year of follow-up.

Malignant Peripheral Nerve Sheath Tumors: Latest Concepts in Disease Pathogenesis and Clinical Management

Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma with limited therapeutic options and a poor prognosis. Although neurofibromatosis type 1 (NF1) and radiation exposure have been identified as risk factors for MPNST, the genetic and molecular mechanisms underlying MPNST pathogenesis have only lately been roughly elucidated. Plexiform neurofibroma (PN) and atypical neurofibromatous neoplasm of unknown biological potential (ANNUBP) are novel concepts of MPNST precancerous lesions, which revealed sequential mutations in MPNST development. This review summarized the current understanding of MPNST and the latest consensus from its diagnosis to treatment, with highlights on molecular biomarkers and targeted therapies. Additionally, we discussed the current challenges and prospects for MPNST management.

3D printed integrated bolus/headrest for radiation therapy for malignancies involving the posterior scalp and neck

Background

Malignancies of the head and neck region, encompassing cutaneous, mucosal, and sarcomatous histologies, are complex entities to manage, comprising of coordination between surgery, radiation therapy, and systemic therapy. Malignancies of the posterior scalp are particular challenging to treat with radiation therapy, given its irregular contours and anatomy as well as the superficial location of the target volume. Bolus material is commonly used in radiation therapy to ensure that the dose to the skin and subcutaneous tissue is appropriate and adequate, accounting for the buildup effect of megavoltage photon treatment. The use of commercially available bolus material on the posterior scalp potentially creates air gaps between the bolus and posterior scalp.

Case presentations

In this report, we created and utilized a custom 3D-printed integrated bolus and headrest for 5 patients to irradiate malignancies involving the posterior scalp, including those with cutaneous squamous cell carcinoma, melanoma, malignant peripheral nerve sheath tumor, and dermal sarcoma. Treatment setup was consistently reproducible, and patients tolerated treatment well without any unexpected adverse effects.

Conclusions

We found that the use of this custom 3D-printed integrated bolus/headrest allowed for comfortable, consistent, and reproducible treatment set up while minimizing the risk of creating significant air gaps and should be considered in the radiotherapeutic management of patients with posterior scalp malignancies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41205-022-00152-w.

Clinical Outcome After Pencil Beam Scanning Proton Therapy of Patients With Non-Metastatic Malignant and Benign Peripheral Nerve Sheath Tumors

Objective

Peripheral nerve sheath tumors (PNSTs) commonly arise from peripheral nerve roots and grow locally invasive. Malignant PNSTs (mPNSTs) represent aggressive sarcomas of neural origin that can originate from PNSTs. Radiation therapy is commonly used as part of the required multimodal treatment. However, both entities tend to occur early in life and are associated with the genetic disorder neurofibromatosis type 1 (NF-1), which is known to cause increased radiosensitivity. Pencil beam scanning proton therapy (PBSPT) allows for a minimization of the dose delivered to organs at risk and the integral dose and, thus, potentially also a reduction of radiation-induced adverse events. We report the clinical outcome and toxicity rates of patients with (m)PNSTs treated with PBSPT.

Methods

We retrospectively reviewed 36 patients who received PBSPT (median dose, 64 GyRBE) with curative intent for (m)PNSTs between 1999 and 2020 at our institute. Twenty-eight (78%) and 8 (22%) patients were treated at diagnosis and for tumor recurrence/progression, respectively. The median age was 32 years (range, 3–75), and 25 (69%) patients were male. mPNST and PNST were diagnosed in 31 (86%) and 5 (14%) patients, respectively. Underlying NF-1 disease was found in 8 (22%) patients. Acute and late toxicities were recorded according to Common Terminology Criteria for Adverse Events, version 4.1 (CTCAE v4.1). Overall survival (OS), local control (LC), and distant control (DC) were estimated using the Kaplan–Meier method.

Results

With a median follow-up time of 31 months (range, 4–194), 13 (36%) patients died from a progressive disease, 8 (22%) experienced local failure, and 14 (39%) experienced distant failure after PBSPT. Estimated 2-year OS, LC, and DC were 75.5%, 73.5%, and 61.2%, respectively. Acute grade 3 toxicity (dermatitis, mucositis, and pain) was observed in 5 (14%) patients. Late grade 3 cataract and osteonecrosis were both observed in 1 (3%) patient at 34 and 194 months after PBSPT, respectively. There was no late grade >3 toxicity or radiation-induced secondary cancer.

Conclusion

To our knowledge, this is the first study to analyze the outcome of (m)PNSTs treated with proton therapy using a PBS delivery paradigm. In our cohort, consisting mainly of patients with mPNSTs, we report reasonable oncological outcomes and low toxicity rates after PBSPT.

Diagnosis and management of malignant peripheral nerve sheath tumors: Current practice and future perspectives

One of the most common malignancies affecting adults with the neurofibromatosis type 1 (NF1) cancer predisposition syndrome is the malignant peripheral nerve sheath tumor (MPNST), a highly aggressive sarcoma that typically develops from benign plexiform neurofibromas. Approximately 8-13% of individuals with NF1 will develop MPNST during young adulthood. There are few therapeutic options, and the vast majority of people with these cancers will die within 5 years of diagnosis. Despite efforts to understand the pathogenesis of these aggressive tumors, the overall prognosis remains dismal. This manuscript will review the current understanding of the cellular and molecular progression of MPNST, diagnostic workup of patients with these tumors, current treatment paradigms, and investigational treatment options. Additionally, we highlight novel areas of preclinical research, which may lead to future clinical trials. In summary, MPNST remains a diagnostic and therapeutic challenge, and future work is needed to develop novel and rational combinational therapy for these tumors.