Interdisciplinary approach allows minimally invasive, nerve-sparing removal of retroperitoneal peripheral nerve sheath tumors

Comprehensive neurosurgical and visceral surgical therapy of retroperitoneal nerve tumors: a descriptive and retrospective analysis

Nerve tumors in the retroperitoneal space are a rarity. Radical surgery according to soft tissue tumors can lead to persistent pain and neurological deficits. This study aims to evaluate clinical outcomes of patients treated by a visceral- / neurosurgical approach. 33 patients with a retroperitoneal nerve tumor underwent surgery between 01/2002 and 12/2022 at our department. A visceral surgeon provided access to the retroperitoneal space, followed by micro-neurosurgical tumor preparation under neuromonitoring. Clinical examination and MRI were performed 12 weeks after surgery and further 3 months (WHO grade > 1) or 12 months (WHO grade 1). Further examinations were based on MRI findings and residual symptoms with median follow-up time of 24 months. One patient was treated for two distinct masses resulting in a total of 34 histological findings. Schwannomas (n = 15; 44.1%) and neurofibromas (n = 10; 29.4%) were the most common tumors. Long-term improvements were noted in radicular pain (15/18 patients; 83.3%), motor deficits (7/16 patients; 43.8%), abdominal discomfort and pain (5/7 patients; 71.4%). Recurrences were observed in 3/33 (9,1%) patients. This study represents the largest series of retroperitoneal BPNSTs treated with microsurgical techniques. Prospective multicenter studies are warranted to establish standardized treatment guidelines.

Preoperative Classification of Peripheral Nerve Sheath Tumors on MRI Using Radiomics

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft-tissue tumors prevalent in neurofibromatosis type 1 (NF1) patients, posing a significant risk of metastasis and recurrence. Current magnetic resonance imaging (MRI) imaging lacks decisiveness in distinguishing benign peripheral nerve sheath tumors (BPNSTs) and MPNSTs, necessitating invasive biopsies. This study aims to develop a radiomics model using quantitative imaging features and machine learning to distinguish MPNSTs from BPNSTs. Clinical data and MRIs from MPNST and BPNST patients (2000-2019) were collected at a tertiary sarcoma referral center. Lesions were manually and semi-automatically segmented on MRI scans, and radiomics features were extracted using the Workflow for Optimal Radiomics Classification (WORC) algorithm, employing automated machine learning. The evaluation was conducted using a 100× random-split cross-validation. A total of 35 MPNSTs and 74 BPNSTs were included. The T1-weighted (T1w) MRI radiomics model outperformed others with an area under the curve (AUC) of 0.71. The incorporation of additional MRI scans did not enhance performance. Combining T1w MRI with clinical features achieved an AUC of 0.74. Experienced radiologists achieved AUCs of 0.75 and 0.66, respectively. Radiomics based on T1w MRI scans and clinical features show some ability to distinguish MPNSTs from BPNSTs, potentially aiding in the management of these tumors.

Multidisciplinary neurofibromatosis conference in the management of patients with neurofibromatosis type 1 and schwannomatosis in a single tertiary care institution

OBJECTIVE

To evaluate the role of weekly neurofibromatosis (NF) multi-disciplinary conferences (MDC) on the diagnostic and therapeutic plan for patients with NF type 1 (NF1) and schwannomatosis (SWN).

MATERIALS AND METHODS

This retrospective study reviewed patients with confirmed or suspected NF1 and SWN discussed in weekly MDC from March to July 2021. Demographic data collected included patient age, sex, pre-conference and post-conference diagnosis, radiological studies reviewed, and provider specialties in attendance. Outcomes reported included changes in imaging interpretation and treatment plans, changes in post-conference diagnosis relative to pre-conference diagnosis, and time to completion of the recommended change in treatment.

RESULTS

Data from 17 MDC "pre-conference" lists included 75 patients (38 female, 37 males, mean age (years): 38 (range: 6-80)) with NF1 (52%, 39/75) and SWN (36%, 27/75) discussed over a total of 91 case reviews. 18.7% (14/75) of all patients had NF2-related SWN, and 17.3% (13/75) of all patients had non-NF2 SWN. The MDC led to changes in imaging interpretation in 18.7% and changes in patient management in 74.7% (diagnostic testing (n = 52), surgical plan (n = 24), medical treatment (n = 9), clinical trial status (n = 4), and radiation treatment (n = 1)) of cases. Among patients for whom a change in management was recorded, 91% (62/68) completed at least one recommendation (mean time to completion (days): 41.4 (range: 0-278)).

CONCLUSION

Weekly MDC changes the diagnostic and therapeutic management of the majority of patients discussed (74.7%) and promotes a high adherence rate to recommendations (91%).

Surgical management of sporadic and schwannomatosis-associated pelvic schwannomas

Pelvic schwannomas are rare tumors that may occur either sporadically or in the context of schwannomatosis. We retrospectively reviewed the charts of patients harboring a pelvic schwannoma under conservative management or operated at our reference center between 2016 and 2023. All patients were operated by a multidisciplinary team, combining a vascular surgeon and a neurosurgeon. Twenty-four patients harboring 33 pelvic tumors were included in the cohort, including 12 patients with sporadic lesions, 2 patients with NF2-related schwannomatosis, and 10 patients with NF2-independent schwannomatosis. Multi-nodular tumors were more frequent in schwannomatosis compared to sporadic cases (p = 0.005). The mean age at diagnosis was 41 years old. Schwannomas were located on branches of the sciatic nerve (23/33, 70%), the femoral nerve (6/33, 18%), and the obturator nerve (4/33, 12%). Over the course of the study, 16 patients were operated, including 11 sporadic cases. The indication for surgery was pain (12/16, 75%) or tumor growth (4/16, 25%). Complete resection was achieved in 14 of 16 patients (87%). The mean post-operative follow-up was 37 months (range: 2-168 months). At last-follow-up, complete pain relief was achieved in all 12 patients with pre-operative pain. Post-operative morbidity included 3 long-term localized numbness and one MRC class 4 motor deficit in a multi-nodular tumor in a schwannomatosis patient. Despite its limited size, our series suggests that nerve-sparing resection of pelvic schwannomas offers satisfying rates of functional outcome both in sporadic and schwannomatosis cases, except for multi-nodular tumors.

Integrated Neurosurgical Management of Retroperitoneal Benign Nerve Sheath Tumors

Peripheral nerve sheath tumors (PNST) of the retroperitoneum are rare and are often treated by general surgeons dealing with retroperitoneal cancers. However, resection without the correct microsurgical technique can cause permanent neurological deficits and pain. Here, we discuss our interdisciplinary approach based on the integration of expertise from neurosurgery and abdominal surgery, allowing for both safe exposure and nerve-sparing microsurgical resection of these lesions. We present a series of 15 patients who underwent resection of benign retroperitoneal or pelvic PNST at our institution. The mean age of patients was 48.4 years; 67% were female. Tumors were 14 schwannomas and 1 neurofibroma. Eight patients (53%) reported neurologic symptoms preoperatively. The rate of complete resection was 87% (n = 13); all symptomatic patients showed improvement of their preoperative symptoms. There were no postoperative motor deficits; one patient (7%) developed a permanent sensory deficit. At a mean postoperative follow-up of 31 months, we observed no recurrences. To our best knowledge, this is the second-largest series of benign retroperitoneal PNST consistently managed with microsurgical techniques. Our experience confirms that interdisciplinary management allows for safe treatment of these tumors with good neurological and oncological outcomes.

Results of surgical treatment of patients with malignant peripheral nerve sheath tumors: a retrospective and prospective study

Background. Peripheral nerve sheath malignancies (PNSM) are a rare and aggressive group of sarcomas that can occur sporadically, after radiation therapy, or related to neurofibromatosis type 1. Loss of function of NF1, TP53, and CDKN2A genes is thought to contribute to the progression of benign neurofibroma to PNSM and is a poor prognostic sign. The optimal management of patients with this disease is currently unresolved, and specific prognostic factors have not been established. Aim. To analyze the results of surgical treatment in patients with PNSM and establish prognostic factors of overall and recurrence-free survival rate. Materials and methods. The retrospective and prospective studies enrolled adult patients with histologically confirmed PNSM treated between 1998 and 2021 at the N.N. Blokhin National Medical Research Center for Oncology. Surgical intervention was performed on 61 patients, 38 (62%) females and 23 (38%) males. The most common PNSM localization was paravertebral (22 [36%] patients), followed by retroperitoneal (14 [23%] patients), and upper and lower extremities (13 [21%] and 12 [20%] patients, respectively). Results. For PNSM patients with a history of surgery, the median overall survival (OS) was 46 months (95% confidence interval 26.165.9). The 3-year and 5-year OS was 46% and 31%, respectively. The median recurrence-free survival (RFS) was 27 months (8.745.3), and 3-year and 5-year RFS was 26% and 13%, respectively. Median OS for grade 1 malignancies was not achieved, while grade 2 and grade 3 malignancy was 53 and 33 months, respectively (p=0.033). The median RFS for grade 1, 2, and 3 tumors was 119, 43, and 15 months, respectively (p=0.078). Patients who underwent radical (R0) surgery had higher RFS (p=0.006) and OS (p0.0001). After radical (R0) surgery, the median OS was not achieved; after nonradical (R1/R2) surgery, the median was 34 months. The median RFS was 124 months after R0-resection and 48 months after R1/R2. Conclusion. The most significant prognostic factors in PNSM patients are the radicality of the surgery performed and the malignancy grade. In our study, tumor size and localization did not affect the long-term treatment results.

Diagnostic value of 18F-FDG PET-CT in detecting malignant peripheral nerve sheath tumors among adult and pediatric neurofibromatosis type 1 patients

Purpose

Detecting malignant peripheral nerve sheath tumors (MPNSTs) remains difficult. ¹⁸F-FDG PET-CT has been shown helpful, but ideal threshold values of semi-quantitative markers remain unclear, partially because of variation among scanners. Using EU-certified scanners diagnostic accuracy of ideal and commonly used ¹⁸F-FDG PET-CT thresholds were investigated and differences between adult and pediatric lesions were evaluated.

Methods

A retrospective cohort study was performed including patients from two hospitals with a clinical or radiological suspicion of MPNST between 2013 and 2019. Several markers were studied for ideal threshold values and differences among adults and children. A diagnostic algorithm was subsequently developed.

Results

Sixty patients were included (10 MPNSTs). Ideal threshold values were 5.8 for SUVmax (sensitivity 0.70, specificity 0.92), 5.0 for SUVpeak (sensitivity 0.70, specificity 0.97), 1.7 for TLmax (sensitivity 0.90, specificity 0.86), and 2.3 for TLmean (sensitivity 0.90, specificity 0.79). The standard TLmean threshold value of 2.0 yielded a sensitivity of 0.90 and specificity of 0.74, while the standard SUVmax threshold value of 3.5 yielded a sensitivity of 0.80 and specificity of 0.63. SUVmax and adjusted SUV for lean body mass (SUL) were lower in children, but tumor-to-liver ratios were similar in adult and pediatric lesions. Using TLmean > 2.0 or TLmean < 2.0 and SUVmax > 3.5, a sensitivity and specificity of 1.00 and 0.63 can be achieved.

Conclusion

¹⁸F-FDG PET-CT offers adequate accuracy to detect MPNSTs. SUV values in pediatric MPNSTs may be lower, but tumor-to-liver ratios are not. By combining TLmean and SUVmax values, a 100% sensitivity can be achieved with acceptable specificity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11060-021-03936-y.

A Bayesian approach for diagnostic accuracy of malignant peripheral nerve sheath tumors: a systematic review and meta-analysis

Background

Malignant peripheral nerve sheath tumors (MPNST) carry a dismal prognosis and require early detection and complete resection. However, MPNSTs are prone to sampling errors and biopsies or resections are cumbersome and possibly damaging in benign peripheral nerve sheath tumor (BPNST). This study aimed to systematically review and quantify the diagnostic accuracy of noninvasive tests for distinguishing MPNST from BPNST.

Methods

Studies on accuracy of MRI, FDG-PET (fluorodeoxyglucose positron emission tomography), and liquid biopsies were identified in PubMed and Embase from 2000 to 2019. Pooled accuracies were calculated using Bayesian bivariate meta-analyses. Individual level-patient data were analyzed for ideal maximum standardized uptake value (SUV_max) threshold on FDG-PET.

Results

Forty-three studies were selected for qualitative synthesis including data on 1875 patients and 2939 lesions. Thirty-five studies were included for meta-analyses. For MRI, the absence of target sign showed highest sensitivity (0.99, 95% CI: 0.94-1.00); ill-defined margins (0.94, 95% CI: 0.88-0.98); and perilesional edema (0.95, 95% CI: 0.83-1.00) showed highest specificity. For FDG-PET, SUV_max and tumor-to-liver ratio show similar accuracy; sensitivity 0.94, 95% CI: 0.91-0.97 and 0.93, 95% CI: 0.87-0.97, respectively, specificity 0.81, 95% CI: 0.76-0.87 and 0.79, 95% CI: 0.70-0.86, respectively. SUV_max ≥3.5 yielded the best accuracy with a sensitivity of 0.99 (95% CI: 0.93-1.00) and specificity of 0.75 (95% CI: 0.56-0.90).

Conclusions

Biopsies may be omitted in the presence of a target sign and the absence of ill-defined margins or perilesional edema. Because of diverse radiological characteristics of MPNST, biopsies may still commonly be required. In neurofibromatosis type 1, FDG-PET scans may further reduce biopsies. Ideal SUV_max threshold is ≥3.5.