Erector Spinae Plane Block Reduces Immediate Postoperative Pain and Opioid Demand After Minimally Invasive Transforaminal Lumbar Interbody Fusion

STUDY DESIGN

Matched cohort comparison.

OBJECTIVE

To determine perioperative outcomes of erector spinae plane (ESP) block for minimally invasive transforaminal lumbar interbody fusion (MI-TLIF).

SUMMARY OF BACKGROUND DATA

There is a paucity of data on the impact of lumbar ESP block on perioperative outcomes and its safety in MI-TLIF.

MATERIALS AND METHODS

Patients who underwent 1-level MI-TLIF and received the ESP block (group E ) were included. An age and sex-matched control group was selected from a historical cohort that received the standard-of-care (group NE). The primary outcome of this study was 24-hour opioid consumption in morphine milligram equivalents. Secondary outcomes were pain severity measured by a numeric rating scale, opioid-related side effects, and hospital length of stay. Outcomes were compared between the two groups.

RESULTS

Ninety-eight and 55 patients were included in the E and NE groups, respectively. There were no significant differences between the two cohorts in patient demographics. Group E had lower 24-hour postoperative opioid consumption ( P = 0.117, not significant), reduced opioid consumption on a postoperative day (POD) 0 ( P = 0.016), and lower first pain scores postsurgery ( P < 0.001). Group E had lower intraoperative opioid requirements ( P < 0.001), and significantly lower average numeric rating scale pain scores on POD 0 ( P = 0.034). Group E reported fewer opioid-related side effects as compared with group NE, although this was not statistically significant. The average highest postoperative pain score within 3 hours postprocedurally was 6.9 and 7.7 in the E and NE cohorts, respectively ( P = 0.029). The median length of stay was comparable between groups with the majority of patients in both groups being discharged on POD 1.

CONCLUSIONS

In our retrospective matched cohort, ESP blocks resulted in reduced opioid consumption and decreased pain scores on POD 0 in patients undergoing MI-TLIF.

LEVEL OF EVIDENCE

Level 3.

Predictors of Subsidence and its Clinical Impact After Expandable Cage Insertion in Minimally Invasive Transforaminal Interbody Fusion

STUDY DESIGN

Retrospective review of prospectively collected multisurgeon data.

OBJECTIVE

Examine the rate, clinical impact, and predictors of subsidence after expandable minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) cage.

SUMMARY OF BACKGROUND DATA

Expandable cage technology has been adopted in MI-TLIF to reduce the risks and optimize outcomes. Although subsidence is of particular concern when using expandable technology as the force required to expand the cage can weaken the endplates, its rates, predictors, and outcomes lack evidence.

MATERIALS AND METHODS

Patients who underwent 1 or 2-level MI-TLIF using expandable cages for degenerative lumbar conditions and had a follow-up of >1 year were included. Preoperative and immediate, early, and late postoperative radiographs were reviewed. Subsidence was determined if the average anterior/posterior disc height decreased by >25% compared with the immediate postoperative value. Patient-reported outcomes were collected and analyzed for differences at the early (<6 mo) and late (>6 mo) time points. Fusion was assessed by 1-year postoperative computed tomography.

RESULTS

One hundred forty-eight patients were included (mean age, 61 yr, 86% 1-level, 14% 2-level). Twenty-two (14.9%) demonstrated subsidence. Although statistically not significant, patients with subsidence were older, had lower bone mineral density, and had higher body mass index and comorbidity burden. Operative time was significantly higher ( P = 0.02) and implant width was lower ( P < 0.01) for subsided patients. Visual analog scale-leg was significantly lower for subsided patients compared with nonsubsided patients at a >6 months time point. Long-term (>6 mo) patient-acceptable symptom state achievement rate was lower for subsided patients (53% vs . 77%), although statistically not significant ( P = 0.065). No differences existed in complication, reoperation, or fusion rates.

CONCLUSIONS

Of the patients, 14.9% experienced subsidence predicted by narrower implants. Although subsidence did not have a significant impact on most patient-reported outcome measures and complication, reoperation, or fusion rates, patients had lower visual analog scale-leg and patient-acceptable symptom state achievement rates at the >6-month time point.

LEVEL OF EVIDENCE

Level 4.

Severe Obesity Is an Independent Risk Factor of Early Readmission and Nonhome Discharge After Cervical Disc Replacement

OBJECTIVE

Despite growing interest in cervical disc replacement (CDR) for conditions such as cervical radiculopathy, limited data exists describing the impact of obesity on early postoperative outcomes and complications. These data are especially important as nearly half of the adult population in the United States is expected to become obese (body mass index [BMI] ≥ 30 kg/m2) by 2030. The goal of this study was to compare the demographics, perioperative variables, and complication rates following CDR.

METHODS

The 2005-2020 American College of Surgeons National Surgical Quality Improvement Program datasets were queried for patients who underwent primary 1- or 2-level CDR. Patients were divided into 3 cohorts: Nonobese (BMI: 18.5-29.9 kg/m2), Obese class-I (BMI: 30-34.9 kg/m2), Obese class-II/III (BMI ≥ 35 kg/m2). Morbidity was defined as the presence of any complication within 30 days postoperatively. Rates of 30-day readmission, reoperation, morbidity, individual complications, length of stay, frequency of nonhome discharge disposition were collected.

RESULTS

A total of 5,397 patients were included for analysis: 3,130 were nonobese, 1,348 were obese class I, and 919 were obese class II/III. There were more 2-level CDRs performed in the class II/III cohort compared to the nonobese group (25.7% vs. 21.5%, respectively; p < 0.05). Class-II/III had more nonhome discharges than class I and nonobese (2.1% vs. 0.5% vs. 0.7%, respectively; p < 0.001). Readmission rates differed as well (nonobese: 0.5%, class I: 1.1%, class II/III: 2.1%; p < 0.001) with pairwise significance between class II/II and nonobese. Class II/III obesity was an independent risk factor for both readmission (odds ratio [OR], 3.32; p = 0.002) and nonhome discharge (OR, 2.51; p = 0.02). Neither 30-day reoperation nor morbidity rates demonstrated significance. No mortalities were reported.

CONCLUSION

Although obese class-II/III were risk factors for 30-day readmission and nonhome discharge, there was no significant difference in reoperation rates or morbidity. CDR procedures can continue to be safely preformed independent of obesity status.

A vertebral skeletal stem cell lineage driving metastasis

Vertebral bone is subject to a distinct set of disease processes from long bones, including a much higher rate of solid tumour metastases1-4. The basis for this distinct biology of vertebral bone has so far remained unknown. Here we identify a vertebral skeletal stem cell (vSSC) that co-expresses ZIC1 and PAX1 together with additional cell surface markers. vSSCs display formal evidence of stemness, including self-renewal, label retention and sitting at the apex of their differentiation hierarchy. vSSCs are physiologic mediators of vertebral bone formation, as genetic blockade of the ability of vSSCs to generate osteoblasts results in defects in the vertebral neural arch and body. Human counterparts of vSSCs can be identified in vertebral endplate specimens and display a conserved differentiation hierarchy and stemness features. Multiple lines of evidence indicate that vSSCs contribute to the high rates of vertebral metastatic tropism observed in breast cancer, owing in part to increased secretion of the novel metastatic trophic factor MFGE8. Together, our results indicate that vSSCs are distinct from other skeletal stem cells and mediate the unique physiology and pathology of vertebrae, including contributing to the high rate of vertebral metastasis.

Floor-Mounted Robotic Pedicle Screw Placement in Lumbar Spine Surgery: An Analysis of 1,050 Screws

OBJECTIVE

To analyze the usage of floor-mounted robot in minimally invasive lumbar fusion.

METHODS

Patients who underwent minimally invasive lumbar fusion for degenerative pathology using floor-mounted robot (ExcelsiusGPS) were included. Pedicle screw accuracy, proximal level violation rate, pedicle screw size, screw-related complications, and robot abandonment rate were analyzed.

RESULTS

Two hundred twenty-nine patients were included. Most surgeries were primary single-level fusion. Sixty-five percent of surgeries had intraoperative computed tomography (CT) workflow, 35% had preoperative CT workflow. Sixty-six percent were transforaminal lumbar interbody fusion, 16% were lateral, 8% were anterior, and 10% were a combined approach. A total of 1,050 screws were placed with robotic assistance (85% in prone position, 15% in lateral position). Postoperative CT scan was available for 80 patients (419 screws). Overall pedicle screw accuracy rate was 96.4% (prone, 96.7%; lateral, 94.2%; primary, 96.7%; revision, 95.3%). Overall poor screw placement rate was 2.8% (prone, 2.7%; lateral, 3.8%; primary, 2.7%; revision, 3.5%). Overall proximal facet and endplate violation rates were 0.4% and 0.9%. Average diameter and length of pedicle screws were 7.1 mm and 47.7 mm. Screw revision had to be done for 1 screw (0.1%). Use of the robot had to be aborted in 2 cases (0.8%).

CONCLUSION

Usage of floor-mounted robotics for the placement of lumbar pedicle screws leads to excellent accuracy, large screw size, and negligible screw-related complications. It does so for screw placement in prone/lateral position and primary/revision surgery alike with negligible robot abandonment rates.

Discovery of a Vertebral Skeletal Stem Cell Driving Spinal Metastases

Vertebral bone is subject to a distinct set of disease processes from those of long bones, notably including a much higher rate of solid tumor metastases that cannot be explained by passive blood flow distribution alone. The basis for this distinct biology of vertebral bone has remained elusive. Here we identify a vertebral skeletal stem cell (vSSC), co-expressing the transcription factors ZIC1 and PAX1 together with additional cell surface markers, whose expression profile and function are markedly distinct from those of long bone skeletal stem cells (lbSSCs). vSSCs display formal evidence of stemness, including self-renewal, label retention and sitting at the apex of their differentiation hierarchy. Lineage tracing of vSSCs confirms that they make a persistent contribution to multiple mature cell lineages in the native vertebrae. vSSCs are physiologic mediators of spine mineralization, as genetic blockade of the ability of vSSCs to generate osteoblasts results in defects in the vertebral neural arch and body. Human counterparts of vSSCs can be identified in vertebral endplate specimens and display a conserved differentiation hierarchy and stemness. Multiple lines of evidence indicate that vSSCs contribute to the high rates of vertebral metastatic tropism observed clinically in breast cancer. Specifically, when an organoid system is used to place both vSSCs and lbSSCs in an identical anatomic context, vSSC-lineage cells are more efficient than lbSSC-lineage cells at recruiting metastases, a phenotype that is due in part to increased secretion of the novel metastatic trophic factor MFGE8. Similarly, genetically targeting loss-of-function to the vSSC lineage results in reduced metastasis rates in the native vertebral environment. Taken together, vSSCs are distinct from other skeletal stem cells and mediate the unique physiology and pathology of vertebrae, including contributing to the high rate of metastatic seeding of the vertebrae.

Improvement following minimally invasive transforaminal lumbar interbody fusion in patients aged 70 years or older compared with younger age groups

OBJECTIVE

The goal of this study was to assess the outcomes of minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) in patients ≥ 70 years old and compare them to younger age groups.

METHODS

This was a retrospective study of data that were collected prospectively. Patients who underwent primary single-level MI-TLIF were included and divided into 3 groups: age < 60, 60-69, and ≥ 70 years. The outcome measures were as follows: 1) patient-reported outcome measures (PROMs) (i.e., visual analog scale [VAS] for back and leg pain, Oswestry Disability Index [ODI], 12-Item Short-Form Health Survey Physical Component Summary [SF-12 PCS]); 2) minimum clinically important difference (MCID) achievement; 3) return to activities; 4) opioid discontinuation; 5) fusion rates; and 6) complications/reoperations.

RESULTS

A total of 147 patients (age < 60 years, 62; 60-69 years, 47; ≥ 70 years, 38) were included. All the groups showed significant improvements in all PROMs at the early (< 6 months) and late (≥ 6 months) time points and there was no significant difference between the groups. Although MCID achievement rates for VAS leg and ODI were similar, they were lower in the ≥ 70-year-old patient group for VAS back and SF-12 PCS. Although the time to MCID achievement for ODI and SF-12 PCS was similar, it was greater in the ≥ 70-year-old patient group for VAS back and leg. There was no significant difference between the groups in terms of return to activities, opioid discontinuation, fusion rates, and complication/reoperation rates.

CONCLUSIONS

Although patients > 70 years of age may be less likely and/or take longer to achieve MCID compared to their younger counterparts, they show an overall significant improvement in PROMs, a similar likelihood of returning to activities and discontinuing opioids, and comparable fusion and complication/reoperation rates following MI-TLIF.

Association between muscle health and patient-reported outcomes after lumbar microdiscectomy: early results

BACKGROUND CONTEXT

Poor muscle health has been implicated as a source of back pain among patients with lumbar spine pathology. Recently, a novel magnetic resonance imaging (MRI)-based lumbar muscle health grade was shown to correlate with health-related quality of life scores. However, the impact of muscle health on postoperative functional outcomes following spine surgery remains to be investigated.

PURPOSE

To determine whether muscle health grade measured by preoperative psoas and paralumbar muscle cross-sectional areas impact the achievement of minimal clinically important difference (MCID) following lumbar microdiscectomy.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

Consecutive patients who underwent 1-level lumbar microdiscectomy in a single institution between 2017 and 2021.

OUTCOME MEASURES

Rate of MCID achievement, time to MCID achievement, PROMs including Oswestry Disability Index (ODI), visual analog scale for back pain (VAS back), VAS leg, Short Form 12 Physical Component Summary (SF-12 PCS), SF-12 Mental Component Summary (SF-12 MCS), and Patient Reported Outcomes Measurement Information System Physical Function (PROMIS PF).

METHODS

Two previously validated methods for muscle health grading were applied. Axial T2 MRI were analyzed for muscle measurements. The psoas-based method utilized the normalized total psoas area (NTPA), which is the psoas cross-sectional area divided by the square of patient height (mm²/m²). Patients were divided into low and high NTPA groups based on sex-specific lowest quartile NTPA thresholds. The paralumbar-based method incorporated the paralumbar cross-sectional area normalized by body mass index (PL-CSA/BMI) and Goutallier classification. Score of 1 was added for either PL-CSA/BMI >130 or Goutallier class of ≤2. "Good" muscle health was defined as score of 2, and "poor" muscle health was defined as score of 0 to 1. Prospectively collected PROMs were analyzed at 2-week, 6-week, 3-month, 6-month, 1-year, and 2-year postoperative timepoints. The rate of and time to MCID achievement were compared among the cohorts. Bivariate analyses were performed to assess for correlations between psoas/paralumbar cross-sectional areas and change in PROM scores from baseline.

RESULTS

The total cohort included 163 patients with minimum follow-up of 6 months and mean follow-up of 16.5 months. 40 patients (24.5%) were categorized into the low NTPA group, and 55 patients (33.7%) were categorized into the poor paralumbar muscle group. Low NTPA was associated with older age, lower BMI, and greater frequencies of Charlson Comorbidity Index (CCI) ≥1. Poor paralumbar muscle health was associated with older age, female sex, higher BMI, and CCI ≥1. There were no differences in rates of MCID achievement for any PROMs between low versus high NTPA groups or between poor versus good paralumbar groups. Low NTPA was associated with longer time to MCID achievement for ODI, VAS back, VAS leg, and SF-12 MCS. Poor paralumbar muscle health was associated with longer time to MCID achievement for VAS back, VAS leg, and SF-12 PCS. NTPA negatively correlated with change in VAS back (6-week, 12-week) and VAS leg (6-month). PL-CSA/BMI positively correlated with change in PROMIS-PF at 3 months follow-up.

CONCLUSIONS

Among patients undergoing lumbar microdiscectomy, patients with worse muscle health grades achieved MCID at similar rates but required longer time to achieve MCID. Lower NTPA was weakly correlated with larger improvements in pain scores. PL-CSA/BMI positively correlated with change in PROMIS-PF. Our findings suggest that with regards to functional outcomes, patients with worse muscle health may take longer to recuperate postoperatively compared to those with better muscle health.

Undetectable Tumor Cell-Free DNA in a Patient With Metastatic Breast Cancer With Complete Response and Long-Term Remission

The ability to serially monitor tumor-derived cell-free DNA (cfDNA) brings with it the potential to measure response to anticancer therapies and detect minimal residual disease (MRD). This report describes a patient with HER2-positive metastatic breast cancer with an exceptional response to trastuzumab and nab-paclitaxel who remains in complete remission several years after cessation of therapy. Next-generation sequencing of the patient's primary tumor tissue showed several mutations, including an oncogenic hotspot PIK3CA mutation. A sample of cfDNA was collected 6 years after her last therapy and then analyzed for mutant PIK3CA using digital PCR. No detectable mutations associated with the primary tumor were found despite assaying >10,000 genome equivalents, suggesting that the patient had achieved a molecular remission. Results of this case study suggest that serial monitoring of MRD using liquid biopsies could provide a useful method for individualizing treatment plans for patients with metastatic disease with extreme responses to therapy. However, large-scale clinical studies are needed to validate and implement these techniques for patient care.

Abstract P6-10-05: TBCRC 040: Pathologic response evaluation and detection in circulating tumor DNA (PREDICT DNA): Initial results piloting a tissue-biopsy independent method of identifying and monitoring tumor-specific mutations in early stage breast cancer

Introduction: The PREDICT DNA trial is the first prospective, multi-center study aimed at validating cell-free plasma derived circulating tumor DNA (ctDNA) as a biomarker for treatment response and recurrence in early stage, triple-negative or HER2-positive (any hormone receptor status) breast cancer. Its primary aim is to determine the negative predictive value (NPV) of the absence of ctDNA after neoadjuvant therapy (NAT) for the achievement of pathologic complete response (pCR). This study has met its accrual goals and results of the overall trial are anticipated within the next year. The initial PREDICT DNA study design stipulated that tumor specific mutations (TSMs) to be tracked in blood would be identified by next gen sequencing (NGS) of tumor biopsy tissue. A disadvantage of this design is the dependence on adequate biopsy tissue. Recently, the advent of Safe-SeqS technology has enabled robust detection of rare variants using NGS with a sensitivity of approximately 0.05% mutant allele fraction. We employed these new NGS methods to pilot a novel tissue-independent approach to ctDNA detection and monitoring. Objective: The primary objective of this pilot study was to determine whether ultrasensitive NGS using a targeted cancer mutation panel can identify TSMs in ctDNA of early-stage breast cancer patients without the use of biopsy tissue. Methods: The PREDICT DNA trial enrolled 228 women from 22 sites with stage II/III breast cancer for whom standard neoadjuvant therapy was planned. Of these, 58 patients had matched pre-and post-NAT samples available for analysis at the time of this pilot. All pre-NAT samples were analyzed for the presence of TSMs using Sysmex Inostics’ SafeSEQ. Patients with detectable ctDNA before NAT were also evaluated for residual ctDNA after completion of NAT but prior to surgery. Five samples were also tested by digital PCR (BEAMing) for cross-platform comparison. Results: TSMs in ctDNA were identified in 29 of 58 patients (50%) prior to NAT. Of pre-NAT ctDNA(+) patients, TSMs were detected in TP53 (90%) and PIK3CA (10%); three patients (10%) were found to have 2 TSMs. Concordance between SafeSEQ and BEAMing was 100% in five samples tested [3 ctDNA(+), 2 ctDNA(-)]. Of 29 ctDNA(+) patients, 24 (83%) demonstrated reduction or elimination of detectable ctDNA following neoadjuvant therapy, with 16 (55%) converting to ctDNA(-). Conclusion: Identification of TSMs in the plasma of early-stage breast cancer patients without the need for biopsy tissue is feasible using a SafeSEQ cancer mutation panel. Further measures to improve the sensitivity of pre-treatment TSM analysis, such as increased plasma volume input and comprehensive TP53 mutational analysis are currently under investigation. Correlations between clinicopathologic factors with ctDNA detection and burden, as well as the NPV of post-NAT ctDNA for pCR and residual cancer burden, will be reported at the time of abstract presentation.

NH and HP contributed equally to this work.

Citation Format: Natasha Hunter, Heather Parsons, Alexander Sherry, Daniel Shinn, Dong Ho Shin, Alex Cole, Giovanni Cragnotti, Taylor Groginski, Margaret Leathers, Andrea L Richardson, Pedram Argani, Antonio Wolff, Leslie Cope, Dan Edelstein, Frank Holtrup, Hilary Sloane, Bapsi Chakravarthy, Vered Stearns, Ben H Park. TBCRC 040: Pathologic response evaluation and detection in circulating tumor DNA (PREDICT DNA): Initial results piloting a tissue-biopsy independent method of identifying and monitoring tumor-specific mutations in early stage breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-10-05.

Hotspot SF3B1 mutations induce metabolic reprogramming and vulnerability to serine deprivation

Cancer-associated mutations in the spliceosome gene SF3B1 create a neomorphic protein that produces aberrant mRNA splicing in hundreds of genes, but the ensuing biologic and therapeutic consequences of this missplicing are not well understood. Here we have provided evidence that aberrant splicing by mutant SF3B1 altered the transcriptome, proteome, and metabolome of human cells, leading to missplicing-associated downregulation of metabolic genes, decreased mitochondrial respiration, and suppression of the serine synthesis pathway. We also found that mutant SF3B1 induces vulnerability to deprivation of the nonessential amino acid serine, which was mediated by missplicing-associated downregulation of the serine synthesis pathway enzyme PHGDH. This vulnerability was manifest both in vitro and in vivo, as dietary restriction of serine and glycine in mice was able to inhibit the growth of SF3B1MUT xenografts. These findings describe a role for SF3B1 mutations in altered energy metabolism, and they offer a new therapeutic strategy against SF3B1MUT cancers.

Oligodendrocyte precursors gain Schwann cell-like phenotype and remyelinate axons upon engraftment into peripheral nerves

The ability to treat large peripheral nerve injuries may be greatly advanced if an accessible source of human myelinating cells is identified, as it overcomes one of the major limitations of acellular or synthetic nerve guides compared with autografts, the gold standard for large defect repair. Methods to derive oligodendrocyte precursor cells (OPCs) from human pluripotent stem cells have advanced to the point where they have been shown capable of myelination and are being evaluated in clinical trials. Here, we test the hypothesis that OPCs can survive and remyelinate axons in the peripheral nervous system during a repair process. Using freshly isolated OPCs from mouse post-natal brains, we engrafted these OPCs into the tibial nerve immediately after it being subjected to cryolesioning. At 1-month postengraftment, we found numerous graft-derived cells that survived in this environment, and many transplanted cells expressed Schwann cell markers such as periaxin and S100β coexpressed with myelin basic protein, whereas oligodendrocyte markers O4 and Olig2 were virtually absent. Our results demonstrate that OPCs can survive in a peripheral nervous system micro-environment and undergo niche-dependent transdifferentiation into Schwann cell-like cells as has previously been observed in central nervous system focal demyelination models, suggesting that OPCs constitute an accessible source of cells for peripheral nerve cell therapies.

Genetic Alterations Detected in Cell-Free DNA Are Associated With Enzalutamide and Abiraterone Resistance in Castration-Resistant Prostate Cancer

PURPOSE

Androgen receptor (AR) gene alterations, including ligand-binding domain mutations and copy number (CN) gain, have yet to be fully established as predictive markers of resistance to enzalutamide and abiraterone in men with metastatic castration-resistant prostate cancer (mCRPC). The goal of this study was to validate AR gene alterations detected in cell-free DNA (cfDNA) as markers of enzalutamide and abiraterone resistance in patients with mCRPC.

METHODS

Patients with mCRPC (N = 62) were prospectively enrolled between 2014 and 2018. Blood was collected before therapies-enzalutamide (n = 25), abiraterone (n = 35), or enzalutamide and abiraterone (n = 2)-and at disease progression. We used deep next-generation sequencing to analyze cfDNA for sequence variants and CN status in AR and 45 additional cancer-associated genes. Primary end points were prostate-specific antigen response, progression-free survival (PFS), and overall survival (OS).

RESULTS

Elevated tumor-specific cfDNA (circulating tumor DNA) was associated with a worse prostate-specific antigen response (hazard ratio [HR], 3.17; 95% CI, 1.11 to 9.05; P = .031), PFS (HR, 1.76; 95% CI, 1.03 to 3.01; P = .039), and OS (HR, 2.92; 95% CI, 1.40 to 6.11; P = .004). AR ligand-binding domain missense mutations (HR, 2.51; 95% CI, 1.15 to 5.72; P = .020) were associated with a shorter PFS in multivariable models. AR CN gain was associated with a shorter PFS; however, significance was lost in multivariable modeling. Genetic alterations in tumor protein p53 (HR, 2.70; 95% CI, 1.27 to 5.72; P = .009) and phosphoinositide 3-kinase pathway defects (HR, 2.62; 95% CI, 1.12 to 6.10; P = .026) were associated with a worse OS in multivariable models.

CONCLUSION

These findings support the conclusion that high circulating tumor DNA burden is associated with worse outcomes to enzalutamide and abiraterone in men with mCRPC. Tumor protein p53 loss and phosphoinositide 3-kinase pathway defects were associated with worse OS in men with mCRPC. AR status associations with outcomes were not robust, and additional validation is needed.

Abstract P4-01-16: Detection of plasma tumor DNA (ptDNA) in patients with hormone receptor-positive HER2-negative (HR+HER2-) early breast cancer (EBC) in clinical remission

Background: Detection of ptDNA in patients with HR+HER2- EBC in clinical remission may impact recommendations for type and duration of adjuvant endocrine therapy. A sensitive technique to identify tumor mutations in plasma is BEAMing digital PCR. The frequency and timing of detectable mutations in plasma of patients in clinical remission from HR+HER2- EBC are unknown.

Methods: We screened a prospective institutional repository for patients that met inclusion criteria. Eligible patients must have been enrolled to the repository between 12/1/2008 (repository start) and 12/31/2016, had HR+HER2- EBC, received follow-up at Johns Hopkins with appointment scheduled between 3/1/2017 and 12/31/2017, completed curative surgery at least 6 months prior to this appointment, been recommended or initiated adjuvant endocrine therapy, and been in clinical remission. Appropriate patients were approached for a current blood sample during their follow-up appointment in 2017. Blood was analyzed using a BEAMing digital PCR platform (Sysmex Inostics OncoBEAM™) for AKT1, PIK3CA, and ESR1 mutations.

Results: We identified 67 eligible patients and collected blood from 60. Most patients had relatively low risk disease including 40 patients (67%) with stage I disease, and only 21 patients (35%) received chemotherapy. Patients were evenly divided between receiving tamoxifen or an aromatase inhibitor, and some patients switched from one to the other. The majority of patients (68%) had surgery between 1 and 5 years prior to the current blood draw. Detailed patient characteristics are provided in Table 1.

Two out of the 60 patients had detectable ptDNA, both with stage IIA disease. One patient had a mutation in the ESR1 ligand-binding domain P535H 9 months after surgery and while taking adjuvant tamoxifen for 7 months. Sanger sequencing of primary tumor tissue did not reveal this mutation. Another patient had a mutation in PIK3CA exon 9 E542K 9.5 years after surgery and after taking adjuvant tamoxifen for at least 7 years. Amplifying this locus in DNA from primary tumor tissue was unsuccessful; further analysis using droplet digital PCR (ddPCR) is planned.

Conclusions: Detection of ptDNA was feasible in a relatively low-risk group of patients with HR+HER2- EBC in clinical remission. Sampling a larger number of patients is needed to gain more understanding of the frequency and timing of detectable ptDNA. Next steps should also focus on determining the natural history of detectable ptDNA in patients with HR+HER2 EBC in clinical remission which may impact adjuvant treatment recommendations.

Funding sources: Komen SAC110053, P30 CA06973, Breast Cancer Research Foundation

Table 1:Characteristics of included patients N (%)Total patients60Age at diagnosis, median(range)57 (30-77)Female59 (98)Caucasian54 (90)Postmenopausal at diagnosis36 (60)Tumor size &lt;2 cm42 (70)Node negative45 (75)Invasive ductal histology44 (73)Received adjuvant chemotherapy21 (35)Type of adjuvant endocrine therapy Tamoxifen25 (42)Aromatase inhibitor26 (43)Tamoxifen and AI7 (12)None2 (3)Time after surgery 6 months to &lt;1 year6 (10)1 year to &lt;5 years41 (68)5 years to &lt;10 years13 (22)

Citation Format: Shah M, Hunter N, Ensminger J, Shinn D, Cole AJ, Quinn HE, Edelstein DL, Wang C, Smith KL, Richardson AL, Cimino-Mathews A, Wolff AC, Cravero K, Park BH, Stearns V. Detection of plasma tumor DNA (ptDNA) in patients with hormone receptor-positive HER2-negative (HR+HER2-) early breast cancer (EBC) in clinical remission [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-01-16.

Egr2 overexpression in Schwann cells increases myelination frequency in vitro

Schwann cells are key players in peripheral nerve regeneration, and are uniquely capable of remyelinating axons in this context. Schwann cells orchestrate this process via a set of transcription factors. While it has been shown that overexpression of specific genes, e.g. Egr2, upregulates myelin-related transcripts, it remains unknown if such manipulation can functionalize the cells and enhance their myelination frequency. The ability to do so could have implications in the use of human stem cell-derived Schwann cells, where myelination is hard to achieve. After screening four candidate transcription factors (Sox10, Oct6, Brn2 and Egr2), we found that overexpression of Egr2 in rat Schwann cells co-cultured with sensory neurons enhanced myelination frequency and reduced cell proliferation. However, in a mouse model of sciatic nerve repair with cells engrafted within a nerve guide, myelination frequency in the engrafted cells was reduced upon Egr2 overexpression. Our results show that while overexpression of Egr2 can enhance the myelination frequency in vitro, it is context-dependent, potentially influenced by the microenvironment, timing of association with axons, expression level, species differences, or other factors.

Abstract 1408: SF3B1 mutations induce proteome remodeling, metabolic reprogramming, and a novel kind of tumor surface antigen in human cells

Mutations in the SF3B1 gene occur in multiple cancers, creating a neomorphic spliceosome protein that induces aberrant mRNA splicing in thousands of genes. Little is known about the downstream oncogenic or therapeutic consequences of this missplicing. To study this, we engineered knockins of SF3B1 mutation in untransformed breast epithelial cells, as well as “reverse” knockins in which SF3B1-mutant uveal melanoma cells were corrected to wild type. Transcriptomic analysis of these isogenic pairs showed cryptic splicing induced by mutant SF3B1, and SILAC proteomics demonstrated a broad reshaping of the proteome dominated by downregulation of misspliced genes. Interestingly, pathway analysis revealed a suppression of proteins involved in energy metabolism. This included mitochondrial complex III, which rescue experiments showed was downregulated through missplicing of its assembly factor UQCC1, and PHGDH, a serine synthesis enzyme likewise misspliced and downregulated. Metabolomic analysis also showed evidence of metabolic reprogramming by mutant SF3B1, including suppression of serine, glycine, and aspartate levels. Because serine and glycine (SG) starvation can have anticancer activity in vivo—and because PHGDH expression modulates this effect—we tested SG starvation on SF3B1-mutant cells. Growth of our SF3B1-mutant isogenic cells was differentially suppressed by SG starvation, and two independent AML cell lines with endogenous SF3B1 mutation demonstrated significant cell death upon SG starvation, in contrast to multiple AML cell lines wild type for SF3B1. These data suggest impaired serine synthesis may be a therapeutic vulnerability in SF3B1-mutant cancers. In addition to downregulation of genes induced by mutant SF3B1, our proteomic data also revealed a novel cryptic protein that was highly enriched in SF3B1-mutant cells. This protein, CD98, is a surface membrane protein, and the cryptic peptide change occurred in its extracellular domain. Additional transcriptome analysis revealed eleven more candidate surface proteins with mutant SF3B1-induced cryptic isoforms containing in-frame peptide changes in extracellular domains, and overexpression studies demonstrated at least two of these cryptic proteins can traffic to the cell surface. We have named these putative proteins MASAs, for Missplicing-Associated Surface Antigens, and we believe they represent a novel kind of tumor surface antigen that may be targetable with antibody-based immunotherapeutics. In summary, our data provide evidence that SF3B1 mutations induce proteome alterations, metabolic reprogramming, and a new kind of tumor surface antigen in human cells.

Citation Format: William B. Dalton, Daniel Shinn, Noel Walsh, Eric Christenson, Taylor Groginski, Dhanashree Kelkar, Anil Magugundu, Arun Patil, Daniel Zabransky, Arielle Medford, Justin Lee, Alex Cole, Josh Donaldson, Amy DeZern, Karen Cravero, David Chu, Natasha Hunter, Akhilesh Pandey, Josh Lauring, Ben Park. SF3B1 mutations induce proteome remodeling, metabolic reprogramming, and a novel kind of tumor surface antigen in human cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1408.

Centralization of Services: Standard Setting and Outcomes

Objective

To test specific standards set in the newly established cleft lip and palate service in three regions of the U.K. The standards relate to record collection and outcomes.

Design

Retrospective analysis.

Patients

Records of 31 children, 5 years of age, who were born in 1997 with complete unilateral clefts of lip and palate and were treated by surgeons in three regions.

Main outcome measures

Record collection standards were measured by collecting dental study models. Outcomes were measured with the 5-Year-Old Index.

Results

Of the 31 subjects, 52% had excellent and good outcomes. The 31 cases represented 62% of the total records collected.

Conclusions

The three regions examined fell short of the standards set, but the outcomes were improved compared with previous national outcomes. The failings in record collection need to be rectified. This study provides baseline data for further development of cleft services within three regions.

Detection fidelity of AR mutations in plasma derived cell-free DNA

Somatic genetic alterations including copy number and point mutations in the androgen receptor (AR) are associated with resistance to therapies targeting the androgen/AR axis in patients with metastatic castration resistant prostate cancer (mCRPC). Due to limitations associated with biopsying metastatic lesions, plasma derived cell-free DNA (cfDNA) is increasingly being used as substrate for genetic testing. AR mutations detected by deep next generation sequencing (NGS) of cfDNA from patients with mCRPC have been reported at allelic fractions ranging from over 25% to below 1%. The lower bound threshold for accurate mutation detection by deep sequencing of cfDNA has not been comprehensively determined and may have locus specific variability. Herein, we used NGS for AR mutation discovery in plasma-derived cfDNA from patients with mCRPC and then used droplet digital polymerase chain reaction (ddPCR) for validation. Our findings show the AR (tTC>cTC) F877L hotspot was prone to false positive mutations during NGS. The rate of error at AR (tTC>cTC) F877L during amplification prior to ddPCR was variable among high fidelity polymerases. These results highlight the importance of validating low-abundant mutations detected by NGS and optimizing and controlling for amplification conditions prior to ddPCR.