Incidence of avascular necrosis of native femur following hip transposition surgery for periacetabular malignancies: a single-centre experience

BACKGROUND

Hip transposition surgery after surgical resection of large pelvic tumours is a well-established alternate to endoprosthetic reconstruction. The major goals of surgery are to ensure adequate resection margins with limb salvation, albeit with acceptable levels of morbidity. While surveillance is aimed at diagnosing local recurrence or distant metastasis primarily, other complications may occasionally be seen.The aim of this study was to assess incidence of avascular necrosis (AVN) in the preserved native femoral heads after hip transposition surgery for periacetabular malignancies, also known as hanging hip surgery.

PATIENTS AND METHODS

Patient records and follow-up imaging of 22 patients who had undergone hanging hip surgery from 1999 to 2020 were retrospectively analysed to assess for any probable causes of AVN.

RESULTS

Of the 22 patients, 5 (22.7%) had developed AVN on follow-up with a mean time of onset of about 10.5 months from surgery (5 months-2 years). A review of the patient demographics, surgical notes, preoperative management did not offer any clues as to the cause of AVN in these patients. Osteopenia was the most common radiological finding (59%) in most patients, but this also did not herald AVN onset.

CONCLUSIONS

The theory that loss of major vascular supply to the femoral head from capsular disruption during hip transposition surgery would lead to AVN in most patients did not hold true as AVN occurred in a small number of patients.

An evaluation of AI generated literature reviews in musculoskeletal radiology

PURPOSE

The use of artificial intelligence (AI) tools to aid in summarizing information in medicine and research has recently garnered a huge amount of interest. While tools such as ChatGPT produce convincing and naturally sounding output, the answers are sometimes incorrect. Some of these drawbacks, it is hoped, can be avoided by using programmes trained for a more specific scope. In this study we compared the performance of a new AI tool (the-literature.com) to the latest version OpenAI's ChatGPT (GPT-4) in summarizing topics that the authors have significantly contributed to.

METHODS

The AI tools were asked to produce a literature review on 7 topics. These were selected based on the research topics that the authors were intimately familiar with and have contributed to through their own publications. The output produced by the AI tools were graded on a 1-5 Likert scale for accuracy, comprehensiveness, and relevance by two fellowship trained consultant radiologists.

RESULTS

The-literature.com produced 3 excellent summaries, 3 very poor summaries not relevant to the prompt, and one summary, which was relevant but did not include all relevant papers. All of the summaries produced by GPT-4 were relevant, but fewer relevant papers were identified. The average Likert rating was for the-literature was 2.88 and 3.86 for GPT-4. There was good agreement between the ratings of both radiologists (ICC = 0.883).

CONCLUSION

Summaries produced by AI in its current state require careful human validation. GPT-4 on average provides higher quality summaries. Neither tool can reliably identify all relevant publications.

Controversies in Oncologic Pediatric Limb Salvage

With advances in chemotherapy and radiation therapy, surgical treatment of patients with bone sarcomas has advanced from most patients undergoing an amputation to now most patients undergoing a limb salvage procedure. With the advances of limb salvage surgical techniques, reconstructive procedures have expanded to include autografts, allografts, endoprosthetic replacements, and rotationplasty. In a growing child, the decision to perform each of these reconstructive options is individualized and each needs to be considered to provide the patient with the optimal oncologic and functional outcome, while being durable to minimize the risk of complications and subsequent surgeries.

Effect of radiotherapy on local recurrence, distant metastasis and overall survival in 1200 extremity soft tissue sarcoma patients. Retrospective analysis using IPTW-adjusted models

BACKGROUND AND PURPOSE

Neoadjuvant (NRTX) and adjuvant radiotherapy (ARTX) reduce local recurrence (LR) risk in extremity soft tissue sarcoma (eSTS), yet their impact on distant metastasis (DM) and overall survival (OS) is less well defined. This study aimed at analysing the influence of NRTX/ARTX on all three endpoints using a retrospective, multicentre eSTS cohort.

MATERIALS AND METHODS

1200 patients (mean age: 60.7 ± 16.8 years; 44.4 % females) were retrospectively included, treated with limb sparing surgery and curative intent for localised, high grade (G2/3) eSTS. 194 (16.2 %), 790 (65.8 %), and 216 (18.0 %) patients had received NRTX, ARTX and no RTX, respectively. For the resulting three groups (no RTX vs. NRTX, no RTX vs. ARTX, NRTX vs. ARTX) Fine&Gray models for LR and DM, and Cox-regression models for OS were calculated, with IPTW-modelling adjusting for imbalances between groups.

RESULTS

In the IPTW-adjusted analysis, NRTX was associated with lower LR-risk in comparison to no RTX (SHR [subhazard ratio]: 0.236; p = 0.003), whilst no impact on DM-risk (p = 0.576) or OS (p = 1.000) was found. IPTW-weighted analysis for no RTX vs. ARTX revealed a significant positive association between ARTX and lower LR-risk (SHR: 0.479, p = 0.003), but again no impact on DM-risk (p = 0.363) or OS (p = 0.534). IPTW-weighted model for NRTX vs. ARTX showed significantly lower LR-risk for NRTX (SHR for ARTX: 3.433; p = 0.003) but no difference regarding DM-risk (p = 1.000) or OS (p = 0.639).

CONCLUSION

NRTX and ARTX are associated with lower LR-risk, but do not seem to affect DM-risk or OS. NRTX may be favoured over ARTX as our results indicate better local control rates.

Frequent microbiological profile changes are seen in subsequent-revision hip and knee arthroplasty for prosthetic joint infection

A proportion of patients with hip and knee prosthetic joint infection (PJI) undergo multiple revisions with the aim of eradicating infection and improving quality of life. The aim of this study was to describe the microbiology cultured from multiply revised hip and knee replacement procedures to guide antimicrobial therapy at the time of surgery. Patients and methods: Consecutive patients were retrospectively identified from databases at two specialist orthopaedic centres in the United Kingdom between 2011 and 2019. Patient were included who had undergone repeat-revision total knee replacement (TKR) or total hip replacement (THR) for infection, following an initial failed revision for infection. Results: A total of 106 patients were identified. Of these patients, 74 underwent revision TKR and 32 underwent revision THR. The mean age at first revision was 67 years (SD 10). The Charlson comorbidity index was ≤  2 for 31 patients, 3-4 for 57 patients, and ≥  5 for 18 patients. All patients underwent at least two revisions, 73 patients received three, 47 patients received four, 31 patients received five, and 21 patients received at least six. After six revisions, 90 % of patients had different organisms cultured compared with the initial revision, and 53 % of organisms were multidrug resistant. The most frequent organisms at each revision were coagulase-negative Staphylococcus (36 %) and Staphylococcus aureus (19 %). Fungus was cultured from 3 % of revisions, and 21 % of infections were polymicrobial. Conclusion: Patients undergoing multiple revisions for PJI are highly likely to experience a change in organism, with 90 % of patients having a different organism cultured by their sixth revision. It is therefore important to administer empirical antibiotics at each subsequent revision, taking into account known drug resistance from previous cultures. Our results do not support the routine use of empirical antifungals.

The Importance of Awaiting Biopsy Results in Solitary Pathological Proximal Femoral Fractures : Do We Need to Biopsy Solitary Pathological Fractures?

BACKGROUND

The optimal surgical treatment for patients presenting with (impending and complete) pathological proximal femoral fractures is predicated on prognosis. Guidelines recommend a preoperative biopsy to exclude sarcomas, however no evidence confirms a benefit.

OBJECTIVE

This study aimed to describe the diagnostic accuracy, morbidity and sarcoma incidence of biopsy results in these patients.

MATERIAL AND METHODS

All patients (n = 153) presenting with pathological proximal femoral fractures between 2000 and 2019 were retrospectively evaluated. Patients after inadvertent surgery (n = 25) were excluded. Descriptive statistics were used to evaluate the accuracy and morbidity of diagnostic biopsies.

RESULTS

Of 112/128 patients who underwent biopsy, nine (8%) biopsies were unreliable either due to being inconclusive (n = 5) or because the diagnosis changed after resection (n = 4). Of impending fractures, 32% fractured following needle core biopsy. Median time from diagnosis to surgery was 30 days (interquartile range 21-46). The overall biopsy positive predictive value (PPV) to differentiate between sarcoma and non-sarcoma was 1.00 (95% confidence interval [CI] 0.88-1.00). In patients with a previous malignancy (n = 24), biopsy (n = 23) identified the diagnosis in 83% (PPV 0.91, 95% CI 0.71-0.99), of whom five (24%) patients had a new diagnosis. In patients without a history of cancer (n = 61), final diagnosis included carcinomas (n = 24, 39.3%), sarcomas (n = 24, 39.3%), or hematological malignancies (n = 13, 21.3%). Biopsy (n = 58) correctly identified the diagnosis in 66% of patients (PPV 0.80, 95% CI 0.67-0.90).

CONCLUSION

This study confirms the importance of a preoperative biopsy in solitary pathological proximal femoral fractures due to the risk of sarcoma in patients with and without a history of cancer. However, biopsy delays the time to definite surgery, results can be inconclusive or false, and it risks completion of impending fractures.

Beyond type III Paprosky acetabular defects: are partial pelvic replacements with iliosacral fixation successful?

PURPOSE

Supra-acetabular bone loss close beyond the sciatic notch is one of the most challenging defect types for stable anatomical reconstruction in revision arthroplasty. Using reconstruction strategies from tumour orthopaedic surgery, we adapted tricortical trans-iliosacral fixation options for custom-made implants in revision arthroplasty. The aim of the present study was to present the clinical and radiological results of this extraordinary pelvic defect reconstruction.

METHODS

Between 2016 and 2021, 10 patients with a custom-made pelvic construct using tricortical iliosacral fixation (see Fig. 1) were included in the study. Follow-up was 34 (SD 10; range 15-49) months. Postoperatively CT scans evaluating the implant position were performed. Functional outcome and the clinical results were recorded.

RESULTS

Implantation was possible as planned in all cases in 236 (SD 64: range 170-378) min. Correct centre of rotation (COR) reconstruction was possible in nine cases. One sacrum screw crossed a neuroforamen in one case without clinical symptoms. During the follow-up period, four further operations were required in two patients. There were no individual implant revisions or aseptic loosening recorded. The Harris Hip Score increased significantly from 27 Pts. to 67 Pts. with a mean improvement of 37 (p < 0.005). EQ-5D developed from 0.562 to 0.725 (p = 0.038) as a clear improvement in quality of life.

CONCLUSION

Custom-made partial pelvis replacement with iliosacral fixation offers a safe solution in "beyond Paprosky type III defects" for hip revision arthroplasty. Due to meticulous planning, precise implantation with good clinical outcome can be achieved. Furthermore, the functional outcome and patient satisfaction increased significantly showing promising early results with a relatively low complication rate.

Accuracy of MRI scans in predicting intra-articular joint involvement in high-grade sarcomas around the knee

Aims

Intra-articular (IA) tumours around the knee are treated with extra-articular (EA) resection, which is associated with poor functional outcomes. We aim to evaluate the accuracy of MRI in predicting IA involvement around the knee.

Methods

We identified 63 cases of high-grade sarcomas in or around the distal femur that underwent an EA resection from a prospectively maintained database (January 1996 to April 2020). Suspicion of IA disease was noted in 52 cases, six had IA pathological fracture, two had an effusion, two had prior surgical intervention (curettage/IA intervention), and one had an osseous metastasis in the proximal tibia. To ascertain validity, two musculoskeletal radiologists (R1, R2) reviewed the preoperative imaging (MRI) of 63 consecutive cases on two occasions six weeks apart. The radiological criteria for IA disease comprised evidence of tumour extension within the suprapatellar pouch, intercondylar notch, extension along medial/lateral retinaculum, and presence of IA fracture. The radiological predictions were then confirmed with the final histopathology of the resected specimens.

Results

The resection histology revealed 23 cases (36.5%) showing IA disease involvement compared with 40 cases without (62%). The intraobserver variability of R1 was 0.85 (p < 0.001) compared to R2 with κ = 0.21 (p = 0.007). The interobserver variability was κ = 0.264 (p = 0.003). Knee effusion was found to be the most sensitive indicator of IA involvement, with a sensitivity of 91.3% but specificity of only 35%. However, when combined with a pathological fracture, this rose to 97.5% and 100% when disease was visible in Hoffa's fat pad.

Conclusion

MRI imaging can sometimes overestimate IA joint involvement and needs to be correlated with clinical signs. In the light of our findings, we would recommend EA resections when imaging shows effusion combined with either disease in Hoffa's fat pad or retinaculum, or pathological fractures.

YBX1-interacting small RNAs and RUNX2 can be blocked in primary bone cancer using CADD522

Primary bone cancer (PBC) comprises several subtypes each underpinned by distinctive genetic drivers. This driver diversity produces novel morphological features and clinical behaviour that serendipitously makes PBC an excellent metastasis model. Here, we report that some transfer RNA-derived small RNAs termed tRNA fragments (tRFs) perform as a constitutive tumour suppressor mechanism by blunting a potential pro-metastatic protein-RNA interaction. This mechanism is reduced in PBC progression with a gradual loss of tRNAGly^TCC cleavage into 5' end tRF-Gly^TCC when comparing low-grade, intermediate-grade and high-grade patient tumours. We detected recurrent activation of miR-140 leading to upregulated RUNX2 expression in high-grade patient tumours. Both tRF-Gly^TCC and RUNX2 share a sequence motif in their 3' ends that matches the YBX1 recognition site known to stabilise pro-metastatic mRNAs. Investigating some aspects of this interaction network, gain- and loss-of-function experiments using small RNA mimics and antisense LNAs, respectively, showed that ectopic tRF-Gly^TCC reduced RUNX2 expression and dispersed 3D micromass architecture in vitro. iCLIP sequencing revealed YBX1 physical binding to the 3' UTR of RUNX2. The interaction between YBX1, tRF-Gly^TCC and RUNX2 led to the development of the RUNX2 inhibitor CADD522 as a PBC treatment. CADD522 assessment in vitro revealed significant effects on PBC cell behaviour. In xenograft mouse models, CADD522 as a single agent without surgery significantly reduced tumour volume, increased overall and metastasis-free survival and reduced cancer-induced bone disease. Our results provide insight into PBC molecular abnormalities that have led to the identification of new targets and a new therapeutic.

Repeat revision TKR for failed management of peri-prosthetic infection has long-term success but often require multiple operations: a case control study

BACKGROUND

Prosthetic joint infection (PJI) is associated with poor outcomes and catastrophic complications. The aim of this study was to present the outcomes of re-revision surgery for PJI of the knee following previous failed two-stage exchange arthroplasty.

MATERIALS AND METHODS

A retrospective analysis was performed of 32 patients who underwent re-revision knee arthroplasty, having already undergone at least one previous two-stage exchange for PJI with a minimum follow-up of two-years for alive patients. Outcomes were compared to a matched control of two-stage revisions for PJI of a primary knee replacement also containing 32 patients. Outcomes investigated were eradication of infection, re-operation, mortality and limb-salvage rate.

RESULTS

Successful eradication of infection was achieved in 50% of patients following re-revision surgery, compared with 91% following two-stage exchange of primary knee replacement for PJI (p < 0.001). Fourteen (44%) patients required further re-operation compared with three (9%) patients in the primary group (p = 0.006). Amputation was performed in one case (3%) with thirteen patients (92%) who had infection controlled by debridement, antibiotics and implant retention (DAIR), further revision surgery or arthrodesis. Two patients died with infection (6%) and the long-term rate for infection control was 91%. The mean number of procedures following surgery for the re-revision group was 2.8 (0-9) compared with 0.13 (0-1) for the primary two-stage group (p < 0.001). Five-year patient survival was 90.6% (95% CI 77.1-100). The limb-salvage rate for the re-revision cohort was 97%.

CONCLUSION

Outcomes for re-revision knee arthroplasty for PJI have higher re-operation and failure rates, but no worse mortality than in revisions of primary knee replacements. Failures can successfully be managed by further operation.

Membrane-type 1 matrix metalloproteinase as predictor of survival and candidate therapeutic target in Ewing sarcoma

BACKGROUND

Ewing sarcoma (ES) is the second most common primary bone malignancy, with an urgent need for new treatments. ES is associated with high rates of progression and relapse, driven by drug-resistant cells capable of migration, self-renewal and single-cell tumorigenesis, termed cancer stem-like cells (CSCs). Membrane-type 1 matrix metalloproteinase (MT1-MMP) is a membrane-bound proteolytic enzyme, which, via direct and indirect mechanisms, digests four of the main types of collagen. This can be hijacked in malignancy for invasion and metastasis, with high expression predicting decreased survival in multiple cancers. In this study, we have examined the hypothesis that MT1-MMP is expressed by ES cells and explored the relationship between expression and outcomes.

PROCEDURE

MT1-MMP expression in ES established cell lines, primary patient-derived cultures and daughter ES-CSCs was characterised by RNA sequencing, Western blotting, immunocytochemistry and flow cytometry. Immunohistochemistry was used to detect MT1-MMP in tumour biopsies, and the relationship between expression, event-free and overall survival examined.

RESULTS

MT1-MMP was detected at both RNA and protein levels in five of six established cell lines, all primary cultures (n = 25) and all daughter ES-CSCs (n = 7). Immunohistochemistry of treatment-naïve biopsy tissue demonstrated that high MT1-MMP expression predicted decreased event-free and overall survival (p = .017 and .036, respectively; n = 47); this was not significant in multivariate analysis.

CONCLUSIONS

MT1-MMP is expressed by ES cells, including ES-CSCs, making it a candidate therapeutic target. The level of MT1-MMP expression at diagnosis may be considered as a prognostic biomarker if validated by retrospective analysis of a larger cohort of clinical trial samples.

A comparison of the microbiology profile for periprosthetic joint infection of knee arthroplasty and lower-limb endoprostheses in tumour surgery

Abstract. Aims: this study compared the patient and microbiological profile of prosthetic joint infection (PJI) for patients treated with two-stage revision for knee arthroplasty with that of lower-limb endoprostheses for oncological resection. Patient and methods: a total of 118 patients were treated with two-stage revision surgery for infected knee arthroplasty and lower-limb endoprostheses between 1999 and 2019. A total of 74 patients had two-stage revision for PJI of knee arthroplasty, and 44 had two-stage revision of oncology knee endoprostheses. There were 68 men and 50 women. The mean ages of the arthroplasty and oncology cohorts were 70.2 years (range of 50–89) and 36.1 years (range of 12–78) respectively (p<0.01). Patient host and extremity criteria were categorized according to the Musculoskeletal Infection Society (MSIS) host and extremity staging system. The patient microbiological culture, the incidence of polymicrobial infection, and multidrug resistance (MDR) were analysed and recorded. Results: polymicrobial infection was reported in 16 % (12 patients) of knee arthroplasty PJI cases and in 14.5 % (8 patients) of endoprostheses PJI cases (p=0.783). There was a significantly higher incidence of MDR in endoprostheses PJI, isolated in 36.4 % of cultures, compared with knee arthroplasty PJI (17.2 %, p=0.01). Gram-positive organisms were isolated in more than 80 % of cultures from both cohorts. Coagulase-negative Staphylococcus (CoNS) was the most common Gram-positive organism, and Escherichia coli was the most common Gram-negative organism in both groups. According to the MSIS staging system, the host and extremity grades of the oncology PJI cohort were significantly worse than those for the arthroplasty PJI cohort (p<0.05). Conclusion: empirical antibiotic prophylaxis against PJI in orthopaedic oncology is based upon PJI in arthroplasty, despite oncology patients presenting with worse host and extremity staging. CoNS was the most common infective organism in both groups; however, pathogens showing MDR were significantly more prevalent in oncological PJI of the knee. Therefore, empirical broad-spectrum treatment is recommended in oncological patients following revision surgery.

The influence of site on the incidence and diagnosis of solitary central cartilage tumours of the femur. A 21st century perspective

OBJECTIVE

To determine the incidence of central cartilage tumours (CCTs) in the femur and the impact of site (proximal, mid and distal thirds) on tumour grade. To compare study results with historically published data.

MATERIALS AND METHODS

Retrospective review of solitary CCTs arising in the femur over the past 13 years. Data collected included location (proximal, mid and distal thirds) and final diagnosis in terms of tumour grade based on imaging features ± histology. Case material collected from three bone tumour textbooks provided historical data.

RESULTS

430 solitary CCTs were included in the femur. 73% cases arose in the distal, 3.7% in the mid and 23% in the proximal femur. The ratio of "benign" (combining enchondroma and atypical cartilaginous tumour (ACT)) to higher grade chondrosarcoma (CS) was 11:1 in the distal, 1:1 in the mid and 1:1.5 in the proximal femur, the distribution of benign to malignant tumours being significantly different between the regions (F test, p < 0.05). Comparison with historical data showed a reversal of the benign (enchondroma) to malignant (ACT and higher grade CS) of 30%:70%-84%:16% in the current series.

CONCLUSIONS

The site of origin of a CCT in the femur has an impact on final diagnosis with CS uncommon in the distal as compared with the mid and proximal femur. This is in contradistinction to historical data where the incidence of CS exceeded that of enchondroma at all sites.

Anatomical distribution, the incidence of malignancy and diagnostic workup in the pathological lesions of the clavicle: a review of 410 cases

BACKGROUND

The clavicle poses a diagnostic dilemma of the pathological lesions due to the wide range of pathologies seen at this site. This study aimed to identify and stratify various pathologies seen in the clavicle and to guide ways of investigation for diagnosis based on age, site and investigation findings.

MATERIALS AND METHODS

Four hundred and ten cases with clavicle lesions were identified in our database. Data were collected about the patient's medical history, previous investigation, inflammatory markers radiological investigations and biopsy. All patients were worked up and managed after discussion in a multidisciplinary team meeting (MDT).

RESULTS

Non-malignant lesions accounted for 79% of cases. Infection was the most common diagnosis (39%) and the commonest diagnosis in those less than 20 years of age. 73% of the lesions were found at the medial end of the clavicle. Malignant tumours were 21%, while primary benign bone tumours accounted for only 14%. 50% of the malignant lesions were due to metastatic disease. The risk of malignancy increases with advancing age. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were not sensitive as a diagnostic tool in cases of osteomyelitis confirmed by histology. Magnetic resonance imaging (MRI) was noted to have high sensitivity and specificity for identifying the nature of a lesion and diagnosis.

CONCLUSION

We have identified age as a positive predictor of a malignant cause in pathological lesions of the clavicle. MRI should be considered in all these cases. CRP and ESR have poor predictive values in diagnosing infection in the clavicle. Patients presenting with clavicle lesions should be discussed in a specialist MDT and undergo a systemic diagnostic workup, still in some cases, diagnosis can be speculated based on the patient's age, location of the lesion within the clavicle and the features seen on the MRI scan.

LEVEL OF EVIDENCE

IV.

Circulating tumour DNA is a promising biomarker for risk stratification of central chondrosarcoma with IDH1/2 and GNAS mutations

Chondrosarcoma (CS) is a rare tumour type and the most common primary malignant bone cancer in adults. The prognosis, currently based on tumour grade, imaging and anatomical location, is not reliable, and more objective biomarkers are required. We aimed to determine whether the level of circulating tumour DNA (ctDNA) in the blood of CS patients could be used to predict outcome. In this multi-institutional study, we recruited 145 patients with cartilaginous tumours, of which 41 were excluded. ctDNA levels were assessed in 83 of the remaining 104 patients, whose tumours harboured a hotspot mutation in IDH1/2 or GNAS. ctDNA was detected pre-operatively in 31/83 (37%) and in 12/31 (39%) patients postoperatively. We found that detection of ctDNA was more accurate than pathology for identification of high-grade tumours and was associated with a poor prognosis; ctDNA was never associated with CS grade 1/atypical cartilaginous tumours (ACT) in the long bones, in neoplasms sited in the small bones of the hands and feet or in tumours measuring less than 80 mm. Although the results are promising, they are based on a small number of patients, and therefore, introduction of this blood test into clinical practice as a complementary assay to current standard-of-care protocols would allow the assay to be assessed more stringently and developed for a more personalised approach for the treatment of patients with CS.

Extra-articular resection of the hip joint for pelvic sarcomas: Are there any oncological and functional risks compared with intra-articular resection?

BACKGROUND

While extra-articular resection (EAR) of the knee and shoulder joint is associated with poorer clinical outcomes, the oncological and functional risks of EAR of the hip joint are unknown. We aimed to compare these risks between EAR of the hip joint and intra-articular resection (IAR).

METHODS

We conducted a comparative study of 75 patients who underwent en-bloc tumour resection and limb-salvage reconstruction for bone sarcomas of the peri-acetabulum between 1996 and 2016. We divided patients into two groups for analyses; EAR (n = 21) and IAR (n = 54).

RESULTS

There was no statistical difference in oncological outcomes; the 5-year cumulative incidence of disease-specific death was 34% and 35% in the EAR and IAR groups, respectively (p = 0.943), and the 5-year cumulative incidence of LR was 26% and 34%, respectively (p = 0.482). The most common complications were dislocation (28%) and deep infection (28%); there was equally no difference between the groups. The mean Musculoskeletal Tumour Society score was 66% and 65% in the EAR and IAR groups, respectively (p = 0.795), and were significantly lower in patients with deep infection (52% vs. 69%; p = 0.013). In a sub-analysis on the outcomes in patients who underwent PI-uninvolved PII-resection for chondrosarcoma, no major differences in oncologic and functional outcomes were confirmed.

CONCLUSION

Patients undergoing EAR and limb-salvage reconstructions of the hip joint have undistinguishable oncological, clinical and functional outcomes compared to those undergoing IAR and reconstructions. If preoperative imaging suggests articular tumour involvement, there appears to be no detrimental effect of undertaking EAR to optimise local control.

Outcomes of the gastrocnemius flap performed by orthopaedic surgeons in salvage revision knee arthroplasty

Introduction: The gastrocnemius myofascial flap is used to manage soft-tissue defects over the anterior aspect of the knee in the context of a patient presenting with a sinus and periprosthetic joint infection (PJI) or extensor mechanism failure. The aim of this study was twofold: firstly, to evaluate the outcomes of gastrocnemius flaps performed by appropriately trained orthopaedic surgeons in the context of PJI and, secondly, to evaluate the infection-free survival of this patient group. Patients and methods: We retrospectively reviewed 30 patients who underwent gastrocnemius flap reconstruction during staged revision total knee arthroplasty for prosthetic joint infection (PJI). All flaps were performed by an orthopaedic surgeon with orthoplastics training. Patients had a mean age of 68.9 years (range 50-84) and were followed up for a mean of 50.4 months (range 2-128 months). A total of 29 patients (97 %) were categorized into Musculoskeletal Infection Society (MSIS) local extremity grade 3 (greater than two compromising factors), and 52 % of PJIs were polymicrobial. The primary outcome measure was flap failure, and the secondary outcome measure was recurrent infection. Results: Flap survival was 100 % with no failures or early returns to theatre for flap problems such as necrosis or haematoma. Overall infection-free survival during the study period was 48 % (13 of 27 infected cases). Using limb salvage as the outcome, 77 % (23 of 30 patients) retained the limb. Infection recurrence occurred in 48 % (10 patients) in the type B3 cohort and 67 % (4 patients) in the type C3 cohort ( p = 0.65 ). Conclusions: The surgical technique for a gastrocnemius myofascial flap is reliable and reproducible when performed by appropriately trained orthopaedic surgeons, even in high-risk groups. However, the risks of recurrent infection and amputation remain high within our series due to poor host and extremity factors.

Acetabular complications are the most common cause for revision surgery following proximal femoral endoprosthetic replacement : what is the best bearing option in the primary and revision setting?

AIMS

Proximal femoral endoprosthetic replacements (PFEPRs) are the most common reconstruction option for osseous defects following primary and metastatic tumour resection. This study aimed to compare the rate of implant failure between PFEPRs with monopolar and bipolar hemiarthroplasties and acetabular arthroplasties, and determine the optimum articulation for revision PFEPRs.

METHODS

This is a retrospective review of 233 patients who underwent PFEPR. The mean age was 54.7 years (SD 18.2), and 99 (42.5%) were male. There were 90 patients with primary bone tumours (38.6%), 122 with metastatic bone disease (52.4%), and 21 with haematological malignancy (9.0%). A total of 128 patients had monopolar (54.9%), 74 had bipolar hemiarthroplasty heads (31.8%), and 31 underwent acetabular arthroplasty (13.3%).

RESULTS

At a mean 74.4 months follow-up, the overall revision rate was 15.0%. Primary malignancy (p < 0.001) and age < 50 years (p < 0.001) were risk factors for revision. The risks of death and implant failure were similar in patients with primary disease (p = 0.872), but the risk of death was significantly greater for patients who had metastatic bone disease (p < 0.001). Acetabular-related implant failures comprised 74.3% of revisions; however, no difference between hemiarthroplasty or arthroplasty groups (p = 0.209), or between monopolar or bipolar hemiarthroplasties (p = 0.307), was observed. There was greater radiological wear in patients with longer follow-up and primary bone malignancy. Re-revision rates following a revision PFEPR was 34.3%, with dual-mobility bearings having the lowest rate of instability and re-revision (15.4%).

CONCLUSION

Hemiarthroplasty and arthroplasty PFEPRs carry the same risk of revision in the medium term, and is primarily due to acetabular complications. There is no difference in revision rates or erosion between monopolar and bipolar hemiarthroplasties. The main causes of failure were acetabular wear in the hemiarthroplasty group and instability in the arthroplasty group. These risks should be balanced and patient prognosis considered when contemplating the bearing choice. Dual-mobility, constrained bearings, or large diameter heads (> 32 mm) are recommended in all revision PFEPRs. Cite this article: Bone Joint J 2021;103-B(10):1633-1640.

RNA sequencing and functional studies of patient-derived cells reveal that neurexin-1 and regulators of this pathway are associated with poor outcomes in Ewing sarcoma

Purpose

The development of biomarkers and molecularly targeted therapies for patients with Ewing sarcoma (ES) in order to minimise morbidity and improve outcome is urgently needed. Here, we set out to isolate and characterise patient-derived ES primary cell cultures and daughter cancer stem-like cells (CSCs) to identify biomarkers of high-risk disease and candidate therapeutic targets.

Methods

Thirty-two patient-derived primary cultures were established from treatment-naïve tumours and primary ES-CSCs isolated from these cultures using functional methods. By RNA-sequencing we analysed the transcriptome of ES patient-derived cells (n = 24) and ES-CSCs (n = 11) to identify the most abundant and differentially expressed genes (DEGs). Expression of the top DEG(s) in ES-CSCs compared to ES cells was validated at both RNA and protein levels. The functional and prognostic potential of the most significant gene (neurexin-1) was investigated using knock-down studies and immunohistochemistry of two independent tumour cohorts.

Results

ES-CSCs were isolated from all primary cell cultures, consistent with the premise that ES is a CSC driven cancer. Transcriptional profiling confirmed that these cells were of mesenchymal origin, revealed novel cell surface targets for therapy that regulate cell-extracellular matrix interactions and identified candidate drivers of progression and relapse. High expression of neurexin-1 and low levels of regulators of its activity, APBA1 and NLGN4X, were associated with poor event-free and overall survival rates. Knock-down of neurexin-1 decreased viable cell numbers and spheroid formation.

Conclusions

Genes that regulate extracellular interactions, including neurexin-1, are candidate therapeutic targets in ES. High levels of neurexin-1 at diagnosis are associated with poor outcome and identify patients with localised disease that will relapse. These patients could benefit from more intensive or novel treatment modalities. The prognostic significance of neurexin-1 should be validated independently.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13402-021-00619-8.

What Proportion of Patients with Bone and Soft Tissue Tumors Contracted Coronavirus-19 and Died From Surgical Procedures During the Initial Period of the COVID-19 Pandemic? Results From the Multicenter British Orthopaedic Oncology Society Observational Study

BACKGROUND

Delivering uninterrupted cancer treatment to patients with musculoskeletal tumors has been essential during the rapidly evolving coronavirus 2019 (COVID-19) pandemic, as delays in management can be detrimental. Currently, the risk of contracting COVID-19 in hospitals when admitted for surgery and the susceptibility due to adjuvant therapies and associated mortality due to COVID-19 is unknown, but knowledge of these potential risks would help treating clinicians provide appropriate cancer care.

QUESTIONS/PURPOSES

(1) What is the risk of hospital-acquired COVID-19 in patients with musculoskeletal tumors admitted for surgery during the initial period of the pandemic? (2) What is the associated mortality in patients with musculoskeletal tumors who have contracted COVID-19? (3) Are patients with musculoskeletal tumors who have had neoadjuvant therapy (chemotherapy or radiation) preoperatively at an increased risk of contracting COVID-19? (4) Is a higher American Society of Anesthesiologists (ASA) grade in patients with musculoskeletal tumors associated with an increased risk of contracting COVID-19 when admitted to the hospital for surgery?

METHODS

This retrospective, observational study analyzed patients with musculoskeletal tumors who underwent surgery in one of eight specialist centers in the United Kingdom, which included the five designated cancer centers in England, one specialist soft tissue sarcoma center, and two centers from Scotland between March 12, 2020 and May 20, 2020. A total of 347 patients were included, with a median (range) age of 53 years (10 to 94); 60% (207 of 347) were men, and the median ASA grade was II (I to IV). These patients had a median hospital stay of 8 days (0 to 53). Eighteen percent (61 of 347) of patients had received neoadjuvant therapy (8% [27] chemotherapy, 8% [28] radiation, 2% [6] chemotherapy and radiation) preoperatively. The decision to undergo surgery was made in adherence with United Kingdom National Health Service and national orthopaedic oncology guidelines, but specific data with regard to the number of patients within each category are not known. Fifty-nine percent (204 of 347) were negative in PCR testing done 48 hours before the surgical procedure; the remaining 41% (143 of 347) were treated before preoperative PCR testing was made mandatory, but these patients were asymptomatic. All patients were followed for 30 days postoperatively, and none were lost to follow-up during that period. The primary outcome of the study was contracting COVID-19 in the hospital after admission. The secondary outcome was associated mortality after contracting COVID-19 within 30 days of the surgical procedure. In addition, we assessed whether there is any association between ASA grade or neoadjuvant treatment and the chances of contracting COVID-19 in the hospital. Electronic patient record system and simple descriptive statistics were used to analyze both outcomes.

RESULTS

Four percent (12 of 347) of patients contracted COVID-19 in the hospital, and 1% (4 of 347) of patients died because of COVID-19-related complications. Patients with musculoskeletal tumors who contracted COVID-19 had increased mortality compared with patients who were asymptomatic or tested negative (odds ratio 55.33 [95% CI 10.60 to 289.01]; p < 0.001).With the numbers we had, we could not show that adjuvant therapy had any association with contracting COVID-19 while in the hospital (OR 0.94 [95% CI 0.20 to 4.38]; p = 0.93). Increased ASA grade was associated with an increased likelihood of contracting COVID-19 (OR 58 [95% CI 5 to 626]; p < 0.001).

CONCLUSION

Our results show that surgeons must be mindful and inform patients that those with musculoskeletal tumors are at risk of contracting COVID-19 while admitted to the hospital and some may succumb to it. Hospital administrators and governmental agencies should be aware that operations on patients with lower ASA grade appear to have lower risk and should consider restructuring service delivery to ensure that procedures are performed in designated COVID-19-restricted sites. These measures may reduce the likelihood of patients contracting the virus in the hospital, although we cannot confirm a benefit from this study. Future studies should seek to identify factors influencing these outcomes and also compare surgical complications in those patients with and without COVID-19.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Limb-salvage reconstruction following resection of pelvic bone sarcomas involving the acetabulum

AIMS

Limb salvage for pelvic sarcomas involving the acetabulum is a major surgical challenge. There remains no consensus about what is the optimum type of reconstruction after resection of the tumour. The aim of this study was to evaluate the surgical outcomes in these patients according to the methods of periacetabular reconstruction.

METHODS

The study involved a consecutive series of 122 patients with a periacetabular bone sarcoma who underwent limb-salvage surgery involving a custom-made prosthesis in 65 (53%), an ice-cream cone prosthesis in 21 (17%), an extracorporeal irradiated autograft in 18 (15%), and nonskeletal reconstruction in 18 (15%).

RESULTS

The rates of major complications necessitating further surgery were 62%, 24%, 56%, and 17% for custom-made prostheses, ice-cream cone prostheses, irradiated autografts and nonskeletal reconstructions, respectively (p = 0.001). The ten-year cumulative incidence of failure of the reconstruction was 19%, 9%, 33%, and 0%, respectively. The major cause of failure was deep infection (11%), followed by local recurrence (6%). The mean functional Musculoskeletal Tumour Society (MSTS) scores were 59%, 74%, 64%, and 72%, respectively. The scores were significantly lower in patients with major complications than in those without complications (mean 52% (SD 20%) vs 74% (SD 19%); p < 0.001). For periacetabular resections involving the ilium, the mean score was the highest with custom-made prostheses (82% (SD 10%)) in patients without any major complication; however, nonskeletal reconstruction resulted in the highest mean scores (78% (SD 12%)) in patients who had major complications. For periacetabular resections not involving the ilium, significantly higher mean scores were obtained with ice-cream cone prostheses (79% (SD 17%); p = 0.031).

CONCLUSION

Functional outcome following periacetabular reconstruction is closely associated with the occurrence of complications requiring further surgery. For tumours treated with periacetabular and iliac resection, skeletal reconstruction may result in the best outcomes in the absence of complications, whereas nonskeletal reconstruction is a reasonable option if the risk of complications is high. For tumours requiring periacetabular resection without the ilium, reconstruction using an ice-cream cone prosthesis supported by antibiotic-laden cement is a reliable option. Cite this article: Bone Joint J 2021;103-B(4):795-803.

Pelvic reconstruction using an ice-cream cone prosthesis: correlation between the inserted length of the coned stem and surgical outcome

BACKGROUND

Acetabular reconstruction using an ice-cream cone prosthesis has been a reliable reconstruction option following pelvic tumour resection. However, it remains unknown which factor determines the success of this procedure. We aimed to determine risk factors for complications and functional loss in acetabular reconstruction using an ice-cream cone prosthesis.

PATIENTS AND METHODS

Fifty-four patients with malignant bone tumours who underwent acetabular reconstruction using an ice-cream cone prosthesis between 2004 and 2016 were studied. The bone-stem ratio was calculated as the ratio of the inserted length into the bone per the entire stem length.

RESULTS

A total of 26 (48%) patients had at least one complication and 11 patients (20%) required surgical interventions. The complication rates were 71% and 40% with a bone-stem ratio ≤ 50% and > 50%, respectively (p = 0.026), and the bone-stem ratio significantly stratified the risk of complications (≤ 50%: OR, 4.67 versus > 50%; p = 0.048). The mean MSTS score at the final follow-up was 60% (range 23-97%): the scores were significantly lower in patients with complications/leg-length discrepancy (52%) than in those without (79%; p = 0.002). The mean score with a bone-stem ratio ≤ 50% was significantly lower than the score with a ratio > 50%, especially in patients who underwent non-navigated reconstructions (33% versus 64%; p = 0.001).

CONCLUSION

The inserted length of the coned stem into residual bone was predictive of complications and functional outcome. Surgical indication for this procedure should be considered with the size of the remaining ilium to stabilise the prosthesis with a coned stem longer than half length.

Investigation and management of prosthetic joint infection in knee replacement: A BASK Surgical Practice Guideline

BACKGROUND

The burden of knee replacement prosthetic joint infection (KR PJI) is increasing. KR PJI is difficult to treat, outcomes can be poor and it is financially expensive and limited evidence is available to guide treatment decisions.

AIM

To provide guidelines for surgeons and units treating KR PJI.

METHODS

Guideline formation by consensus process undertaken by BASK's Revision Knee Working Group, supported by outputs from UK-PJI meetings.

RESULTS

Improved outcomes should be achieved through provision of care by revision centres in a network model. Treatment of KR PJI should only be undertaken at specialist units with the required infrastructure and a regular infection MDT. This document outlines practice guidelines for units providing a KR PJI service and sets out: CONCLUSIONS: KR PJI patients treated within the NHS should be provided the best care possible. This report sets out guidance and support for surgeons and units to achieve this.

Seeking international consensus on approaches to primary tumour treatment in Ewing sarcoma

BACKGROUND

The local treatment of Ewing sarcoma of bone involves surgery, radiotherapy or both. The selection of treatment depends on the anatomical extent of the tumour, the effectiveness of the proposed treatment, its morbidity, and the expectation of cure. However, not only are there variations in the approach to local treatment between individual patients, but also between treatment centres and countries. Our aim was to explore variation in practice and develop consensus statements about local treatment.

METHODS

A three stage modified Delphi technique was used with international collaborators. This involved an expert panel to identify areas of controversy, an online survey of international collaborators and a consensus meeting in London, UK in June 2017. In the consensus meeting, teams of clinicians discussed the local management of selected cases and their responses were collected with electronic voting.

RESULTS

Areas of greater or less consensus were identified. The lack of evidence underpinning different approaches was noted and areas for collaborative research became apparent.

CONCLUSION

This has demonstrated that there is an international consensus around many aspects of the local treatment of Ewing sarcoma of bone, including the use of specialist MultiDisciplinary Team (MDT) meetings with access to all appropriate treatments. However, considerable variation remains including the use of different staging investigations, decision making, definitions of response, and radiotherapy doses and timing. Further collaborative work should be undertaken to determine the impact of these variations in order to define best practice.

Additive manufacturing of porous titanium metaphyseal components: Early osseointegration and implant stability in revision knee arthroplasty

AIMS

Metaphyseal cones and sleeves are components used in revision knee arthroplasty to ensure load transfer, encourage bone on-growth and prevent stress shielding. Additive manufacturing of titanium alloy implants is a novel technique with limited clinical outcome reports in the literature. The aim of this study was to determine radiographic evidence of osseointegration and early results of a single manufacturer porous titanium metaphyseal components in the proximal tibia.

METHODS

We retrospectively reviewed the prospectively collected database of two institutions. Patients who underwent revision knee arthroplasty using porous titanium components by a single manufacturer were identified. Immediate post-operative and latest follow-up radiographs were independently analysed by 2 reviewers to determine metaphyseal bone contact and level of osseointegration in relevant Knee Society Radiographic Evaluation and Scoring System zones.

RESULTS

22 patients (15 males; 7 females) with a mean age of 71 (49-92) years were included. The mean follow-up period was 14 months (2-44 months). Cones were used in 16 patients and sleeves in 6. Interobserver reliability assessment showed substantial agreement (weighted Kappa 0.71, (95% CI: 0.60, 0.81). There was significant correlation between the bone contact in the immediate postop radiograph and osseointegration at final follow-up (kendall's tau-b: 0.698, p < 0.001). Infection free prosthetic joint survival was 20/22 at final follow-up.

CONCLUSION

Porous titanium metaphyseal components produced with additive manufacturing provided excellent osseointegration and no early clinical failures. Partial or complete contact of the cone with native bone in the immediate postoperative radiograph resulted in osseointegration in all cases.

Expandable distal femur megaprosthesis: A European Musculoskeletal Oncology Society study on 299 cases

BACKGROUND AND OBJECTIVES

Expandable distal femur prostheses have become more popular over the last decades, but scientific data is limited.

METHODS

A retrospective study was performed, including cases treated between 1986 and 2019 in 15 European referral centers for bone sarcomas.

RESULTS

A total of 299 cases were included. Average follow-up was 80 months (range, 8-287 months). Mean patient age was 10 years. Most (80%) of the implants were noninvasive growers and a fixed hinge knee was used more often (64%) than a rotating hinge. Most prosthetic designs showed good (>80%) implant survival at 10 years, but repeat surgery was required for 63% of the patients. The most frequent reason for revision procedure was the completion of lengthening potential. Noninvasive expandable implants showed less risk of infection compared to invasive growers (11.8% vs 22.9% at 10 years). No difference in aseptic loosening was found between cemented and uncemented stems.

CONCLUSIONS

This study shows the increasing popularity of expandable distal femur prostheses, with overall good results for function and implant survival. However, repeat surgery is frequently required, especially in patients under the age of 10 years old. Infection is less frequent in noninvasive growers compared to implants that require invasive lengthening procedures.

Which factors affect the ability to kneel following total knee arthroplasty? An outpatient study of 100 postoperative knee replacements

BACKGROUND

Kneeling is an important activity of daily living, holding social, religious and occupational value. Following total knee replacement (TKR), many patients report they are unable to kneel or have been advised not to kneel.

METHODS

We observed 100 consecutive knee replacements in 79 patients attending outpatient clinic at a minimum 5 months post-TKR. The patients were asked to fill out a questionnaire detailing whether they were able to kneel prior to their knee replacement and whether they thought they were able to kneel since their knee replacement. The patients were then asked to kneel on a padded examination couch and then onto a pillow on the floor for 15 s. Degree of flexion achievable was also recorded.

RESULTS

Of the knees with patella resurfacing, 78.6% were able to kneel compared to only 45.6% knees with native patellae. Two-tailed Fisher's exact test showed this difference to be statistically significant (p = 0.001). The χ² analysis showed that those patients with an achievable flexion of angle of greater than 100° were significantly more likely to be able to kneel than those with a flexion angle of less than 100° (p = 0.0148). Comparing posterior cruciate ligament (PCL) retaining against PCL sacrificing implants, there was no statistically significant difference in kneeling ability (p = 0.541).

CONCLUSION

Kneeling remains an important function in patients undergoing TKR, with patella resurfacing significantly improving the likelihood of a patient being able to kneel.

Targeting the MAPK7/MMP9 axis for metastasis in primary bone cancer

Metastasis is the leading cause of cancer-related death. This multistage process involves contribution from both tumour cells and the tumour stroma to release metastatic cells into the circulation. Circulating tumour cells (CTCs) survive circulatory cytotoxicity, extravasate and colonise secondary sites effecting metastatic outcome. Reprogramming the transcriptomic landscape is a metastatic hallmark, but detecting underlying master regulators that drive pathological gene expression is a key challenge, especially in childhood cancer. Here we used whole tumour plus single-cell RNA-sequencing in primary bone cancer and CTCs to perform weighted gene co-expression network analysis to systematically detect coordinated changes in metastatic transcript expression. This approach with comparisons applied to data collected from cell line models, clinical samples and xenograft mouse models revealed mitogen-activated protein kinase 7/matrix metallopeptidase 9 (MAPK7/MMP9) signalling as a driver for primary bone cancer metastasis. RNA interference knockdown of MAPK7 reduces proliferation, colony formation, migration, tumour growth, macrophage residency/polarisation and lung metastasis. Parallel to these observations were reduction of activated interleukins IL1B, IL6, IL8 plus mesenchymal markers VIM and VEGF in response to MAPK7 loss. Our results implicate a newly discovered, multidimensional MAPK7/MMP9 signalling hub in primary bone cancer metastasis that is clinically actionable.

The adequacy of resection margin for non-infiltrative soft-tissue sarcomas

OBJECTIVES

There remains no consensus on what constitutes an adequate margin of resection for non-infiltrative soft-tissue sarcomas (STSs). We aimed to investigate the role of resection margins in millimetres for non-infiltrative STSs.

METHODS

502 patients who underwent surgical resection for a localized, non-infiltrative, high-grade STSs were studied. The prognostic significance of margin width was analysed and compared with the conventional R- and R+1-classification of surgical margins.

RESULTS

The overall local recurrence (LR) rate was 13%; 9% and 27% with negative and positive margins, respectively (p < 0.001). In patients with negative margins, the LR rates were greater than 10% in patients with margins ≤5.0 mm but reduced to less than 4% with margins >5.0 mm. When classified by the R- (or R+1)-classification, the 5-year cumulative LR incidence was 8%, 23% (16%), and 31% for R0, R1, and R2, respectively, which did not stratify the LR risk with negative margins. On the other hand, an accurate risk stratification was possible by metric distance; the 5-year cumulative incidence of LR was 29%, 10%, and 1% with 0 mm, 0.1-5.0 mm, and >5.0 mm, respectively (p < 0.001). This classification also stratified the LR risk in patients with or without adjuvant radiotherapy.

CONCLUSION

While a negative margin is essential to optimize local control in patients with non-infiltrative STSs, surgical margin width greater than 5 mm minimises the risk of local failure regardless of the use of adjuvant radiotherapy.

Mortality of high-risk orthopaedic oncology patients during the COVID-19 pandemic: A prospective cohort study

BACKGROUND AND OBJECTIVES

Should the threshold for orthopaedic oncology surgery during the coronavirus disease-2019 (COVID-19) pandemic be higher, particularly in men aged 70 years and older? This study reports the incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during, respiratory complications and 30-day mortality during the COVID-19 pandemic.

METHODS

This prospective observational cohort study included 100 consecutive patients. The primary outcome measure was 14-day symptoms and/or SARS-CoV-2 test. The secondary outcome was 30-day postoperative mortality.

RESULTS

A total of 100 patients comprising 35 females and 65 males, with a mean age of 52.4 years (range, 16-94 years) included 16 males aged greater than 70 years. The 51% of patients were tested during their admission for SARS-CoV-2; 5% were diagnosed/developed symptoms of SARS-CoV-2 during and until 14 days post-discharge; four were male and one female, mean age 41.2 years (range, 17-75 years), all had primary malignant bone or soft-tissue tumours, four of five had received immunosuppressive therapy pre-operatively. The 30-day mortality was 1% overall and 20% in those with SARS-CoV-2. The pulmonary complication rate was 3% overall.

CONCLUSIONS

With appropriate peri-operative measures to prevent viral transmission, major surgery for urgent orthopaedic oncology patients can continue during the COVID-19 pandemic. These results need validating with national data to confirm these conclusions.

Navigation-assisted pelvic resections and reconstructions for periacetabular chondrosarcomas

OBJECTIVES

Survival in patients with chondrosarcomas has not improved over 40 years. Although emerging evidence has documented the efficacy of navigation-assisted surgery, the prognostic significance in chondrosarcomas remains unknown. We aimed to assess the clinical benefit of navigation-assisted surgery for pelvic chondrosarcomas involving the peri-acetabulum.

METHODS

We studied 50 patients who underwent limb-sparing surgery for periacetabular chondrosarcomas performed with navigation (n = 13) without it (n = 37) at a referral musculoskeletal oncology centre between 2000 and 2015.

RESULTS

The intralesional resection rates in the navigated and non-navigated groups were 8% (n = 1) and 19% (n = 7), respectively; all bone resection margins were clear in the navigated group. The 5-year cumulative incidence of local recurrence was 23% and 56% in the navigated and non-navigated groups, respectively (p = 0.035). There were no intra-operative complications related to use of navigation. There was a trend toward better functional outcomes in the navigated group (mean MSTS score, 67%) than the non-navigated group (mean MSTS score, 60%; p = 0.412). At a mean follow-up of 63 months, the 5-year disease-specific survival was 76% and 53% in the navigated and non-navigated group, respectively (p = 0.085), whilst the 5-year progression-free survival was 62% and 28% in the navigated and non-navigated group, respectively (p = 0.032).

CONCLUSION

This study confirmed improved local control and progression-free survival with the use of computer navigation in patients with limb-salvage surgery for periacetabular chondrosarcomas, although the advancement in other treatment modalities is required for improvement of disease-specific survival.

Computer assisted tumour surgery - An insight

Success in the management of bone sarcomas entails being able to achieve wide margins, which helps decrease the risk of local recurrence and provide an improvement in overall survival. The role of computer-assisted surgery has been investigated across various areas of orthopaedics, including joint replacement, cruciate ligament reconstruction, and pedicle screw placements which has led to increased interested in computer assisted tumour surgery (CATS). CATS can be used in a wide array of tumour surgeries, however its role in pelvic and sacral tumours is unparalled. Its importance lies in being able to provide radiological information to guide the surgeon at the time of surgery i.e. the distance from the tumour to the resection margin can be determined precisely based on preoperative planning and intra-operative image guidance. This minimises unnecessary bone resection, aiming to achieve good oncological and functional results which can be challenging in pelvic surgery. Most published articles on CATS have concentrated on the surgical aspects of navigation surgery. Although advanced imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) scans can provide anatomic detail about the primary tumour, the successful transfer of that information from a viewing screen to the intraoperative field can be difficult. The role of the radiologist lies in being able to provide appropriate imaging (CT, MRI) to facilitate surgical planning. This article aims at providing the radiologist a surgical insight on CATS and to facilitate optimal imaging in a patient tentatively being planned for CATS.

Extra-articular resection for bone sarcomas involving the hip joint

AIM

The aim of this study was to determine the oncologic, functional, and clinical outcomes after the extra-articular resection and limb-salvage reconstruction of the hip joint.

METHODS

A retrospective study of 34 patients who underwent extra-articular resection of the hip joint for bone sarcomas between 1996 and 2016 was conducted. The primary tumor site was pelvis in 26 patients (76%) and femur in eight (24%).

RESULTS

The surgical margins achieved were clear in 31 (91%) patients, and seven (21%) patients developed local recurrence; mostly occurring in pelvic tumors (n = 6). The 3-year overall survival was 63% with a median follow-up of 38 months (range, 5-219), which showed no statistical difference in tumor location. The most common complication was deep infection (n = 7) and dislocation (n = 7), mostly seen in pelvic tumors. Implant failure was seen in two patients with pelvic tumors, while no failure was noted in patients with femoral tumors. The median Musculoskeletal Tumour Society score was 69%; 67% for pelvic tumors and 73% for femoral tumors (P = .535).

CONCLUSION

Despite complex surgery, extra-articular resection of the hip joint can achieve oncologically and functionally acceptable outcomes. While tumors of the pelvis are associated with a higher incidence of infection and local recurrence after resection, resection of tumors involving the femur are well tolerated.

Outcome of Ewing's sarcoma of the scapula-a long-term follow-up study

OBJECTIVE

The aim of this study was to review our experience of managing Ewing's sarcoma of scapula and to identify features predictive of a good outcome.

HYPOTHESIS

Surgery and neo-adjuvant chemotherapy would have a better survival than surgery alone.

PATIENTS AND METHODS

Between 1988 and 2018, 29patients, (14females and 15males) were treated at a single hospital: The median age at diagnosis was 17.6years (range: 2 to 51years). Of the 29cases, 3 were primary soft tissue Ewing's invading bone and remainder were bony sarcoma. Twenty three patients underwent surgery and 6 patients were managed non-operatively. All surgical resection specimens were classified according to Musculoskeletal Tumour Society based on surgical margins assessed by specialist musculoskeletal pathologists. The function was assessed using the Musculoskeletal Tumour Society Score.

RESULTS

The median follow-up for all patients was 10 years (range: 2 months to 30 years) and for survivors, median follow-up was 13.7 years (range: 18months to 30 years). The estimated disease-specific survival for all patients was 71.4% (95% CI 84.6-50.7%) at five years and 63% (95% CI 78.3-41.9%) at ten years. The estimated disease-specific survival for patients that underwent surgery was 86.5% (95% CI 95.5-63.7%) at five years and 81% (95% CI 92.5-56.9%) at ten years. The median MSTS score was 67.4%.

CONCLUSION

In this, the largest single series of patients with an Ewing's sarcoma of the scapula treated in a single hospital, those treated with surgery and neo-adjuvant chemotherapy had the best chance for survival compared to chemotherapy and/or radiotherapy alone. Local recurrence did not have an affect on survival.

LEVEL OF EVIDENCE

IV, retrospective study.

Sacral chordoma: do the width of surgical margin and the use of photon/proton radiotherapy affect local disease control?

PURPOSE

Chordoma is a rare but highly aggressive primary bone sarcoma that arises commonly from the sacrum. While en bloc resection has been the mainstay of the treatment, the role of resection margin in millimetres with/without adjuvant radiotherapy (RT) has been unknown. We investigated the prognostic impact of surgical margin width, adjuvant RT, and their combined factor for sacral chordoma.

METHODS

Forty-eight patients who underwent surgical treatment between 1996 and 2016 were studied. Of these, 11 patients (23%) received adjuvant RT; photon RT in 7 (15%) and proton RT in 4 (8%). Margins were microscopically measured in millimetres from the resection surface to the closest tumour on histologic slides.

RESULTS

The five year and ten year disease-specific survival was 88% and 58%, respectively, and the local recurrence (LR) rate was 48%. The LR rate with 0-mm, < 1.5-mm, and ≥ 1.5-mm margin was 50% (group 1), 50% (group 2: RT-, 61%; group 3: RT+, 14%), and 0% (group 4), respectively. We observed a significantly lower LR rate in patients with adjuvant photon/proton RT (18%) than without it (57%; p = 0.026), and no LR was observed after post-operative proton RT. The combined factor of margin with RT clearly stratified the LR risk: patients of group 1 (positive margin) and 2 (< 1.5-mm margin, RT-) had approximately 7.5× LR risk (p = 0.049) compared with those of group 3 (< 1.5-mm margin, RT+) and 4 (≥ 1.5-mm margin).

CONCLUSION

This study identified the lowest risk of local failure in tumour resection with ≥ 1.5-mm margin or negative but < 1.5-mm margin with the use of adjuvant photon/proton radiotherapy for sacral chordoma. Early results of adjuvant proton RT demonstrated excellent local control.

Survival of osteosarcoma patients following diagnosis of synchronous skip metastases

Background

We aim to investigate the prognostic implications of synchronous skip metastases in osteosarcoma by presenting the largest single centre series to date.

Methods

Retrospective study of 21 osteosarcoma patients with skip metastases treated between 1983 and 2004.

Results

No statistical difference in overall survival was demonstrated when comparing presence of lung metastases to those without (p = 0.859). No statistical difference was found in overall survival according to age group (<18yrs vs >18yrs; p = 0.126), or to percentage chemotherapy-induced bone necrosis (<90% vs >90%; p = 0.056).

Conclusions

The presence of skip metastases confers a very poor prognosis as an independent variable.

Level of evidence

III.

Musculoskeletal Infection in Orthopaedic Oncology: Assessment of the 2018 International Consensus Meeting on Musculoskeletal Infection

BACKGROUND

The first International Consensus Meeting (ICM) on Musculoskeletal Infection convened in 2013 in order to provide agreement on the prevention, the diagnosis, and the treatment of surgical site infection (SSI) and periprosthetic joint infection (PJI). Recognizing the added susceptibility of orthopaedic oncology patients to SSI and PJI, the second ICM in 2018 included questions and corresponding recommendations from this subspecialty of orthopaedics.

METHODS

The 13 steps of the Delphi method were followed over the course of 26 months, starting in June 2016. From July 25 to 27, 2018, delegates from 93 countries convened at Thomas Jefferson University in Philadelphia, Pennsylvania. Delegates were divided into their subspecialty workgroups, where questions and recommendations were discussed, modified, and subsequently voted upon. The level of consensus measured the agreement among the delegates on the basis of the voting results. The level of evidence that accompanied each question and recommendation was dependent on the types of studies that were reviewed for each question and the number of flaws that were present in those studies.

RESULTS

There were 30 orthopaedic oncology questions and recommendations that were voted on by 14 delegates with expertise in either orthopaedic oncology or infectious disease. Twenty-six (87%) of the questions were unanimous among the delegates. The remaining 13% (n = 4) were agreed upon by 93% of the delegates, with 7% of the delegates abstaining from the vote.

CONCLUSIONS

The inclusion of orthopaedic oncology in the 2018 ICM on Musculoskeletal Infection was particularly important because of the high rate of SSI and PJI following these procedures. Despite there being strong consensus among voting delegates, these recommendations are based on limited levels of evidence and tend to reflect the recommendations from hip and knee arthroplasty. We hope that high-quality prospective studies in the field of orthopaedic oncology are available for the third ICM.

Is Arthrodesis a Reliable Salvage Option following Two-Stage Revision for Suspected Infection in Proximal Tibial Replacements? A Multi-Institutional Study

The aim of this multicentric retrospective study was to verify whether knee arthrodesis (KA) is a viable reconstructive option after two-stage revision for infection of proximal tibia (PT) endoprosthetic reconstruction (EPR). Sixty patients who underwent a two-stage revision were included. Definitive EPR or a KA with a modular system was performed following consideration of soft tissue and extensor mechanism conditions. Patients were evaluated with Musculoskeletal Tumor Society Score and Oxford Knee Score. Implant survival was assessed on the basis of recurrence of infection. Five patients did not receive any reconstruction after the first stage. In 14 cases, a KA was performed, and in 41, an EPR was implanted. At 5 years follow-up, reinfection rate in the KA group was lower (10 vs. 17.5% in KA and EPR groups, respectively). In reinfected patients, the KA group had a reduced rate of amputation when compared with those with EPR (50 vs. 88%). Functional evaluation did not show any significant differences between the two groups. A successful KA using a modular implant can eradicate infection and allow preservation of the limb with good function and good pain relief in after two-stage revision for an infected PT EPR.

Preoperative surgical risk stratification in osteosarcoma based on the proximity to the major vessels

Aims

The aim of this study was to determine the risk of local recurrence and survival in patients with osteosarcoma based on the proximity of the tumour to the major vessels.

Patients and Methods

A total of 226 patients with high-grade non-metastatic osteosarcoma in the limbs were investigated. Median age at diagnosis was 15 years (4 to 67) with the ratio of male to female patients being 1.5:1. The most common site of the tumour was the femur (n = 103) followed by tibia (n = 66). The vascular proximity was categorized based on the preoperative MRI after neoadjuvant chemotherapy into four types: type 1 > 5 mm; type 2 ≤ 5 mm, > 0 mm; type 3 attached; type 4 surrounded.

Results

Limb salvage rate based on the proximity type was 92%, 88%, 51%, and 0% for types 1 to 4, respectively, and the overall survival at five years was 82%, 77%, 57%, and 67%, respectively (p < 0.001). Local recurrence rate in patients with limb-salvage surgery was 7%, 8%, and 22% for the types 1 to 3, respectively (p = 0.041), and local recurrence at the perivascular area was observed in 1% and 4% for type 2 and 3, respectively. The mean microscopic margin to the major vessels was 6.9 mm, 3.0 mm, and 1.4 mm for types 1 to 3, respectively. In type 3, local recurrence-free survival with limb salvage was significantly poorer compared with amputation (p = 0.025), while the latter offered no overall survival benefit. In this group of patients, factors such as good response to chemotherapy or limited vascular attachment to less than half circumference or longitudinal 10 mm reduced the risk of local recurrence.

Conclusion

The proximity of osteosarcoma to major blood vessels is a poor prognostic factor for local control and survival. Amputation offers better local control for tumours attached to the blood vessels but does not improve survival. Limb salvage surgery offers similar local control if the tumour attachment to blood vessels is limited. Cite this article: Bone Joint J 2019;101-B:1024–1031.

Prosthetic fungal infections: poor prognosis with bacterial co-infection

AIMS

The aims of this study were to report the efficacy of revision surgery for patients with co-infective bacterial and fungal prosthetic joint infections (PJIs) presenting to a single institution, and to identify prognostic factors that would guide management.

PATIENTS AND METHODS

A total of 1189 patients with a PJI were managed in our bone infection service between 2006 and 2015; 22 (1.85%) with co-infective bacterial and fungal PJI were included in the study. There were nine women and 13 men, with a mean age at the time of diagnosis of 64.5 years (47 to 83). Their mean BMI was 30.9 kg/m² (24 to 42). We retrospectively reviewed the outcomes of these PJIs, after eight total hip arthroplasties and 14 total knee arthroplasties. The mean clinical follow-up was 4.1 years (1.4 to 8.8).

RESULTS

The median number of risk factors for PJI was 5.5 (interquartile range (IQR) 3.25 to 7.25). All seven patients who initially underwent debridement and implant retention (DAIR) had a recurrent infection that led to a staged revision. All 22 patients underwent the first of a two-stage revision. None of the nine patients with negative tissue cultures at the second stage had a recurrent infection. The rate of recurrent infection was significantly higher in the presence of multidrug-resistant bacteria (p = 0.007), a higher C-reactive protein (CRP) at the time of presentation (p = 0.032), and a higher number of co-infective bacterial organisms (p = 0.041). The overall rate of eradication of infection after two and five years was 50% (95% confidence interval (CI) 32.9 to 75.9) and 38.9% (95% CI 22.6 to 67), respectively.

CONCLUSION

The risk of failure to eradicate infection with the requirement of amputation associated with this diagnosis is much higher than in patients with PJI without bacterial and fungal co-infection, and this risk is heightened when the fungal organism is joined by polymicrobial and multidrug-resistant bacterial organisms. Cite this article: Bone Joint J 2019;101-B:582-588.

Mechanisms of failure and survival of total femoral endoprosthetic replacements

AIMS

The aim of this study was to evaluate the prosthesis characteristics and associated conditions that may modify the survival of total femoral endoprosthetic replacements (TFEPR).

PATIENTS AND METHODS

In all, 81 patients treated with TFEPR from 1976 to 2017 were retrospectively evaluated and failures were categorized according to the Henderson classification. There were 38 female patients (47%) and 43 male patients (53%) with a mean age at diagnosis of 43 years (12 to 86). The mean follow-up time was 10.3 years (0 to 31.7). A survival analysis was performed followed by univariate and multivariate Cox regression to identify independent implant survival factors.

RESULTS

The revision-free survival of the implant was 71% at five years and 63.3% at ten years. Three prostheses reached 15 years without revision. The mean Musculoskeletal Tumor Society score in the group was 26 (23 to 28). The mechanisms of failure were infection in 18%, structural failures in 6%, tumour progression in 5%, aseptic loosening in 2%, and soft-tissue failures in 1%. Prostheses used for primary reconstruction after oncological resections had lower infection rates than revision implants (8% vs 25%; p = 0.001). The rates of infection in silver-coated and non-silver-coated prosthesis were similar (17.4% vs 19.%; p = 0.869). The incidence of hip dislocation was 10%. Rotating hinge prosthesis had a lower failure rate than fixed hinge prosthesis (5.3% vs 11%). After Cox regression, the independent factors associated with failures were the history of previous operations (hazard ratio (HR) 3.7; p = 0.041), and the associated arthroplasty of the proximal tibia (HR 3.8; p = 0.034). At last follow-up, 11 patients (13%) required amputation.

CONCLUSION

TFEPR offers a reliable reconstruction option for massive bone loss of the femur, with a good survival when the prosthesis is used as a primary implant. The use of a rotating hinge at the knee and dual mobility bearing at the hip may be adequate to reduce the risk of mechanical and soft-tissue failures. Infection remains the main concern and there is insufficient evidence to support the routine use of silver-coated endoprosthesis. Cite this article: Bone Joint J 2019;101-B:522-528.

Long-term outcomes after an initial experience of computer-navigated resection of primary pelvic and sacral bone tumours

Aims

The aim of this study was to investigate the local recurrence rate at an extended follow-up in patients following navigated resection of primary pelvic and sacral tumours.

Patients and Methods

This prospective cohort study comprised 23 consecutive patients (nine female, 14 male) who underwent resection of a primary pelvic or sacral tumour, using computer navigation, between 2010 and 2012. The mean age of the patients at the time of presentation was 51 years (10 to 77). The rates of local recurrence and mortality were calculated using the Kaplan–Meier method.

Results

Bone resection margins were all clear and there were no bony recurrences. At a mean follow-up for all patients of 59 months (12 to 93), eight patients (34.8%) developed soft-tissue local recurrence, with a cumulative rate of local recurrence at six-years of 35.1% (95% confidence interval (CI) 19.3 to 58.1). The cumulative all-cause rate of mortality at six-years was 26.1% (95% CI 12.7 to 49.1).

Conclusion

Despite the positive early experience with navigated-assisted resection, local recurrence rates remain high. With increasing knowledge of the size of soft-tissue margins required to reduce local recurrence and the close proximity of native structures in the pelvis, we advise against compromising resection to preserve function, and encourage surgeons to reduce local recurrence by prioritizing wide resection margins of the tumour. Cite this article: Bone Joint J 2019;101-B:484–490.

Localized synovial sarcoma: A single institutional study of 191 patients with a minimum follow-up of 5 years for survivors

PURPOSE

Factors affecting long-term outcomes of synovial sarcoma (SS) remain unknown. Here, we aimed to investigate the long-term oncological outcomes and prognostic factors in a large group of patients with surgically-treated localized SS.

PATIENTS AND METHODS

Between 1980 and 2011, 191 patients (94 males and 97 females) were treated at a single hospital with a minimum follow-up of 5 years for survivors. The median age was 35 years (range, 3-80 years), and the median follow-up period was 83 months (range, 3-235 months).

RESULTS

Disease-specific survival was 76.4% and 60.4% at 5 and 10 years, respectively. Local recurrence occurred in 23 patients at a median of 33 months (range, 6-158 months), and metastasis occurred in 73 patients at a median of 20 months (range, 2-166 months). In multivariate analysis, grade 3 tumors sized ≥5 cm were significantly associated with worse survival. Ten patients (5.2%) developed metastasis more than 5 years after surgery.

CONCLUSION

Tumor size and grade govern prognosis in surgically-treated localized SS in long-term settings. If adequately treated patients have not developed metastases for 5 years after surgery, the risk of subsequently developing metastases was lower than previously reported.

Synovial sarcoma: Do children do better?

OBJECTIVES

Synovial sarcoma, a distinct subtype of soft tissue sarcomas (STS), is typically found in young patients. Long history of symptoms and heterogeneous clinical presentation sometimes delays diagnosis. Children have been reported to have a better prognosis than adults in some series. The main emphasis of this study was to determine differences between children and adults and to investigate prognostic factors regarding cancer specific survival (CSS).

METHODS

248 patients treated between 1982 and 2014 at one department were included. Mean age was 37.0 years, including 43 patients <16 years. Demographic, pathology- and treatment-related information was ascertained. Median follow-up was 5.2 years.

RESULTS

Median duration of symptoms was 11.5 months in children and 12 months in adults (p = 0.238). Patients with a prior unplanned excision had a significantly longer duration of symptoms (p = 0.001). No difference was present between children and adults regarding tumour size, site, grade and superficial/deep location. Treatment was with surgical excision and (usually) adjuvant radiotherapy but five patients received preoperative radiotherapy and 43 patients chemotherapy. In patients treated with curative intent, five-year CSS rates were 75.5% for adults and 89.0% for children, with 10-year CSS rates of 56.1% and 82.2% (p = 0.026). In multivariate analysis, large tumour size (p < 0.005) and patient age (p = 0.024) were associated with worse CSS, irrespective of tumour location and site.

CONCLUSION

Clinical presentation of synovial sarcoma is similar in children and adults, with no significant difference in tumour size, site, grade or location. Small tumour size and young patient age are independent positive prognostic factors influencing CSS.

Abstract 3696: RNAseq of patient-derived cancer stem-like cells and exosomes provides new insights into Ewing's sarcoma

Background

Cancer stem-like cells (CSCs) are responsible for disease progression and relapse (Schatton et al, Bioessays 2009, 31:1038-49). Therefore, the eradication of Ewing's sarcoma (ES)-CSCs is expected to improve outcome for patients. Since the transfer of exosome cargo between cells drives ES progression (Ventura et al, Oncogene, 2016, 35:3944-54) or can be exploited as biomarker (Miller et al, Biology of the Cell 2013, 105:289-303; Tsugita et al, PLoS ONE 2013, 8:e77416) we have characterized primary patient-derived ES, paired ES-CSCs, and the exosomal cargo from these cultures to identify potential prognostic biomarkers of risk and targets for the development of new treatments.

Methods

ES taken at diagnosis and resection were collected following patient consent (GenoEwing; IRAS-167880). ES-CSCs were isolated using a functional self-renewing assay. EWSR1 translocations were confirmed by FISH using a break-apart probe and RT-PCR. Exosomes were collected after incubation of cultures in serum-free media for 48h, isolated using exoEasy Maxi kit (Qiagen) and characterized by Nanoparticle tracking, Western blot and flow cytometry. The expression of the ES-marker CD99 was investigated by immunocytochemistry, Western blot and flow cytometry. RNA was extracted from ES cells and paired exosomes using the miRNeasy Micro kit (Qiagen) and RNA quality confirmed employing the Agilent Bioanalyser. Total RNA libraries were prepared and sequenced using the HiSeq3000 (Illumina®). Reads were processed using fqtools (Droop, Bioinformatics 2016, 32:1883-4), aligned by STAR (Dobin et al, Bioinformatics 2013, 29:15-21) and differential expression was determined by DESeq2 (Anders et al, Genome Biology 2010, 11:R106). Genes were ranked on adjusted p value and log2 fold change; candidates were validated by RTqPCR.

Results

ES patient-derived cells expressed CD99 and contained an EWSR1 gene translocation (23/23). The median size of isolated ES exosomes was 84nm (range 32-132nm). Exosomes were enriched for small RNA (53±5% in exosomes vs 12±3% in cells). The optimal protein panel to identify ES exosomes is CD81, CD63 and TSG-101; CD9 was not detected. Consistent with the exosomal cell of origin, expression of CD99 was detected in 71-79% of isolated vesicles.

The RNA profile of parental cultures and daughter ES-CSCs was compared and two genes with increased expression in ES-CSCs were validated by RTqPCR (p&lt;0.0001). Using a novel experimental approach in ES, we have sequenced the total RNA profile of paired exosomes from patient-derived ES cultures and confirmed the expression of CD99 and one putative ES-CSC biomarker in exosomes.

Conclusions

For the first time, we have sequenced paired exosomes and patient-derived ES cells to identify a potential prognostic biomarker and novel target for therapy.

Work funded by University of Leeds, Ewing's Sarcoma Research Trust (ESRT) and Bone Cancer Research Trust (BCRT).

Citation Format: Mariona Chicón Bosch, Elizabeth A. Roundhill, Alastair P. Droop, Michael Parry, Lee Jeys, Susan A. Burchill. RNAseq of patient-derived cancer stem-like cells and exosomes provides new insights into Ewing's sarcoma [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 3696.