Robotic living donor nephrectomy is associated with reduced post-operative opioid use compared to hand-assisted laparoscopic approach.

BACKGROUND: Robotic donor nephrectomy (RDN) has emerged as a safe alternative to laparoscopic donor nephrectomy (LDN). Having previously demonstrated comparable efficacy, this study aims to examine postoperative analgesia use (opioid and non-opioid) in the two groups. METHODS: We conducted a retrospective review of 300 living donor nephrectomies performed at our center, comparing 150 RDN's with a contemporary cohort of 150 hand-assisted LDN's. In addition to clinical and demographic information, data on postoperative inpatient opioid and non-opioid analgesia (from patient's arrival to the surgical floor after surgery till the time of discharge) was collected. Opioid dosages were standardized by conversion to morphine milligram equivalents (MME). All patients were managed post-operatively under a standardized ERAS pathway for living donor nephrectomy patients. RESULTS: There were no significant differences in donor age, gender, and BMI between RDN and LDN groups. Total post-operative opioid use (MME's) was significantly lower in RDN patients (RDN 27.1 vs. LDN 46.3; P < 0.0001). Breakdown of opioid use with post-operative (POD) day demonstrated significantly lower use in RDN group on POD1 (RDN 8.6 vs. LDN 17.0; P < 0.05), and POD2 (RDN 3.9 vs LDN 10; P < 0.05). RDN patients had a shorter post-operative length of stay (LOS) (RDN 1.69 days vs. LDN 1.98; P = 0.0003). There were no differences between groups in non-opioid medication use, complications, and readmission rates. CONCLUSION: RDN has comparable safety to hand-assist LDN and offers additional benefits of lower postoperative opioid requirement and a shorter hospital LOS.

Total robotic liver transplant: the final frontier of minimally invasive surgery.

The use of robotic surgery in transplantation is increasing; however, robotic liver transplantation (RLT) remains a challenging undertaking. To our knowledge, this is a report of the first RLT in North America and the first RLT using a whole graft from a deceased donor in the world. This paper describes the preparation leading to the RLT and the surgical technique of the operation. The operation was performed in a 62-year-old man with hepatitis C cirrhosis and hepatocellular carcinoma with a native Model for End-Stage Liver Disease score of 10. The total console time for the operation was 8 hours 30 minutes, and the transplant hepatectomy took 3 hours 30 minutes. Warm ischemia time was 77 minutes. Biliary reconstruction was performed in a primary end-to-end fashion and took 19 minutes to complete. The patient had an uneventful recovery without early allograft dysfunction or surgical complications and continues to do well after 6-months follow-up. This paper demonstrates the feasibility of this operation in highly selected patients with chronic liver disease. Additional experience is required to fully understand the role of RLT in the future of transplant surgery. Narrated video is available at https://youtu.be/TkjDwLryd3I.

Global liver transplantation: emerging trends and ethical challenges.

PURPOSE: Liver transplant (LT) is the only definitive treatment for end-stage liver disease (ESLD). This review aims to explore current global LT practices, with an emphasis on challenges and disparities that limit access to LT in different regions of the world. METHODS: A detailed analysis was performed of present-day liver transplant practices throughout the world, including the etiology of liver disease, patient access to transplantation, surgical costs, and ongoing ethical concerns. RESULTS: Annually, only 10% of the patients needing a liver transplant receive an organ. Currently, the USA performs the highest volume of liver transplants worldwide, followed by China and Brazil. In both North America and Europe, nonalcoholic fatty liver disease is becoming the most common indication for LT, compared to hepatitis B and C in most Asian, South American, and African countries. While deceased donor liver transplant remains the most performed type of LT, living donor liver transplant is becoming increasingly popular in some parts of the world where it is often the only option due to a lack of well-developed infrastructure for deceased organ donation. Ethical concerns in liver transplantation fundamentally revolve around the definition of a deceased donor and the exploitation of living donor liver donation systems. CONCLUSION: Globally, liver transplant practices and outcomes are varied, with differences driven by healthcare policies, inequities in healthcare access, and ethical concerns.

The impact of a dedicated operating room team on robotic transplant program growth and fellowship training.

INTRODUCTION: Despite considerable interest in robotic surgery, successful incorporation of robotics into transplant programs has been challenging. Lack of a dedicated OR team with expertise in both robotics and transplant is felt to be a major barrier. This paper assesses the impact of a dedicated robotic transplant team (DART) on program growth and fellowship training at one of the largest robotic transplant programs in North America. METHODS: This is a single center, retrospective review of all robotic operations performed on the transplant surgery service from October 2017 to October 2022. DART was incorporated in February 2020 and included transplant first assists (RFAs), scrub technologists and circulating nurses who received robotic training. Robotic experience before and after DART was compared to assess its impact on program growth and training. RESULTS: Four hundred and two robotic cases were performed by five transplant surgeons: 63 pre-DART and 339 post-DART. 40% of cases were transplant-related and 59.5%, HPB. There was a significant increase in case volume (2.5-10.6 cases/month, p < .0001) and complexity (36.5% vs. 70.3% high complexity cases, p < .0001) post-DART. RFA case coverage increased from 17% to 95%, and participation of transplant fellows as primary surgeons increased from 17% to 95% post-DART period (both p < .05). Conversion rates (9.5% vs. 4.1%) and room turn-around-times (TAT) (58.4 vs. 40.3 min) were lower post-DART (p < .05). There were no emergent conversions, conversions in transplant patients, or robot-related complications in either group. CONCLUSION: OR teams with expertise in robotics and transplant surgery can accelerate growth of robotic transplant programs while maintaining patient safety.

Liver Transplantation After Hepatic Artery Infusion Pump Therapy: Single-Center Experience and Technical Considerations.

BACKGROUND: Hepatic artery infusion pump (HAIP) therapy has become increasingly commonplace in the treatment of intrahepatic tumors. When combined with standard chemotherapy, HAIP therapy demonstrates a higher response rate than chemotherapy alone. Biliary sclerosis is observed in up to 22 % of patients, for whom no treatment has been standardized. This report describes orthotopic liver transplantation (OLT) both as a treatment for HAIP-induced cholangiopathy and as a possible definitive oncologic treatment after HAIP-bridging therapy. METHODS: A retrospective study reviewed patients who had undergone HAIP placement followed by OLT at the authors' institution. Patient demographics, neoadjuvant treatment, and postoperative outcomes were reviewed. RESULTS: Seven OLTs were performed for patients with prior HAIP placement. The majority were women (n = 6), and the median age was 61 years (range, 44.5-65.5 years). Transplantation was performed for five patients due to biliary complications secondary to HAIP and two patients because of residual tumor after HAIP therapy. All the OLTs had difficult dissections due to adhesions. Because of HAIP-induced damage, atypical arterial anastomoses were required in six patients (2 patients used a recipient common hepatic artery below the gastroduodenal artery takeoff; 2 patients used recipient splenic arterial inflow; 1 patient used the junction of the celiac and splenic arteries; and 1 patient used the celiac cuff). The one patient with standard arterial reconstruction experienced an arterial thrombosis. The graft was salvaged with thrombolysis. Biliary reconstruction was duct-to-duct in five cases and Roux-en-Y in two cases. CONCLUSIONS: The OLT procedure is a feasible treatment option for end-stage liver disease after HAIP therapy. Technical considerations include a more challenging dissection and an atypical arterial anastomosis.

MR-Guided Radiation Therapy With Concurrent Gemcitabine/Nab-Paclitaxel Chemotherapy in Inoperable Pancreatic Cancer: A TITE-CRM Phase I Trial.

PURPOSE: Ablative radiation therapy for borderline resectable or locally advanced pancreatic ductal adenocarcinoma (BR/LA-PDAC) may limit concurrent chemotherapy dosing and usually is only safely deliverable to tumors distant from gastrointestinal organs. Magnetic resonance guided radiation therapy may safely permit radiation and chemotherapy dose escalation. METHODS AND MATERIALS: We conducted a single-arm phase I study to determine the maximum tolerated dose of ablative hypofractionated radiation with full-dose gemcitabine/nab-paclitaxel in patients with BR/LA-PDAC. Patients were treated with gemcitabine/nab-paclitaxel (1000/125 mg/m2) x 1c then concurrent gemcitabine/nab-paclitaxel and radiation. Gemcitabine/nab-paclitaxel and radiation doses were escalated per time-to-event continual reassessment method from 40 to 45 Gy 25 fxs with chemotherapy (600-800/75 mg/m2) to 60 to 67.5 Gy/15 fractions and concurrent gemcitabine/nab-paclitaxel (1000/100 mg/m2). The primary endpoint was maximum tolerated dose of radiation as defined by 60-day dose limiting toxicity (DLT). DLT was treatment-related G5, G4 hematologic, or G3 gastrointestinal requiring hospitalization >3 days. Secondary endpoints included resection rates, local progression free survival (LPFS), distant metastasis free survival (DMFS), and overall survival (OS). RESULTS: Thirty patients enrolled (March 2015-February 2019), with 26 evaluable patients (2 progressed before radiation, 1 was determined ineligible for radiation during planning, 1 withdrew consent). One DLT was observed. The DLT rate was 14.1% (3.3%-24.9%) with a maximum tolerated dose of gemcitabine/nab-paclitaxel (1000/100 mg/m2) and 67.5 Gy/15 fractions. At a median follow-up of 40.6 months for living patients the median OS was 14.5 months (95% confidence interval [CI], 10.9-28.2 months). The median OS for patients with Eastern Collaborative Oncology Group 0 and carbohydrate antigen 19-9 <90 were 34.1 (95% CI, 13.6-54.1) and 43.0 (95% CI, 8.0-not reached) months, respectively. Two-year LPFS and DMFS were 85% (95% CI, 63%-94%) and 57% (95% CI, 34%-73%), respectively. CONCLUSIONS: Full-dose gemcitabine/nab-paclitaxel with ablative magnetic resonance guided radiation therapy dosing is safe in patients with BR/LA-PDAC, with promising LPFS and DMFS.

Liver Transplantation as a New Standard of Care in Patients With Perihilar Cholangiocarcinoma? Results From an International Benchmark Study.

OBJECTIVE: To define benchmark values for liver transplantation (LT) in patients with perihilar cholangiocarcinoma (PHC) enabling unbiased comparisons. BACKGROUND: Transplantation for PHC is used with reluctance in many centers and even contraindicated in several countries. Although benchmark values for LT are available, there is a lack of specific data on LT performed for PHC. METHODS: PHC patients considered for LT after Mayo-like protocol were analyzed in 17 reference centers in 2 continents over the recent 5-year period (2014-2018). The minimum follow-up was 1 year. Benchmark patients were defined as operated at high-volume centers (≥50 overall LT/year) after neoadjuvant chemoradiotherapy, with a tumor diameter <3 cm, negative lymph nodes, and with the absence of relevant comorbidities. Benchmark cutoff values were derived from the 75th to 25th percentiles of the median values of all benchmark centers. RESULTS: One hundred thirty-four consecutive patients underwent LT after completion of the neoadjuvant treatment. Of those, 89.6% qualified as benchmark cases. Benchmark cutoffs were 90-day mortality ≤5.2%; comprehensive complication index at 1 year of ≤33.7; grade ≥3 complication rates ≤66.7%. These values were better than benchmark values for other indications of LT. Five-year disease-free survival was largely superior compared with a matched group of nodal negative patients undergoing curative liver resection (n=106) (62% vs 32%, P <0.001). CONCLUSION: This multicenter benchmark study demonstrates that LT offers excellent outcomes with superior oncological results in early stage PHC patients, even in candidates for surgery. This provocative observation should lead to a change in available therapeutic algorithms for PHC.

The learning curve of deceased donor liver transplant during fellowship training.

Liver transplantation (LT) is a complex operation that most transplant surgeons learn in fellowship. Training varies as there is lack of objective data that can be used to standardize teaching. We performed a retrospective review of our adult LT database with aim of looking at fellow's experience. Using American Society of Transplant Surgery cutoff of, at least 45 LT during fellowship, data for first 45 LT were compared to LT 45-90. Fellow's cases were also clustered in sequential groups of 15 LT and analyzed to estimate the learning curve (LC). Comparison of LT 1-45 with LT 46-90 showed significantly lower total operative times (TOT) (324 vs. 344 min) and warm ischemia times (WIT) (28 vs. 31 min) in the 45-90 group. Rates of biliary complications (23.8% vs. 16.4%) and bile leaks alone (10.3% vs. 5.5%) were significantly higher for first 45 LT. Analysis of fellows experience in sequential clusters of 15 LT showed decreasing TOT, WIT, biliary complications and rates of unplanned return to the OR with progression of fellowship. This study validates the current ASTS requirement of at least 45 LT. LC generated using these data can help individualize training and optimize outcomes through identification of areas in need of improvement.

Inability to manage non-severe complications on an outpatient basis increases non-white patient readmission rates after pancreaticoduodenectomy: A large metropolitan tertiary care center experience.

BACKGROUND: Pancreaticoduodenectomy (PD) has a high rate of readmission, and racial disparities in care could be an important contributor. METHODS: Patients undergoing PD were prospectively followed, and their complications graded using the Modified Accordion Grading System (MAGS). Patient factors and perioperative outcomes for patients with and without postoperative readmission were compared in univariate and multivariate analysis by severity. RESULTS: 837 patients underwent PD, the overall 90-day readmission rate was 27.5%. Non-white race was independently associated with readmission (OR 1.83, p = 0.007). 51.3% of readmissions were for non-severe complications (MAGS <3). Non-white race was independently associated with MAGS non-severe readmission (OR 2.13, p = 0.006), but not MAGS severe readmission. CONCLUSIONS: Non-white patients are more likely to be readmitted, particularly for non-severe complications. Follow up protocols should be tailored to address race disparities in the rates of readmission as readmission for less severe complications could potentially be avoidable.

Access to Liver Transplantation for Hepatocellular Carcinoma: Does Candidate Age Matter?

BACKGROUND: Liver transplantation (LT) offers an effective alternative treatment for unresectable hepatocellular carcinoma (HCC). Despite its growing acceptance and longer life expectancy rates, survival data in older patients are conflicting and consensus guidelines are lacking in terms of a cut-off age range for operations. STUDY DESIGN: We explored our prospectively maintained institutional database to identify patients diagnosed with HCC between January 1, 2002 and December 31, 2019. Long-term oncologic outcomes were analyzed in patients undergoing LT or hepatic resection, with patient age considered as the primary variable. RESULTS: In total, 1,629 patients with HCC were identified, of whom 700 were considered for curative operations (LT, n = 538; resection, n = 162). Patients older than 65 years were less likely to be considered for LT (p < 0.01), although there were no age-related differences in the de-listing rate among age groups (p = 0.90). Older patients had overall survival (OS) outcomes comparable with younger patients after LT (3-year OS: 85.5% vs 84%; 5-year OS: 73.9% vs 77%; p = 0.26). Long-term survival was lower in the group who underwent resection, however, older patients still demonstrated equivalent OS outcomes (3-year OS: 59% vs 64.8%; 5-year OS: 44.8% vs 49%; p = 0.13). There were no differences in the development of local or distant metastatic disease between groups. CONCLUSIONS: Although older candidates were less likely to be considered for LT in the management of HCC, judicious matching can lead to OS data comparable with their younger counterparts. Previous age misconceptions need to be challenged without the concern of worse long-term oncologic outcomes after surgery.

Liver transplantation for hepatitis C patients in the era of direct-acting antiviral treatment: A retrospective cohort study.

INTRODUCTION: Direct-acting antivirals (DAA's) have revolutionized hepatitis-C virus (HCV) treatment, however controversy remains regarding timing of treatment in relation to liver-transplant (LT). METHODS: Single-center retrospective study assessing outcomes of listed HCV positive patients in the DAA-era (2014-2017). Patients treated with DAA's before LT (DAA pre-LT) were compared to those who were not treated before LT (No DAA pre-LT) RESULTS: 156 HCV positive patients were listed during study-period; 104 (67%) underwent LT while 52 (33%) were de-listed. Of transplanted patients, 48 (46%) received DAA pre-LT while 56 (54%) were treated post-LT. Both groups were comparable in age, gender, MELD, patient and graft survival and cure-rates (98% in DAA pre-LTvs.95% in No DAA pre-LT; p > 0.05). DAA pre-LT group required higher number of treatments-per-patient to clear virus (1.46vs.1.06; p = 0.0006), spent more time on waitlist (331d.vs150d; p = 0.0040) and were less likely to receive livers from HCV positive donors (6%vs.25%; p = 0.0148). Twenty-nine (56%) of the 52 delisted received DAA. They had lower listing-MELD (12vs.18; p = 0.0033), and were more likely to be delisted for "condition improved" (34%vs.4%; p = 0.0143) compared to the 23 (44%) delisted patients who did not receive DAA's. CONCLUSIONS: DAA's were equally effective in clearing HCV in listed patients irrespective of timing. DAA pre-LT can disadvantage some patients through increase number of treatments needed and longer waitlist times, but treatment in some listed patients with low-MELD can improve condition and alleviate need for LT.

A 22-year experience with pancreatic resection for metastatic renal cell carcinoma.

BACKGROUND: The pancreas is a rare site of metastases, although metastatic renal cell carcinoma (mRCC) is the most commonly reported secondary tumor. Pancreatectomy has been described in selected patients with localized metastases, but long-term benefit remains poorly defined. METHODS: A retrospective review of a prospectively maintained database was performed to evaluate the outcomes of patients undergoing pancreatectomy for mRCC at a tertiary care center from 1995-2017. Postoperative complications were evaluated using the Modified Accordion Grading System (MAGS) and Kaplan-Meier curves and log-rank tests were utilized for survival analysis. RESULTS: 29 patients underwent pancreatectomy for mRCC including 15 distal pancreatectomies (DP), 10 pancreaticoduodenectomies (PD) and 4 total-pancreatectomies (TP). The mean age was 67 ± 8 years, and 15 were male. The median time from index nephrectomy to pancreatectomy was 8 (IQR: 3.72-12.2) years. There was no 90 Day post-pancreatectomy mortalities and the morbidity incidence included 13 Minor MAGS and 8 Severe MAGS complications respectively. Post-pancreatectomy disease specific survival at 2- and 4-years were 89% and 80% with 12 patients being alive at last follow up. CONCLUSIONS: Pancreatic resection can be safely performed in select patients with localized mRCC with favorable long-term outcomes.

Composite Length of Stay, An Outcome Measure of Postoperative and Readmission Length of Stays in Pancreatoduodenectomy.

PURPOSE: Postoperative length of stay (PLOS) and readmission rate are pancreatoduodenectomy (PD) outcome measures, which are reported individually but may be interrelated. The purpose of this study was to evaluate how well a composite length of stay measure (CLOS) that included PLOS and readmission length of stay describes outcomes. To do so, we evaluated how well CLOS correlated to postoperative complications absolutely and compared to PLOS. METHODS: A total of 668 PDs performed between 2011 and 2018 were evaluated. CLOS was calculated from PLOS and readmission length of stay. Complication severity was judged by the Modified Accordion Grading System (MAGS). Multinomial logistical regression models (MLRM) were used to investigate the relationship between either PLOS or CLOS and complications. Multilevel and pairwise area under curves (AUC) using SAS macro %MultAUC were provided for both models. RESULTS: A total of 432 of 668 patients (65%) developed complications. One hundred seventy-seven patients (27%) were readmitted. Mean PLOS was 10.2 days (7.1 SD) and mean CLOS was 12.3 days (10.1 SD). PLOS and CLOS both were correlated linearly to MAGS grade. Spearman correlation coefficient for CLOS vs. MAGS of 0.68 was higher than that of 0.49 for PLOS vs. MAGS. Multilevel AUC from MLRM using PLOS was 0.66, but multilevel AUC from MLRM using CLOS was 0.71. DISCUSSION: CLOS provides an accurate estimate of hospital day utilization per patient for PD, reflecting not only the basal hospital recovery time for PD but the added time needed because of readmissions due to complications. It is tightly correlated to number and severity of postoperative complications.

Utility of a multidisciplinary tumor board in the management of pancreatic and upper gastrointestinal diseases: an observational study.

BACKGROUND & OBJECTIVES: Multidisciplinary tumor boards (MDTBs) are frequently employed in cancer centers but their value has been debated. We reviewed the decision-making process and resource utilization of our MDTB to assess its utility in the management of pancreatic and upper gastrointestinal tract conditions. METHODS: A prospectively-collected database was reviewed over a 12-month period. The primary outcome was change in management plan as a result of case discussion. Secondary outcomes included resources required to hold MDTB, survival, and adherence to treatment guidelines. RESULTS: Four hundred seventy cases were reviewed. MDTB resulted in a change in the proposed plan of management in 101 of 402 evaluable cases (25.1%). New plans favored obtaining additional diagnostic workup. No recorded variables were associated with a change in plan. For newly-diagnosed cases of pancreatic ductal adenocarcinoma (n = 33), survival time was not impacted by MDTB (p = .154) and adherence to National Comprehensive Cancer Network guidelines was 100%. The estimated cost of physician time per case reviewed was $190. CONCLUSIONS: Our MDTB influences treatment decisions in a sizeable number of cases with excellent adherence to national guidelines. However, this requires significant time expenditure and may not impact outcomes. Regular assessments of the effectiveness of MDTBs should be undertaken.

Time-to-Surgery and Survival Outcomes in Resectable Colorectal Liver Metastases: A Multi-Institutional Evaluation.

BACKGROUND: Resection of colorectal liver metastases (CRLM) is associated with improved survival; however, the impact of time to resection on survival is unknown. The current multi-institutional study sought to evaluate the influence of time from diagnosis (Dx) to resection (Rx) on survival outcomes among patients with resectable, metachronous CRLM and to compare practice patterns across hospitals. STUDY DESIGN: Medical records of patients with ≤4 metachronous CRLM treated with surgery were reviewed and analyzed retrospectively. Time from Dx to Rx was analyzed as a continuous variable and also dichotomized into 2 groups (group 1: Dx to Rx <3 months and group 2: Dx to Rx ≥3 months) for additional analysis. Survival time distributions after resection were estimated using the Kaplan-Meier method. Between-group univariate comparisons were based on the log-rank test and multivariable analysis was done using Cox proportional hazards model. RESULTS: From 2000 to 2010, six hundred and twenty-six patients were identified. Type of initial referral (p < 0.0001) and use of neoadjuvant (p = 0.04) and/or adjuvant (p < 0.0001) chemotherapy were significantly different among hospitals. Patients treated with neoadjuvant chemotherapy (n = 108) and those with unresectable disease at laparotomy (n = 5) were excluded from final evaluation. Median overall survival and recurrence-free survival were 74 months (range 63.8 to 84.2 months) and 29 months (range 23.9 to 34.1 months), respectively. For the entire cohort, longer time from Dx to Rx was independently associated with shorter overall survival (hazard ratio = 1.12; 95% CI, 1.06-1.18; p < 0.0001), but not recurrence-free survival. Median overall survival for group 1 was 76 months (range 62.0 to 89.2 months) vs 58 months (range 34.3 to 81.7 months) in group 2 (p = 0.10). Among patients with available data pertaining to adjuvant chemotherapy (N = 457; 318 treated and 139 untreated), overall survival (87 months [range 71.2 to 102.8 months] vs 48 months [range 25.3 to 70.7 months]; p <0.0001), and recurrence-free survival (33 months [range 25.3 to 40.7 months] vs 22 months [range 14.5 to 29.5 months]; p = 0.05) were improved significantly. CONCLUSIONS: In select patients undergoing initial resection for CRLM, longer time from Dx to Rx is independently associated with worse overall survival. In addition, despite uniform disease characteristics, practice patterns related to definitely resectable CRLM vary significantly across hospitals.

Bouveret's syndrome complicated by classic gallstone ileus: progression of disease or iatrogenic?

CASE PRESENTATION: Bouveret's syndrome is a rare variant of gallstone ileus resulting in gastroduodenal obstruction from an impacted gallstone. We report two cases of Bouveret's syndrome that were complicated by classic (distal) gallstone ileus, which has previously been reported only twice. The first patient presented with vomiting, epigastric pain, and what was initially believed to be a duodenal diverticulum on computed tomography scan and endoscopy. He initially improved, but later developed symptoms of a small bowel obstruction. Repeat imaging revealed a classic distal gallstone ileus. The second patient presented with nausea, abdominal pain, and imaging consistent with Bouveret's syndrome. Multiple non-operative endoscopic techniques and extracorporeal shock wave lithotripsy were employed to fragment and retrieve the obstructing stone, and she subsequently developed a distal gallstone ileus from a stone fragment. Both patients were managed operatively with enterotomy and stone removal. DISCUSSION: These cases highlight a rare complication of Bouveret's syndrome, classic (distal) gallstone ileus, and juxtapose the natural history of a stone passing versus an iatrogenic etiology. We review the presentation and management of Bouveret's syndrome though no clear consensus exists as to the optimal treatment of these patients. We recommend that therapy should be decided on a case-by-case basis.