Personalized anti-reflux surgery: connecting GERD phenotypes in 690 patients to outcomes

BACKGROUND

Anti-reflux operations are effective treatments for GERD. Despite standardized surgical techniques, variability in post-operative outcomes persists. Most patients with GERD possess one or more characteristics that augment their disease and may affect post-operative outcomes-a GERD "phenotype". We sought to define these phenotypes and to compare their post-operative outcomes.

METHODS

We performed a retrospective review of a prospective gastroesophageal database at our institution, selecting all patients who underwent an anti-reflux procedure for GERD. Patients were grouped into different phenotypes based on the presence of four characteristics known to play a role in GERD: hiatal or paraesophageal hernia (PEH), hypotensive LES, esophageal dysmotility, delayed gastric emptying (DGE), and obesity. Patient-reported outcomes (GERD-HRQL, dysphagia, and reflux symptom index (RSI) scores) were compared across phenotypes using the Wilcoxon rank-sum test.

RESULTS

690 patients underwent an anti-reflux procedure between 2008 and 2022. Most patients underwent a Nissen fundoplication (302, 54%), followed by a Toupet or Dor fundoplication (205, 37%). Twelve distinct phenotypes emerged. Non-obese patients with normal esophageal motility, normotensive LES, no DGE, with a PEH represented the most common phenotype (134, 24%). The phenotype with the best post-operative GERD-HRQL scores at one year was defined by obesity, hypotensive LES, and PEH, while the phenotype with the worst scores was defined by obesity, ineffective motility, and PEH (1.5 ± 2.4 vs 9.8 ± 11.4, p = 0.010). There was no statistically significant difference in GERD-HRQL, dysphagia, or RSI scores between phenotypes after five years.

CONCLUSIONS

We have identified distinct phenotypes based on common GERD-associated patient characteristics. With further study these phenotypes may aid surgeons in prognosticating outcomes to individual patients considering an anti-reflux procedure.

Roux-en-Y gastric bypass versus fundoplication for gastroesophageal reflux disease in patients with obesity results in comparable outcomes

BACKGROUND

Roux-en-Y gastric bypass and fundoplication are effective treatments for gastroesophageal reflux disease, though the optimal procedure of choice in obesity is unknown. We hypothesize that Roux-en-Y gastric bypass is non-inferior to fundoplication for symptomatic control of gastroesophageal reflux disease in patients with obesity.

METHODS

We conducted a retrospective review of a prospectively maintained quality database. Patients with a body mass index ≥of 35 who presented for gastroesophageal reflux disease and subsequently underwent Roux-en-Y gastric bypass or fundoplication were included. Perioperative outcomes and pH testing data were reviewed. Patient-reported outcomes included Reflux Symptom Index, Dysphagia, Gastroesophageal Reflux Disease-Health Related Quality of Life, and Short Form-36 scores. Data were analyzed using the Wilcoxon rank sum test.

RESULTS

Ninety-five patients underwent fundoplication (n = 72, 75.8%) or Roux-en-Y gastric bypass (n = 23, 24.2%) during the study period. All patients saw an improvement in gastroesophageal reflux disease symptoms and overall quality of life. There were no significant differences in postoperative Reflux Symptom Index, Dysphagia, or Short-Form-36 scores. Significant differences in gastroesophageal reflux disease-Health Related Quality of Life scores were seen at preoperative, 1, 2, and 5 years postoperative (P < .05), with better symptom control in the fundoplication group. No significant difference was noted in postoperative DeMeester scores or percent time pH <4. Weight loss was significantly higher in the Roux-en-Y gastric bypass group at all postoperative time points up to 5 years (P < .05).

CONCLUSION

Roux-en-Y gastric bypass and fundoplication both decrease gastroesophageal reflux disease symptoms. Subjective data shows that patients undergoing Roux-en-Y gastric bypass may complain of worse symptoms compared to patients undergoing fundoplication. Objective data notes no significant difference in postoperative pH testing. Despite previous data, offering fundoplication or Roux-en-Y gastric bypass to patients with a body mass index of ≥35 kg/m2 is appropriate. The choice of surgical approach should be more directed to patient needs and desired goals at the time of the initial clinic visit.

Outcomes and predictors of treatment failure after anti-reflux mucosectomy for management of gastroesophageal reflux disease

BACKGROUND

Anti-reflux mucosectomy is a novel endoscopic treatment for gastroesophageal reflux disease that serves as an intermediate therapy between medical and surgical intervention. We aimed to evaluate outcomes and identify predictors of treatment failure in patients requiring anti-reflux mucosectomy.

METHODS

A prospective quality database was retrospectively reviewed. Upper endoscopy, pH testing, and functional luminal impedance planimetry were obtained at preop and 1 year post-operation. Quality of life outcomes were assessed by Gastroesophageal Reflux Disease-Health Related Quality of Life, Reflux Symptom Index, and dysphagia scores preoperatively and up to 5 years postoperatively.

RESULTS

Fifty-eight patients requiring anti-reflux mucosectomy were analyzed between 2016 and 2023. Preop Gastroesophageal Reflux Disease-Health Related Quality of Life mean scores improved at all time points 3 weeks to 2 years postoperatively (all P < .05). Preop mean Reflux Symptom Index scores also significantly improved at 6-month, 1-year, and 2-year timepoints (all P < .05). Dysphagia at 3 weeks was higher than preop scores (1.2 vs 2.1, P < .01) but returned to baseline. Upon follow-up, 43 patients (74.1%) had symptom improvement off proton pump inhibitors, 29 of whom reported complete symptom resolution. Out of 58 patients, 31 (53.4%) failed treatment due to DeMeester score (n = 22), erosive esophagitis (n = 2), Gastroesophageal Reflux Disease-Health Related Quality of Life ≥13 (n = 4), or <70% symptom resolution in the absence of pH or survey data (n = 3). Current smoking status was predictive of treatment failure (odds ratio 3.52, P < .031). Body mass index, DeMeester score, acid exposure time, and hiatal hernia ≤2 cm were not associated with treatment failure.

CONCLUSION

Anti-reflux mucosectomy is associated with significant improvement in quality of life; however, symptom resolution may not correlate with objective reflux control. Smoking is a predictor of treatment failure and should be considered in patient selection.

The Laparoscopy in Biliary Exploration Research and Training Initiative (LIBERTI) trial: simulator-based training for laparoscopic management of choledocholithiasis

BACKGROUND

Laparoscopic cholecystectomy with common bile duct exploration (LCBDE) is equivalent in safety and efficacy to endoscopic retrograde cholangiopancreatography (ERCP) plus laparoscopic cholecystectomy (LC) while decreasing number of procedures and length of stay (LOS). Despite these advantages LCBDE is infrequently utilized. We hypothesized that formal, simulation-based training in LCBDE would result in increased utilization and improve patient outcomes across participating institutions.

METHODS

Data was obtained from an on-going multi-center study in which simulator-based transcystic LCBDE training curricula were instituted for attending surgeons and residents. A 2-year retrospective review of LCBDE utilization prior to LCBDE training was compared to utilization up to 2 years after initiation of training. Patient outcomes were analyzed between LCBDE strategy and ERCP strategy groups using χ2, t tests, and Wilcoxon rank tests.

RESULTS

A total of 50 attendings and 70 residents trained in LCBDE since November 2020. Initial LCBDE utilization rate ranged from 0.74 to 4.5%, and increased among all institutions after training, ranging from 9.3 to 41.4% of cases. There were 393 choledocholithiasis patients analyzed using LCBDE (N = 129) and ERCP (N = 264) strategies. The LCBDE group had shorter median LOS (3 days vs. 4 days, p < 0.0001). No significant differences in readmission rates between LCBDE and ERCP groups (4.7% vs. 7.2%, p = 0.33), or in post-procedure pancreatitis (0.8% v 0.8%, p > 0.98). In comparison to LCBDE, the ERCP group had higher rates of bile duct injury (0% v 3.8%, p = 0.034) and fluid collections requiring intervention (0.8% v 6.8%, p < 0.009) secondary to cholecystectomy complications. Laparoscopic antegrade balloon sphincteroplasty had the highest technical success rate (87%), followed by choledochoscopic techniques (64%).

CONCLUSION

Simulator-based training in LCBDE results in higher utilization rates, shorter LOS, and comparable safety to ERCP plus cholecystectomy. Therefore, implementation of LCBDE training is strongly recommended to optimize healthcare utilization and management of patients with choledocholithiasis.

Impedance planimetry and panometry (EndoFLIP™) can replace manometry in preoperative anti-reflux surgery assessment

BACKGROUND

Endoluminal functional impedance planimetry and panometry assesses secondary peristalsis in response to volumetric distention under sedation. We hypothesize that impedance planimetry and panometry can replace high-resolution manometry in the preoperative assessment prior to anti-reflux surgery.

METHODS

Single institution prospective data were collected from patients undergoing anti-reflux surgery between 2021 and 2023. A 16-cm functional luminal imaging probe (FLIP) assessed planimetry and panometry prior to surgery under general anesthesia at the start of each case. Panometry was recorded and esophageal contractile response was classified as normal (NCR), diminished or disordered (DDCR), or absent (ACR) in real time by a single panometry rater, blinded to preoperative HRM results. FLIP results were then compared to preoperative HRM.

RESULTS

Data were collected from 120 patients, 70.8% female, with mean age of 63 ± 3 years. There were 105 patients with intraoperative panometry, and 15 with panometry collected during preoperative endoscopy. There were 60 patients (50%) who had peristaltic dysfunction on HRM, of whom 57 had FLIP dysmotility (55 DDCR, 2 ACR) resulting in 95.0% sensitivity. There were 3 patients with normal secondary peristalsis on FLIP with abnormal HRM, all ineffective esophageal motility (IEM). No major motility disorder was missed by FLIP. A negative predictive value of 91.9% was calculated from 34/37 patients with normal FLIP panometry and normal HRM. Patients with normal HRM but abnormal FLIP had larger hernias compared to patients with concordant studies (7.5 ± 2.8 cm vs. 5.4 ± 3.2 cm, p = 0.043) and higher preoperative dysphagia scores (1.5 ± 0.7 vs. 1.1 ± 0.3, p = 0.021).

CONCLUSION

Impedance planimetry and panometry can assess motility under general anesthesia or sedation and is highly sensitive to peristaltic dysfunction. Panometry is a novel tool that has potential to streamline and improve patient care and therefore should be considered as an alternative to HRM, especially in patients in which HRM would be inaccessible or poorly tolerated.

Target distensibility index on impedance planimetry during fundoplication by choice of wrap and choice of bougie

INTRODUCTION

Impedance planimetry (FLIP) provides objective feedback to optimize fundoplication outcomes. Ideal FLIP ranges for differing wraps and bougies have not yet been established. We report FLIP measurements during fundoplication grouped by choice of wrap and bougie with associated outcomes.

METHODS

A retrospective review of a prospective gastroesophageal database was performed for all Nissen or Toupet fundoplication with intraoperative FLIP using an 8-cm catheter, 30-mL and/or 40-mL fill and/or 16-cm catheter, 60-mL fill. Surgeons used no bougie, the FLIP balloon as bougie, or a hard bougie. Outcomes included perioperative data, Reflux Symptom Index, GERD-HRQL, Dysphagia scores, need for dilation, postoperative EGD findings, and hernia recurrence. Group comparisons were made using two-tailed Kruskal-Wallis and Fisher's exact tests.

RESULTS

Between 2016 and 2022, 333 patients underwent fundoplication and intraoperative FLIP. Procedures included Toupet with hard bougie (TFHB, N = 147), Toupet with FLIP bougie (TFFB, N = 69), Toupet without bougie (TFNB, N = 78), Nissen with hard bougie (NFHB, n = 20), or Nissen with FLIP bougie (NFFB, N = 19). FLIP measurements at 30-mL/40-mL fills varied significantly between groups, notably distensibility index at crural closure (CCDI) and post-fundoplication (FDI). No significant differences in FLIP measurements were seen between those who developed poor postoperative outcomes and those who did not, including when grouping by choice of wrap and bougie. At a 40-mL fill, abnormal motility patients with CCDI > 3.5 mm2/mmHg developed zero postoperative dysphagia. TFFB abnormal motility patients with CCDI > 3.5 mm2/mmHg or FDI > 3.6 mm2/mmHg developed zero postoperative dysphagia.

CONCLUSION

Intraoperative FLIP measurements vary by fundoplication and bougie choice. A CCDI > 3.5 mm2/mmHg (40 mL fill) should be sought in abnormal motility patients, regardless of wrap or bougie, to avoid postoperative dysphagia. TFFB abnormal motility patients with FDI > 3.6 mm2/mmHg (40 mL fill) also developed zero postoperative dysphagia. FDI > 6.2 mm2/mmHg (40 mL fill) was seen in all postoperative hernia recurrences.

Per-Oral Plication of (Neo)Esophagus: Technical Feasibility and Early Outcomes

BACKGROUND

Endoscopic sleeve gastroplasty is an example of endoscopic sutured plications being used to remodel a gastrointestinal organ. With per-oral plication of the esophagus (POPE), similar plications are used to remodel the dilated and redundant megaesophagus of end-stage achalasia. Redundancies and dilations can also develop in the neoesophagus of a patient with prior esophagectomy. Megaesophagus and a redundant neoesophagus can both lead to debilitating dysphagia, regurgitation, and recurrent aspiration pneumonia. Traditionally, this anatomic problem requires complex revisional or excisional surgery, to which POPE offers an incisionless alternative.

METHODS

This is a dynamic manuscript with video demonstration of POPE, as well as review of five cases performed in 1 year. Data were collected in a prospectively maintained database, and the institutional review board approved retrospective review for this publication. The procedure is performed using a dual-channel upper endoscope fixed with an endoscopic suturing device, with the patient supine under general anesthesia.

RESULTS

POPE was technically completed in all cases with no serious complications, and patients either went home the same day or spent one night for observation. Most patients reported immediate and substantial symptomatic improvement. Objective pre- and post-measures include esophagram and nuclear gastric emptying studies.

CONCLUSION

This article discusses early experience at one institution with POPE, with detailed description of the procedure and technical considerations. An accompanying video reviews two cases, one with megaesophagus and one with a gastric conduit. While this novel procedure has limited and rare indications, it offers a low-morbidity solution to a challenging anatomic problem that traditionally requires invasive surgery.

Experience with Impedance Planimetry for Surgical Foregut Disease in 1,097 Cases

BACKGROUND

The geometry and compliance of gastrointestinal sphincters may be assessed by impedance planimetry using a functional lumen imaging probe (FLIP). We describe our institutional foregut surgeon experience using FLIP in 1,097 cases, highlighting instances where FLIP changed operative decision making.

STUDY DESIGN

A retrospective review of an IRB-approved prospective quality database was performed. This included operative and endoscopic suite foregut procedures using FLIP between February 2013 and May 2022.

RESULTS

During the study period, FLIP was used a total of 1,097 times in 919 unique patients by 2 foregut surgeons. Intraoperative FLIP was used during 573 antireflux procedures and 272 endoscopic myotomies. FLIP was also used during 252 endoscopic suite procedures. For those undergoing preoperative workup of GERD, starting in 2021, esophageal panometry was performed in addition to standard FLIP measurements at the lower esophageal sphincter. In 77 cases, intraoperative FLIP changed operative decision making. During antireflux procedures, changes included adding or removing crural sutures, adjusting a fundoplication tightness, choice of full vs partial wrap, and magnetic sphincter augmentation sizing. For endoscopic procedures, changes included aborting peroral endoscopic myotomy or Zenker's peroral endoscopic myotomy, performing a myotomy when preoperative diagnosis was unclear, or performing additional myotomy.

CONCLUSIONS

FLIP is a useful tool for assessing the upper esophageal sphincter, lower esophageal sphincter, pylorus, and secondary esophageal peristalsis that can be used in a wide variety of clinical situations within a foregut surgeon's practice. It can also function as an adjunct in intraoperative decision making.

Acid exposure time better predicts outcomes following anti-reflux surgery than DeMeester score

BACKGROUND

Criteria to diagnose gastroesophageal reflux disease (GERD) vary. The American Gastroenterology Association (AGA) 2022 Expert Review on GERD focuses on acid exposure time (AET) rather than DeMeester score from ambulatory pH testing (BRAVO). We aim to review outcomes following anti-reflux surgery (ARS) at our institution, grouped by differing criteria for the diagnosis of GERD.

METHODS

A retrospective review of a prospective gastroesophageal quality database was performed for all patients undergoing evaluation for ARS with preoperative BRAVO ≥ 48 h. Group comparisons were made using two-tailed Wilcoxon rank-sum and Fisher's exact tests and two-tailed statistical significance of p < 0.05.

RESULTS

Between 2010 and 2022, 253 patients underwent an evaluation for ARS with BRAVO testing. Most patients (86.9%) met our institution's historical criteria: LA C/D esophagitis, Barrett's, or DeMeester ≥ 14.72 on 1+ days. Fewer patients (67.2%) met new AGA criteria: LA B/C/D esophagitis, Barrett's, or AET ≥ 6% on 2+ days. Sixty-one patients (24%) met historical criteria only, with significantly lower BMI, ASA, less hiatal hernias, and less DeMeester and AET-positive days, a less severe GERD phenotype. There were no differences between groups in perioperative outcomes or % symptom resolution. Objective GERD outcomes (need for dilation, esophagitis, and postop BRAVO) were equivalent between groups. Patient-reported quality of life scores, including GERD-HRQL, RSI, and Dysphagia Score did not differ between groups from preop through 1 year postop. Those who met our historical criteria only reported significantly worse RSI scores (p = 0.03) and worse GERD-HRQL scores at 2 years postop, though not statistically significant (p = 0.07).

CONCLUSION

Updated AGA GERD guidelines exclude a portion of patients who historically would have been diagnosed with and surgically treated for GERD. This cohort appears to have a less severe GERD phenotype but equivalent outcomes up to 1 year, with more atypical GERD symptoms at 2 years postop. AET may better define who should be offered ARS than DeMeester score.

Somatic DNA copy number alterations in non-dysplastic Barrett's esophagus

BACKGROUND

The purpose of this study was to analyze non-dysplastic Barrett's esophagus (NDBE) biopsy tissue and compare the rate of somatic DNA copy number alterations (CNAs) in patients who subsequently progressed to high-grade dysplasia (HGD) or esophageal adenocarcinoma (EAC) to those patients who did not.

METHODS

A retrospectively collected database of Barrett's esophagus (BE) patients spanning a 16-year period was queried. Patients who progressed from NDBE to HGD or EAC were identified and compared to patients who did not. Initial biopsy specimens were microdissected and extracted DNA underwent Multiplex Ligation-dependent Probe Amplification (MLPA) for CNAs. Comparisons between progressors and non-progressors were made with Fisher's exact and two-sample t tests. Logistic regression assessed factors associated with progression.

RESULTS

Of the 2459 patients in the BE database, 36 patients progressed from NDBE to either HGD or EAC. There were eight progressors who had biopsy specimens with adequate DNA for analysis. The progressor and non-progressor cohort had similar demographic information and medical history. The progressor group trended towards being older at diagnosis (72 ± 10 vs. 64 ± 13 years, p = 0.097) and fewer progressors reported reflux symptoms (50 vs. 94.7%, p < 0.001). Progressor specimens had more overall CNAs (75% vs. 33.6%, p = 0.026). On univariable analysis, there was an association between progression and absence of GERD symptoms (OR 16.54 [3.42-80.03], p = 0.001), any CNA (OR 5.10 [1.18-23.30], p = 0.035), and CNA in GATA6 or ERBB2 (OR 6.72 [1.18-38.22], p = 0.032).

CONCLUSIONS

Patients who progressed from NDBE to HGD or EAC were older at first diagnosis of BE and fewer of the progressors reported symptoms of reflux when compared to non-progressors. Progression was associated with the presence of any CNA and specific CNAs in GATA6 or ERBB2.

Long-term outcomes of per-oral endoscopic myotomy in achalasia patients with a minimum follow-up of 4 years: a multicenter study

Background and study aims  Per-oral endoscopic myotomy (POEM) is associated with a short-term clinical response of 82 % to 100 % in treatment of patients with achalasia. Data are limited on the long-term durability of the clinical response in these patients. The aim of this study was to determine the long-term outcomes of patients undergoing POEM for management of achalasia. Methods  This was a retrospective multicenter cohort study of consecutive patients who underwent POEM for management of achalasia. Patients had a minimum of 4 years follow-up. Clinical response was defined by an Eckardt score ≤ 3. Results  A total of 146 patients were included from 11 academic medical centers. Mean (± SD) age was 49.8 (± 16) years and 79 (54 %) were female. The most common type of achalasia was type II, seen in 70 (47.9 %) patients, followed by type I seen in 41 (28.1 %) patients. Prior treatments included: pneumatic dilation in 29 (19.9 %), botulinum toxin injection in 13 (8.9 %) and Heller myotomy in seven patients (4.8 %). Eight adverse events occurred (6 mucosotomies, 2 pneumothorax) in eight patients (5.5 %). Median follow-up duration was 55 months (IQR 49.9-60.6). Clinical response was observed in 139 (95.2 %) patients at follow-up of ≥ 48 months. Symptomatic reflux after POEM was seen in 45 (32.1 %) patients, while 35.3 % of patients were using daily PPI at 48 months post POEM. Reflux esophagitis was noted in 16.8 % of patients who underwent endoscopy. Conclusion  POEM is a durable and safe procedure with an acceptably low adverse event rate and an excellent long-term clinical response.

Quality of life after laparoscopic totally extraperitoneal repair of an asymptomatic inguinal hernia

BACKGROUND

When considering an asymptomatic inguinal hernia, surgeons must weigh the risks of watchful waiting against the risk of operative complications. Laparoscopy offers the benefit of reduced postoperative pain, which, for appropriate surgical candidates, may strengthen the case for repair. This study compares general and disease-specific quality of life following totally extraperitoneal (TEP) laparoscopic inguinal hernia repair (LIHR) of asymptomatic and symptomatic hernias.

METHODS

We summarize prospective data from 387 patients who underwent TEP LIHR between 2009 and 2015 by four surgeons at a single institution. Asymptomatic individuals were identified by pain scores of zero at preoperative clinic visits. Validated quality of life (QOL) measurements were administered preoperatively and at 3 weeks, 6 months, and 1-year postop. Comparisons were made using Chi-square test, t test, or Mann-Whitney U test. Changes over time were assessed using longitudinal mixed effects models.

RESULTS

A cohort of 79 asymptomatic cases were compared to 308 symptomatic individuals. The asymptomatic cohort had larger median hernia defects (2.5 vs 2 cm, p < 0.01), was older (mean 63.0 vs 58.9 years, p = 0.03), included fewer indirect hernias (57.7 vs 74.9%, p < 0.01), took pain medication for fewer days (mean 1.2 ± 1.5 vs 2.2 ± 3.0 days, p = 0.02), returned to baseline activities of daily living earlier (median 3 vs 5 days, p < 0.01), and reported decreased postoperative pain (p = 0.02). There was no significant difference in general QOL. There was one recurrence in the asymptomatic group and were two in the symptomatic cohort.

CONCLUSIONS

Asymptomatic individuals undergoing TEP LIHR reported less postoperative pain, returned to baseline activities, and discontinued pain medication sooner than symptomatic patients. These results are encouraging and may inform patient-centered discussions about asymptomatic hernia repair.

DNA-dependent protein kinase catalytic subunit is not required for dysfunctional telomere fusion and checkpoint response in the telomerase-deficient mouse

Telomeres are key structural elements for the protection and maintenance of linear chromosomes, and they function to prevent recognition of chromosomal ends as DNA double-stranded breaks. Loss of telomere capping function brought about by telomerase deficiency and gradual erosion of telomere ends or by experimental disruption of higher-order telomere structure culminates in the fusion of defective telomeres and/or the activation of DNA damage checkpoints. Previous work has implicated the nonhomologous end-joining (NHEJ) DNA repair pathway as a critical mediator of these biological processes. Here, employing the telomerase-deficient mouse model, we tested whether the NHEJ component DNA-dependent protein kinase catalytic subunit (DNA-PKcs) was required for fusion of eroded/dysfunctional telomere ends and the telomere checkpoint responses. In late-generation mTerc(-/-) DNA-PKcs(-/-) cells and tissues, chromosomal end-to-end fusions and anaphase bridges were readily evident. Notably, nullizygosity for DNA Ligase4 (Lig4)--an additional crucial NHEJ component--was also permissive for chromosome fusions in mTerc(-/-) cells, indicating that, in contrast to results seen with experimental disruption of telomere structure, telomere dysfunction in the context of gradual telomere erosion can engage additional DNA repair pathways. Furthermore, we found that DNA-PKcs deficiency does not reduce apoptosis, tissue atrophy, or p53 activation in late-generation mTerc(-/-) tissues but rather moderately exacerbates germ cell apoptosis and testicular degeneration. Thus, our studies indicate that the NHEJ components, DNA-PKcs and Lig4, are not required for fusion of critically shortened telomeric ends and that DNA-PKcs is not required for sensing and executing the telomere checkpoint response, findings consistent with the consensus view of the limited role of DNA-PKcs in DNA damage signaling in general.