A Narrative Review of Pain in Pediatric Oncology: The Opioid Option.

Opioid therapy is the mainstay for managing pain in pediatric oncology. This narrative review describes the current literature regarding opioids for pediatric cancer pain. The review explores the multifaceted landscape of opioid utilization in this population, including the role of opioids in certain clinical circumstances, modalities of opioid delivery, unique opioids, outpatient and at-home pain management strategies, and other key concepts such as breakthrough pain. This review highlights the importance of individualized dosing and multimodal approaches to enhance efficacy and minimize adverse effects. Drawing from a wide range of evidence, this review offers insights to optimize pediatric oncology pain management.

Development of an enhanced recovery after surgery program for pediatric solid tumors.

Introduction: Enhanced recovery after surgery (ERAS) is an evidence-based, multi-modal approach to decrease surgical stress, expedite recovery, and improve postoperative outcomes. ERAS is increasingly being utilized in pediatric surgery. Its applicability to pediatric patients undergoing abdominal tumor resections remains unknown. Methods and Analysis: A group of key stakeholders adopted ERAS principles and developed a protocol suitable for the variable complexity of pediatric abdominal solid tumor resections. A multi-center, prospective, propensity-matched case control study was then developed to evaluate the feasibility of the protocol. A pilot-phase was utilized prior to enrollment of all patients older than one month of age undergoing any abdominal, retroperitoneal, or pelvic tumor resections. The primary outcome was 90-day complications per patient. Additional secondary outcomes included: ERAS protocol adherence, length of stay, time to administration of adjuvant chemotherapy, readmissions, reoperations, emergency room visits, pain scores, opioid usage, and differences in Quality of Recovery 9 scores. Ethics and Dissemination: Institutional review board approval was obtained at all participating centers. Informed consent was obtained from each participating patient. The results of this study will be presented at pertinent society meetings and published in peer-reviewed journals. We expect the results will inform peri-operative care for pediatric surgical oncology patients and provide guidance on initiation of ERAS programs. We anticipate this study will take four years to meet accrual targets and complete follow-up. Trial Registration Number: NCT04344899.

Impact of Propofol Exposure on Neurocognitive Outcomes in Children With High-Risk B ALL: A Children's Oncology Group Study.

PURPOSE: Many children treated for ALL develop long-term neurocognitive impairments. Increased risk of these impairments is associated with treatment and demographic factors. Exposure to anesthesia is an additional possible risk factor. This study evaluated the impact of cumulative exposure to anesthesia on neurocognitive outcomes among a multicenter cohort of children with ALL. METHODS: This study was embedded in AALL1131, a Children's Oncology Group phase III trial for patients with high-risk B-ALL. In consenting patients age 6-12 years, prospective uniform assessments of neurocognitive function were performed during and at 1 year after completion of therapy. Exposure to all episodes of anesthetic agents was abstracted. Multivariable linear regression models determined associations of cumulative anesthetic agents with the primary neurocognitive outcome reaction time/processing speed (age-normed) at 1 year off therapy, adjusting for baseline neurocognitive score, age, sex, race/ethnicity, insurance status (as a proxy for socioeconomic status), and leukemia risk group. RESULTS: One hundred and forty-four children, 76 (52.8%) males, mean age of 9.1 (min-max, 6.0-12.0) years at diagnosis, underwent a median of 27 anesthetic episodes (min-max, 1-37). Almost all patients were exposed to propofol (140/144, 97.2%), with a mean cumulative dose of 112.3 mg/kg. One year after therapy, the proportion of children with impairment (Z-score ≤-1.5) was significantly higher compared with a normative sample. In covariate-adjusted multivariable analysis, cumulative exposure to propofol was associated with a 0.05 Z-score decrease in reaction time/processing speed per each 10 mg/kg propofol exposure (P = .03). CONCLUSION: In a multicenter and uniformly treated cohort of children with B-ALL, cumulative exposure to propofol was an independent risk factor for impairment in reaction time/processing speed 1 year after therapy. Anesthesia exposure is a modifiable risk, and opportunities to minimize propofol use should be considered.

Patient and clinician beliefs about potential barriers to treatment of neuropathic pain for adolescents with sickle cell disease.

Pain is the hallmark symptom causing morbidity for people with sickle cell disease (SCD) and may present as nociceptive, neuropathic, or mixed type pain. Neuropathic pain (NP) is underrecognized and undertreated in patients with SCD and is associated with decreased patient-reported quality of life. Surveys were completed by clinicians caring for adolescents with SCD in the outpatient setting. SCD patients ages 1418 at increased risk of NP completed a patient-facing survey at a scheduled clinic visit. Ninety-four percent of responding clinicians agreed that NP significantly contributes to reported pain in SCD. Clinicians believed that NP medications are effective for reducing chronic pain (62%) and decreasing opioid utilization (44%). Clinician-identified barriers to prescribing NP medications included concerns about medication adherence (82%), lack of pediatric guidelines for NP medications (70%), and perceived patient concern about side effects (65%). More than 1/3 (35%) of clinicians reported that they were not comfortable managing NP medications. Clinician-identified barriers to referral to a pain management specialist included scheduling concerns (88%) and perceived patient/family lack of interest (77%). Most patients expressed willingness to take a medication for NP (78%), see a pain management specialist (84%), or learn more about nonpharmacologic interventions (72%), although most (51%) also reported some concerns about taking a medication for NP, citing insufficient knowledge (34%), and potential for side effects (32%). A minority of respondents (15%) worried about referral to a pain management specialist. Clinician and patient perspectives provide insights that may guide education efforts or other interventions to improve treatment of SCD-related NP.

Regional blocks for pain control at the end of life in pediatric oncology.

Background: Pain management at the end of life is a fundamental aspect of care and can improve patients' quality of life. Interventional approaches may be underutilized for pediatric cancer patients. Objective: To describe a single institution's 10 years of experience with regional pain management at the end of life in pediatric oncology. Methods: A retrospective cohort study of 27 patients with pediatric cancer who died between April 2011 and December 2021 and received continuous nerve block (CNB) catheters or single-shot nerve blocks (SSBs) during their last three months of life. The type of blocks, analgesic efficacy, and palliative care involvement were evaluated. Results: Twenty-two patients (81.5%) had solid tumor diagnoses, including carcinomas, sarcomas, and neuroblastoma. Most (59%) patients received CNB catheters, and 12 patients (44%) received SSBs for pain control. The mean pain score decreases for CNB catheters and SSBs after interventions were -2.5 and -2.8, respectively, on an 11-point scale. Decreases in opioid patient-controlled analgesia dosing requirements were noted in 56% of patients with CNB catheters; likewise, in 25% of patients with SSBs at 24 h and in 8% at 5 days after interventions. Nearly all patients had PC involvement and received care from pain specialists (96% and 93%, respectively). Twenty-three (85%) had physician orders for scope of treatment orders completed before death. Conclusion: Regional pain control interventions can be effective and safe for relieving regional pain and suffering in dying children and young adults. The collaboration between palliative care and pain management specialists at the end of life can help alleviate suffering and improve quality of life.

A retrospective investigation of the relationship between neuroblastoma response to anti-GD2 monoclonal antibodies and exposure to opioids for pain management.

OBJECTIVE: Recent increased awareness and research studies reflect possible associations between opioid exposure and cancer outcomes. Children with neuroblastoma (NB) often require opioid treatment for pain. However, associations between tumor response to chemotherapy and opioid exposure have not been investigated in clinical settings. METHODS: This is a single-institution retrospective review of patients with NB treated between 2013 and 2016. We evaluated opioid consumption quantified in morphine equivalent doses (mg/kg) based on nurse- or patient-controlled analgesia during antibody infusions. We also analyzed their associations with change in primary tumor volume and total tumor burden. RESULTS: Of 42 patients given opioids for pain related to anti-disialoganglioside monoclonal antibodies (anti-GD2 mAb), data completion was achieved for 36, and details of statistical analyses were entered. Median total weight-based morphine equivalent (over 8 days) was 4.71 mg/kg (interquartile range 3.49-7.96). We found a statistically insignificant weak negative relationship between total weight-based morphine equivalents and tumor volume ratio (correlation coefficient -.0103, p-value .9525) and a statistically insignificant weak positive relationship between total weight-based morphine equivalent and Curie score ratio (correlation coefficient .1096, p-value .5247). CONCLUSION: Our study found no statistically significant correlation between opioid consumption and natural killer (NK) cell-mediated killing of NB cells as measured by effects on tumor volume/tumor load.

Chronic postsurgical pain in children and young adults with cancer and choice of regional anesthesia for amputation and limb-sparing surgery.

BACKGROUND: Patients undergoing limb amputation (LA) or limb-sparing (LS) for lower extremity oncologic diagnoses are at similar risk for chronic postsurgical pain of neuropathic nature (CPSP/NP). Regional anesthesia (RA) techniques are pre-emptive measures to prevent the occurrence of the CPS/NP. However, recommendations for epidural (EP) versus peripheral nerve blocks (PNBs) lack in pediatric literature. AIMS: This study investigates the incidence and duration of CPSP/NP and describes NP-directed regimens. METHODS AND RESULTS: Data on demographics, use of EP or PNB, duration of CPSP/NP, and NP-directed medication were retrospectively collected for LA and LS between 2009 and 2019. Mixed effects logistic regression was used to compare the odds of CPSP/NP between EP and PNB. Cox PH model with adjustment for clustering due to multiple surgeries on patients was used to quantify rate of pain relief between surgery groups (LA vs. LS) and RA groups (EP vs. PNB). The incidence of CPSP/NP was 36 (23.8%) after 165 surgeries (150 patients). The odds of CPSP/NP after PNB were 2.5 times those of CPSP/NP after EP (p = .11). The rate of pain relief at any instant after the EP was 1.2 times that after PNB (p = .3). The rate of pain relief for LS with EP was 1.9 times that of pain relief for LA with EP, a statistically significant difference (p = .03). Gabapentin was used (94.5%), with addition of amitriptyline (24.2%) and both amitriptyline and methadone (12.7%). CONCLUSION: The LS with the EP group had a significantly higher rate of relief of CPSP/NP than LA with EP. Odds of CPSP/NP after PNB were 2.5 times those of CPSP after EP.

Palliative Sedation Therapy Practice Comparison - A Survey of Pediatric Palliative Care and Pain Management Specialists.

Context: Palliative sedation therapy (PST) can relieve suffering at end-of-life (EOL) in children with intolerable and refractory symptoms. However, updated and consistent guidance on PST practices are imperative. Objectives: We investigate current variations in clinical practice and PST implementation among pediatric palliative care (PPC) and pain management (PM) specialists. Methods: We distributed an IRB-exempt electronic anonymous survey via email through the Society of Pediatric Pain Medicine, and the American Academy of Hospice and Palliative Medicine. Survey responses were collated and descriptively reported. Results: Of 83 survey responses, the majority (75%) represented large academic children's hospitals. The distribution between PPC and pediatric pain management specialists' responses was 60% and 40%, respectively. Most respondents reported having designated pain management and/or palliative care teams (70% and 90%, respectively). Approximately half (48%) reported following an institutional PST protocol, most not requiring formal ethics consult (69%). Only 54% of respondents noted that the Do Not Resuscitate (DNR) order was required prior to PST initiation. PST was primarily utilized for children with oncologic diagnoses (76%). The primary and secondary medications of choice for PST implementation were reported to be opioids (39%) and benzodiazepines (36%) by pain management specialists, and benzodiazepines (52%) and barbiturates (28%) by palliative care specialists. Conclusions: Our study highlights the variability in the practice and implementation of PST. Further educational efforts are key for establishing PST practices and efficient protocol development.

Perioperative Indications for Gabapentinoids in Pediatrics: A Narrative Review.

In recent years, there has been increased interest in using gabapentinoids (gabapentin and pregabalin) as part of multimodal medication plans or enhanced recovery after surgery protocols to mitigate several perioperative clinical challenges. Outcomes explored in the context of using gabapentinoids perioperatively in children are variable and include acute complications of pain, anxiety, nausea and vomiting, and emergence agitation, as well as the long-term postoperative outcome of chronic postsurgical pain. This narrative review describes the current literature regarding perioperative use of gabapentinoids in pediatric patients and aims to describe the role of gabapentinoids in the perioperative setting for each specific indication.

Dexmedetomidine and Propofol at End of Life in Pediatric Oncology: Trends in Palliative Sedation Therapy.

Context: Palliative sedation therapy (PST) can address suffering at the end of life (EOL) in children with cancer; yet, little is known about PST in this population. Objectives: We sought to describe the characteristics of pediatric oncology patients requiring PST at the EOL. Methods: A retrospective review was completed for pediatric oncology patients who required PST at a United States academic institution over 10 years, including demographics, disease characteristics, EOL characteristics, and medications for PST and symptom management. Results: PST was utilized in 3% of patients at the EOL. Of 24 study participants receiving PST, 83% (n = 20), 12.5% (n = 3), and 4.2% (n = 1) received dexmedetomidine, propofol, or both, respectively. The most frequent diagnosis for patients receiving PST was acute myelogenous leukemia (20.8%, n = 5). All patients were followed up by the palliative care team, and two-thirds (66.6%, n = 16) were also followed up by the pain management service; 79% (n = 19) were enrolled in hospice, and 98.5% (n = 23) had a Physician Orders for Scope of Treatment in place. Pain was the most common refractory symptom leading to PST initiation (33.3%, n = 8), followed by neuroagitation and dyspnea. PST was initiated a median of 2.5 days before death. A third of deaths occurred in the intensive care unit (33.3%, n = 8). Conclusions: PST was rare in this study; dexmedetomidine was used as first-line treatment for PST in patients at the EOL with refractory symptoms. Its place in PST protocols in pediatric oncology should be validated with prospective studies. Our study suggests the potential value of collaboration between palliative care and pain specialists in the context of PST.

COVID-19 infection and pain in adolescents with sickle cell disease: A case series.

Adolescents with sickle cell disease (SCD) have been shown to have pain-related sequelae following COVID-19 infection. In this case series, we discuss five adolescents with SCD and SARS-CoV-2 infection who subsequently developed complex pain circumstances manifested as: (1) increased frequency of acute care visits or admissions for pain; (2) new onset chronic pain; (3) new onset neuropathic pain; (4) escalation in the complexity of pharmacologic therapies; (5) increased use of nonpharmacologic interventions. While more research is needed to fully understand the implications of COVID-19 infection on pain in adolescents with SCD, these cases suggest the presence of a complex relationship.

Palliative Sedation Therapy in Pediatrics: An Algorithm and Clinical Practice Update.

Palliative sedation therapy (PST) is an important clinical intervention for pediatric patients with refractory symptoms and suffering during the end-of-life (EOL) period. Variations in PST implementation including medication selection, limited literature regarding feasibility in various clinical settings, particularly non-intensive care units, and lack of education on evolving definitions and ideal practices may all contribute to the current underutilization of this valuable resource. We therefore offer a clinical algorithm for identifying appropriate patients for PST, ensuring all other modalities for symptom management have been considered and/or optimized, and present a guideline for PST implementation that can be adapted and individualized based on institutional experience and resource availability. Furthermore, through case-based clinical scenarios, we demonstrate how to incorporate this algorithm into EOL practice.

Compassionate de-escalation of life-sustaining treatments in pediatric oncology: An opportunity for palliative care and intensive care collaboration.

Context: Approximately 40%-60% of deaths in the pediatric intensive care unit (PICU) are in the context of de-escalation of life-sustaining treatments (LSTs), including compassionate extubation, withdrawal of vasopressors, or other LSTs. Suffering at the end of life (EOL) is often undertreated and underrecognized. Pain and poor quality of life are common concerns amongst parents and providers at a child's EOL. Integration of palliative care (PC) may decrease suffering and improve symptom management in many clinical situations; however, few studies have described medical management and symptom burden in children with cancer in the pediatric intensive care unit (PICU) undergoing de-escalation of LSTs. Methods: A retrospective chart review was completed for deceased pediatric oncology patients who experienced compassionate extubation and/or withdrawal of vasopressor support at EOL in the PICU. Demographics, EOL characteristics, and medication use for symptom management were abstracted. Descriptive analyses were applied. Results: Charts of 43 patients treated over a 10-year period were reviewed. Most patients (69.8%) were white males who had undergone hematopoietic stem cell transplantation and experienced compassionate extubation (67.4%) and/or withdrawal of vasopressor support (44.2%). The majority (88.3%) had a physician order for scope of treatment (POST - DNaR) in place an average of 13.9 days before death. PC was consulted for all but one patient; however, in 18.6% of cases, consultations occurred on the day of death. During EOL, many patients received medications to treat or prevent respiratory distress, pain, and agitation/anxiety. Sedative medications were utilized, specifically propofol (14%), dexmedetomidine (12%), or both (44%), often with opioids and benzodiazepines. Conclusions: Pediatric oncology patients undergoing de-escalation of LSTs experience symptoms of pain, anxiety, and respiratory distress during EOL. Dexmedetomidine and propofol may help prevent and/or relieve suffering during compassionate de-escalation of LSTs. Further efforts to optimize institutional policies, education, and collaborations between pediatric intensivists and PC teams are needed.

Low-dose ketamine infusions reduce opioid use in pediatric and young adult oncology patients.

BACKGROUND: Ketamine is an NMDA-receptor antagonist with analgesic and opioid-sparing properties. Although well studied in adults, more robust evidence supporting ketamine's use for pediatric pain management is needed. This retrospective study evaluates ketamine's opioid-sparing effectiveness in pediatric and young adult oncology and hematology patients. PROCEDURE: Continuous ketamine infusions administered for pain management between 2010-2020 were reviewed. Data including demographic characteristics, oncology/hematology and pain diagnoses, concurrent pain medications, and ketamine infusions' dose and duration were collected. Opioid consumption data based on delivery via patient-controlled analgesia were collected 1 day before (D1), all days during (cumulatively named D2), and 1 day after (D3) ketamine infusions and calculated as morphine-equivalent doses (mg/kg/day). Data were reported for the entire study group as well as for distinct oncology and end-of-life categories, and short-term acute pain circumstances which included vaso-occlusive crises in hematology patients. Side effects were reviewed. RESULTS: Significantly lower daily opioid consumption was noted in the oncology group, while decreases were not significant in the end-of-life group and in the overall study population. The acute pain group did not show an opioid reduction associated with the ketamine infusions. A largely tolerable side-effect profile was observed, with no differences among each group's incidence. CONCLUSIONS: Ketamine infusions were associated with significantly reduced opioid consumption for oncology patients. The opioid-sparing effects of ketamine may vary according to clinical diagnoses and circumstances of use. Overall, low-dose ketamine infusions present an acceptable safety profile in pediatric and young adult patients; nevertheless, individual risks and benefits should be considered.

Prevalence of neuropathic pain in adolescents with sickle cell disease: A single-center experience.

BACKGROUND: Neuropathic pain (NP) has been previously explored in adolescents with sickle cell disease (SCD). This study aims to describe the prevalence of NP in adolescents with SCD at a single institution and to explore associated risk factors. PROCEDURE: We used the painDETECT questionnaire, one of the few pain phenotyping questionnaires validated for adolescents. We also evaluated the relationships between painDETECT scores and frequency of acute care visits and admissions for pain in the previous 12 months, and age, respectively. Patients 12-18 years old were surveyed from June to July 2019. A retrospective approach was used to answer the remaining research questions. RESULTS: Eighty-one and seven surveys were completed in the outpatient and inpatient settings, respectively. PainDETECT scores suggestive of NP were more prevalent in inpatient surveys than in outpatient surveys. The difference between the mean painDETECT scores of each group was significant when using a general linear mixed model. Most inpatients surveyed had ≥3 pain events in the previous 12 months. Further, older age and increased number of pain events in the previous 12 months were independently associated with higher painDETECT scores. CONCLUSIONS: Overall, in our opinion, NP is not being evaluated for and treated sufficiently in pediatric SCD, especially in the setting of inpatient acute vaso-occlusive crisis. Age and number of acute pain events/admissions in the previous 12 months can be used to identify patients likely to be at risk for NP. It is important to continue to identify NP and develop NP-targeting treatment plans.

Neuropathic pain and neurocognitive functioning in children treated for acute lymphoblastic leukemia.

ABSTRACT: Children with acute lymphoblastic leukemia (ALL) often experience treatment-related neurocognitive deficits and significant pain. Pain may exacerbate these cognitive impairments. This study examined neuropathic pain and neurocognitive outcomes in survivors of childhood ALL treated with contemporary therapy on a clinical trial (NCT00137111). There were 345 survivors (45% female, M = 6.9 years at diagnosis) who completed neurocognitive assessments including measures of sustained attention, learning and memory, and parent ratings of attention during at least one of 4 time points: on-therapy (Induction and Reinduction), end of therapy, and 2 years post-therapy. At-risk performance was defined as a score at least 1SD below the age-adjusted mean. Data on neuropathic pain (events, duration, and severity according NCI Common Toxicity Criteria) and pharmacologic pain management (opioids and gabapentin) were ascertained. Results showed that 135 survivors (39%) experienced neuropathic pain during treatment. Compared with those without pain, survivors with pain had greater memory impairments at end of therapy (California Verbal Learning Test [CVLT]-Total, 24% vs 12%, P = 0.046). Within the pain group, survivors who experienced a greater number of pain events (CVLT-Total = -0.88, P = 0.023) and those who were treated with opioids (versus gabapentin) had poorer learning and memory performance (CVLT-Total = -0.73, P = 0.011; Short Delay = -0.57, P = 0.024; Long Delay = -0.62, P = 0.012; and Learning Slope = -0.45, P = 0.042) across time points. These are considered medium-to-large effects (SD = 0.45-0.88). Neuropathic pain may be a risk factor for learning problems after therapy completion, and treatment for pain with opioids may also adversely affect neurocognitive performance. Therefore, patients who experience pain may require closer monitoring and additional intervention for neurocognitive impairment.

Successful Multimodal Treatment for Complex Regional Pain Syndrome in an Adolescent with Acute Lymphoblastic Leukemia: A Case Report.

Complex regional pain syndrome (CRPS) is a debilitating disorder that causes significant pain and can decrease the quality of life of affected individuals. This is the first report of CRPS in an adolescent oncology patient, whose symptoms successfully resolved with 3 weeks of intensive, multimodal, and multidisciplinary therapies. She experienced a complete return to pre-CRPS functional status within 10 weeks. The successful outcome of this case highlights the importance of early recognition of CRPS in the adolescent population and the need for a multimodal intensive treatment regimen to prevent the development of chronic pain and loss of limb function.

Lidocaine infusions and reduced opioid consumption-Retrospective experience in pediatric hematology and oncology patients with refractory pain.

BACKGROUND: Despite a more robust experience with lidocaine infusions for pain management in adults and general pediatric population, there is limited evidence of efficacy of lidocaine infusions for pain management in patients with pediatric hematology and oncology diagnoses. METHODS: Data pertaining to continuous intravenous lidocaine infusions prescribed between January 2009 and June 2019 were reviewed, including patients' demographic characteristics, hematology/oncology and pain diagnoses, concurrent pain medications, and lidocaine infusion dose regimens and duration. Pain scores and opioid consumption calculations based on morphine equivalent doses (mg/kg/day) of patient-controlled analgesia were collected 1 day before infusion (D1), during infusion (D2), and 1 day after infusion (D3). RESULTS: The mean opioid consumption on D3 was significantly lower than that on D2 (p = .01). The pain scores on D3 were significantly lower than those on D1 when measured as average pain scores per 24 hours (p < .001) or as single pain scores immediately before and after infusions (p < .001). No significant associations were found between cumulative doses of lidocaine (loading dose plus total infusion dose) and either a decrease in the opioid consumption or a decrease in pain scores. CONCLUSIONS: In this retrospective series of pediatric hematology and oncology cases, we report positive outcomes in reducing opioid consumption and pain scores after lidocaine infusions. Prospective investigations designed in a collaborative, multi-institutional fashion, including a variety of pediatric populations are needed to further investigate the efficacy of lidocaine infusions.

A polygenic score for acute vaso-occlusive pain in pediatric sickle cell disease.

Individuals with monogenic disorders can experience variable phenotypes that are influenced by genetic variation. To investigate this in sickle cell disease (SCD), we performed whole-genome sequencing (WGS) of 722 individuals with hemoglobin HbSS or HbSß0-thalassemia from Baylor College of Medicine and from the St. Jude Children's Research Hospital Sickle Cell Clinical Research and Intervention Program (SCCRIP) longitudinal cohort study. We developed pipelines to identify genetic variants that modulate sickle hemoglobin polymerization in red blood cells and combined these with pain-associated variants to build a polygenic score (PGS) for acute vaso-occlusive pain (VOP). Overall, we interrogated the α-thalassemia deletion -α3.7 and 133 candidate single-nucleotide polymorphisms (SNPs) across 66 genes for associations with VOP in 327 SCCRIP participants followed longitudinally over 6 years. Twenty-one SNPs in 9 loci were associated with VOP, including 3 (BCL11A, MYB, and the ß-like globin gene cluster) that regulate erythrocyte fetal hemoglobin (HbF) levels and 6 (COMT, TBC1D1, KCNJ6, FAAH, NR3C1, and IL1A) that were associated previously with various pain syndromes. An unweighted PGS integrating all 21 SNPs was associated with the VOP event rate (estimate, 0.35; standard error, 0.04; P = 5.9 × 10-14) and VOP event occurrence (estimate, 0.42; standard error, 0.06; P = 4.1 × 10-13). These associations were stronger than those of any single locus. Our findings provide insights into the genetic modulation of VOP in children with SCD. More generally, we demonstrate the utility of WGS for investigating genetic contributions to the variable expression of SCD-associated morbidities.