An explanatory sequential mixed-methods design to establish thresholds of within-individual meaningful change on a sleep disturbance numerical rating scale score in atopic dermatitis.

PURPOSE: Establishing a meaningful within-individual change (MWIC) threshold is a key aspect for interpreting scores used as endpoints for evaluating treatment benefit. A new patient-reported outcome (PRO), a sleep disturbance numerical rating scale (SD NRS), was developed in adults and adolescents with moderate-to-severe atopic dermatitis (AD). This research aims to establish a MWIC threshold of the SD NRS score in the context of a drug development program. METHODS: An explanatory sequential mixed-methods design was used to address the research objective. This mixed-methods design used phase IIb data and a stand-alone qualitative study. Quantitative anchor-based and distribution-based approaches supported by qualitative-based approaches were conducted, and results were triangulated to determine preliminary MWIC thresholds of the SD NRS score. RESULTS: Triangulation of results from both quantitative and qualitative approaches suggested that a 2- to 6-point decrease in the SD NRS score change constitutes a preliminary range of MWIC threshold estimates. CONCLUSION: This research determined MWIC threshold estimates for the SD NRS score in both adolescents and adults with moderate-to-severe AD using an explanatory sequential mixed-methods design. This mixed-methods design provides interesting insights for establishing MWIC thresholds of a PRO score in the context of a drug development program.

Comorbidities, healthcare resource utilization & treatment pattern among patients with prurigo nodularis, compared to a benchmark in Germany: A real-world evidence claims data study.

BACKGROUND: Prurigo nodularis (PN) is a rare chronic inflammatory skin disease with a high disease burden, but data on clinical and economic burden are still scarce. OBJECTIVE: To describe the real-world epidemiologic, clinical and therapeutic characteristics and related economic burden of patients with PN compared to a benchmark population in Germany. METHODS: This retrospective study was based on an excerpt of German Statutory Health Insurance data of patients with an initial PN diagnosis between 2012 and 2016. PN cohort contained no record of PN in eight quarters before the index quarter and was followed up for eight quarters (unless deceased). Benchmark cohort without PN was calculated using direct standardization and 1:1 matching to PN cohort. RESULTS: Out of 4,536,002 insured patients, 2309 incident patients with PN were identified and matched to the benchmark cohort out of 3,018,382 patients without PN. Patients were mostly between 45 and 80 years when diagnosed with PN. Higher comorbidity rates were reported for PN than benchmark, with a rising disease burden at follow-up. Most patients with PN (91.3%) were diagnosed outpatient and had >50% more outpatient visits than the benchmark cohort. Hospitalization rates were higher in PN (53.9%) versus benchmark (35.1%), yielding twice longer mean hospital stays for PN (12 days) compared to benchmark (6 days) (p < 0.001). The most common initial therapy for patients with PN was topical corticosteroids (47.6%); ≥10% of patients were treated with antidepressants, antihistamines or systemic corticosteroids. Therapy rates were higher for PN compared to benchmark (p < 0.001). Mean initial costs were twofold higher in PN versus benchmark for outpatient, inpatient and drugs. During follow-up, an increase of >70% in mean PN costs compared to benchmark was identified for outpatient, inpatient and concomitant treatments (p < 0.001). CONCLUSION: This study highlights the significantly higher clinical and economic burden incurred by PN compared to benchmark patients in Germany, reflecting the unmet medical need for PN.

Epidemiology of prurigo nodularis in England: a retrospective database analysis.

BACKGROUND: Prurigo nodularis is a debilitating skin condition that is classified as rare by the Genetic and Rare Diseases Information Center (GARD) and the National Organization for Rare Diseases (NORD). There are currently no estimates of the prevalence of prurigo nodularis in England. OBJECTIVES: We aimed to address this data gap by describing the epidemiology of prurigo nodularis in a representative dataset derived from the English National Health Service. METHODS: The study utilized data from the Clinical Practice Research Datalink linked to Hospital Episode Statistics inpatient data. Patients with a diagnosis of prurigo nodularis were selected by clinical code in the primary care or inpatient datasets. Case definition was based on a minimum of two distinct diagnoses to maximize specificity. Point prevalence was calculated for the midpoint of 2018 and incidence rates from 2008 to 2018 were presented. For those classified as incident cases, demographic and clinical characteristics were reported. In sensitivity analyses the case definition was modified to relax the multiple diagnosis criteria and to restrict cases to those diagnosed within a maximum of 4 or 10 years of the midpoint prevalence date. RESULTS: Overall, 11 656 patients within the dataset had at least one prurigo nodularis diagnosis. Following application of the relevant inclusion criteria, 2743 patients formed the point prevalent cohort; the estimated prevalence was 3·27 patients per 10 000 population [95% confidence interval (CI) 3·15-3·40]. In sensitivity analyses the estimated prevalence ranged from 2·24 (95% CI 2·14-2·34) to 6·98 (95% CI 6·80-7·16). Incidence over the study period was 2·88 per 100 000 patient-years. Comorbidity was relatively high in this population, notably for atopic dermatitis (52·2%), depression (41·1%) and anxiety (35·4%). CONCLUSIONS: This study supports the NORD/GARD classification of prurigo nodularis as a rare disease with a prevalence of 3·27 patients per 10 000 population, which equates to 18 471 patients living with the disease in England in 2018. The relatively high prevalence of comorbidity observed for these patients may increase the complexity of management.

Longitudinal course and predictors of depressive symptoms in atopic dermatitis.

BACKGROUND: Atopic dermatitis (AD) is associated with eczematous lesions, pruritus, pain, and sleep disturbance, which may negatively impact mental health over time. OBJECTIVE: To determine the predictors and longitudinal course of depressive symptoms in adults with AD. METHODS: A prospective, dermatology practice-based study was performed (N = 695). AD signs, symptoms, and severity and patient health questionnaire-9 (PHQ-9) were assessed. RESULTS: At baseline, of the 695 participants, 454 (65.32%) had minimal, 139 (20.00%) had mild, 57 (8.20%) had moderate, 27 (3.88%) had moderately severe, and 8 (2.59%) had severe depression. Most had fluctuating levels of depressive symptoms. Feeling bad, thoughts of self-harm, difficulty concentrating, and slow movement were most persistent. Predictors of persistent depression included older age, non-White race, male sex, public or no insurance, more severe itch, skin pain, facial erythema, nipple eczema, sleep disturbance, and presence of pityriasis alba. LIMITATIONS: Single center study. CONCLUSION: Depressive symptoms are closely related to and fluctuate with AD severity over time. Improved control of AD signs and symptoms, particularly itch, may secondarily improve mental health.

Health-related quality of life and economic burden of prurigo nodularis.

BACKGROUND: Prurigo nodularis (PN) is an understudied, pruritic inflammatory skin disease. Little is known about the effect of PN on quality of life and its associated economic burden. OBJECTIVE: To quantify the impact of PN on quality of life and its economic implications. METHODS: A cohort study of PN patients (n = 36) was conducted using the Health Utilities Index Mark 3 questionnaire. Control data from US adults (n = 4187) were obtained from the 2002-2003 Joint Canada/United States Survey of Health. Quality-adjusted life year loss and economic costs were estimated by comparing the Health Utilities Index Mark 3 scores of the PN patients with those of the controls. RESULTS: The PN patients had lower overall health performance compared to the controls, (mean ± SE, 0.52 ± 0.06 vs 0.86 ± 0.003, respectively, P < .001). In multivariable regression, PN was found to be associated with worse health performance (coefficient -0.34, 95% CI [-0.46 to -0.23]), most prominent in the pain subdomain (coefficient -0.24, 95% CI [-0.35 to -0.13]). This correlated to an average of 6.5 lifetime quality-adjusted life years lost per patient, translating to an individual lifetime economic burden of $323,292 and a societal burden of $38.8 billion. CONCLUSION: These results demonstrate that PN is associated with significant quality-of-life impairment, similar to the level of other chronic systemic conditions. PN is also associated with a substantial individual economic burden, emphasizing the necessity of research on effective treatment options.

Clinical phenotyping of atopic dermatitis using combined itch and lesional severity: A prospective observational study.

BACKGROUND: Patients with atopic dermatitis (AD) have heterogeneous clinical phenotypes, including different combinations of itch and lesional severity. Little is known about the characteristics and course of these subtypes. OBJECTIVE: To determine the characteristics, associations, burden, and course of patients with AD using combined itch and lesional severity. METHODS: A prospective practice-based study was performed using questionnaires and physical examination (n=592). AD subsets were defined using verbal rating scale for average itch combined with either eczema area and severity index, objective-scoring atopic dermatitis (SCORAD), or validated investigator's global assessment as follows: mild-moderate itch and lesions (MI-ML), mild-moderate itch and severe lesions (MI-SL), severe itch and mild-moderate lesions (SI-ML), and severe itch and lesions (SI-SL). RESULTS: At baseline, there were only weak-moderate correlations of numerical rating scales for worst itch or average itch or SCORAD itch with eczema area and severity index, objective-SCORAD, body surface area, and validated investigator's global assessment (Spearman's rho = 0.32-0.62). Most patients had MI-ML (59.4%-62.3%), followed by SI-ML (21.3%-29.1%), SI-SL (6.0%-12.9%), and MI-SL (3.8%-6.4%). Patients with SI-SL, followed by SI-ML and MI-SL, described their AD as being more severe overall and had worse impairment in sleep, mental health, and quality of life. However, those with MI-SL or SI-SL were far more likely to be classified as severe by a physician (multivariable logistic and linear regression, P < .005 for all). Baseline MI-SL, SI-ML, and SI-SL were associated with similar longitudinal courses over time and more AD flares and itch triggers than MI-ML. CONCLUSION: Combined itch and lesional severity seem to describe unique AD phenotypes. Further studies are needed to confirm these findings and understand the optimal treatments for these groups.

Validity and reliability of Patient-Reported Outcomes Measurement Information System Global Health scale in adults with atopic dermatitis.

BACKGROUND: Patient-Reported Outcomes Measurement Information System Global Health (PGH) was validated to assess health-related quality of life in several diseases. Little is known about its measurement properties in adult atopic dermatitis. OBJECTIVE: Examine the measurement properties of PGH in adult atopic dermatitis. METHODS: A prospective dermatology practice-based study of 994 atopic dermatitis patients (18-97 years). RESULTS: PGH physical and mental health 4-item and abridged 2-item T scores, as well as mapped EuroQol-5D score, showed strong to very strong correlation with one another and moderate to strong Spearman correlations with Patient-Oriented Scoring Atopic Dermatitis, Patient-Health Questionnaire-9, Patient-Reported Outcomes Measurement Information System sleep disturbance and related impairment, Eczema Area and Severity Index, objective Scoring Atopic Dermatitis; and weak to moderate correlations with Patient Oriented Eczema Measure, numeric rating scale worst itch and average itch, and Scoring Atopic Dermatitis. The Dermatology Life Quality Index (DLQI) had stronger correlations with Patient Oriented Eczema Measure, Patient-Oriented Scoring Atopic Dermatitis, numeric rating scale worst itch and average itch, Eczema Area and Severity Index, and Scoring Atopic Dermatitis, but weaker correlations with Patient-Health Questionnaire-9 and Patient-Reported Outcomes Measurement Information System sleep disturbance and related impairment (convergent/divergent validity). PGH and DLQI scores had similarly poor ability to differentiate between levels of self-reported global atopic dermatitis severity (known-groups validity). No floor or ceiling effects were observed. No PGH or DLQI items had differential item functioning by demographics. PGH and DLQI scores showed fair to good responsiveness. Finally, PGH and DLQI showed similarly good test-retest reliability. LIMITATIONS: Single-center study. CONCLUSION: PGH scores had sufficient validity and reliability to assess health-related quality of life in atopic dermatitis.

A real-world study of the longitudinal course of adult atopic dermatitis severity in clinical practice.

BACKGROUND: Little is known about the longitudinal course of adult atopic dermatitis (AD) lesional severity and extent in clinical practice. OBJECTIVE: To determine the longitudinal course of AD in clinical practice. METHODS: A prospective, dermatology practice-based study was performed (n = 400). Patients were assessed at baseline and approximately 6, 12, 18, and 24 months by eczema area and severity index (EASI) and objective-scoring atopic dermatitis (objective-SCORAD). Multivariable repeated measures linear regression models were constructed to evaluate AD severity over time. RESULTS: Overall, 36.2% and 18.2% of patients had moderate (6.0-22.9) or severe (23.0-72.0) EASI scores at any visit, respectively. Similarly, 29.0% and 26.4% of patients had moderate (24.0-37.9) or severe (38.0-83.0) objective-SCORAD scores at any visit, respectively. Among patients with baseline moderate (6.0-22.9) or severe (23.0-72.0) EASI scores, 25.0% and 18.6% continued to have moderate or severe scores at 1 or more follow-up visits, respectively. Similarly, among patients with baseline moderate (24.0-37.9) or severe (38.0-83.0) objective-SCORAD scores, 22.6% and 24.5% continued to have moderate or severe scores at 1 or more follow-up visits, respectively. In longitudinal regression models, EASI was significantly associated with body surface area (adjusted ß [95% confidence interval]: 0.16 [0.09-0.23]) and edema/papulation (2.31 [0.19-4.43]). In addition, objective-SCORAD was significantly associated with body surface area (0.12 [0.04-0.21]), edema/papulation (4.69 [2.05-7.32]), and scratch (3.34 [0.45-6.24]) over time. CONCLUSION: AD lesional severity has a heterogeneous longitudinal course. Many patients had fluctuating lesional severity scores over time. A minority of patients had persistently moderate or severe lesions over time. Most patients with moderate-severe disease at baseline were unable to achieve persistent lesional clearance.

Association of itch triggers with atopic dermatitis severity and course in adults.

BACKGROUND: Atopic dermatitis (AD) is associated with heterogeneous triggers of itch, which may affect AD course and severity. OBJECTIVE: To characterize the triggers of itch in adult AD. METHODS: This was a prospective dermatology practice-based study using questionnaires and evaluation by a dermatologist (n = 587). Thirteen itch triggers were assessed using the patient-reported outcomes measurement information system Itch-Triggers. RESULTS: Overall, 381 (64.9%) patients reported greater than or equal to 1 itch trigger in the past week and 212 (36.1%) reported greater than or equal to 3 itch triggers. The most commonly reported triggers were stress (35.4%), sweat (30.5%), weather change (24.7%), dry air (24.4%), and heat (24.0%). In multivariable Poisson regression models, the number of itch triggers was associated with more severe patient-reported global AD severity, Numeric Rating Scale worst itch, Patient-Oriented Eczema Measure, Scoring Atopic Dermatitis sleep, Numeric Rating Scale skin pain, Eczema Area and Severity Index, and objective Scoring Atopic Dermatitis. The seasonality of AD was associated with distinct itch triggers. In multivariable logistic regression models, the number of itch triggers was associated with less than or equal to 3 months of AD remission during the year, greater than or equal to 2 AD flares, and AD being worse during some seasons. Four patterns of itch triggers were identified using latent class analysis, each associated with different clinical characteristics. CONCLUSION: Itch triggers are common and affect the course of AD. Itch triggers are an important end point to assess in patients with AD.

Comparison of Patient-Oriented Eczema Measure and Patient-Oriented Scoring Atopic Dermatitis vs Eczema Area and Severity Index and other measures of atopic dermatitis: A validation study.

BACKGROUND: Little is known about the measurement properties of Patient-Oriented Scoring Atopic Dermatitis (PO-SCORAD) in adults with atopic dermatitis (AD). Even less is known about how PO-SCORAD performs compared with the Patient-Oriented Eczema Measure (POEM). OBJECTIVE: To examine the measurement properties of PO-SCORAD and compare them with those of POEM. METHODS: A prospective dermatology practice-based study of 291 patients with AD (age range, 18-72 years). RESULTS: PO-SCORAD and POEM were moderately correlated with each other (Spearman ρ = 0.56) and had weak-moderate correlations with the Numeric Rating Scale (NRS) worst itch and average itch, Dermatology Life Quality Index (DLQI), ItchyQOL, Patient-Reported Outcomes Measurement Information System (PROMIS) Sleep Disturbance (SD) and Sleep-Related Impairment (SRI), Patient Health Questionnaire-9 (PHQ-9), and Eczema Area and Severity Index (EASI) (P < .001). POEM had significantly stronger correlations with DLQI, ItchyQOL, and EASI than did PO-SCORAD. PO-SCORAD and POEM had fair discriminant validity. Changes from baseline in PO-SCORAD and POEM were moderately correlated with each other; were weakly to strongly correlated with NRS worst itch and average itch, DLQI, ItchyQOL, PROMIS SD, PROMIS SRI, PHQ-9, and EASI; and had good test-retest reliability. There was no differential item functioning of items or floor or ceiling effects for PO-SCORAD or POEM. The thresholds for meaningful change for PO-SCORAD and POEM were -15.5 and -5.0, respectively. Median completion times for PO-SCORAD and POEM were 3 minutes and 1 minute, respectively. CONCLUSION: PO-SCORAD and POEM had good construct and cross-cultural validity, reliability, and responsiveness in adults with AD and were feasible for use in clinical trials and practice. However, POEM had better measurement properties than PO-SCORAD.

Validation of four single-item patient-reported assessments of sleep in adult atopic dermatitis patients.

BACKGROUND: The optimal approaches for monitoring sleep disturbances in adults with atopic dermatitis (AD) is not established. Multiple patient-reported outcome measures for AD and itch have sleep-related items. These items have not been validated previously. OBJECTIVE: Assess the measurement properties of sleep-related items from the Patient-Oriented Eczema Measure (POEM), SCORing AD (SCORAD), 5-dimensions of itch (5D), and ItchyQOL in adults with AD. METHODS: We performed a prospective dermatology practice-based study using questionnaires and evaluation by a dermatologist (n = 115). RESULTS: There was modest overlap and weak-moderate concordance of responses to the different assessments. Regarding concurrent validity, POEM-sleep, SCORAD-sleep, 5D-sleep, and ItchyQOL-sleep showed moderate correlations with each other. Regarding convergent validity, all items showed moderate correlation with total POEM, but weak correlations with Eczema Area and Severity Index (EASI), objective and total SCORAD, moderate to strong correlations with mean ItchyQOL and Dermatology Life Quality Index (DLQI), but poor or no significant correlation with Numeric Rating Scale (NRS) for worst or average itch. Regarding discriminant validity, all items showed significant and stepwise increases with increasing self-reported and physician-reported AD severity (Kruskal-Wallis, P < .01 for all). Floor effects were observed for POEM-sleep (n = 53, 46.1%), SCORAD-sleep (n = 28, 24.4%), 5D-sleep (n = 41, 35.7%), and ItchyQOL-sleep (n = 33, 28.7%); no ceiling effects were observed. Change in sleep-related item scores showed moderate strong correlations with change in POEM, 5Ditch, mean ItchyQOL, DLQI, objective and total SCORAD, and EASI, but inconsistent correlations with change of itch severity. CONCLUSION: Sleep-related items from POEM, SCORAD, 5D and ItchyQOL showed good validity and responsiveness to monitor sleep disturbances in adult AD patients.

Association of atopic dermatitis severity with cognitive function in adults.

BACKGROUND: Atopic dermatitis (AD) is associated with itch, pain, and sleep disturbance, all of which may contribute toward cognitive dysfunction. OBJECTIVE: To determine the relationship of AD severity and cognitive function in adults. METHODS: We performed a prospective dermatology practice-based study using questionnaires and evaluation by a dermatologist (n = 386). Cognitive function was assessed using the Patient-Reported Outcomes Measurement Information System (PROMIS) Cognitive Function 8-item Short-Form. RESULTS: At baseline, 118 patients (58.1%) reported ≥1 symptoms of cognitive dysfunction in the past 4 weeks, with 29 (14.3%) having mild, 11 (5.4%) moderate, and 4 (2.0%) severe PROMIS Cognitive Function T-scores. In propensity score-weighted regression models, PROMIS Cognitive Function T-scores were inversely associated with patient-reported global AD severity, Patient Oriented Eczema Measure (POEM), Numeric Rating Scale worst itch and skin pain, SCORing Atopic Dermatitis (SCORAD)-sleep, POEM-sleep, Eczema Area and Severity Index, and SCORAD, with stepwise decreases of cognitive function with worsening AD severity. At all AD severity levels, cognitive dysfunction was associated with increased Dermatology Life Quality Index and ItchyQoL scores. Changes from baseline in PROMIS Cognitive Function T-scores were weakly to moderately inversely correlated with changes from baseline in multiple AD outcomes. LIMITATIONS: Single-center study without non-AD controls. CONCLUSION: Cognitive dysfunction is associated with AD severity. Cognitive function may be an important end point for monitoring treatment response in AD.

Early-stage Mycosis Fungoides: Epidemiology and Prognosis.

Most patients with mycosis fungoides are diagnosed with early-stage disease. However, prevalence of early-stage disease is unknown, and evidence of its burden is scarce. The aim of this study is to estimate the prevalence of early-stage mycosis fungoides, how long patients live with early-stage disease and to characterise these patients. Data were obtained from 4 key publications and from US cancer registries (Surveillance, Epidemiology and End Results Program; SEER). The derived incidence of early-stage mycosis fungoides was 0.26/100,000 (UK), 0.29/100,000 (US) and 0.38/100,000 (US-SEER) and the prevalence was 4.8/100,000 (UK), 5.2/100,000 (US) and 6.6/100,000 (US-SEER). Early-stage disease may last for 18 years. From SEER registries, 3,132 were diagnosed at early stage (mostly stage IA). Median age at diagnosis was 58 years. Compared with stage IA, the relative risk of death was 1.3 for stage IB and 3.5 for stage IIA. We confirm the rarity of early-stage mycosis fungoides, a differential prognosis and the potential for elevated burden of disease.

Epidemiology of Prurigo Nodularis compared with Psoriasis in Germany: A Claims Database Analysis.

Prurigo nodularis is an itchy skin disease with unknown epidemiology. This study aimed to describe the epidemiology of prurigo nodularis compared with that of psoriasis. The German sickness fund claims database, with 2,783,175 continuously insured patients, included 1,720 patients diagnosed with prurigo nodularis and 51,390 with psoriasis. Patients with prurigo nodularis were averagely 8 years older than psoriasis patients and more often were women (p < 0.001). Annual incidence was a constant 0.02% in prurigo nodularis, and decreased steadily from 0.53 to 0.42% in psoriasis; cumulative incidence was 0.1% for prurigo nodularis and 1.9% for psoriasis. Prevalence was 0.1% for prurigo nodularis and 4.7% for psoriasis, with a 1-year mortality of 5.4% for prurigo nodularis and 1.2% for psoriasis (p < 0.001). The most frequent pre-existing comorbidities in patients with prurigo nodularis were inflammatory dermatoses and depression. This epidemiological study found a low prevalence of prurigo nodularis, manifesting different demographics and comorbidities compared with psoriasis.

Cost-of-illness of metastatic gastroenteropancreatic neuroendocrine tumours in Sweden-A population-based register-linkage study.

The objective was to estimate the cost-of-illness of grades 1 and 2 metastatic gastroenteropancreatic neuroendocrine tumours (GEP-NETs) in Sweden in 2013 in a population-based study including all patients diagnosed between 2005 and 2013. Data were obtained from national registers, and patients who utilised healthcare resources due to metastatic GEP-NETs in 2013 were included. The study included 478 patients (mean age 64 [SD=11] years, 51% men). The majority (80%) had small intestinal NET, 10% had pancreatic NET, and 41% had carcinoid syndrome. The total cost-of-illness was €12,189,000 in 2013, of which direct costs constituted 77% and costs from production loss constituted 22%. The largest contributor to the direct medical costs was prescription drugs (54%; primarily somatostatin analogues [91% of the total drug cost]). Production loss due to sickness absence constituted 52% of the total costs of production loss. The total annual cost per patient was €25,500. By patient group, the cost was €24,800 (95% CI €21,600-€28,100) for patients with small intestinal NET, €37,300 (95% CI €23,300-€51,300) for those with pancreatic NET and €18,600 (95% CI €12,600-€24,500) for patients with other GEP-NETs. To conclude, the total annual cost of grades 1 and 2 metastatic GEP-NETs in Sweden was €25,500 per patient and year.

Association Between Tumor Progression Endpoints and Overall Survival in Patients with Advanced Neuroendocrine Tumors.

Endpoints related to tumor progression are commonly used in clinical trials of novel therapeutic agents for neuroendocrine tumors (NETs). Whether improved tumor control translates into improved overall survival (OS), however, is uncertain. We assessed associations between tumor progression endpoints and OS in observational cohorts of patients with advanced neuroendocrine tumors treated with somatostatin analogs or with everolimus. We identified 440 patients with advanced NET who had received treatment with single-agent somatostatin analogs and 109 patients treated with everolimus, all of whom were treated at our institution and were evaluable for both tumor progression and survival. We assessed associations between progression-free survival (PFS) and OS by using the Kendall tau test, and we assessed associations between tumor progression and OS by using a landmark analysis. In the 440 patients treated with somatostatin analogs, we observed a significant correlation between PFS and OS by using the Kendall tau test (0.31; p < .0001). Additionally, the development of progressive disease was associated with OS in a landmark analysis, at landmark times of 6, 12, 18, and 24 months. In the 109 patients treated with everolimus, we similarly observed a significant correlation between PFS and OS by using the Kendall tau test (0.44; p < .0001) and associations between progressive disease and OS by using a landmark analysis at 3, 6, and 12 months. In these observational cohorts of patients with metastatic NET treated with single-agent somatostatin analogs or everolimus, longer times to disease progression and longer PFS were both associated with improved OS. Our findings support the continued use of disease progression endpoints in NET clinical trials. The Oncologist 2017;22:165-172Implications for Practice: Clinical trials in patients with advanced neuroendocrine tumors have used progression-free survival as a primary endpoint. While there is a general assumption that slowing or halting tumor growth is beneficial, little direct evidence links improvements in progression endpoints to improvements in overall survival. This study assessed associations between tumor progression endpoints and overall survival in observational cohorts of patients with advanced neuroendocrine tumor treated with somatostatin analogs or everolimus. Longer times to disease progression and improved progression-free survival were both associated with improved overall survival. The findings support the continued use of tumor progression endpoints in clinical trials for neuroendocrine tumors.