2.1 Study design, setting, and participating centers

This prospective cohort study was performed from 1 May 2016 through 30 April 2019 in 23 different Hospitals from Argentina, Brazil, Chile, Colombia, and Uruguay. All eligible patients were enrolled consecutively at each clinical site. Study data were entered into a web-based electronic system. Central revision and resubmission were requested when erroneous or missing data were detected.

Written informed consent was obtained from each patient before enrollment. All study procedures were conducted in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.¹⁶ The Austral University Ethics Committee approved this study and each Ethical Committee from all the participating centers approved the study protocol. All procedures followed ethical standards (institutional and national) as well as those mandated by the Helsinki Declaration of 1975, as revised in 2008. The study had a public database for all the investigators on a web link (https://temasis.com.ar/lalrean-org) and received a Research National Grant from the Argentinean National Institute of Cancer. All authors had access to the study data, reviewed and approved the final version of this manuscript. This study was registered in an open public registry (NCT03775798; www.clinicaltrials.gov).

2.2 Cohort characteristics and study variables recorded before DAAs initiation

We included adult patients, older than 18 years old, with chronic HCV infection confirmed by the quantitative real-time polymerase method, and with any degree of liver fibrosis. Genotyping/subgenotyping was conducted before treatment initiation. All patients who received at least one pill of any DAAs were included in the study, as an intention-to-treat analysis.

Baseline exposure variables were recorded for all enrolled subjects including detailed demographic data and relevant past medical history. Evaluation of liver fibrosis stage was assessed by liver biopsy or noninvasive methods (transient elastography or serum biomarkers). Liver stiffness measurements were recorded as a continuous variable in kilopascals (kPa), as obtained from liver elastography and categorized according to international consensus guidelines.¹⁷ The cutoffs for advanced fibrosis and cirrhosis were 9.5 and 12.5 kPa, respectively, obtained by transient elastography. Cirrhosis could also be determined by the site investigator or treating physician based on a combination of clinical signs of portal hypertension, biochemical parameters, and/or radiologic findings consistent with cirrhosis.¹⁸ The severity of liver disease was evaluated according to the Child-Turcotte Pugh (CTP) score. Decompensated cirrhosis was defined by the CTP B o C and/or a history of ascites, variceal hemorrhage, hepatic encephalopathy, and/or other complications secondary to portal hypertension. Clinically significant portal hypertension (CSPH) was defined as the presence of gastroesophageal varices on endoscopy or presence of a platelet count less than 100 000/mm³ associated with splenomegaly (spleen larger than 120 mm on radiographic imaging).¹⁸

2.3 Intervention and main exposure variables

The specific DAAs treatment prescription was based on physicians' criteria according to the available regimens in each country, following national and international guidelines.^{3, 4} Available DAAs at the time of the study in the LatAm region were asunaprevir + daclatasvir (ASV/DCV), sofosbuvir + daclatasvir (SOF/DCV), sofosbuvir + simeprevir (SOF/SMV), paritaprevir/r/ombitasvir/dasabuvir (PrOD), ledipasvir/sofosbuvir (LDV/SOF), elbasvir/grazoprevir (EBR/GZR), sofosbuvir/velpatasvir (SOF/VEL), and glecaprevir/pibrentasvir (GLE/PIB). All DAA regimens were prescribed according to label and genotypes defined in indications. We assessed the response to DAAs therapy by measuring SVR, defined as an undetectable HCV RNA (HCV viral load <15 UI/mL), 12 weeks after completion of therapy. Laboratory operators were blind to baseline patient characteristics, treatment regimens, and primary outcome events. However, according to study protocol, standard laboratory tests including Model for End-stage Liver Disease (MELD) score and CTP score parameters, as well as assessment of the primary outcome and adverse events, were scheduled at baseline, end-of-treatment, and week 12 posttreatment in all patients.

2.4 Outcome assessment

The primary endpoint analysis was unachieved SVR. Non-SVR or DAAs failure, was defined as a failure to achieve undetectable HCV RNA at 12 weeks after completion or early discontinuation of HCV therapy. Clinical and laboratory assessments were performed at each participant hospital including HCV RNA assays with a lower detection limit of 15 IU/mL.

The secondary objective of the study was a composite end-point including safety profile evaluating adverse events according to Common Terminology Criteria for Adverse Events version 4.03 (CTCAE V4.03), new hepatic decompensation (defined as the development of ascites, hepatic encephalopathy, or variceal bleeding), development of de novo hepatocellular carcinoma (HCC), need for LT or death from any cause during and after treatment completion.¹⁹ Safety data were collected from all patients from the time of starting treatment until completion or early discontinuation as per protocol analysis. Serious adverse events (SAEs) including urgent clinic visits, hospitalizations, and/or death were thoroughly reviewed to identify the causal relationship with treatment regimen.

2.5 Statistical analysis

Categorical data were compared using Fisher's exact test (two-tailed) or χ² test as appropriate. Continuous variables are shown with mean (±standard deviation) or median (interquartile ranges [IQR] 25%-75%) and were compared with the Student t or Mann-Whitney U tests according to their distributions. SVR rates were reported with 95% confidence intervals (CIs). A multiple logistic regression analysis was performed to evaluate baseline exposure variables associated with non-SVR. Unadjusted and adjusted odds ratios (ORs) and its corresponding 95% CI were estimated to evaluate potential confounding effects, defined by a change in the crude OR larger than 20% observed step by step. Variables with a P < .1 after the univariate analysis were included in the multivariable model, generated by stepwise forward selection and comparing each model's performance with the Likelihood ratio test to prioritize a parsimonious model. To avoid overfitting, 1 variable per at least 10 events was included in the multivariate analysis. Final model's calibration and discrimination power was performed using Hosmer-Lemeshow test and receiving operator curve (ROC), respectively. All analyses were performed with STATA 13.0 (StataCorp LLC, College Station, TX).

3.1 Population characteristics

From 2167 HCV infected patients prospectively followed and enrolled in LALREAN's registry, 1938 completed 12 weeks posttreatment evaluation and were included in the analysis. The remaining 229 patients were still under treatment, and thus, SVR was not assessed at time of analysis. Baseline characteristics of the study population are shown in Table 1. The mean age of the cohort was 59 (±11) years old, with 55.4% being male. Genotype 1 was the most frequent (72.5%), followed by Genotype 3 (16.9%). Most patients presented with advanced fibrosis (Metavir Score F3-4) (67.9%) and a CPT score A of 81.3% among cirrhotic subjects. Other clinical baseline characteristics regarding HCV infection are shown in Table 2. Regarding treatment history, 1158 (64%) subjects were naive and 780 (36%) were treatment-experienced with at least one IFN-based regimen. Table 3 describes previous treatment history.

The most frequently used DAAs regimen was SOF/DCV, being applied in 68.3% patients (n = 1480), followed by PrOD in 12% (n = 260), and LDV/SOF in 6.1% (n = 132). Overall median treatment duration was 12 weeks (IQR 11.8-15.3 weeks). Ribavirin was prescribed in 809 (37.3%) patients (Table 4). Median treatment duration in noncirrhotic and cirrhotic patients was 12.0 weeks (IQR 11.8-12.3 weeks) and 12.6 weeks (IQR 12.0-23.8 weeks) (P < .0001), respectively. According to genotypes, median treatment duration was 12 weeks (IQR 11.8-17.0 weeks) in Genotype 1, 12 weeks (IQR 11.8-14.0 weeks) in Genotype 1a, 12 weeks (IQR 11.8-23.8 weeks) in Genotype 1b, 12 weeks (IQR 12.0-13 weeks) in Genotype 2, 12 weeks (IQR 11.8-24 weeks) in Genotype 3, and 12 weeks (IQR 11.8-13.8 weeks) in Genotype 4.

Overall, the SVR rate was 95.1% (95% CI, 93.9-96.1). According to fibrosis stages, the SVR rate was 95.7% (95% CI, 94.4-96.8) in F0-2% and 93.6% (95% CI, 91.1-95.5) in F3-4 patients. SVR rates were not significantly different among genotypes (P = .80) and fibrosis stages (P = .09) (Figure 1). Stratified SVR rates according to liver disease severity (noncirrhotic vs cirrhotic patients) are shown in Table 5. In noncirrhotic subjects' median treatment duration was shorter (12 weeks [IQR 11.8-12.3] vs 12.6 weeks [IQR 12-23.8]; P < .0001) and fewer patients required ribavirin (22.5% vs 49.4%; P < .0001). Regarding clinical outcomes, there was a lower rate of adverse events (20.0% [95% CI, 17.5-22.6] vs 29.8% [95% CI, 27.2-32.5]; P < .0001) and similar SVR rates (94.7% [95% CI, 92.8-96.2] vs 95.4 [95% CI, 93.9-96.6]; P = .51) when comparing noncirrhotic and cirrhotic patient groups, respectively.

3.2 Baseline variables independently associated to DAAs failure

In univariate analysis, pretreatment variables associated with DAAs failure were male gender, LT, previous IFN-based treatment, decompensated cirrhosis (CTP B or C vs A), CSPH, and platelet count less than 100 000 mm³. Independently associated variables with DAAs failure were liver function impairment according to the Child-Pugh score B OR, 2.09 (95% CI, 0.95-4.61; P = .06) and Child-Pugh C OR, 11.7 (95% CI, 3.15-43.58; P < .0001) vs Child A as reference value; decompensated cirrhosis OR, 2.40 (95% CI, 1.33-4.35; P < .0001) vs nondecompensated cirrhosis as reference value; and LT recipient OR, 3.75 (95% CI, 1.37-10.28; P = .01) (Table 6). Baseline characteristics of decompensated cirrhosis and LT patients are shown in Tables S1 and S2. There were some differences in treatment regimens according to current treatment guidelines for these special populations.

3.3 Safety

During a median follow-up period of 22.3 months (IQR 12.6-32.2 months), 91 patients presented evidence of clinical disease progression, with a cumulative incidence of 4.2% (95% CI, 3.4-5.2%). From them, 16 patients died, 66 patients presented a new liver decompensation event, 8 patients underwent LT, and 41 patients developed de novo HCC.

During treatment, any adverse event was reported in 25.4% (95% CI, 23.5-27.3%) of patients. The main adverse events were asthenia 15% (n = 325), headache 5.6% (n = 122), vomiting 3.1% (n = 67), insomnia 3.0% (n = 65), diarrhea 2.4% (n = 52), arthralgia or myalgia 1.5% (n = 32), rash 1.1% (n = 25), increased total bilirubin levels in 1.1% (n = 23), and fever 0.5% (n = 12). Definitive treatment discontinuation was observed in 1.5% of patients (n = 26) due to intolerance in one patient, access barriers in 4 patients and loss of follow-up in 18 patients.