Analysis: Therapies Equally Effective in African Americans with SSc-ILD

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

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African Americans with interstitial lung disease (ILD) caused by scleroderma (SSc-ILD) had largely similar outcomes compared to non‐African Americans in two clinical trials testing immunosuppressive therapies, according to an analysis. 

Because all trial participants received the same treatment and follow‐up, the worse outcomes for African Americans with SSc-ILD found in prior studies may reflect other factors such as access to care, the scientists said. 

The analysis, “Racial Disparities in Systemic Sclerosis: Short‐ and Long‐Term Outcomes Among African American Participants of SLS I and II,” was published in the journal ACR Open Rheumatology. 

Several studies have demonstrated that African Americans with scleroderma have a worse prognosis and are more likely to have heart, kidney, and lung involvement, along with a higher disease incidence and prevalence than non‐African Americans.

While some studies also suggest higher mortality rates among African American patients, others have found that difference decreases after adjusting for socioeconomic status.

A way to further understand racial disparities in scleroderma is to examine the outcomes from well-controlled clinical trials, as all participants receive standardized treatment and follow‐up, as well as equal access to care.

To this end, researchers in the U.S. examined the severity and progression of lung disease among African Americans who participated in two clinical trials: Scleroderma Lung Studies (SLS) I (NCT00004563 and follow-up NCT01762449); and SLS II (NCT00883129). A secondary objective was to compare the long-term morbidity and mortality between African American and non‐African American patients.

SLS I assessed the effects of Cytoxan (cyclophosphamide, from Bristol Myers Squibb) on lung function in scleroderma patients with ILD (progressive scarring of lung tissue). SLS II compared CellCept (mycophenolate mofetil, by Roche) to Cytoxan treatment on lung function and health-related symptoms in SSc-ILD patients. 

The primary goal of SLS I and SLS II was to assess lung function as measured by forced vital capacity (FVC) — the total amount of air exhaled after taking a deep breath. An additional goal was changes in the diffusing capacity for carbon monoxide (DLCO), or the lungs’ ability to transfer oxygen into the bloodstream. 

Also, SLS I assessed long‐term morbidity and mortality for up to 12 years, while SLS II assessed these parameters for up to eight years. 

Of the 158 SLS I participants with SSc-ILD, 26 (16.5%) were African Americans, a lower percentage than in SLS II (23.2%). 

In SLS I (Cytoxan and placebo), no difference in FVC between African Americans and non‐African American participants was found from three to 24 months (two years). African American patients experienced a faster FVC decline from 18 to 24 months, but this was not statistically significant.

In those who received Cytoxan in SLS II, African Americans had an improved lung function response compared with non‐AA participants from three to 12 months. This effect was not observed in those who received CellCept. 

“One possible explanation for these observations is that AA [African Americans] may demonstrate a preferential treatment response to [Cytoxan],” the researchers wrote. 

However, after Cytoxan treatment concluded, African American participants had a faster decline in the FVC compared with non‐African American participants, indicating that “in addition to upfront aggressive therapy for SSc‐ILD, AA patients may need to be monitored more closely for ILD progression when therapy is stopped,” the team wrote.  

In the group on CellCept in SLS II, the scientists found no difference in the course of FVC, and both groups demonstrated a similar improvement in this parameter.

Also, no difference was seen in DLCO change between African Americans and non‐African American participants throughout two years in both Cytoxan and placebo groups in SLS I. Likewise, no differences were seen between these patients in the Cytoxan and CellCept groups in SLS II. 

Apart from significant treatment effects favoring Cytoxan over placebo, scores based on CT scans found no differences between African American and non‐African American participants up to one year in SLS I, and over two years in both Cytoxan and CellCept groups in SLS II. 

No African Americans died during the two years of SLS I, and long-term follow-up found no significant difference in long‐term survival comparing to non‐African American participants. After adjusting for age, FVC, and the modified Rodnan skin score (a measure of skin thickness) before the study, being African American with SSc-ILD did not correlate with time to death. 

Over the two years of SLS II, two African American participants (6.1%) died compared with 14 non‐African American(12.8%). In the long-term follow-up, the team found a non-significant trend for improved long‐term survival in African Americans. No association of being African American with time to death was seen, as in SLS I.

These results suggested “there may be other factors mediating the relationship between AA race and health outcomes reported in prior observational studies, such as access to care,” the scientists wrote. 

In SLS I, no difference was found in time to respiratory failure requiring either supplemental oxygen or lung transplant between African Americans and non‐African American participants. A trend for longer time to respiratory failure was seen in African American participants in SLS II, which disappeared after adjustments. 

“In summary, the present study demonstrated that when AA patients with SSc‐ILD are treated early and aggressively with upfront immunosuppressive therapy, they have similar rates of ILD progression and long‐term morbidity and mortality outcome, as non‐AA patients,” the researchers wrote. “These findings should motivate us to help ensure that our AA patients with SSc have the same follow‐up and treatment opportunities as our non‐AA patients with SSc.”