Marked differences in renal cell carcinoma (RCC) subtype were observed by race and by sex in patients who underwent nephrectomy at a large tertiary care academic center, a new study showed. Even after multivariate adjustment for RCC risk factors, results showed that black patients and men were significantly more likely to have papillary RCC compared with white patients and women.
“These observed racial differences in histologic subtype distributions may have important treatment implications, as the majority of targeted therapies for advanced RCC target clear cell histology,” wrote researchers led by Loren Lipworth, ScD, of Vanderbilt University Medical Center. “Therefore, black patients may be less likely to achieve benefit from available systemic treatments as they frequently develop other histologic subtypes of RCC.”
The study was a single-center retrospective examination of RCC samples taken from 1,532 consecutive patients who underwent partial or radical nephrectomy at Vanderbilt University Medical Center between 1998 and 2012. The researchers classified tumor samples as clear cell, papillary, chromophobe, and “other” RCC subtypes. They used multivariate logistic regression to estimate odds ratio for subtypes associated with race, sex, age, end-stage renal disease, and body mass index at diagnosis. The results of the study were published in BJU International.
Of the study population, 91.6% were white and 8.4% were black. Median age at surgery and distribution of BMI did not differ greatly between white and black patients. However, a higher proportion of black patients (19%) had end-stage renal disease compared with white patients (1.3%). The majority of patients in the study had clear cell RCC (72.9%); fewer had papillary (15.7%) or chromophobe (5%) subtypes.
Data showed that a significantly higher proportion of black patients had the papillary RCC subtype (35.7% vs 13.8%) and chromophobe RCC subtype (6.2% vs 4.9%) compared with white patients. Papillary cases of RCC were more than 4 times more likely to be in black patients (OR = 4.15; 95% CI, 2.64–6.52). In addition, data showed that 63.6% of RCC tumors in black patients were classified as stage T1 compared with 56.2% among whites. Specifically, 71.7% of papillary and 65.8% of chromophobe subtypes were classified in this earlier stage compared with 55% of clear cell subtypes.
“In our study papillary tumors were more likely than clear cell tumors to be small and localized, and to present more frequently among blacks, perhaps partially explaining the descriptive epidemiology trends,” the researchers wrote. “It is possible that papillary RCC tumors are less biologically aggressive, and therefore diagnosed at an earlier stage than other types of RCC.”
Differences in subtype were also found by sex. Cases of papillary RCC were less likely to be found in women (OR = 0.60; 95% CI, 0.43–0.83) compared with men. In addition, cases of chromophobe were more likely to be found in woman compared with clear cell cases (OR = 2.32; 95% CI, 1.44–3.74).
Finally, patients with papillary (OR = 6.26; 95% CI, 2.75–14.24) and chromophobe RCC subtypes (OR = 7.07; 95% CI, 2.13–23.46) were more likely to have end-stage renal disease compared with clear cell RCC cases.
The researchers concluded that “a lack of therapeutic options targeting histologies common in blacks, and a lack of focus on outcomes among black participants in clinical trials, may lead to a significant disparity in treatment efficacy among blacks.” However, they added that more research on the topic is needed.