Please could you give a brief introduction to the different forms of kidney cancer?
There are two major forms of kidney cancer. One is called renal cell cancer, which is an adenocarcinoma that occurs in the renal parenchyma. The other major type is called renal pelvis cancer, which is mostly of transitional cell type and they form in the centre of the kidney where the urine collects.
Within the renal cell carcinoma there are histological subtypes. The two major forms are the clear cell renal cell carcinoma and the papillary adenocarcinoma. But there are many other types.
Which form of kidney cancer did your recent research look at and how common is this form?
We looked at renal cell carcinoma which accounts for around 90% of the kidney cancers, so it is the most common type of kidney cancer.
How did your research into the survival rates of kidney cancer patients originate?
I have been interested in kidney cancer for many years - since the 1990’s. First we discovered that kidney cancer incidence rates are increasing and they are increasing more rapidly in African Americans than in Caucasian Americans. Because of this, there has been a crossover in incidence rates, which used to be lower in African Americans, but since the mid-1990’s, the incidence rates of renal cell carcinoma are higher in African Americans than Caucasian Americans.
In our previous research, we identified that obesity, high blood pressure, and cigarette smoking are risk factors for renal cell carcinoma, and that the increasing prevalence of obesity and hypertension probably have contributed to the increasing incidence trends of this cancer and the more rapid increases among African Americans. As the next step of our research, we wanted to know if there is racial disparity in survival of renal cell carcinoma patients, and if so, what may be the contributing factors to the disparity.
What did your research involve?
We looked at the data collected by the National Cancer Institute’s Surveillance Epidemiology and End Results (SEER) program. This included kidney cancer incidence and survival data reported by population-based cancer registries to the SEER program. Our research included data from registries in 12 geographic areas, covering about 14% of the U.S. population.
The registries collected clinical data such as cancer stage, size, histological subtype, and treatment, and also follow-up the patients for survival status. We looked at the 5 year relative survival rates of renal cell carcinoma patients stratified by clinical and demographic characteristics of the patients.
What did your research find?
We found that, in general, survival rates are better when cancer is caught at an early stage, when the tumors are of a smaller size. But even within the stages, tumor sizes, treatment categories and cell types, African Americans consistently have poorer survival than Caucasian Americans.
How do you think these results can be explained?
It is difficult to explain at this point, because it cannot be explained by the data that we have. It cannot be explained by age, gender, stage, size, treatment or even cell type. But our study did not have information on renal cell carcinoma risk factors, such as high blood pressure and obesity status, so we cannot examine their association with survival or whether adequate control of these conditions may improve survival patterns.
Did your research account for other factors that may explain these disparities?
Our study accounted for many important demographic and clinical characteristics, such as age, gender, and cancer stage, size, histologic subtype and treatment. However, as I mentioned earlier, we did not have information on comorbidity, such as obesity and hypertension, or changes in lifestyle after cancer diagnosis, access to follow-up care, or social support that may affect survival.
What impact do you think your research will have?
At this point, we do not have enough information to give advice in terms of policy on what needs to be done in order to reduce racial disparity in renal cell carcinoma patient survival. In general, the earlier the cancer diagnosis the better is the survival. Also, I think clinicians should be aware that such a potential disparity exists.
Do you have plans for further research into kidney cancer survival rates?
Yes, we are making plans to follow up this unexplained disparity. In order to take this to the next level, we would need information on the patients’ risk factors – this would be in addition to the clinical and treatment information that we already had in this study. We would also need information on the quality of survival, lifestyle changes after cancer diagnosis, etc.
Where can readers find more information?
They can find our paper here: http://onlinelibrary.wiley.com/doi/10.1002/cncr.27690/abstract
If people would like more information on kidney cancer in general, the National Cancer Institute has very good information: http://www.cancer.gov/
Also, the American cancer society has useful information: http://www.cancer.org/
As well as the Kidney Cancer Association: http://www.kidneycancer.org/
About Dr Wong-Ho Chow
Dr. Wong-Ho Chow, who joined the University of Texas M.D. Anderson Cancer Center as a Professor of Epidemiology in June, 2012, was a Senior Investigator at the U.S. National Cancer Institute where she spent over twenty years conducting cancer epidemiologic research.
Her research focuses on cancers that are rapidly increasing in incidence or that have disparate occurrence in population subgroups for clues to etiology and preventive strategies.
Among the cancers that Dr. Chow has researched include renal cell carcinoma, which has been increasing rapidly over the past four decades. In her seminal work published in the New England Journal of Medicine in 2000, Dr. Chow showed that risk of developing renal cell carcinoma increased with increasing levels of body mass and blood pressure, and that better control of hypertension may temper the risk.
Recently, Dr. Chow and colleagues reported that hypertension explains a substantial portion of the excess renal cell carcinoma incidence among African Americans compared to their Caucasian counterparts.