Little information exists regarding the epidemiology of renal cell carcinoma (RCC) in South Africa, or Africa [1]. There are global disparities in the incidence of RCC, with a higher incidence in Europe and North America and a lower incidence in Asia and South America [2]. There are also known population group and gender disparities with regards to stage at presentation and prognosis of RCC.
Studies from the USA have shown a significantly increased incidence of RCC and lower associated survival rate in African American and Hispanic patients, with poorer survival in African American patients, despite presenting at a younger age and earlier stage [3, 4] Possible explanations include socioeconomic factors, increased presence of comorbidities such as hypertension, or genetic factors [4]. Presentation in Africa is typically at a younger age and with a more advanced stage [5, 6].
In recent years, there has been a plateau in the incidence of RCC, after decades of increase [7]. A downward stage migration has occurred to favour smaller, organ confined tumours, likely due to more liberal use of imaging modalities [2]. Incidental discovery is now the most likely presentation of RCC in much of the world, with 82% of masses less than 4 cm and 56% of those greater than 6 cm discovered incidentally [8,9,10]. In contrast, one study from South Africa reported the median size at presentation as 10 cm, with only 26% being smaller than 7 cm (stage T1) [1]. Globally, men have almost double the risk of developing RCC, and also an increased mortality rate from RCC, with females being 19% less likely to die from the disease [11]. The incidence of RCC steadily increases with age according to the Surveillance, Epidemiology and End Results (SEER) database, peaking between 60 and 70 years, with an impression of declining incidence after 70 years. This might be explained by less aggressive diagnostic pursuit in the elderly [3].
Histologically the most common forms of RCC are clear cell RCC (70–75%), papillary RCC (10%) and chromophobe RCC (5%) [12]. Data from Africa are lacking, but one study from Nigeria showed a marked difference in pathological profile compared to global data, with clear cell (47%) comprising a much lower proportion of cases than usual, while papillary RCC (30%) and chromophobe RCC (17%) were more common than global incidences [5].
There are several defined risk factors for RCC. Smoking is an independent risk factor for RCC, the risk is cumulative and dose dependent [13]. Obesity has been estimated to account for over 30% of RCC cases in Europe and 40% of cases in the USA [14]. The hazard ratio for patients with a body mass index (BMI) above 35 kg/m2 is 1.8 compared to patients with a normal BMI [15]. Although obesity and hypertension are frequently present in the same patient population, there is evidence that hypertension is an independent risk factor for the development of RCC [16].
This study is the first of its type, designed to give an accurate report on the demographics, stage, pathological profile and risk factors for RCC in a South African centre and to compare the results to global and other African studies. We also evaluated if the presence of known risk factors for RCC translates into a more advanced stage at presentation, or a higher International Society of Urologic Pathologists (ISUP) grade.