- To evaluate ABO blood group as a prognostic marker in patients with renal cell carcinoma (RCC).
Renal cell carcinoma is the third leading tumour type of the genitourinary tract with >60 000 new cases being diagnosed in the USA annually . Tobacco use, obesity, and arterial hypertension are modifiable risk factors for the disease , and a familial history in a first-degree relative increases the lifetime risk 1.6-fold . RCC is also associated with several genetic syndromes such as von Hippel–Lindau disease, hereditary papillary RCC, and Birt–Hogg–Dubé's syndrome . Surgery is the mainstay of therapy for RCC, and TNM stage and grade are its most established prognostic factors [5-8].
ABO blood group is a potential inherited marker of cancer susceptibility and progression. Studies show that blood group is associated with the risk of various solid malignancies [9-11], and may also serve as a prognostic marker [12, 13]. In RCC, a study conducted several decades ago suggested a relationship between blood group antigens and the risk of developing the disease , whereas other studies have reported no association [15-17]. Kaffenberger et al.  recently showed, in a cohort of 900 patients with RCC without distant metastases, that blood group O was associated with better overall survival (OS). Thus, data suggest a possible role of ABO blood group in the progression of RCC. The aim of the present study was to verify this blood group status as a prognostic marker.
The cohort of the present retrospective study consisted of 556 consecutive white patients, who underwent radical or partial nephrectomy for RCC of all subtypes and all stages at our institution between January 2002 and December 2012. Patients with familial RCC and hereditary RCC were excluded.
Patient data were collected prospectively in the institutional kidney cancer database. The database was analysed retrospectively after obtaining institutional review board approval (protocol registration number 1958/2012). Clinical, pathological, laboratory and follow-up information was gathered. Clinical data included ABO blood group, age, gender, self-reported history of smoking and body mass index (BMI). Comorbidity status was graded using the Charlson comorbidity index (CCI). Pathological data comprised histological subtype, according to the WHO classification , TNM stage, according to the 2010 criteria , and Fuhrman grade . All surgical specimens were examined by an expert urological pathologist (A.H.). N stage was assigned from radiological and pathological data. Patients with clinically positive nodes, defined as the presence of at least one node >10 mm in size in the retroperitoneal lymphatic area at preoperative imaging, underwent a node dissection. In patients with negative nodes on imaging, the node dissection was performed at the surgeon's discretion. The positive nodes reported in the present study were all confirmed pathologically. No adjuvant therapy was administered. Postoperative surveillance was performed according to established guidelines .
The continuous variables age and BMI were found to be non-normally distributed (Kolmogorov–Smirnov P > 0.3). These variables are therefore presented as median values with interquartile ranges (IQRs).
Because of the low numbers of patients in several stratums, ABO blood group was evaluated as O and non-O, as previously suggested . Univariable associations with clinical and pathological factors (age, gender, BMI, smoking history, CCI, TNM stage, grade, bilaterality and subtype) were analysed using Kruskal–Wallis and chi-squared tests, as appropriate. Significant univariable predictor variables were tested in multivariable logistic regression models.
The Kaplan–Meier product limit method was used to estimate functions for OS and RCC-specific survival (RCC-SS). Follow-up information was available for 442 of the 556 RCC patients (79.5%). The survival times were calculated from the date of surgery to the date of last follow-up, death or death from RCC, respectively. Differences in Kaplan–Meier curves were assessed using log-rank tests. Univariable and multivariable Cox proportional hazards regression models were used to evaluate the relationship of OS and RCC-SS with ABO blood group and clinical and pathological variables. To reduce the risk of over-fitting in multivariable Cox models, only factors that were significantly (P < 0.05) associated with survival in univariable analysis were included for multivariable modelling with ABO blood group. Multivariable Cox models were bootstrap-corrected to account for dichotomization bias (200 resamples). All statistical testing was two-sided and a P value <0.05 was considered to indicate statistical significance. The statistical package stata 11.2 (Stata Corp., College Station, TX, USA) was used for all analyses.
Results are shown in Table 1. Blood group O was associated with a significantly lower risk of lymph node metastases (1.0% vs 4.0%, P = 0.034). Of the 16 patients with positive nodes, 14 (87.5%) had a non-O blood group. In multivariable logistic regression analysis, non-O blood group (odds ratio [OR] 5.79, 95% CI 1.22–27.51, P = 0.027), M stage (OR 5.29, 95% CI 1.64–17.12, P = 0.005), and grade (hazard ratio [HR] 22.32, 95% CI 2.69–185.42, P = 0.004) were independent predictors of lymph node metastases.
|Variable||All patients, N = 556||Blood group||P|
|O, n = 210||Non-O, n = 346|
|Median (IQR) age, years||64 (55–72)||63 (56–70)||65 (54–73)||0.47|
|Male, n (%)||367 (49.2)||140 (66.7)||227 (65.6)||0.80|
|Median (IQR) BMI||27.0 (24.1–30.1)||27.1 (24.2–30.4)||26.9 (23.9–29.8)||0.32|
|Pack years, n (%)||0.77|
|0||358 (64.4)||139 (66.2)||219 (63.3)|
|1–40||108 (19.4)||38 (18.1)||70 (20.2)|
|>40||90 (16.2)||33 (15.7)||57 (16.5)|
|CCI >1, n (%)||239 (43.0)||85 (40.5)||154 (44.5)||0.35|
|pT stage, n (%)||0.69|
|T1–2||309 (55.6)||119 (56.7)||190 (54.9)|
|T3–4||247 (44.4)||91 (43.3)||156 (45.1)|
|pN stage, n (%)||0.034|
|pNx/N0||540 (97.1)||208 (99.0)||332 (96.0)|
|pN+||16 (2.9)||2 (1.0)||14 (4.0)|
|M stage, n (%)||0.65|
|M0||484 (87.1)||181 (86.2)||303 (87.6)|
|M1||72 (12.9)||29 (13.8)||43 (12.4)|
|Fuhrman grade, n (%)||0.74|
|1–2||399 (71.8)||149 (71.0)||250 (72.3)|
|3–4||157 (28.2)||61 (29.0)||96 (27.7)|
|Laterality, n (%)||0.017|
|Unilateral||527 (94.8)||193 (91.9)||334 (96.5)|
|Bilateral||29 (5.2)||17 (8.1)||12 (3.5)|
|Subtype, n (%)||0.48|
|Clear-cell||394 (70.9)||154 (73.3)||240 (69.4)|
|Papillary||107 (19.2)||35 (16.7)||72 (20.8)|
|Chromophobe||55 (9.9)||21 (10.0)||34 (9.8)|
Furthermore, blood group O increased the risk of bilateral RCC (OR 2.45, 95% CI 1.15–5.24, P = 0.017). Of 29 (58.6%) patients with bilateral RCC, 17 had blood group O, compared with 193 of 527 (36.6%) patients with unilateral disease. In multivariable analysis, blood group O was an independent predictor of bilateral disease (OR 0.42, 95% CI 0.19–0.87, P = 0.023), while age, gender, T stage, N stage, M stage and grade were not.
No associations of ABO blood group with age, gender, BMI, smoking history, CCI, T stage, M stage, grade or subtype were observed (Table 1).
The median (IQR) follow-up was 39 (45) months. There were 93 overall deaths, of which 61 (66%) were attributable to RCC. The 5-year OS and RCC-SS rates (±se) were 75 (±3) % and 83 (±2) %, respectively, with no difference between patients with blood group O and non-O (P = 0.33 and P = 0.99, respectively). Similarly, if blood groups were analysed unstratified as O, A, B, and AB, no differences in the Kaplan–Meier functions were seen (every P value >0.4; Fig. 1). Similar results were obtained when the cohort was stratified into non-metastatic (P = 0.14 and P = 0.75) and metastatic disease (P = 0.91 and P = 0.91). In non-metastatic disease, there was also no association with recurrence-free survival (P = 0.81). In univariable and multivariable Cox models predicting OS and RCC-SS, ABO blood group was not a significant prognostic factor (Table 2).
|HR||95% CI||P||HR||95% CI||P||HR||95% CI||P||HR||95% CI||P|
|Age >65 years||1.88||1.24–2.85||0.003||2.33||1.50–3.60||<0.001||1.64||0.98–2.73||0.06|
|Male vs female||1.25||0.80–1.95||0.33||1.25||0.72–2.17||0.43|
|T3–4 vs T1-||2.86||1.86–4.39||<0.001||1.63||0.99–2.66||0.052||7.42||3.76–14.63||<0.001||3.08||1.44–6.60||0.004|
|N+ vs Nx/0||9.23||4.88–17.46||<0.001||4.04||1.97–8.29||<0.001||14.95||7.69–29.07||<0.001||3.63||1.76–7.46||<0.001|
|M1 vs M0||8.11||5.30–12.39||<0.001||5.99||3.70–9.70||<0.001||18.83||10.96–32.37||<0.001||10.20||5.53–18.82||<0.001|
|Grade 3/4 vs 1/2||3.05||2.02–4.60||<0.001||1.85||1.16–2.96||0.010||5.25||3.09–8.95||<0.001||2.23||1.21–4.10||0.010|
|Non-clear-cell vs clear-cell||0.96||0.61–1.50||0.84||0.75||0.41–1.36||0.34|
|Bilateral vs unilateral||0.88||0.41–1.91||0.75||0.81||0.29–2.24||0.69|
|Blood group non-O vs O||0.82||0.54–1.23||0.33||0.72||0.48–1.10||0.13||1.00||0.60–1.67||0.99||0.86||0.51–1.45||0.56|
In the present study, we analysed the association of ABO blood group with clinicopathological factors and prognosis of patients with RCC. Blood group O was associated with the absence of lymph node metastases and the presence of bilateral RCC, but was not linked to survival.
The primary goal of our study was to validate ABO blood group as a prognostic factor. Recently, Kaffenberger et al.  found in a cohort of 900 patients without distant metastases that blood group O was associated with improved OS. The 3-year OS rates were 75% for patients with blood group O and 68% for those with blood group non-O. In the multivariable analysis, patients with blood group non-O had a 1.68-fold greater risk of death from all causes. In addition, a nonsignificant trend (P = 0.065) was observed for RCC-SS. In the present study, we could not demonstrate a survival difference between patients with blood group O and non-O. There are several possible explanations for the discrepancy between the two studies. First, the inclusion criteria differed. We included patients of all stages, whereas Kaffenberger et al.  excluded patients with distant metastases. This difference in inclusion criteria, however, should have been balanced with multivariable modelling. Second, the distribution of blood groups differs among countries and races and thus among the institutions, which subsequently affects statistical power. Finally, a significant association may have been blurred by the lower number of patients (n = 556) and the relatively low number of events (n = 93), so that the present study may have been underpowered to detect a significant difference. The β error may have been a limitation of the present study, i.e. that the null hypothesis (no survival difference) is false, but is not rejected; however, it is also possible that a significant difference would not have been detected with more patients and events. To the best of our knowledge, no other data regarding the prognostic impact of ABO blood group in RCC are available. Further studies are necessary.
Our data suggest that blood group O is associated with a lower risk of lymph node metastases. As the number of patients with positive nodes was small (n = 16) and the majority of these patients presented with concomitant distant metastases, this did not translate into a survival difference in either univariable or multivariable analyses. Data suggest that different routes of metastatic spread (lymphatic vs haematogenous spread) are the result of unique biological propensities . One could thus hypothesize that blood group O may be protective with regard to lymphatic, but not haematogenous spread. Our finding is in contrast to the study by Kaffenberger et al. , who reported no association with lymph node involvement. This may, in part, be attributed to selection bias, as these authors excluded patients with distant metastasis. We did not exclude patients with distant metastases; these patients accounted for the majority of those with metastatic lymph nodes. The results of the present study further suggest that blood group O is associated with bilateral RCC. To the best of our knowledge, this is the first study showing this relationship. Reflecting the overall low incidence of positive nodes and bilateral disease, our data are derived from a small number of patients. The present study generates hypotheses, and external validation in larger datasets is necessary.
The mechanisms through which blood group may influence cancer risk and progression are largely unknown. The ABO gene is located on chromosome 9q34 and is encoding for glycosyl-transferases, which catalyse the transfer of sugars to the H antigen to form the blood group antigen . The O allele encodes a non-functional glycosyl-transferase and the H antigen, which leaves the H antigen unaltered. ABO blood group antigens are expressed on red blood cells and several other normal and tumour tissues, including the kidney and several RCC cell lines [24, 25]. Blood group antigens may contribute by modifying cell adhesion, membrane signalling, and immune surveillance, which may in turn affect cancer development and progression . These processes may in part be influenced by TNF-α, as polymorphisms at the ABO gene locus are linked with TNF-α serum levels .
The best data on the impact of ABO blood group on cancer risk and survival come from studies on pancreatic cancer. Two large, independent, prospective cohort studies showed that the risk of pancreatic cancer is increased 1.32–1.72-fold if a non-O blood group is present . Moreover, it has been shown that a non-O blood group decreases the risk of skin cancer  and that the B antigen increases the incidence of ovarian cancer , while other studies have not shown an association of blood group with cancer risk [16, 30]. A few studies have investigated the role of blood group as a prognostic marker in malignancies other than RCC, with varying results [12, 13, 18, 30].
The present study has several limitations. Its design was retrospective and we analysed a relatively small cohort of patients with a short follow-up. Some hypotheses, e.g. that blood group O is associated with the absence of lymph node metastases and the presence of bilateral RCC, are generated from sub-analyses of small cohorts and should be confirmed with larger datasets. The study did not confirm the previously reported association of ABO blood group with OS , but our analysis may have been underpowered to detect a significant difference. Since the study population and inclusion criteria differed considerably, the two studies should be interpreted as complementary, not oppositional. We suggest that there is a different impact of ABO blood group on survival, although our conclusions are limited.
In conclusion, the present study showed ABO blood group was not associated with RCC prognosis. Blood group O was, however, associated with the absence of lymph node metastasis and the presence of bilateral RCC. External validation of these findings on larger well-defined cohorts is necessary.
body mass index
Charlson comorbidity index