Renal cell carcinoma survival and body mass index: a dose-response meta-analysis reveals another potential paradox within a paradox.
In healthy subjects increasing body mass index (BMI) leads to greater mortality from a range of causes. Following onset of specific diseases, however, the reverse is often found: called the 'obesity paradox'. But we recently observed the phenomenon called the 'paradox within the paradox' for stroke patients.



The objective of our study was to examine the effect of each unit increase in BMI on renal cancer-specific survival (CSS), cancer-specific mortality, overall survival (OS) and overall mortality.



Random-effects generalized least squares models for trend estimation were used to analyze the data. Eight studies, comprising of 8699 survivals of 10 512 renal cell carcinoma (RCC) patients met the inclusion criteria, including 5 on CSS and 3 on OS.



The association of BMI with CSS and OS was non-linear (P<0.0001, P=0.004, respectively). We observed that CSS increased in relation to BMI, indicating that there was the obesity paradox in RCC. However, each unit increase in BMI over 25 was associated with decreased OS, indicating that RCC may also exhibit a paradox within the paradox.



Inconsistent effects of increases in BMI on CSS and OS, as previously observed for stroke, creates a paradox (different directions of mortality for different causes) within the obesity paradox.
Department of Community Nutrition, School of Nutritional Sciences and Dietetic, Tehran University of Medical Sciences, Tehran, Iran.|Students' Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran.
M
M
Bagheri
Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK.|State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
J R
JR
Speakman
Department of Community Nutrition, School of Nutritional Sciences and Dietetic, Tehran University of Medical Sciences, Tehran, Iran.
F
F
Shemirani
Department of Clinical Nutrition, School of Nutritional Sciences and Dietetic, Tehran University of Medical Sciences, Tehran, Iran.
K
K
Djafarian
D015992:Body Mass Index; D002292:Carcinoma, Renal Cell / Q000401:mortality* / Q000503:physiopathology; D006801:Humans; D007680:Kidney Neoplasms / Q000401:mortality* / Q000503:physiopathology; D009765:Obesity / Q000401:mortality* / Q000503:physiopathology; D016016:Proportional Hazards Models; D012307:Risk Factors
JAMA. 2013 Jan 2;309(1):71-82
23280227
J Korean Med Sci. 2013 Feb;28(2):227-36
23400428
Int J Stroke. 2015 Jan;10(1):99-104
25635277
J Natl Cancer Inst. 2013 Dec 18;105(24):1862-70
24285872
Prog Cardiovasc Dis. 2014 Jan-Feb;56(4):415-25
24438733
N Engl J Med. 2010 Dec 2;363(23):2211-9
21121834
Am J Clin Nutr. 2005 Mar;81(3):543-54
15755821
Urology. 2006 Oct;68(4):741-6
17070345
Int J Obes (Lond). 2014 Aug;38(8):1110-4
24173404
Int J Urol. 2013 Jun;20(6):585-92
23176631
Mayo Clin Proc. 2014 Aug;89(8):1080-100
25039038
Eur Urol. 2011 Jun;59(6):923-8
21295907
Am J Med. 2007 Oct;120(10):863-70
17904457
BJU Int. 2008 May;101(10):1243-6
18261150
Clin Genitourin Cancer. 2013 Dec;11(4):458-64
23810440
Kidney Int. 2003 Sep;64(3):1138; author reply 1138
12911569
Cancer Causes Control. 2012 Mar;23(3):505-11
22350955
J Am Coll Cardiol. 2004 Apr 21;43(8):1439-44
15093881
Prog Cardiovasc Dis. 2014 Jan-Feb;56(4):401-8
24438731
Mayo Clin Proc. 2014 Aug;89(8):1033-5
25092364
Stat Med. 2008 Mar 30;27(7):954-70
17676579
Stroke. 2011 Jan;42(1):30-6
21127299
Clin Geriatr Med. 2009 Nov;25(4):643-59, viii
19944265
Am J Epidemiol. 1992 Jun 1;135(11):1301-9
1626547
J Bone Miner Res. 2014 Aug;29(8):1737-44
24615695
Int J Cancer. 2013 Feb 1;132(3):625-34
22610826
BMJ. 2007 Dec 1;335(7630):1134
17986716
Prog Cardiovasc Dis. 2014 Jan-Feb;56(4):409-14
24438732
Kidney Int. 2003 Mar;63(3):793-808
12631061
J Urol. 2006 Jan;175(1):46-52
16406867
Am J Clin Nutr. 2004 Aug;80(2):324-32
15277152
Diabetes Care. 2013 Aug;36 Suppl 2:S276-81
23882059
Lancet. 2009 Mar 28;373(9669):1083-96
19299006
Ann Epidemiol. 2005 Feb;15(2):87-97
15652713
Prog Cardiovasc Dis. 2014 Sep-Oct;57(2):127-33
25216611
Neurology. 2011 Feb 8;76(6):567-73
21228300
J Urol. 2010 Feb;183(2):448-54
20006879
Scand J Urol Nephrol. 2011 Feb;45(1):5-14
20846080
Obes Rev. 2015 May;16(5):416-23
25753533
Am Heart J. 2008 Jul;156(1):13-22
18585492