Blog - Latest News

New evidence for the relationship between PSA value and BMI in diagnosing prostate cancer: obesity should be reckoned

Sir,

We read with great interest the paper by Oh et al. [1] and the paper by Pater et al. [2]. Their study confirmed the previously reported inverse relationship between prostate-specific antigen (PSA) value and body mass index (BMI). Indeed, they indicated a decrease in PSA for an increasing BMI with a 0.026 decrease in PSA for every unit increase in BMI. To date, the detection of prostate cancer (PCa) has become more common since the introduction of PSA, but overall mortality remains high with an estimated 27,360 deaths in 2009, and relative survival of patients diagnosed with prostate cancer has changed little.

One possible reason that screening for PCa using PSA has not achieved reduced mortality is that PSA can be confounded by weight. In fact, several previous studies have demonstrated an inverse association between PSA and BMI. Kim et al. demonstrated that PSA shows a significant linear trend only in the group with a BMI ≥ 25 kg/m with prostate examination [3].

Pater et al. investigated 767 patients, with mean BMI 28.7 kg/m2; where 78% were overweight or obese (BMI ≥25). Mean PSA was 1.28 ng/ml. Notably, 44 patients had at least 1 PSA level over 4.0 ng/ml [2]. There was a small, but statistically significant trend toward decreasing PSA for an increasing BMI.

However, multiple findings showed that obese men had lower serum PSA concentrations than normal weight men. PSA mass tended to be lower in obese patients, but is unlikely to be a consequence of lower serum testosterone concentrations. Oh et al. declared that the accuracy of PSA in predicting PCa did not change regardless of BMI category in Asian men [1]. Recently it was shown that initial PSA levels of 3471 patients were <30 ng/ml, undergoing multicore (≥12) transrectal ultrasound-guided prostate biopsy. The median PSA level in each BMI category was 7.84, 7.75, 7.33 and 5.79 ng/ml with BMI of <23, 23-24.9, 25-29.9, and ≥30 kg/m2 respectively [1]. Therefore, it may be suggested that the PSA threshold should be lower in obese men to discriminate between PCa and benign conditions in the real clinical situation. Similarly, Yang et al. recruited 20,509 native Korean men and found a statistically significant trend towards a lower likelihood of having a serum PSA level ≥2.5 ng/ml with an increased BMI [4]. These results might affect PCa screening using serum total PSA. Indeed, the relationship between obesity and PSA is confounded by a number of factors, which likely explain the observed inverse association previously reported. These data showed that obesity can help clinical staff to interpret the value of PSA in screening for PCa. Meanwhile, Li et al. demonstrated the inverse relationship between PSA concentration and BMI, and hold that this might be explained by a hemodilution effect among obese men. A value between 3.32 and 3.68 ng/ml might be recommended for PSA screening in middle-aged obese Asian men [5].

Of note, a recent study showed that the result accuracy of PSA as a predictor of PCa in 917 Italian men, performing trans-rectal ultrasound-guided prostate needle biopsy, is not significantly altered by BMI. Bañez et al. highlighted that obesity does not negatively impact the overall ability of PSA to discriminate between PCa and benign conditions [6].

In summary, available evidence has demonstrated an inverse relationship between PSA and BMI. However, much of the data regarding the role of PSA in obese patients with PCa has been obtained from distinct populations and proves controversial. Therefore, further clinical studies may be required to explore comprehensively the accurate diagnosis of prostate cancer in obese men in the real clinical situation.

Chang-ming Lin1,2, Chao-zhao Liang1*

1Department of Urology, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230032, China, 2Department of Urology, The Central Hospital of Maanshan The Affiliated Hospital of Wannan Medical College,Maanshan, Anhui 243011, China

*Correspondence: Chao-zhao Liang, e-mail: [email protected]

References

  1. Oh JJ, Jeong SJ, Lee BK et al. Does obesity affect the accuracy of prostate-specific antigen (PSA) for predicting prostate cancer among men undergoing prostate biopsy. BJU Int 2013; 112: E265–E271
  2. Pater LE, Hart KW, Blonigen BJ, Lindsell CJ, Barrett WL. Relationship between prostate-specific antigen, age, and body mass index in a prostate cancer screening population. Am J Clin Oncol 2012; 35: 490–492
  3. Kim JH, Doo SW, Yang WJ, Song YS, Kwon SS. Prostate-specific antigen density: a better index of obesity-related PSA decrease in ostensibly healthy Korean men with a PSA <3.0 ng/mL. Urology 2013; 81: 849–852
  4. Yang WJ. The likelihood of having a serum PSA level of >/=2.5 or >/=4.0 ng ml-1 according to obesity in a screened Korean population. Asian J Androl 2013; 15: 770–772
  5. Li F, Shen Z, Lu Y, Yun J, Fan Y. Serum prostate-specific antigen concentration and hemodilution among Chinese middle-aged obese men: a hematocrit-based equation for plasma volume estimation is induced. Cancer Epidemiol Biomarkers Prev 2012; 21: 1731–1734
  6. Bañez LL, Albisinni S, Freedland SJ, Tubaro A, De Nunzio C. The impact of obesity on the predictive accuracy of PSA in men undergoing prostate biopsy. World J Urol 2012; doi: 10.1007/s00345-012-0919-9

1 reply
  1. Seong Jin Jeong
    Seong Jin Jeong says:

    Sir,

    We thank Dr. Lin and Dr. Liang for their interest in our article. Our previous study about prostate specific antigen (PSA) level for predicting prostate cancer among men undergoing prostate biopsy showed that PSA level is significantly lower in obese men. However, the accuracies of PSA for predicting prostate cancer may not be significantly different in each body mass index (BMI) level [1]. Conclusively, PSA threshold should be lowered in obese men to discriminate between prostate cancer and other benign conditions.

    Although only 1.7% (58/3471) of obese men included in the Asian study had a BMI of ≥30 kg/m2, a recently published Western study showed similar results. Banez et al. [2] showed obesity did not alter PSA accuracy for predicting prostate cancer in an Italian cohort. Their cohort had a relatively large number of obese men with 21% (193/917) having a BMI of ≥30 kg/m2. They showed similarities to our previous study for the under-curve value according to BMI categories.

    An important message from these studies relates to a hemodilutional effect in obese men. Men who were obese had lower PSA level than those who were not obese. However, in a current real clinic situation, we usually recommend prostate biopsy to patients whose PSA level is above the cut off value (e.g. 3 ng/ml). But what about the total PSA amount (PSA mass) in obese men with PSA 3 ng/ml and in non-obese men with PSA 3 ng/ml? PSA mass is higher in obese men by a hemodilutional effect. Theoretically, it means a large amount of body circulating volume masked as lower PSA value, therefore we should lower the threshold in obese men. Rundle and Neugut [3] also proposed that alternative PSA thresholds should be used for prostate cancer screening, especially in obese men. Hekal and Ibrahiem [4] proposed a new formula to increase the sensitivity of PSA value in detecting prostate cancer while factoring in obesity.

    We need to validate these results in a large-scale prospective study and we also should confirm how much obesity influences the degree of accuracy for predicting prostate cancer by the current PSA cut-off value.

    Seong Jin Jeong1, Jong Jin Oh2
    On behalf of the authors

    1Department of Urology, Seoul National University Bundang Hospital, Seongnam, Korea, 2Department of Urology, CHA Bundang Medical Center, CHA University, Seongnam, Korea

    References
    1. Oh JJ, Jeong SJ, Lee BK, et al. Does obesity affect the accuracy of prostate-specific antigen (PSA) for predicting prostate cancer among men undergoing prostate biopsy. BJU Int 2013; 112: E265-71
    2. Banez LL, Albisinni S, Freedland SJ, Tubaro A, De Nunzio C. The impact of obesity on the predictive accuracy of PSA in men undergoing prostate biopsy. World J Urol 2012; doi: 10.1007/s00345-012-0919-9
    3. Rundle A, Neugut AI. Obesity and screening PSA levels among men undergoing an annual physical exam. Prostate 2008; 68: 373–80
    4. Hekal IA, Ibrahiem EI. Obesity-PSA relationship: a new formula. Prostate Cancer Prostatic Dis 2010; 13: 186–90

Comments are closed.

© 2022 BJU International. All Rights Reserved.