The results of the present study suggest that IOM mass index is not associated with BCR after RP in Korean men. The present study is the first to show no significant association between IOM mass index and BCR in men with RP. Thus, IOM mass index may not be a prognostic marker for BCR in Korean men with localized PCa undergoing RP.
Previous studies suggest that high BMI is associated with increased risk of PCa.15, 16 A meta-analysis by Bergstrom et al. reports a 6% increase in the risk of PCa in overweight men and a 12% increase in obese men compared with men of normal weight.16 Maclnnis et al. reported a weak positive association between BMI and risk of PCa; BMI was associated with moderate increase in the risk of advanced PCa.15
The relationship between BMI and BCR after RP remains controversial. Freedland et al. reported that obesity among men treated with RP was associated with high-grade tumors, a trend toward increased risk of a positive surgical margin, and high BCR.17 Magheli et al. reported that high BMI is associated with adverse pathological findings and is a strong independent predictor of BCR after RP.18 Asmar et al. reported that both obesity and hypertension are associated with an increased risk of BCR after RP, independent of age at the time of diagnosis or tumor pathological features.19 By contrast, Tomaszewski et al. reported that obesity is not associated with adverse pathologic features, positive surgical margin, or BCR.20 They suggested that their data provide evidence that obese men undergoing RP are not more likely to suffer PCa progression. In addition, Siddiqui et al. reported that obese patients appeared to have worse pathologic features at the time of prostatectomy; however, BMI did not appear to be an independent predictor of recurrence or survival after prostatectomy.21 The present study found no association between BMI and BCR. Therefore, we believe that the relationship between BMI and BCR after RP remains unclear.
Sarcopenia is a process associated with normal aging; however, it is exacerbated by the hypercatabolic state and inflammatory responses caused by malignancy.22 A systematic review by Joglekar et al. investigated the impact of sarcopenia on outcome following surgical resection of cancer and reported that sarcopenia is an independent prognostic factor for both complications and survival following surgical resection.23 Sarcopenia is a more objective and comprehensive pre-operative risk factor that predicts all-cause survival for bladder cancer after radical cystectomy (RC).9, 24 With respect to PCa, several reports link sarcopenia and survival 12, 25. Thus, sarcopenia could be used to predict non-cancer-related death in men with PCa after RT 12 and may be a poor prognostic factor for CRPC treated with chemotherapy.25 However, the association between sarcopenia and survival after RP is very unclear. Long-term follow-up studies are necessary to identify (or not) any association between sarcopenia or IOM mass index and survival.
We recognize that this study has several limitations. First, we only measured internal obturator muscle mass, but not SMI. In general, SMI was defined as the cross-sectional area of the rectus abdominis; internal, external, and transverse obliques; psoas; quadratus lumborum; and erector spinae muscles from L3 down. However, because this was a multi-institutional study, different authors have different protocols for pre-operative CT and MRI. Therefore, we selected only the internal obturator muscle area in the pelvis in the MRI, because of internal obturator muscle is the oncly measurable muscle in the pelvis MRI axial cut. So, we couldn't compared IOM mass with general SMI. Second, many patients who underwent RP at these institutions were excluded from the analysis due to differences in CT or MRI protocols. In some institutions, radiologists were not able to measure the internal obturator muscle at the same levels. Third, the follow-up period was too short to get an accurate picture of survival. In this case we did not examine cancer-specific or overall survival; studies may need follow-up data spanning more than 15 years to get an accurate picture of the association between IOM mass index and the survival of PCa patients.