4. Discussion
The development of VEGF pathway blocking agents led to a significant
breakthrough in the outcome of mRCC patients. Besides, immune checkpoint
inhibitors are used either alone or in combination with VEGF blocking
agents for the treatment mRCC patients [20, 21]. With the
availability of alternative treatment options, novel prognostic markers
are of paramount importance to provide better personalized treatments.
Current prognostic scoring systems have been developed based on clinical
and laboratory parameter values [3, 4]. Obesity is not included
among these values, and its impact on the prognosis of mRCC patients is
still controversial [22]. For this reason, in addition to BMI; VBC
measurements, suggested as more reliable indicators of obesity, have
been investigated in our study. In the present study, the impact of
baseline VBC and sarcopenia parameters as well as their post-treatment
changes at the third-fourth month in the mRCC patients treated with
targeted therapy were analyzed. To the best of our knowledge, we for the
first time analyzed the associations of several VBC parameters and their
changes with PFS and OS in one cohort. Although obesity is a
well-defined risk factor for RCC; as a paradox to this situation, we
found that TATI, SATI, and VATI were independent predictive factors for
OS.
Body composition may be defined as the amount and distribution of lean
tissue, fat tissue, and bones. Up to this decade, studies on body
composition and clinical outcomes of mRCC have been mainly investigated
with BMI values. However, the exact amount of fat tissue or rate of fat
to muscle tissues could not be predicted from BMI values alone. With
advances in imaging technologies, specific analysis of muscle and fat
tissue may be obtained from CT taken for the staging of oncologic
diseases, and response assessment purposes. Thus, in addition to BMI,
the studies focused on the measurement of SAT and VAT components of the
intra-abdominal fat tissue at the umbilicus-level using CT. Steffens et
al. conducted a study focusing on the impact of VAT and SAT on the
prognosis of 116 mRCC patients and found that contrary to the BMI, above
average values for VFA and SFA are related to longer PFS and OS in mRCC
patients (SAT; HR: 3.41, 95% CI: 1.61–7.25, P=0.001; VAT; HR: 2.97,
95% CI: 1.36–6.47, P=0.006) [8]. Ladoire et al. assessed the
prognostic value of SAT, VAT, and BMI in 64 mRCC patients treated with
targeted therapy using same measurement techniques as in the Steffens’
trial [17]. However, they reported that high VAT was associated with
significantly worse OS (HR: 6.26, 95% CI: 2.29–17.08,
P<0.001) [17]. The contradicting results in these studies
may have been due to cut-off points not defined per gender and/or CT
measurements of VBC through umbilicus level. It would be incorrect to
evaluate the CT measurements taken at this level to estimate the
full-body fat and muscle tissues. Hence, VAT and SAT were not associated
with prognosis of mRCC in a study by Antoun et al. when these
measurements were performed on a more appropriate level as L3 and
adjusted per gender [19]. Additionally, these studies were performed
with baseline measurements. Based on these results, VBC were measured
with at the L3 level and adjusted according to gender in the present
study and we also evaluated the effect of CT measurement changes (the
value between the initial CT and the CT performed 3-4 months after
treatment initiation) on PFS and OS.
Nevertheless, the present study had several limitations. Firstly, the
study population was relatively small and consisted of single-center
patients. Secondly, the present study had a retrospective design and the
relatively short median follow-up time. Furthermore, because most
patients in our cohort were categorized as an intermediate-risk group
(61%), our results should be further investigated in favorable and poor
risk groups in a more homogeneous population. From this perspective,
these disparate results in the literature mentioned above may emerge
from an disparity in prognostic factors not regulated in one study than
in another.