This prospective study aimed to assess the impact of visceral obesity on clinical outcomes and QOL in MM patients enrolled in the BMT CTN 0702 trial. The results showed that visceral obesity, as measured by WHR, was not associated with any significant difference in clinical outcomes or QOL in MM patients who underwent HCT. Importantly, more African-Americans had higher BMI but low WHR in comparison to White patients but there was no difference in outcomes based on race or age. Given a high number of enrolled patients resulting in relatively low type II error and high power to detect a difference in outcome based on visceral obesity, the negative result of our study can be informative. Furthermore, our finding suggests obesity should not count as an important decision making factor when it comes to HCT eligibility for MM. Hence, commonly used Comorbidity indices such as Sorror score [29] that includes obesity as important prognostic factor, should not be extrapolated for MM patients.
Trajectories of quality-of-life recovery and symptom burden after HCT from this trial were reported previously [25]. Survivors of MM who achieve disease control after HCT experience a significant recovery in FACT-BMT and subscale scores, with scores returning to population norms within one year of HCT. However, many patients still report moderate to severe symptoms at the one-year mark and beyond, including frequent infections, and gastrointestinal and skin problems. In this study, we investigated whether obesity assessed by BMI either WHR would predict worse QOL, but we found no significant association between neither, whether as a binary or continuous variable. Further, overall QOL outcomes after adjusting for factors such as race, gender, age, KPS score, and treatment regimen did not differ.
Interpreting reports of obese patients undergoing HCT is challenging due to variations in obesity definitions, underlying disease and chemotherapy preparative regimens used. Additionally, the lack of a consistent standard for calculating chemotherapy doses in this population makes it challenging to interpret these findings. Future studies using specific regimens in this population are urgently needed [12].
Our study provides a prospective approach, which allowed for accurate measurement of anthropomorphic variables and minimized the risk of race- or age-related biases. The standardized techniques for measuring anthropomorphic variables across all participating sites further enhance the feasibility of acquiring WHR and ensuring reliability of the data. Melphalan dosing was also standardized and uniform in this study based on patient weight.
WHR is emerging as a strong tool enabling practitioners to assess cardiometabolic risk associated with increased adiposity in adults. Unequivocal evidence supporting its superiority to BMI lead to recommendations regarding this measurement as ‘vital signs’ in routine clinical practice [30]. STaMINA trial utilized the measurement for the first time in the field as a better indicator for visceral fat. Despite that, our study didn’t show a clinical difference in outcomes using this measure.
Although we used a valid as well as feasible method to assess fat distribution, WHR probably does not capture a full topography of adipose tissue throughout body. Modern imaging technology provides even more accurate approaches to quantitate body fat and characterize its distribution. Total body dual energy X-ray absorptiometry (DEXA) scans, often employed for diagnosing osteoporosis or osteopenia, can be used to also distinguish fat mass and lean body mass, assess regional distribution and provide quantitative estimates of components and total adiposity. Other techniques, such as magnetic resonance imaging (MRI), now are also used to provide images to quantitate visceral and subcutaneous adipose tissue volume and ectopic fat [31, 32]. These technologies provide high dimensional data on fat composition (e.g., three-dimensional volume of visceral, abdominal subcutaneous and gluteofemoral adipose tissue) that can be utilized to train machine learning models predicting health risks associated with different levels and patterns of adiposity [33, 34].
Despite these strengths, there are limitations to this study that should be acknowledged. First, although our data were collected prospectively, this approach was a secondary data analysis of the BMT CTN 0702 trial, which was not designed specifically to assess the impact of obesity on MM outcomes. Second, the follow-up period for this study was relatively short, which may have limited the ability to detect differences in long-term outcomes. Finally, there might be an inherent selection bias as patients enrolled on a clinical trial generally have better functional and socioeconomic status and easier access to anti-cancer therapies at an earlier stage [35]. These factors could potentially jeopardize the generalizability of the negative finding of this trial.
In conclusion, this study suggests that visceral obesity, as measured by WHR, is not associated with any significant difference in clinical outcomes or QOL in MM patients who underwent HCT. While the use of WHR is a significant improvement over previous studies that relied upon BMI alone, we could not detect a clinically meaningful difference between using BMI and WHR. Further studies are needed to confirm these findings and to assess the impact of visceral obesity using modern imaging technologies on the outcomes of MM patients undergoing other treatments or in different stages of the disease.