Loss of Skeletal Muscle Density During Neoadjuvant Chemotherapy in Elderly Women with Advanced Stage Ovarian Cancer is Associated with Postoperati ve Complicati ons

OBJECTIVE
To assess the association between loss of lumbar skeletal muscle mass and density during neoadjuvant chemotherapy (NACT) and postoperative complications after interval cytoreductive surgery (CRS) in older patients with ovarian cancer.


MATERIALS AND METHODS
This multicenter, retrospective cohort study included patients aged 70 years and older with primary advanced stage ovarian cancer (International Federation of Gynecology and Obstetrics stage III-IV), treated with NACT and interval CRS. Skeletal muscle mass and density were retrospectively assessed using Skeletal Muscle Index (SMI) and Muscle Attenuation (MA) on routinely made Computed Tomography scans before and after NACT. Loss of skeletal muscle mass or density was defined as >2% decrease per 100 days in SMI or MA during NACT.


RESULTS
In total, 111 patients were included. Loss of skeletal muscle density during NACT was associated with developing any postoperative complication ≤30 days after interval CRS both in univariable (Odds Ratio (OR) 3.69; 95% Confidence Interval (CI) 1.57-8.68) and in multivariable analysis adjusted for functional impairment and WHO performance status (OR 3.62; 95%CI 1.27-10.25). Loss of skeletal muscle density was also associated with infectious complications (OR 3.67; 95%CI 1.42-9.52) and unintended discontinuation of adjuvant chemotherapy (OR 5.07; 95%CI 1.41-18.19). Unlike loss of skeletal muscle density, loss of skeletal muscle mass showed no association with postoperative outcomes.


CONCLUSION
In older patients with ovarian cancer, loss of skeletal muscle density during NACT is associated with worse postoperative outcomes. These results could add to perioperative risk assessment, guiding the decision to undergo surgery or the need for perioperative interventions.


Introducti on
Forty-seven percent of all new epithelial ovarian cancers are diagnosed in pati ents aged 70 years and older, 71 and this percentage is expected to increase. Primary treatment of advanced stage ovarian carcinoma (Internati onal Federati on of Gynecology and Obstetrics (FIGO) stage III-IV) comprises cytoreducti ve surgery (CRS), followed by six courses of adjuvant plati num and taxane-based chemotherapy. Neoadjuvant chemotherapy (NACT) with interval CRS is off ered if primary CRS is considered not feasible due to extent of disease or poor pati ent conditi on 72 . Individual perioperati ve risk assessment can help clinicians and pati ents in shared decision making. It contributes to the decision whether or not to undergo surgery, or guide the need for perioperati ve interventi ons aiming to improve postoperati ve outcomes, such as prehabilitati on 101 .
In several studies among older oncological pati ents, preoperati ve low skeletal muscle mass and density have been associated with poor postoperati ve outcomes and chemotoxicity. 102 In younger pati ents with ovarian cancer, low preoperati ve skeletal muscle mass has been associated with adverse postoperati ve outcomes and mortality 31,83,90,91,102 . Low skeletal muscle density indicates enhanced fat infi ltrati on within muscle and refl ects low muscle quality, while low skeletal muscle mass is a surrogate for low muscle quanti ty 84 .
In line with low preoperati ve skeletal muscle mass and density, loss of skeletal muscle mass during NACT could be a useful marker in predicti ng adverse treatment outcomes in pati ents with ovarian cancer 103,104 , but current evidence is not unanimous yet 105 . Loss of skeletal muscle mass or density could be target points for prehabilitati on, to prevent or minimize loss and decreasing the risk for worse postoperati ve outcomes. The clinical implicati ons of loss of skeletal muscle density have not yet been assessed in this populati on. Thus far, studies on loss of skeletal muscle mass and density in an older populati on with ovarian cancer are lacking.
In this study, we investi gated the associati on between loss of skeletal muscle mass and density during NACT and postoperati ve outcomes aft er interval CRS in older pati ents with advanced ovarian cancer. We hypothesized that pati ents experiencing loss of skeletal muscle mass or density during NACT suff er from postoperati ve complicati ons more oft en than pati ents who are able to maintain or improve skeletal muscle status.

Study design and setting
In this multicenter, retrospective cohort study patients aged ≥70 years treated with interval CRS for primary ovarian carcinoma FIGO stage III or IV were included from three hospitals in the Netherlands (The Netherlands Cancer Institute (NKI), Amsterdam; University Medical Center Groningen (UMCG); and Reinier de Graaf (RDG), Delft). In NKI and RDG, patients receiving interval CRS between January 2014 and January 2017 were selected from the local Dutch Gynecological Oncology Audit (DGOA) database 76 . Patient selection in UMCG was based on the local OncoLifeS 77 database, including patients who consented to participate between January 2016 and August 2019. Two preoperative CT scans (one before start and one after ≥2 cycles of NACT) had to be available for each patient to be included in the analysis. Patients receiving combined surgery for ovarian cancer and a second malignancy were excluded. The Medical Research Ethics Committee stated that the study was not subject to the Dutch Medical Research Involving Human Subjects Act and local approval was obtained from all participating centers. The study was performed in compliance with the Declaration of Helsinki and Good Clinical Practice guidelines.

Data collection
From the DGOA and OncoLifeS databases and the electronic medical records, we registered age, living situation, preoperative American Society of Anesthesiologists (ASA) score 63 , preoperative WHO performance status 78 , Body Mass Index (BMI), comorbidity using the Charlson Comorbidity Index 61 (applying a cut-off score of ≥2), history of abdominal surgery and polypharmacy (daily use of ≥5 different medicaments). A standardized geriatric risk questionnaire, conducted at hospital admission before surgery of all older patients in the Netherlands, was used to collect 1) patient-or caregiver-reported memory problems or history of confusion during illness or hospital admission 26 ; 2) fall risk (≥1 fall incident in the last six months 26 ); 3) risk for malnutrition (Short Nutritional Assessment Questionnaire score ≥2 79 or Malnutrition Universal Screening Tool score ≥1 80 ); 4) functional impairment (score of ≥2 26 in the Katz Index of Independence in Activities of Daily Living (KATZ-ADL) 59 ); and 5) use of a walking aid. We collected tumor histology and grade, FIGO stage, preoperative involvement of a geriatrician, completeness of CRS (no macroscopic residual disease, ≤1 cm residual disease or >1 cm residual disease), performance of bowel surgery, intraoperative blood loss >1000 cc, and intraoperative injury (lesions of the bowel, bladder, ureters or major blood vessels).

Skeletal muscle mass and density
Contrast enhanced abdominal CT scans (in the portal venous phase), performed as part of standard clinical care before and aft er ≥2 cycles of NACT, were used to determine skeletal muscle mass and density. We extracted transversal slices on the level of the midpoint of L3 from every included CT scan. In this slice, skeletal muscle was manually outlined by an experienced, board-certi fi ed radiologist who was blinded for all outcomes. Within these contours, muscle voxels were defi ned by radiodensity ranging from -29 to +150 Hounsfi eld Units (HU) 81 . Next, the Skeletal Muscle Index (SMI) was calculated by dividing the total muscle surface area on level L3 by the square of the length of the pati ent (cm 2 /m 2 ) 106 . Skeletal muscle density was defi ned as the mean Muscle Att enuati on (MA) in HU of the muscle voxels in this slice. All CT scan assessments were executed using in-house developed analysis soft ware (SarcoMeas version 0.60) 82 .
Low skeletal muscle mass was defi ned as a SMI <38.50 cm 2 /m 2 , as suggested by a systemati c review and meta-analysis on sarcopenia and survival in ovarian cancer 83 . The cut-off for low MA was defi ned as one standard deviati on (SD) below the mean (if normally distributed) or the lowest quarti le of MA (if non-normally distributed) 83 . BMI-dependent cut-off points as suggested by Marti n et al. 85 could not be applied to our populati on, since BMI is oft en infl uenced by ascites in pati ents with advanced ovarian cancer.
We assessed changes in SMI and MA between the fi rst and second CT scan. The individual percentage change was divided by the number of days between scans and multi plied by 100 days (percent change per 100 days), because ti me between CT scans was not equal for all pati ents 103,107 . Changes between −2% and +2% were determined as maintenance of skeletal muscle mass or density. A measurement error of 2% was used based on previously reported accuracy of CT for muscle and fat ti ssue analysis. 103,107 Loss/gain of skeletal muscle mass or density was defi ned as >2% decrease/increase per 100 days, in line with Rutt en et al 103 and Ubachs et al. 105

Outcomes
Our primary outcome was any postoperati ve complicati on ≤30 days of CRS (i.e. cardiac complicati ons, infecti ons, wound defects, postoperati ve hemorrhage or hematomas, thromboembolisms, kidney or liver dysfuncti on, urinary retenti on, ileus, other systemic complicati ons and death). Intraoperati ve blood loss, injuries or technical problems were not included as postoperati ve complicati on.
The secondary outcome measures composed severe complications (Clavien-Dindo classification ≥ grade 3 60 , including only the complication with the highest grade per patient); infectious complications; postoperative delirium; extended hospital stay (>14 days); discharge to a care facility previously not residing in (indicating functional decline); readmission ≤30 days after discharge; unintentional discontinuation of adjuvant chemotherapy; and 30-day, 6-months and 12-months mortality (calculated from the date of surgery to date of death). Linkage with the Dutch Personal Records Database provided data on mortality. If linkage was not possible, information on mortality was retrieved from the electronic medical records. Patients with inadequate follow-up were not included in the mortality analyses.

Statistical analysis
Differences in baseline characteristics and outcomes between groups with and without loss of skeletal muscle mass or density were compared using a Fisher's exact test for binominal variables, a Fisher-Freeman-Halton exact test for nominal or ordinal data, an unpaired T-test for normally distributed continuous variables or a Mann-Whitney U test for not normally distributed continuous variables. Absolute changes between pre-and post-NACT skeletal muscle mass and density were assessed using a Wilcoxon signed-rank test. The association between loss of skeletal muscle mass and density during NACT and the outcome measurements was determined using univariable logistic regression analysis. Multivariable analysis was performed if skeletal muscle mass or density was associated with postoperative complications in univariable analysis.
We considered the following factors that were collected before, during or after NACT as potential confounders: age 87 ; comorbidity 86 ; polypharmacy 86 ; WHO performance status ≥2 86 ; ASA classification 86 ; functional impairment 86 ; living situation; fall risk; pre-existing memory problems; history of confusion during illness; malnutrition risk; use of a walking aid; and pre-NACT skeletal muscle mass and density. We added performance of bowel surgery and completeness of CRS as measures of surgical complexity. To be included in the multivariable analysis, potential confounders had to be associated with both loss of skeletal muscle density or mass and the outcome (p <0.30) in univariable analysis. Confounders were kept in the model if they altered the regression coefficient of the determinant with more than 10%. Only complete cases were included in the analysis.
Level of statistical significance was defined as p <0.05. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS), version 23.0.

Parti cipants and baseline characteristi cs
One hundred eleven of the 123 pati ents that met the inclusion criteria were included in the fi nal analysis. In eleven pati ents only one CT scan was available and one pati ent had simultaneous surgery for a second malignancy. Table 1 shows the baseline characteristi cs of all included pati ents distributed by loss of skeletal muscle density. Supplementary table S1 presents the baseline characteristi cs of all included pati ents distributed by loss of skeletal muscle mass. Median age at surgery was 76.6 years (IQR 73.6-78.7).
Tumor characteristi cs were equally distributed between pati ents with and without loss of skeletal muscle mass or density. Most pati ents (n=88; 80%) lived at home without professional care. Fall risk was available for 89 pati ents (80%), of whom thirteen pati ents (15%) were known to be at risk for falls. For 80% of pati ents a KATZ-ADL score was available, and eight pati ents (9%) had functi onal impairment. For 59 pati ents (53%) risk for malnutriti on was available, of whom 18 pati ents (31%) were actually at risk. Use of a walking aid was known for 93 pati ents, of whom fourteen pati ents indeed used a walking aid (15%). Five pati ents (6%) reported pre-existi ng memory problems and 6% had a history of confusion during illness or hospital admission, which were both known in 90 pati ents (81%). Twenty-nine pati ents (26%) had polypharmacy, which diff ered signifi cantly between pati ent with and without loss of skeletal muscle density (42% and 19%, respecti vely).

Skeletal muscle mass and density
Median interval ti me between CT scans was 66 days (IQR 53-96 days). Table 2 shows median pre-NACT and preoperati ve skeletal muscle mass and density and the median changes in skeletal muscle mass and density during NACT. In 27 pati ents (24%), low skeletal muscle density (<26.10 HU, < lowest quarti le) was present before the start of NACT. Thirty-six parti cipants (32%) had a decrease in skeletal muscle density, eight pati ents (7%) maintained skeletal muscle density, and 67 pati ents (60%) gained skeletal muscle density during NACT.
Before start of NACT, 50 pati ents (45%) had a low skeletal muscle mass. Seventy-six pati ents (69%) had a decrease in skeletal muscle mass, 11 pati ents (10%) maintained skeletal muscle mass, and 24 pati ents (22%) gained skeletal muscle mass during NACT.  Table 3 shows the incidence of all outcome variables. Thirty-four pati ents (31%) had a postoperati ve complicati on. Twenty-three pati ents (21%) had one complicati on, eight pati ents (7%) had two complicati ons, one pati ent had three complicati ons and two pati ents had four complicati ons. Table 3 shows the results from univariable and multi variable analysis for loss in skeletal muscle density. Loss of skeletal muscle density during NACT was signifi cantly associated with developing any postoperati ve complicati on within 30 days aft er surgery both in univariable (OR 3.69; 95%CI 1.57-8.68) and in multi variable analysis (OR 3.62; 95%CI 1.27-10.25) adjusted for KATZ-ADL ≥2 and WHO performance status ≥2. Loss of skeletal muscle density was also associated with the secondary outcomes infecti ous complicati ons within 30 days (OR 3.67; 95%CI 1.42-9.52) and unintended disconti nuati on of adjuvant chemotherapy (OR 5.07;) in univariable analysis. Because of the low frequency of events, multi variable analysis of the secondary outcome measures was not performed.

Loss of skeletal muscle mass
Supplementary table S2 shows the results of univariable analysis for loss of skeletal muscle mass. Loss of skeletal muscle mass during NACT was not associated with development of any postoperati ve complicati ons within 30 days aft er surgery (OR 1.42; 95%CI 0.58-3.47), nor with any of our secondary outcome measurements.

Discussion
To the best of our knowledge this is the fi rst study to evaluate the relati on between loss of skeletal muscle density and postoperati ve complicati ons in pati ents with interval CRS aft er NACT in ovarian cancer. Single measured preoperati ve low skeletal muscle density has been shown to be more strongly associated with negati ve outcomes than low skeletal muscle mass in gynecologic cancer 31,83,90,91 . Only one recent study evaluated the change in skeletal muscle density during NACT for ovarian cancer 108 . This retrospecti ve cohort study reported that skeletal muscle density signifi cantly increased during NACT, while SMI signifi cantly decreased. These fi ndings are in line with our study. We were able to additi onally assess the impact of loss of skeletal muscle mass and density on postoperati ve outcomes.
Sarcopenia and cachexia are frequent problems in older pati ents with cancer 102 . It is diffi cult to disti nguish between sarcopenia and cancer cachexia with CT measurements only, since both conditi ons overlap in diagnosti c criteria as assessed using CT. The defi niti on of sarcopenia focusses on low muscle strength with reduced muscle quality or quanti ty and/ or low physical performance 13 . Cancer cachexia is defi ned as ongoing muscle wasti ng with or without loss of fat mass 109 . Preoperati ve low skeletal muscle density is associated with both the infl ammatory and the nutriti onal component of cachexia 110 and evidence suggests that skeletal muscle density may be of equal or greater value than skeletal muscle mass in assessing cachexia 111 . Thus, loss of skeletal muscle density during NACT might refl ect ongoing sarcopenia as well as cancer cachexia, although both conditi ons cannot be diagnosed without clinical assessments.
Even though the underlying mechanisms of sarcopenia and cachexia diff er, current treatment strategies have similar goals: to improve muscle mass, muscle functi on, pati ent functi on and physical performance. 102 Therefore, loss of skeletal muscle density during NACT could be treated similarly in a prehabilitati on program containing at least physical exercise and adequate protein intake. To design an eff ecti ve prehabilitati on program, it is highly relevant to identi fy pati ents at risk for skeletal muscle density loss and to investi gate how to achieve muscle density maintenance or gain during chemotherapy in future studies. We hypothesize that the increase of skeletal muscle density during NACT could be caused by improved physical conditi on aft er start of chemotherapy. Currently, two clinical trials, the PADOVA trial and the TRAINING-Ovary 01 trial, are investi gati ng prehabilitati on during NACT in pati ents with ovarian cancer. 112,113 It would be very interesti ng to additi onally assess loss of skeletal muscle density in relati on to prehabilitati on and outcomes within these trials as well.
This study is the fi rst study to investi gate the eff ect of loss of skeletal muscle mass and density in a cohort consisti ng exclusively of older pati ents with advanced stage ovarian cancer receiving interval CRS, thus a populati on with an elevated surgical risk. It is of great added value that we found a potentially modifiable preoperative risk factor, since it indicates that future prehabilitation programs to lower the risk for postoperative complications could target on preventing decline in skeletal muscle density. Furthermore, we used the same method to define loss of skeletal muscle mass and density as the largest of the three currently available studies 103-105 on CT-measured changes in body composition among patients treated with NACT for ovarian cancer, facilitating the ability to compare results. Also, all CT measurements were executed by a board certified radiologist with extensive experience 82 . Lastly, complications can negatively impact quality of life and functional status. Since older patients often prevail preservation of independence over improved survival 69 , we studied a highly relevant primary outcome for these patients.
Nevertheless, this study has some limitations. Since CT protocols were not completely standardized for this study, slight variation in contrast enhancement could be present between the different hospitals. However, since all scans were acquired in the portal venous phase, only minimal influence on skeletal muscle density is expected. 97 Due to retrospective data collection we also encountered missing data in some baseline characteristics and secondary outcomes. Next, we could not further elaborate the relationship between loss of skeletal muscle density and discontinuation of adjuvant chemotherapy in multivariable analysis due to the small number of events. It would be of interest to evaluate this outcome in larger studies. Additionally, confounders adjusted for in the multivariable analysis were assessed during the preoperative phase, mostly during or after NACT. We considered those suitable to represent pre-NACT frailty, however changes during the preoperative phase cannot be excluded. Furthermore, pre-NACT skeletal muscle density showed no association with loss of skeletal muscle density during NACT (p >0.30) and was therefore not included in the multivariable analysis, while this theoretically could have affected the extend of change in skeletal muscle density during NACT. This influence is possibly diluted by a ground effect of patients with low pre-NACT skeletal muscle density. This could have reduced the association between loss of skeletal muscle density and postoperative complications we found. Lastly, patients who did not receive CRS after NACT were not included in the current study. To extrapolate our results to all patients for whom interval CRS is considered, this subgroup should be included in future studies.

Conclusions
Loss of skeletal muscle density during NACT for ovarian cancer in older patients is associated with occurrence of postoperative complications after CRS and discontinuation of adjuvant chemotherapy. Further research should elaborate which patients lose, maintain, or gain skeletal muscle density during NACT and how this is affected, with the ultimate goal to develop successful prehabilitation strategies to improve surgical outcomes.