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no longer significant in multivariate analysis112. Other studies210,211 could not detect any association
of higher hospital volume with better survival Table 3.
Eleven original studies178,183,207,215-222 not included in the systematic review mentioned above were
also identified. As part of large studies, Mercado et al.215 31,897 stage IIIC -IV patients and Bristow
et al.207,216,221 10,641 stage IIIC -IV patients216, 47,160 stage I-IV patients221 and 9,933 stage I-IV
patients207, showed that the pati ent volume of the hospital have a significant impact on survival
Cox regressions controlling for 1 age, comorbidity, hospital location 215, 2 stage, ethnicity, age,
payer status, household income, and tumour grade216, 3 adherence to NCCN guidelines, age, race,
proportion with college degree, median household, primary payer at diagnosis, stage, grade and
histology221 or 4 age, stage, tumour size, and grade 207.
Another large study222 was identified 36,624 patients. Authors suggest that women who undergo
surgery for ovarian cancer at high-volume hospitals have superior outcomes. Patients treated at low-
volume hospitals who experienced complications were more likely to die as a result of the
complications. Among women who experienced a complication, the mortality rate was 8.0% at low-
volume, 6.1% at intermediate-volume, and 4.9% at high-volume hospitals p = 0.001. After
adjusting for age, year of surgery, race, comorbidity, urgency of operation, performance of extended
cytoreduction, and hospital teaching status, the failure-to-rescue rate was 48% higher at low-volume
compared with high-volume hospitals OR = 1.48, 95% CI = 1.11 -1.99. Similar trends were noted
for medical and infectious complications 9.5% versus 5.8%, p < 0.001, adjusted OR = 1.49, 95% CI
= 1.09-2.04 ; 14.3% versus 8.3%, p < 0.001, adjusted OR = 1.79, 95% CI = 1.21-2.64, respectively.
It should be noted that these results have to be interpreted cautiously because 1 the groups were not
comparable notably in terms of age, comorbidities, lymphadenectomies, extended cytoreductive
surgeries, urgency of operation, and 2 the presence of an important under -reporting bias.
Marth et al.183 and Ioka et al.219 reported also an impact of hospital volume on survival after
adjustment for stage, lymphadenectomy, age, grade, residual disease183 and for sex, age, stage219.
Other studies178,217,218,220 could not detect any association of higher hospital volume with better
survival.
Impact of hospital volume on surgical outcome: LoE 2-
among the studies included in the systematic review published by du Bois et al.209, three
studies211,223,224 addressed the effect of hospital volume on surgical outcome. The reports used
several residual postoperative tumor criteria no residual tumour, maximum diameter of residual
tumor ≤ 1 cm, ≤ 2 cm. In one study, patients treated in hospitals managing more than 10 cases per
year were more likely to be optimally debulked residual tumour < 2 cm, even after adjustment for
age, stage, grade, and physician specialty224. The two other studies only performed univariate
analyses211,223. Du Bois et al.211 used a similar cut-off of 12 patients per year and found no evidence
of any effect regardless of the surgical outcome criterion used. The third study described a non-
systematically significant association between higher volume and poorer outcome Table 4. One
original study220 not included in the systematic review mentioned above was also identified and
showed that hospital volume did not affected the results of cytoreductive surgery. It should be noted
that these results concerning the impact of hospital volume on surgical outcome must take into
account that a potential interobserver bias in assessing the diameter of residual disease may influence
the results.
Impact of hospital volume on the likelihood of repeat surgery: Elit et al.217 assessed whether the LoE 2-
hospital procedure volume determined the likelihood of unnecessary repeated surgery. Univariate
analysis showed that the hospital procedure volume was found to be significantly associated with
risk of repeat surgery 16 -99/y vs. ≥ 100/y: RR = 1.89, 95% CI = 0.39-9.23, p < 0.05; 1-15/y vs. ≥
100/y : RR = 5.70, 95% CI = 1.22-26.73, p < 0.05. However, this volume-outcome association lost
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