Het volume van chirurgische ingrepen en de impact ervan op ... - KCE

KCE Reports 113 Volume Outcome 63
As mentioned, several authors adjusted for use of neoadjuvant (given before the
primary treatment) or adjuvant (given after the primary treatment). Most of them found
that the use of adjuvant radiation therapy and chemotherapy did not vary systematically
by hospital volume. 124, 127, 148, 153 In addition, Birkmeyer et al. assessed that adjusting for
differences in the use of this therapy only had a negligible effect in attenuating
differences in 5-year survival. 153
Wouters et al., on the other hand, found that (neo) adjuvant treatment varied widely
between the Dutch volume groups. However, these factors were not significantly
related to mortality. 152
VOLUME OUTCOME ASSOCIATION
The present study did not find an inverse relationship between hospital volume and 2year
mortality. This result contrasts with the findings from the literature review which
concluded that there is evidence for an inverse relationship between hospital volume
and mortality for oesophageal cancer surgery.
The question rises whether this discrepancy between our findings and literature has
something to do with the missing data on stage. The fact that mortality rate was not
substantially higher in the patients whose stage was missing in the BCR (see Figure 5.3)
seems to indicate, however, that these patients are randomly divided into the four
disease stages. Ideally, though, this assumption should be checked with the help of
sensitivity analyses, which was not done due to time constraints. In addition, we noticed
that many hospitals – low-volume as well as high-volume – missed data on stage and
that the percentage of missing data varied among these hospitals (see Figure 5.1).
Despite the failure to retrieve information on disease stage, this problem did not
restrain us from drawing conclusions on the volume outcome association.
In 2003, Birkmeyer et al. proved that 46% of the apparent effect of hospital volume was
actually attributable to surgeon volume. 116 When we consider this possibility, a possible
explanation for the fact that low-volume hospitals have such low mortality could be that
these patients were treated by high-volume surgeons. This hypothesis was tested,
however, and rejected since we found that patients at low-volume hospitals were
operated on by low-volume surgeons.
With respect to surgeon volume, the data suggest that there is an inverse association
with 3 month mortality, although it did not reach statistical significance. 3 months
mortality was 13.5% for surgeons with less than 6 interventions per year and 6.4% for
surgeons with at least 6 interventions per year. Results at two years were consistent.
Several years of observations are required to increase precision of effects.