Strengths and Limitations
The main strength of our study is that it is the first one to assess the
usefulness of SAD as a predictive tool for surgical morbidity. Few
studies examine the role of a minimally invasive approach and the aortic
lymphadenectomy technique in surgical morbidity, our study sheds light
in this regard.
We believe u-SAD could have clinical applicability because of two
reasons: preoperative imaging use is widespread, and u-SAD is reliable,
straightforward, and easy to measure.
Also, this measurement is not limited to MRI, it has been described in
CT-scans 33.
Research results in surgery are subject to several biases: surgeon
volume, experience, and procedure complexity. In our study, these biases
were mitigated because the surgeries were carried out in three referral
hospitals, by a small group of expert oncologic surgeons; and most
patients had the same diagnosis and underwent the same procedure. Since
data were collected prospectively, this prevented observer and recall
bias. The long-term follow-up helped to reduce underreporting, and the
precise measuring of variables (e.g. haematocrit drop instead of
estimated blood loss) reduced measurement error or estimator bias.
The major limitation of our study is the lack of validation of the core
outcome set. Some variables were defined as percentiles (Table S1), so
they are affected by the surgical results of each centre. This requires
everyone to determine their cut-off point.
We did not include lymph node count in the composite outcome measure
(but it was recorded and analysed), as we found in a previous study that
all minimally invasive techniques yielded the same number of aortic
nodes 24. Instead, we estimated surgical difficulty by
accounting for the completion of the aortic lymphadenectomy.
We did not calculate the sample size for the second phase, and given the
limited number of patients, some differences were not statistically
significant.