The level of tie of the inferior mesenteric artery in rectal cancer surgery has been a
controversy for decades. Proponents argue that lymph node harvest and bowel length can be
improved, while detractors state that nerve damage is likely and that blood perfusion to an
anastomosis is compromised. Few randomized clinical trials are available and these are
underpowered for long-term outcomes, mainly stating no difference. Observational studies
usually indicate no differences either, while lymph node harvest might be increased (though
not concerning node metastasis). Long-term outcomes such as survival and recurrence have not
been investigated with proper sample sizes to detect small effects. In effect, large scale
trials are unlikely to be conducted, and only population-based studies are likely to
accumulate adequate statistical power. One way would be to use nationwide registry data, such
as the Swedish Colorectal Cancer Registry, in which tie level as well as recurrence and
survival data are recorded. However, it is not always easy to determine the level of tie
while in the operating room and registries might also contain erroneous data. In order to
determine the validity of such data, comparisons to objective measures are needed. This study
is an attempt to correlate radiographic imaging to the suggested tie level, as indicated by
the surgeon in the operative report and by the nationwide Swedish Colorectal Cancer Registry.
If the registry variable tie level has a high correlation with imagining, researchers can
more reliably use the registry to establish the benefits and drawbacks with high tie in
rectal cancer surgery.
The RAVAL study plans to include 100 patients from the University Hospitals in Umeå and
Örebro, Sweden. Patients have been operated for rectal cancer and are contacted by telephone
or at the postoperative visit, before their planned 1-year radiological follow-up. All
patients sign informed consent for additional imaging with arterial phase contrast-enhanced
computerized tomography (CT), performed at the same time as their planned follow-up (for
detection of metastasis).
A dedicated study radiologist interprets the images, in conjunction with the routine
preoperative imaging, and determines the tie level that was performed at the rectal cancer
operation. Additional parameters such as vessel anatomy and the length of the artery stump
are recorded. Clinical data from operative reports and histopathology will also be noted.
When the study inclusion is completed, radiological determination of tie level will be
compared with the surgeon's impression of tie level as well as the tie level in the Swedish
Colorectal Cancer Registry.
The primary objective is to validate the level of tie in the registry, using sensitivity,
specificity and Cohen's kappa. The secondary objectives include validation of tie level in
comparison to operative reports, as well as artery stump length in relation to lymph node
harvest, use of laparoscopy, and cancer recurrence (using appropriate techniques such as
linear and Cox regression). The sample size is calculated per the primary objective, and
assumes 90% sensitivity and specificity, which requires 86 and 58 patients, respectively,
with a 10% margin of error. Attrition is expected, why 100 patients is determined to be
adequate.
