4.3 Clinical applicability
The exact time point that a recurrent nodule becomes large enough to be radiologically traceable is unknown. Therefore, it seems unlikely that a recurrence that manifests clinically 15 years post surgery, will have a radiologically detectable signal in the first 6 years. The role of post surgery MRI is well defined in clinically manifest recurrences: better delineation and extent of recurrent nodules, their location and size as well the size of the remaining parotid gland provides important information for surgical planning3. However, a single MRI to detect an occult RPA at 6 years post CD does not provide any clinical benefit. The rarity of the event and the cost of annual scanning for 10-20 years may not justify the potential but unproven benefit of early recurrence detection. On the other hand, recurrences after encapsulation tend to occur soon after the operation so there may be a potential for close radiologic surveillance in these cases. Re-recurrences after resection of RPAs are common. Rooker et al have noted that if a re-recurrence does not occur within 10 years after the second operation, it is unlikely to develop later10. Therefore a re-recurrence within the first 5 years of surgery requires close follow up which could justify annual imaging.