4.1 Synopsis of key findings and comparison with other studies
The natural history of RPA is not well understood. Recurrences usually
develop at 7 years and occasionally 20 years after the
operation1. The annual growth rate of identified
recurrences, as measured on repeat MRI, is variable: 21% of tumours are
stable, 10.2% increase and 14% reduce in volume4. It
is not known if clinical recurrences following conservative parotid
resections become evident after a long subclinical course. Our study is
the first to search radiologically for occult recurrent foci after
capsular dissection of PA with a mean postoperative follow up of 6 years
(median 5.6 years). We were not able to find any occult recurrence.
Schapher et al performed clinical and ultrasound examinations in 98
patients after PA resection (31 patients underwent ECD) at the 1st and
>10th postoperative year2. They found no
recurrence in the ECD group. One patient (after partial parotidectomy)
developed a subclinical recurrence, detected by routine ultrasound.
Moonis et al also performed follow up MRI or CT scans in patients who
underwent PA resection (ranging from enucleation to formal
parotidectomy) but do not provide details on the frequency of the
imaging protocol5. They have detected 2/24 recurrences
with MRI: one as an incidental finding after a neck MRI for a different
indication and another one on regular scanning.
Our 3.2% recurrence rate lies within the range of reported figures from
large CD series with adequate followup (2%)6. The
overall recurrence rate in two large cohort studies including 9003 PA
resections, irrespective of surgical approach, is
3.1%1. Thirteen patients (21.3%) in our study had an
incomplete capsule and two of them recurred. Dulguerov et al have
summarised the histological evidence that supports the association of an
incomplete capsule and recurrence7. However, other
histological characteristics such as pseudopodia and satellite nodules
are also common in specimens with an incomplete capsule and may be more
relevant to the risk of subsequent recurrence8.