Page 55 - New epidemiological and PSMA-expression based paradigms in salivary gland tumors

Natural history of recurrent pleomorphic adenoma
Recurrent disease occurs in younger patients and females are afflicted 1.6 times as often as males [1,2]. The majority of recurrent lesions are multifocal in nature, and surgical elimination is understandably unreliable even with radical surgery [13]. The peculiar aspect of surgical intervention is that the time to recurrence decreases with repeated surgery. Time to the first recurrence is 7-10 years, then 2-5 years to the second recurrence and even shorter intervals to the 3rd and 4th recurrences [2,33]. The biological background for this is unknown. Repeat surgery carries another penalty in the form of injury to the facial nerve. This risk is difficult to gauge from the literature because it depends on the extent of the initial surgery, administration of adjuvant RT, and how aggressively the second operation is pursued which is known to vary between institutions. The first surgery for primary tumor carries ~1-4% risk of permanent injury to one or more branches of the facial nerve, and this increases to 3-16% at the next procedure. But if a traditional superficial parotidectomy has been performed previously, then the patient should be counselled about injury rates as high as 30% [6,13]. Recent reviews and meta-analyses indicate that modern minimally invasive parotid techniques have a similar recurrence rate to traditional superficial parotidectomy, although this should be consolidated by longer follow-up [34-36]. Their advantage in this context is that a definitive parotid dissection is still possible.
The incidences of RPA after surgery for the first recurrence in the two populations studies are quite different with the Danish being 46% (mean follow-up 14.5 years) and 14% in the Dutch group (mean follow-up 9.9 years). A possible explanation for this difference is that the Danish study related only to parotid PA whereas the Dutch included also minor salivary glands. These are reported to have a lower risk of recurrence [2]. Also, recurrences occurring within 6 months after primary PA surgery were excluded in the Dutch series, as they were regarded as residual tumor. Another contributing factor could be the option of adjuvant RT which was available in the Netherlands but not in Denmark. A fourth reason is the longer follow-up in the Danish material and finally the theoretical but unlikely possibility of differences in the quality of surgical approach between the two nations.
Although there seems to be a clear advantage of adjuvant RT from earlier mentioned case series, no randomized controlled trials (RCTs) have been carried out and enthusiasm is tempered by known side-effects in a target population that is relatively young. There is not only radiation toxicity, but a theoretical risk of radiation-induced tumors or MT of the RPA [37]. The limited data in the current
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