Page 52 - New epidemiological and PSMA-expression based paradigms in salivary gland tumors

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Chapter 3
Outcome after recurrent pleomorphic adenoma treatment
Recurrence: In the combined Danish and Dutch cohorts with a mean overall follow- up of 12.5 years, 276/9,003 (3.1%) of patients developed 1st recurrent disease in whom further re-recurrence occurred at a rate of 70/151 (46%, mean follow-up of 14.1 years) and 20/125 (16%, mean follow-up of 9.9 years), respectively (Fig. 2) [1,2]. Re-recurrence specifically after 1st RPA treatment is described in only a few institutional studies [3,6,18,20,23]. These single center series similarly showed an overall 2nd RPA rate of 15-50% and even up to 60% if further recurrences were included (Supplementary Table C). The time interval to recurrence decreased from (median) 7 years for a 1st RPA to 2 years for a 2nd RPA in the Dutch national series [2]. Similarly, a decrease in interval is reported in numerous single center series [6,7,10,14,19-23,25]. Roughly, each surgical intervention halved the time to recurrence.
Malignant Transformation: The Danish/Dutch studies seem to have the most comprehensive data on this topic. In the combined PA data set (N=9,003) with a collective mean follow-up of 12.5 years, 276 cases (3.1%) had recurrent disease, including 23 malignancies (0.3%) (after the original publication that is used in this review, one additional patient had MT in the Dutch series). At 1st recurrence, malignant salivary gland tumor was present in 17/276 cases (6.2%). In the remaining 259 benign cases, 90 patients had 1-8 further episodes of recurrence, and in this population six developed MT (6/90, 6.6%), at a mean of 15 years following primary PA surgery (Table 2 and 3) (range 2.1-27 years). Treatment of the latter group was by surgery and RT in all cases and local recurrence occurred in 4/6. One patient died of disease. Overall, 23 of 276 recurring tumors (8.3%) were diagnosed with malignant salivary disease. These figures can be interpreted in different ways (see discussion).
In the literature, the three single institution series describing >100 treated RPAs showed a MT rate of 0-7%, occurring at different stages of recurrence [6,10,13]. A pattern of higher MT rates following RT could not be discerned. The reported rates of MT in RPA with surgery alone as well as with adjuvant RT were 0-9% (Supplementary Table D).