Page 87 - New epidemiological and PSMA-expression based paradigms in salivary gland tumors

Risk of breast cancer after a salivary gland tumor in the Netherlands
Discussion
In this large and nationwide study with long-term complete follow-up, including 3,650 women diagnosed with SGC and SGPA, the risk of developing a subsequent BC is moderately increased. This roughly 50% higher relative risk of BC can be better interpreted by mentioning absolute numbers in an example. For a 50-year old woman, the risk to develop breast cancer in the next 10 years (until the age of 60) equals 2.9%[33]. After a previous diagnosis with SGC or SGPA, this risk would be 4.3%.
In contrast to many previous studies on BC risk after a salivary gland tumor, the nationwide cohorts used in our study either consisted solely of malignant or of benign tumors. The high number of patients allowed unbiased estimation of relative and absolute risk in both type of lesions and gave rise to the possibility of subgroup analysis.
The lower age at diagnosis of second tumors in the SGPA-cohort compared to the SGC-cohort (Table 2), was in line with the lower age of the SGPA patients and earlier publications[1,2]. The increased BC risk after SGC or SGPA did not vary much with age at index tumor diagnosis nor with SGC histological subtype. The finding of an increased risk in patients diagnosed with BC ≥3 months after the salivary gland tumor, showed that the increased BC incidence was not likely based on surveillance bias caused by diagnostic evaluation of the index tumor.
Results of previous studies varied from no risk increase upto 8-fold increased risks (Table 4). Many of these studies had methodological shortcomings which made comparison and generalization of these results difficult[21–28]. For instance, most studies did not provide a confidence interval for the risk estimates presented [23–26,28]. The completeness of follow-up may have been a problem in single institution cohorts[21,22,28]. Missing a diagnosis of even one patient with a second primary BC, would have had a substantial negative impact on the estimated risk in these cohorts which included between 4 to 15 BC cases each. Also, there could be a referral bias in comprehensive cancer centers, because of inclusion of a higher proportion of patients with second or multiple primaries. Variation in BC incidence between the USA and Europe unlikely explains the high risk in two American studies[21,26]. Additionally, BC incidence rates in the SEER registry are generally lower than in European populations[34]. A later conducted population based SEER study could not confirm the reported higher BC risk after an earlier
5
85