Uncounted members of the pedigree have been removed, and the pedigree has been nondestructively altered to preserve privacy. Note the salivary gland cancer highlighted with a blue label. Square denotes male; circle, female; diamond, sex unknown; black dot, cancer case; diagonal line, twins; number, multiple individuals; slash, deceased; and arrowhead, proband. NOS indicates not otherwise specified.
Uncounted members of the pedigree have been removed, and the pedigree has been nondestructively altered to preserve privacy. Note the salivary cancer highlighted with a blue label. Square denotes male; circle, female; black dot, cancer case; slash, deceased; and arrowhead, proband.
Uncounted members of the pedigree have been removed, and the pedigree has been nondestructively altered to preserve privacy. Note the parotid cancer highlighted with a blue label. Square denotes male; circle, female; diamond, sex unknown; black dot, cancer case; number, multiple individuals; slash, deceased; and arrowhead, proband. b/l Indicates bilateral.
Uncounted members of the pedigree have been removed, and the pedigree has been nondestructively altered to preserve privacy. Note the parotid gland acinic carcinoma and the adenoid cystic carcinoma highlighted with blue labels. Square denotes male; circle, female; diamond, sex unknown; black dot, cancer case; diagonal line, twins; number, multiple individuals; slash, deceased; and arrowhead, proband.
Tim K. Shen, Theodoros N. Teknos, Amanda E. Toland, Leigha Senter, Rebecca Nagy. Salivary Gland Cancer in BRCA-Positive Families A Retrospective Review. JAMA Otolaryngol Head Neck Surg. 2014;140(12):1213–1217. doi:10.1001/jamaoto.2014.1998
Although an association between breast cancer and salivary gland cancers has been noted for decades, this is the first study, to our knowledge, to evaluate the possible linkage of BRCA gene mutations and this malignant neoplasm.
To compare the prevalence of salivary gland cancers in a large BRCA gene mutation database with background rates in the general population.
Design, Setting, and Participants
This is a retrospective review (June 1, 2012, through April 31, 2013) of pedigrees from patients with breast cancer in The Clinical Cancer Genetics Program at The Ohio State University Wexner Medical Center. A total of 5754 individuals were identified from 187 pedigrees, and their medical histories were reviewed for diagnoses of salivary gland tumors and BRCA testing. The pedigrees were restricted to provide a cohort of individuals with reasonable accuracy in family history by considering 3 generations of each pedigree, starting with the proband’s generation and adding 1 generation above and below. The youngest generation was replaced with another older generation if there were no BRCA-related cancers or BRCA mutations recorded. Nonblood relatives of the proband (ie, stepparents and stepsiblings) were also excluded.
Main Outcomes and Measures
The rate of salivary gland cancers in the Clinical Center Genetics Program was compared with background incidence rates.
After applying the restrictions to the 187 pedigrees in the database, 5754 individuals were included in the cohort. Two parotid gland cancers, 2 salivary gland cancers not otherwise specified, and 1 adenoid cystic carcinoma were identified. One of these cancers likely did not segregate with the BRCA mutation, and another individual tested negative for the BRCA mutation, resulting in a rate of 3 of 5754 (0.052%).The observed rate of 3 of 5754 cases (0.052%) of head and neck cancers in BRCA-positive probands and likely carriers is significantly higher than the background incidence rate of 3 of 100 000 (0.003%) per year (P < .001).
Conclusions and Relevance
We believe this is a significant observation that, when considered alongside other similarities between salivary glands and breast tissue, warrants further investigation into the nature of a possible linkage between germline BRCA mutations and salivary gland cancer.
BRCA2 (OMIM 113705) is a tumor suppressor and DNA repair gene of the Fanconi anemia–BRCA pathway. A previous study1 has also suggested the involvement of BRCA1 (OMIM 600185) in this pathway. Mutations in these 2 genes have been linked to greatly increased risks for breast cancer and ovarian cancer. BRCA2 gene mutations have long been known to be involved in DNA repair syndromes, such as Fanconi anemia, which is associated with various cancers, including squamous cell carcinoma, acute myeloid leukemia, esophageal cancer, and various gynecologic cancers.1,2BRCA1 and BRCA2 mutations have also been implicated in other cancers, including prostate cancer and pancreatic cancer.3 Our study was undertaken to determine whether BRCA mutations could also be linked to salivary gland cancers, given the similarity between salivary glands and breast tissue as exocrine tissues and the similar development of various salivary gland and breast disease.4,5
Salivary glands and breast tissue are exocrine tissues that have a number of similarities that increase our suspicion of a linkage between cancers in these tissues. Salivary glands exhibit pathologic features similar to the breast in cases of sclerosing polycystic adenosis, which are benign lesions with similar histologic features and a growth pattern analogous to fibrocystic change in the breast.4 Salivary duct carcinomas also resemble some forms of breast cancer in regard to pathologic structure and histologic features, with overexpression of ERBB2 (formerly HER2 or HER2/neu) or expression of estrogen receptor or progesterone receptor noted in various cases of salivary duct carcinoma.6,7 Also of note is a 2013 study5 in which the similarities between breast cancers and salivary duct carcinomas led the authors to treat ERBB2-positive salivary duct carcinomas with trastuzumab, resulting in a markedly positive response in patients with ERBB2-positive salivary duct carcinomas. Last, because BRCA2 gene mutations are known to increase the risk of pancreatic cancer,3 another exocrine gland, we are suspicious as to whether BRCA may also play a role in the development of cancers in the exocrine salivary glands.
Although observations regarding the association between breast cancer and head and neck cancers have been noted for decades,8 the possible linkage of BRCA gene mutations and head and neck cancers appears to have been studied only in a 2008 Polish cohort.9 Whereas the Polish study examined the peripheral blood of patients with benign pleomorphic adenoma tumor resection for 3 common Polish founder BRCA1 mutations and did not analyze BRCA2, this study uses a large and established BRCA gene mutation database housed in the Clinical Cancer Genetics Program at The Ohio State University Wexner Medical Center to search for any salivary gland cancers. By establishing the prevalence of head and neck cancers in this database and comparing with rates in the general population, we tested the hypothesis that head and neck cancers are more prevalent in individuals carrying the BRCA mutation. Although all first-degree relatives of individuals carrying BRCA gene mutations stand a 50% chance of carrying the same mutation, we believe that evidence of a connection between BRCA gene mutations and salivary gland cancers will aid in genetic counseling for these families.
The Clinical Cancer Genetics Program at The Ohio State University Wexner Medical Center includes more than 200 BRCA1 and BRCA2 mutation–positive patients with breast cancer and their family pedigrees. This study was approved by The Ohio State University Institutional Review Board and was granted a waiver of consent because of the nature of the research (ie, retrospective medical record review study). In this retrospective review (June 1, 2012, through April 31, 2013), the medical records of 187 pedigrees from individuals enrolled in institutional review board–approved cancer genetics research were searched for diagnoses of salivary gland and parotid gland cancers or other cancers of the head and neck because many of the patients are related and are therefore included in overlapping pedigrees.
The pedigrees were restricted to provide a cohort of individuals with reasonable accuracy in family history and to control for differences in the extensiveness of provided family histories. This restriction was accomplished by considering only 3 generations of each pedigree. Individuals in the 3 youngest generations of each pedigree were first considered. If the youngest generation had no confirmed BRCA mutation testing and no signs of BRCA-related neoplasms, the youngest generation in the pedigree was removed from consideration and the next older generation was added. These generations were removed because they were considered too young for neoplastic manifestations to occur, which could cause a false decrease in the prevalence of cancers in this analysis. Nonblood relatives of the proband (ie, stepparents and stepsiblings) were also excluded because they would not have any genetic association with the proband or the rest of the pedigree.
After applying the restrictions to the 187 pedigrees in the database, we included 5754 individuals in the cohort, including 2636 maternal relatives and 2093 paternal relatives. The remainder of the cohort consisted of 1025 individuals and included the probands, their children, or the proband’s siblings and sibling’s children. Two parotid gland cancers, 2 salivary gland cancers not otherwise specified, and 1 adenoid cystic carcinoma were identified for a prevalence of 5 of 5754 (0.087%) in this population. One of these cancers likely did not segregate with the BRCA mutation, and another individual tested negative for the BRCA mutation, resulting in an observed rate of 3 of 5754 cases (0.052%) of possible BRCA-related salivary gland cancers.
The first identified salivary gland cancer occurred in a paternal uncle in pedigree 1 (Figure 1). Significantly, this was the same side of the pedigree that carried a BRCA2 mutation. However, the individual with salivary gland cancer was never definitively tested for the BRCA2 mutation in the family. The second identified salivary gland cancer occurred in a maternal grandfather in pedigree 2 (Figure 2). Although the maternal grandfather was not tested for the family’s BRCA1 mutation, he has a 50% chance of carrying the mutation because his daughter, the proband’s mother, was tested and is a BRCA1 mutation carrier. The salivary gland cancers in these 2 families may be segregating from the BRCA mutation, but this determination has not been directly verified in either case with genetic testing.
The first identified parotid gland cancer occurred in the proband’s mother in pedigree 3 (Figure 3). However, the BRCA mutation in this pedigree was found in the paternal side, not the maternal side. The second identified parotid gland cancer occurred in the proband’s sister in pedigree 4 (Figure 4). This individual was tested and did not carry a BRCA1 mutation. Therefore, one of these parotid gland cancers (from pedigree 3) does not segregate from the BRCA mutation. The other parotid gland cancer occurred in an individual known to be negative for the BRCA1 mutation.
Last, the adenoid cystic carcinoma was found in the proband’s mother in pedigree 4. The mother was tested and found to carry the BRCA1 mutation. Overall, from these pedigree reviews, we identified 5 salivary gland cancers in 5754 individuals in BRCA mutation–positive families, 1 of which was identified in a known BRCA1 carrier and 2 of which may be segregating from germline BRCA mutations.
The possible association between BRCA gene mutations and head and neck cancers is not well established. One study9 specifically examined 268 patients with benign pleomorphic salivary gland adenomas that were surgically resected in 2 Polish hospitals and found no statistically significant increase in the number of BRCA1 mutations. However, this study was limited in that individuals were only tested for 3 common BRCA1 mutations found in individuals of Polish descent. Most individuals in our study had full sequencing and targeted deletion or duplication testing for BRCA1 and BRCA2. The aim of our study was to use a long-term breast cancer database to consider this question from another angle. By including confirmed BRCA mutation carriers presenting with breast cancers and their close family members, this study examines 5754 individuals. With this considerably larger cohort, we believe this result will contribute significantly to the emerging literature regarding BRCA mutations and a possible linkage to malignant salivary gland cancers.
It is, however, important to keep in mind the limitations of this approach. Although we attempted to analyze the pedigrees in a manner consistent with extant genetics literature, we are still limited by the accuracy of the patients’ family histories with regard to the number of family members included in the pedigree and their specific medical histories. Some diagnoses of salivary cancers may not have been included in the reported family histories, and some cases may be erroneous. Records were also incomplete with regard to histologic descriptions of the identified cancers and the specific location of the adenoid cystic carcinoma found in pedigree 4. We are also limited by the inability to test many of these individuals for BRCA mutations. Last, we attempted to limit the effects of age of presentation by excluding the youngest generations in which no possible BRCA effects had been observed.
Of note, we were initially interested in including only relatives from the side of the pedigrees that carried the BRCA mutations. Such a step would have enabled us to reduce the number of relatives involved, further increasing the proportion of head and neck cancers found in BRCA mutation–carrying individuals. However, the lack of definitive genetic testing in older family members would have limited the meaningfulness of this analysis, and ultimately we decided to retain the more conservative analysis. As a result, our proportion likely represents a lower rate of salivary gland cancers than actually exists in the BRCA mutation–carrying family members found in this database. It is notable that our study population has a prevalence of head and neck cancers in BRCA mutation–negative individuals (2 of 5754 [0.035%]) that is also elevated above the background incidence rate. It is possible that these individuals, although not carrying known BRCA mutations, may be carrying other low-penetrance gene mutations that increase the risk of these cancers throughout the pedigrees. Because the family histories for these pedigrees were collected without specifically referencing head and neck cancers, it is unlikely that these cancers were overreported.
The observed rate of 3 of 5754 cases (0.052%) of head and neck cancers in BRCA mutation–positive probands and likely carriers is significantly higher than the background incidence rate of 3 per 100 000 (0.003%) per year (P < .001).10 This statistical analysis was performed using a 1-sample z test for proportions. This study resulted in a significant observation that we believe, when considered alongside other similarities between salivary glands and breast tissue, warrants further investigation into the nature of a possible linkage between germline BRCA mutations and salivary gland cancer.
Submitted for Publication: March 24, 2014; final revision received July 8, 2014; accepted August 1, 2014.
Corresponding Author: Tim K. Shen, MS, The Ohio State University College of Medicine, 1424 Bayshore Dr, Apt 3D, Columbus, OH 43204 (firstname.lastname@example.org).
Published Online: September 25, 2014. doi:10.1001/jamaoto.2014.1998.
Author Contributions: Mr Shen had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Shen, Teknos, Nagy.
Acquisition, analysis, or interpretation of data: Shen, Teknos, Toland, Senter.
Drafting of the manuscript: Shen, Toland, Nagy.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Shen.
Administrative, technical, or material support: Toland, Senter, Nagy.
Study supervision: Teknos, Nagy.
Conflict of Interest Disclosures: None reported.
Funding/Support: This study was supported by the Sandy Slomin Foundation.
Role of the Sponsor: The funding source had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Previous Presentation: This study was presented at the Fifth World Congress of the International Federation of Head and Neck Oncologic Societies and the Annual Meeting of the American Head & Neck Society; July 27, 2014; New York, New York.
Additional Contributions: Kyle Porter, MAS, at The Ohio State University Center for Biostatistics, Columbus, provided statistical support. He was not compensated for his work.