Somatic Tumor Testing in Prostate Cancer: Experience of a Tertiary-Care Center Including Pathologist-Driven Reflex Testing of Localized Tumors at Diagnosis

Somatic tumor testing in prostate cancer (PCa) can guide treatment options by identifying clinically actionable variants in DNA damage repair (DDR) genes, including acquired variants not detected by germline testing alone. Guidelines currently recommend performing somatic tumor testing in metastatic PCa, while there is no consensus on the role of testing in regional disease and the optimal testing strategy is involving. This study evaluates the frequency, distribution, and pathologic correlates of somatic DDR mutations in metastatic and localized PCa following the implementation of pathologist-driven reflex testing at diagnosis. A cohort of 516 PCa were sequenced using a custom NGS panel including homologous recombination repair (HRR) and mismatch repair (MMR) genes. Variants were classified based on the AMP/ASCO/CAP guidelines. In total 183 (35.5%) patients had at least one variant: 72/516 (13.9%) had at least one Tier I or Tier II variant while 111/516 (21.5%) had a Tier III variant. Tier I/II variant(s) were identified in 27% (12/44) of metastatic biopsies and 13% (61/472) of primary samples. Overall, 12% (62/516) of patients had at least one Tier I/II variant in a HRR gene while 2.9% (10/516) had at least one Tier I/II variant in a MMR gene. The presence of a Tier I/II variant was not significantly associated with the grade group (GG) or presence of intraductal/cribriform carcinoma in the primary tumor. Among 309 reflex-tested hormone-naïve primary tumors, Tier I/II variants were identified in 10% (31/309) of cases: 9.2% (9/98) GG2; 9% (9/100) GG3; 9.1% (4/44) GG4 and 13.4% (9/67) GG5 cases. Our findings confirm the utility of somatic tumor testing to detect variants of clinical significance in PCa and provide insights that can inform the design of testing strategies. Pathologist-initiated reflex testing streamlines the availability of the results for clinical decision-making, however pathologic parameters such as grade group and intraductal/cribriform carcinoma may not be reliable to guide patient selection.

Discrepancies between tumor genomic profiling and germline genetic testing

BACKGROUND

Tumor genomic profiling (TGP) often incidentally identifies germline pathogenic variants (PVs) associated with cancer predisposition syndromes. Methods used by somatic testing laboratories, including germline analysis, differ from designated germline laboratories that have optimized the identification of germline PVs. This study evaluated discrepancies between somatic and germline testing results, and their impact on patients.

PATIENTS AND METHODS

Chart reviews were carried out at a single institution for patients who had both somatic and designated germline genetic testing. Cases with discrepant results in which germline PVs were not detected by the somatic laboratory or in which variant classification differed are summarized.

RESULTS

TGP was carried out on 2811 cancer patients, 600 of whom also underwent designated germline genetic testing. Germline PVs were identified for 109 individuals. Discrepancies between germline genetic testing and tumor profiling reports were identified in 20 cases, including 14 PVs identified by designated germline genetic testing laboratories that were not reported by somatic testing laboratories and six variants with discrepant classifications between the designated germline and somatic testing laboratories. Three PVs identified by designated germline laboratories are targets for poly adenosine diphosphate-ribose polymerase (PARP) inhibitors and resulted in different treatment options. Of the PVs identified by designated germline laboratories, 60% (n = 12) were in genes with established associations to the patients' cancer, and 40% of the PVs were incidental. The majority (90%) of all discrepant findings, both contributory and incidental, changed management recommendations for these patients, highlighting the importance of comprehensive germline assessment.

CONCLUSIONS

Methods used by somatic laboratories, regardless of the inclusion of germline analysis, differ from those of designated germline laboratories for identifying germline PVs. Unrecognized germline PVs may harm patients by missing hereditary syndromes and targeted therapy opportunities (e.g. anti-programmed cell death protein 1 immunotherapy, PARP inhibitors). Clinicians should refer patients who meet the criteria for genetic evaluation regardless of somatic testing outcomes.

Validation of BRCA testing on cytologic samples of high-grade serous carcinoma

BACKGROUND

Testing for BRCA1/2 gene alterations in patients with high-grade serous carcinoma (HGSC) is a critical determinant of treatment eligibility for poly(adenosine diphosphate-ribose) polymerase inhibitors in addition to providing vital information for genetic counselling. Many patients present with effusions necessitating therapeutic drainage, and this makes cytologic specimens (CySs) the initial diagnostic material for HGSC, often before histologic sampling. Initiating somatic BRCA testing on a CyS allows the BRCA status to be determined sooner, and this affects clinical management.

METHODS

Retrospectively, 8 cases of formalin-fixed, paraffin-embedded (FFPE) CySs of peritoneal or pleural fluid from patients with HGSC and known BRCA1/2 alterations previously established by the testing of FFPE surgical specimens (SpSs) underwent next-generation sequencing (NGS). Prospectively, 11 cases of peritoneal or pleural fluid from patients with HGSC but an unknown BRCA1/2 status underwent NGS with fresh, alcohol-fixed, and FFPE CySs, and they were compared with subsequent NGS on 4 SpSs.

RESULTS

CySs yielded high-quantity and high-quality DNA for NGS analysis when sufficient tumor cellularity was present. Fresh, alcohol-fixed, and FFPE CySs were all suitable for NGS and provided identical NGS results. SpS and CyS BRCA testing was concordant in 10 of 12 cases. The 2 discordant cases showed low tumor cellularity and quality in the CyS and the SpS, respectively.

CONCLUSION

Effusion CySs of HGSC are excellent sources for NGS testing for BRCA1/2 genetic alterations when sufficient tumor cellularity is present. Fresh, alcohol-fixed, and FFPE CySs are equivalent for NGS of BRCA1/2. NGS testing of HGSC CySs demonstrates good concordance with SpSs for the BRCA1/2 status.

Somatosensory Pulsatile Tinnitus Syndrome (SSPT) Revisited

INTRODUCTION

Our initial study reported consecutive patients with constant cardiac synchronous subjective tinnitus (pulsatile tinnitus without an identifiable acoustic source (P)) all of whom could suppress their pulsations with head and neck intense muscle contractions ("somatic testing" (ST)). The term somatosensory pulsatile tinnitus syndrome (SSPT) was coined to refer to this type of P. With now more than a decade of clinical experience with P, herein are reported (a) other ways P can present, beside SSPT, (b) how P is related to the somatosensory system and recumbency, and (c) what treatments have been effective.

METHODS

Retrospective case series of 58 adults with P encountered in an outpatient clinic or through telemedicine.

RESULTS

P could be constant or intermittent, with or without non-pulsatile tinnitus (nP). 90% of cases could suppress their pulsations with ST; 9% could not. In 7 of 11 cases that had no P at time of testing, ST elicited P. The most common type of P was SSPT (constant pulsatile tinnitus suppressible by ST) (60%). Treatment of head and neck muscle dysfunction (muscle dry needling and Botulinum toxin injection) has abolished P; auricular electrical stimulation was effective in 2 cases.

CONCLUSION

Suppression of pulsations by ST, eliciting P by ST, and abolishment of P by head and neck muscle treatments all support a major role of the craniocervical somatosensory system in the etiology of most, if not all, cases of P. Three mechanisms are proposed: (A) somatosensory afferents causing dysfunction of the CNS mechanisms that normally suppress self-generated cardiac and vascular sounds, (B) cardiac synchronous disinhibition of the auditory CNS by somatosensory afferents and (C) some combination of A and B.

Somatic Testing: Implications for Targeted Treatment

OBJECTIVE

To provide an overview of key considerations for somatic testing for the purpose of targeting cancer treatment.

DATA SOURCES

Literature; research reports.

CONCLUSION

Genomic testing of cancer cells to identify variants that drive the carcinogenic process is becoming common in clinical settings. Providers and patients need to weigh the potential benefits of testing with technologic and logistic issues.

IMPLICATIONS FOR NURSING PRACTICE

Testing is available for thousands of genomic variants to identify one or more to guide targeted treatment. Oncology nurses need to understand the benefits and limitations of participating in patient-centered implementation of this testing.