Distinct histopathological features are associated with molecular subtypes and outcome in low grade serous ovarian carcinoma

High throughput screening identifies dasatinib as synergistic with trametinib in low grade serous ovarian carcinoma

BACKGROUND

Low grade serous ovarian carcinoma (LGSOC) is a distinct histotype of ovarian cancer characterised high levels of intrinsic chemoresistance, highlighting the urgent need for new treatments. High throughput screening in clinically-informative cell-based models represents an attractive strategy for identifying candidate treatment options for prioritisation in clinical studies.

METHODS

We performed a high throughput drug screen of 1610 agents across a panel of 6 LGSOC cell lines (3 RAS/RAF-mutant, 3 RAS/RAF-wildtype) to identify novel candidate therapeutic approaches. Validation comprised dose-response analysis across 9 LGSOC models and 5 high grade serous comparator lines.

RESULTS

16 hits of 1610 screened compounds were prioritised for validation based on >50% reduction in nuclei counts in over half of screened cell lines at 1000 nM concentration. 11 compounds passed validation, and the four agents of greatest interest (dasatinib, tyrosine kinase inhibitor; disulfiram, aldehyde dehydrogenase inhibitor; carfilzomib, proteasome inhibitor; romidepsin, histone deacetylase inhibitor) underwent synergy profiling with the recently approved MEK inhibitor trametinib. Disulfiram demonstrated excellent selectivity for LGSOC versus high grade serous ovarian carcinoma comparator lines (P = 0.003 for IC50 comparison), while the tyrosine kinase inhibitor dasatinib demonstrated favourable synergy with trametinib across multiple LGSOC models (maximum zero interaction potency synergy score 46.9). The novel, highly selective Src family kinase (SFK) inhibitor NXP900 demonstrated a similar trametinib synergy profile to dasatinib, suggesting that SFK inhibition is the likely driver of synergy.

CONCLUSION

Dasatinib and other SFK inhibitors represent novel candidate treatments for LGSOC and demonstrate synergy with trametinib. Disulfiram represents an additional treatment strategy worthy of investigation.

The survival benefit associated with complete macroscopic resection in epithelial ovarian cancer is histotype specific

BACKGROUND

Complete macroscopic resection is a key factor associated with prolonged survival in ovarian cancer. However, most evidence derives from high-grade serous ovarian carcinoma, and the benefit of complete macroscopic resection in other histotypes is poorly characterized. We sought to determine which histotypes derive the greatest benefit from complete macroscopic resection to better inform future decisions on radical cytoreductive efforts.

METHODS

We performed multivariable analysis of disease-specific survival across 2 independent patient cohorts to determine the magnitude of benefit associated with complete macroscopic resection within each histotype.

RESULTS

Across both cohorts (Scottish: n = 1622; Surveillance, Epidemiology, and End Results [SEER]: n = 18 947), complete macroscopic resection was associated with prolonged disease-specific survival; this was more marked in the Scottish cohort (multivariable hazard ratio [HR] = 0.44, 95% confidence interval [CI] = 0.37 to 0.52 vs HR = 0.59, 95% CI = 0.57 to 0.62 in SEER). In both cohorts, clear cell ovarian carcinoma was among the histotypes to benefit most from complete macroscopic resection (multivariable HR = 0.23 and HR = 0.50 in Scottish and SEER cohorts, respectively); high-grade serous ovarian carcinoma patients demonstrated highly statistically significant and clinically meaningful survival benefit, but this was of lower magnitude than in clear cell ovarian carcinoma and endometrioid ovarian carcinoma across both cohorts. The benefit derived in low-grade serous ovarian carcinoma is also high (multivariable HR = 0.27 in Scottish cohort). Complete macroscopic resection was associated with prolonged survival in mucinous ovarian carcinoma patients in the SEER cohort (multivariable HR = 0.65), but the association failed to reach statistical significance in the Scottish cohort.

CONCLUSIONS

The overall ovarian cancer patient population demonstrates clinically significant survival benefit associated with complete macroscopic resection; however, the magnitude of benefit differs between histotypes.

Molecular Surrogate Subtypes of Ovarian and Peritoneal Low-grade Serous Carcinoma

Low-grade serous carcinoma (LGSC) is an uncommon histotype of ovarian carcinoma, accounting for ~3% of cases. There is evidence that survival of peritoneal LGSC (pLGSC) is longer than that of ovarian LGSC (oLGSC). Key molecular alterations of LGSC have been established, including loss of CDKN2A and PR expression, MAPK pathway alterations, and loss of USP9X expression. We hypothesized that LGSC could be subclassified into clinically applicable molecular subtypes by a few surrogate tests similar to endometrioid carcinomas using a hierarchical decision tree based on the strength of the prognostic associations of the individual alterations. Our study included 71 LGSCs. Immunohistochemistry for CDKN2A, ER, PR, NF1, and USP9X and sequencing for KRAS, NRAS, and BRAF were performed. Our data showed the co-occurrence of key molecular alterations, and despite suggestive trends, hierarchical molecular subtyping did not provide significantly different stratification of patients according to survival in this cohort. We confirmed that patients diagnosed with pLGSC have a longer survival than high-stage oLGSC, with the intriguing observation that normal CDKN2A and PR status were associated with excellent survival in pLGSC. Therefore, CDKN2A and PR status might aid in the classification of indeterminate implants, where abnormal findings favor pLGSC over noninvasive implants. Molecular subtypes should be further evaluated in larger cohorts for their prognostic and potentially predictive value.

Ovarian carcinosarcoma is highly aggressive compared to other ovarian cancer histotypes

Background

Ovarian carcinosarcoma (OCS) is an unusual ovarian cancer type characterized by distinct carcinomatous and sarcomatous components. OCS has been excluded from many of the pan-histotype studies of ovarian carcinoma, limiting our understanding of its behavior.

Methods

We performed a multi-cohort cross-sectional study of characteristics and outcomes in ovarian cancer patients from Scotland (n=2082) and the Surveillance, Epidemiology and End Results Program (SEER, n=44946) diagnosed with OCS or one of the other major histotypes: high grade serous (HGSOC), endometrioid (EnOC), clear cell (CCOC), mucinous (MOC) or low grade serous ovarian carcinoma (LGSOC). Differences in overall survival were quantified using Cox regression models to calculate hazard ratios (HR).

Results

Across both cohorts, OCS patients were significantly older at diagnosis compared to all other histotypes (median age at diagnosis 69 and 67 in Scottish and SEER cohorts) and demonstrated the shortest survival time upon univariable analysis. Within the Scottish cohort, 59.3% and 16.9% of OCS patients presented with FIGO stage III and IV disease, respectively; this was significantly higher than in EnOC, CCOC or MOC (P<0.0001 for all), but lower than in HGSOC (P=0.004). Multivariable analysis accounting for other prognostic factors identified OCS as independently associated with significantly shorter survival time compared to HGSOC, EnOC, LGSOC and MOC in both the Scottish (multivariable HR vs OCS: HGSOC 0.45, EnOC 0.39, LGSOC 0.26, MOC 0.43) and SEER cohorts (multivariable HR vs OCS: HGSOC 0.59, EnOC 0.34, LGSOC 0.30, MOC 0.81). Within the SEER cohort, OCS also demonstrated shorter survival compared to CCOC (multivariable HR 0.63, 95% CI 0.58-0.68), but this was not replicated within the Scottish cohort (multivariable HR for CCOC: 1.05, 95% CI 0.74-1.51). Within early-stage disease specifically (FIGO I-II or SEER localized stage), OCS was associated with the poorest survival of all histotypes across both cohorts. In the context of late-stage disease (FIGO III-IV or SEER distant stage), OCS, MOC and CCOC represented the histotypes with poorest survival.

Conclusion

OCS is a unique ovarian cancer type that affects older women and is associated with exceptionally poor outcome, even when diagnosed at earlier stage. New therapeutic options are urgently required to improve outcomes.

Efficacy and safety of bevacizumab in patients with low-grade serous ovarian cancer

Aim: To investigate the efficacy and safety of bevacizumab in patients with recurrent low-grade serous ovarian carcinoma. Materials & methods: The data of patients who received at least two cycles of bevacizumab in combination with chemotherapy were retrospectively recorded. Results: The median age of 51 patients was 56 (range: 33-75) years. The complete response rate was 10.4% and the partial response rate was 43.7%. The objective response rate was 54.1%. Median progression-free survival was 15.9 months (95% CI: 9.1-22.6) and median overall survival was 42.5 months (95% CI: 37.2-47.8). Conclusion: Bevacizumab with chemotherapy is an effective option for treating recurrent ovarian low-grade serous carcinoma.