Decreased HER2 expression in endometrial cancer following anti-HER2 therapy

Trastuzumab has demonstrated clinical efficacy in the treatment of HER2-positive serous endometrial cancer (EC), which led to its incorporation into standard-of-care management of this aggressive disease. Acquired resistance remains an important challenge, however, and its underlying mechanisms in EC are unknown. To define the molecular changes that occur in response to anti-HER2 therapy in EC, targeted next-generation sequencing (NGS), HER2 immunohistochemistry (IHC), and fluorescence in situ hybridization (FISH) were performed on pre- and post-treatment tumour samples from 14 patients with EC treated with trastuzumab or trastuzumab emtansine. Recurrent tumours after anti-HER2 therapy acquired additional genetic alterations compared with matched pre-treatment ECs and frequently showed decreased HER2 protein expression by IHC (7/14, 50%). Complete/near-complete absence of HER2 protein expression (score 0/1+) observed post-treatment (4/14, 29%) was associated with retained HER2 gene amplification (n = 3) or copy number neutral status (n = 1). Whole-exome sequencing performed on primary and recurrent tumours from the latter case, which exhibited genetic heterogeneity of HER2 amplification in the primary tumour, revealed selection of an early HER2-non-amplified clone following therapy. Our findings demonstrate that loss of target expression, by selection of HER2-non-amplified clones or, more commonly, by downregulation of expression, may constitute a mechanism of resistance to anti-HER2 therapy in HER2-positive EC. © 2023 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

HER2 Genetic Intratumor Heterogeneity Is Associated With Resistance to Trastuzumab and Trastuzumab Emtansine Therapy in Recurrent High-Grade Endometrial Cancer

Anti-HER2 targeted therapies have recently demonstrated clinical activity in the treatment of high-grade endometrial carcinomas (ECs), particularly serous carcinomas with HER2 amplification and/or overexpression. Intratumor heterogeneity of HER2 amplification or HER2 genetic intratumor heterogeneity (G-ITH) has been associated with resistance to anti-HER2 therapies in breast and gastroesophageal cancers; however, its clinical relevance in EC is unknown. To characterize HER2 G-ITH in EC, archival specimens from a clinically annotated cohort of 57 ECs treated with trastuzumab or trasutuzmab emtansine in the recurrent (n = 38) or adjuvant (n = 19) setting were subjected to central pathology review, HER2 assessment by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), and next-generation sequencing. HER2 G-ITH, defined as HER2 amplification in 5% to 50% of tumor cells examined by FISH, was identified in 36% (19/53) of ECs and was associated with lower HER2 copy number and levels of protein expression. HER2 IHC revealed spatially distinct areas of strong expression juxtaposed with areas of low/absent expression in tumors with the "cluster" pattern of G-ITH, whereas the "mosaic" pattern was typically associated with a diffuse admixture of cells with variable levels of HER2 expression. HER2 G-ITH was frequently observed in cases with IHC/FISH or FISH/next-generation sequencing discrepancies and/or with an equivocal/negative FISH result (9/13, 69%). Although the objective response rate to anti-HER2 therapy in recurrent ECs was 52% (13/25) for tumors lacking HER2 G-ITH, none (0%, 0/10) of the patients with HER2 G-ITH achieved a complete or partial response (P = .005). HER2 G-ITH was significantly associated with worse progression-free survival (hazard ratio, 2.88; 95% CI, 1.33-6.27; P = .005) but not overall survival. HER2 IHC score, HER2/CEP17 ratio, HER2 copy number, histologic subtype, and other genetic alterations, including PIK3CA hotspot mutations, were not significantly associated with therapeutic response or survival outcomes. Treatment responses were not restricted to serous carcinomas, supporting consideration of anti-HER2 therapy in patients with HER2-positive high-grade ECs of non-serous histology. Our results demonstrate that HER2 G-ITH is an important determinant of response to trastuzumab and trastuzumab emtansine in EC, providing a rationale for the development of novel therapeutic strategies to target HER2-nonamplified resistant tumor subpopulations, such as HER2 antibody-drug conjugates with bystander effects.

Predicting recurrence and recurrence-free survival in high-grade endometrial cancer using machine learning

OBJECTIVE

To develop machine-learning models to predict recurrence and time-to-recurrence in high-grade endometrial cancer (HGEC) following surgery and tailored adjuvant treatment.

METHODS

Data were retrospectively collected across eight Canadian centers including 1237 patients. Four models were trained to predict recurrence: random forests, boosted trees, and two neural networks. Receiver operating characteristic curves were used to select the best model based on the highest area under the curve (AUC). For time to recurrence, we compared random forests and Least Absolute Shrinkage and Selection Operator (LASSO) model to Cox proportional hazards.

RESULTS

The random forest was the best model to predict recurrence in HGEC; the AUCs were 85.2%, 74.1%, and 71.8% in the training, validation, and test sets, respectively. The top five predictors were: stage, uterus height, specimen weight, adjuvant chemotherapy, and preoperative histology. Performance increased to 77% and 80% when stratified by Stage III and IV, respectively. For time to recurrence, there was no difference between the LASSO and Cox proportional hazards models (c-index 71%). The random forest had a c-index of 60.5%.

CONCLUSIONS

A bootstrap random forest model may be a more accurate technique to predict recurrence in HGEC using multiple clinicopathologic factors. For time to recurrence, machine-learning methods performed similarly to the Cox proportional hazards model.

Disparities in adjuvant treatment of high-grade endometrial cancer in the Medicare population

BACKGROUND

Black women experience worse survival effects with high-grade endometrial cancer. Differences in adjuvant treatment have been proposed to be major contributors to this disparity. However, little is known about the differences in type or timing of adjuvant treatment as it relates to race and ethnicity in the Medicare population.

OBJECTIVE

This study aimed to examine patterns of adjuvant therapy and survival for non-Hispanic Black women vs non-Hispanic White women and Hispanic women who have undergone surgery for high-grade endometrial cancer in the Medicare population.

STUDY DESIGN

We used the Medicare-linked Surveillance, Epidemiology, and End Results database to identify women who underwent surgery as a primary treatment for uterine grade 3 endometrioid adenocarcinoma, carcinosarcoma, clear-cell carcinoma, or serous carcinoma between the years 2000 and 2015. Women who did not identify as White or Black race or Hispanic ethnicity were excluded. Multinomial logistic regression was used to estimate odds ratios and 95% confidence intervals for receiving a treatment delay or not receiving adjuvant treatment (compared with those who received adjuvant treatment within 12 weeks) adjusted for clinical and demographic characteristics. Overall survival was stratified by race and ethnicity, route of surgery, operative complications, and type and timing of adjuvant therapy, which were analyzed using the Kaplan-Meier method. Cox proportional-hazards regression was used to estimate the hazard ratio of death by race and ethnicity adjusted for known predictors and surgical outcomes and adjuvant therapy patterns.

RESULTS

A total of 12,201 women met the study inclusion criteria. Non-Hispanic Black patients had a significantly worse 5-year overall survival than Hispanic and non-Hispanic White patients (30.9 months vs 51.0 months vs 53.6 months, respectively). Approximately 632 of 7282 patients (8.6%) who received adjuvant treatment experienced a treatment delay. Delay in treatment of ≥12 weeks was significantly different by race and ethnicity (P=.034), with 12% of Hispanic, 9% of non-Hispanic Black, and 8% of non-Hispanic White women experiencing a delay. After adjustment for the number of complications, age, histology (endometrioid vs nonendometroid), International Federation of Gynecology and Obstetrics stage, marital status, comorbidity count, surgical approach, lymph node dissection, and urban-rural code, Hispanic women had a 71% increased risk of treatment delay (odds ratio, 1.71; 95% confidence interval, 1.23-2.38) for all stages of disease. In the same model, non-Hispanic Black race was independently predictive of decreased use of adjuvant treatment for the International Federation of Gynecology and Obstetrics stage II and higher (odds ratio, 1.32; 95% confidence interval, 1.04-1.68). Non-Hispanic Black race, number of perioperative complications, and nonendometrioid histology were predictive of worse survival in univariate models. Treatment delay was not independently predictive of worse 1- or 5-year survival at any stage.

CONCLUSION

Non-Hispanic Black race was predictive of worse 5-year survival across all stages and was associated with omission of adjuvant treatment in International Federation of Gynecology and Obstetrics stage II or higher high-grade endometrial cancer. In unadjusted analyses, patients who experience treatment omission or delay experienced poorer overall survival, but these factors were not independently associated in multivariate analyses. This study suggests that race and ethnicity are independently associated with the type and timing of adjuvant treatment in patients with high-grade endometrial cancer. Further efforts to identify specific causes of barriers to care and timely treatment are imperative.