Vivek Podder

Phase II Trial of Ribociclib Plus Letrozole in Women With Recurrent Low-Grade Serous Carcinoma of the Ovary, Fallopian Tube, or Peritoneum: A GOG Partners Trial (GOG 3026)

PURPOSE Low-grade serous carcinoma (LGSOC) of the ovary, fallopian tube, or peritoneum is a hormonally driven, relatively chemoresistant malignancy with limited treatment options in the recurrent setting. Given frequent estrogen receptor (ER) expression and dysregulation of the cyclin-dependent kinases 4 and 6 (CDK4/6)–p16–Rb pathway, features shared with hormone receptor–positive breast cancer, dual endocrine, and CDK4/6 inhibition is a biologically rational strategy. This phase II trial evaluated ribociclib plus letrozole in recurrent LGSOC. METHODS This open-label, single-arm, multicenter phase II study enrolled women with measurable, recurrent LGSOC. Patients received ribociclib (600 mg orally, once daily, days 1-21 of a 28-day cycle) and letrozole (2.5 mg orally, once daily). The primary end point was investigator-assessed objective response rate (ORR) per RECIST 1.1. Secondary end points included clinical benefit rate (CBR), progression-free survival (PFS), overall survival (OS), and safety. RESULTS Of 74 patients screened, 51 were enrolled and 49 treated. The confirmed ORR was 30.6% (90% CI, 19.9 to 43.2), including one complete and 14 partial responses. Among responders, the median duration of response was 21.2 months. The CBR was 84% (90% CI, 72.5 to 91.6). The median PFS was 14.5 months (90% CI, 10.1 to 28.8), and the median OS was 44.5 months (90% CI, 31.8 to not reached). The most common grade ≥3 adverse event (AE) was neutropenia (47%), managed with dose modifications. Three grade 5 events (6%) occurred but were unrelated to treatment. Treatment discontinuation because of AEs occurred in 4%. No dose-limiting toxicities were observed. CONCLUSION Ribociclib plus letrozole met the primary end point, achieving meaningful response rates and durable disease control in recurrent LGSOC. The safety profile was consistent with prior CDK4/6 inhibitor studies. This combination represents a therapeutic option in this rare and genomically distinct subtype.

Repurposing Food and Drug Administration-approved cancer therapies: exploring endocrine and targeted pathways in low-grade serous ovarian cancer treatment

Low-grade serous ovarian cancer is a rare epithelial ovarian cancer with limited responsiveness to conventional chemotherapy, particularly, in advanced or recurrent settings. Low-grade serous ovarian cancer is characterized by an indolent growth pattern and a high prevalence of mitogen-activated protein kinase pathway alterations (KRAS, BRAF, NRAS) and hormone receptor positivity, highlighting the potential for targeted therapies. MEK inhibitors (eg, trametinib, binimetinib) specifically target the mitogen-activated protein kinase pathway, whereas endocrine therapies and cyclin-dependent kinase 4/6 (CDK4/6) inhibitors exploit hormone-driven pathways. This review explores the repurposing of the therapeutic potential of both MEK inhibitors and breast cancer therapies, as endorsed by the National Comprehensive Cancer Network, to improve outcomes in low-grade serous ovarian cancer. This review synthesizes evidence supporting the repurposing of MEK inhibitors and breast cancer therapies (endocrine therapies, CDK4/6 inhibitors, and mammalian target of rapamycin inhibitors) as treatment approaches for low-grade serous ovarian cancer. Trametinib significantly improved progression-free survival in the GOG 281 trial, establishing MEK inhibition as a key therapeutic option. In addition, molecular similarities in estrogen receptor/progesterone receptor, phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin, and CDK4/6 pathways between low-grade serous ovarian cancer and breast cancer provide a strong rationale for therapeutic crossover. Endocrine therapies demonstrated efficacy in low-grade serous ovarian cancer, particularly when combined with targeted agents to address resistance mechanisms. CDK4/6 inhibitors showed promise by blocking cell cycle progression and enhancing the response to endocrine therapies. In addition, mammalian target of rapamycin inhibitors have yielded clinical benefits in selected patients, emphasizing the importance of biomarker-driven treatment. Repurposing MEK inhibitors and endocrine-based approaches is shaping the treatment landscape for low-grade serous ovarian cancer, particularly in recurrent or advanced cases with limited treatment options. However, the variability in pathway alterations necessitates precise molecular profiling and optimized combination strategies. Future studies leveraging patient-derived models and advanced profiling techniques are critical for refining these approaches. These efforts may help expand National Comprehensive Cancer Network-endorsed options, and provide new hope for patients with hormone-sensitive low-grade serous ovarian cancer.

Homologous recombination deficiency in endometrial cancer: shedding light on recent clinical findings

Endometrial cancer is the most common gynecologic malignancy in the United States, with rising incidence and high recurrence rates. Immune checkpoint inhibitors (ICIs) benefit patients with mismatch repair-deficient (dMMR) tumors, but options remain limited for those with mismatch repair-proficient (pMMR) disease. Homologous recombination deficiency (HRD), a genomic instability phenotype, has emerged as a therapeutic target. Poly(adenosine diphosphate-ribose) polymerase inhibitors (PARPis) are being investigated in endometrial cancer, with studies exploring whether HRD predicts response, particularly in combination with ICIs or chemotherapy. This review examines HRD in endometrial cancer, focusing on its molecular basis, clinical implications, and emerging therapeutic strategies. HRD occurs in a sub-set of endometrial cancers, particularly non-endometrioid sub-types, and is linked to genomic instability and platinum sensitivity. The Cancer Genome Atlas (TCGA) molecular classification has improved understanding of HRD prevalence across sub-types. HRD testing remains challenging due to a lack of standardization, with current methods including genomic-scar assays, next-generation sequencing, and functional assays. Clinical trials, such as DUO-E and RUBY-2, suggest that PARPi combined with ICIs or chemotherapy may improve outcomes in pMMR tumors, whereas PARPi monotherapy offers limited benefits. Resistance to PARPi is common, driven by the restoration of homologous recombination repair, replication fork stabilization, and drug efflux. HRD is a promising biomarker and therapeutic target in endometrial cancer. Evidence supports the integration of PARPi for select populations, although further research is needed to refine testing, optimize patient selection, and overcome resistance. Future trials should prioritize predictive biomarkers and novel combinations to maximize the benefits of PARPi in HRD endometrial cancer.

Checkpoint inhibitor rechallenge in advanced endometrial cancer: revisiting the immune landscape beyond first-line therapy

The integration of immune checkpoint inhibitors into frontline therapy for advanced or recurrent endometrial cancer has transformed treatment paradigms, particularly for patients with mismatch repair-deficient (dMMR) tumors. However, this advancement has introduced a pressing clinical challenge: how to manage patients who experience disease progression following exposure to a prior immune checkpoint inhibitor. Despite the absence of prospective guidance, immune checkpoint inhibitor rechallenge is already occurring in clinical practice. Notably, 35% of patients in the dostarlimab arm of the RUBY trial received subsequent immunotherapy off-protocol, highlighting the gap between evolving clinical behavior and available evidence. Emerging retrospective data suggest that retreatment with immune checkpoint inhibitors may be clinically and biologically plausible, particularly in biomarker-enriched populations. In a study, 54.5% of patients with dMMR endometrial cancer responded to second-line immune checkpoint inhibitor rechallenge, including complete responses. Additional reports indicate that combining immune checkpoint inhibitors with anti-vascular endothelial growth factors or multi-kinase inhibitors, such as lenvatinib or cabozantinib, may enhance immune reactivation even in microsatellite-stable or carcinosarcoma histologies. Nonetheless, toxicity remains a concern, with grade 3 to 4 immune-related adverse events and high rates of dose modification reported. Mechanistic insights point to immune escape pathways, including vascular endothelial growth factor-driven immunosuppression, MLH1 methylation, and high subclonal neoantigen burden, as contributors to immune checkpoint inhibitor resistance. These findings support the use of rational combinations and novel targets. Prospective trials such as NRG-GY025 are now evaluating dual checkpoint blockade in immune checkpoint inhibitor-pretreated dMMR endometrial cancer. In contrast, synthetic lethality strategies, such as the Werner helicase inhibitor HRO761 in high microsatellite instability tumors, represent promising non-immune-based rechallenge approaches. As immune checkpoint inhibitor exposure becomes commonplace in earlier treatment settings, there is an urgent need for biologically informed, individualized strategies to guide post-immune checkpoint inhibitor management. Future progress will depend on refining rechallenge criteria, optimizing combination regimens, and developing predictive biomarkers to identify patients most likely to benefit from retreatment.

Validation of comprehensive genomic profiling for prognostic and potential therapeutic molecular classification of endometrial cancer

We sought to validate the prognostic utility of comprehensive genomic profiling (CGP)-based molecular stratification for patients with endometrial carcinoma and to assess co-occurring biomarkers across subtypes. This study included patients from a de-identified nationwide (US-based) endometrial cancer clinicogenomic database who underwent CGP testing as part of routine care. Molecular subtypes were classified as POLE mutated (POLEmut), MSI-H, TP53 mutated (TP53mut), and no specific molecular profile (NSMP). Time to next treatment and overall survival were compared between molecular subtypes, with multivariable Cox models adjusted for relevant covariables. Of 1,139 evaluated patients with advanced or recurrent endometrial carcinoma, the prevalence of the 4 molecular subtypes was 1% POLEmut, 22% high microsatellite instability, 47% TP53mut, and 31% NSMP. Compared with NSMP patients, POLEmut patients had numerically more favorable time to next treatment (HR 0.50, 95% CI 0.21 to 1.21) and overall survival (HR 0.52, 95% CI 0.17 to 1.66). High microsatellite instability patients had similar time to next treatment (HR 1.08, 95% CI 0.89 to 1.30) and overall survival (HR 0.91, 95% CI 0.71 to 1.19) relative to NSMP patients. TP53mut patients had the least favorable outcomes for time to next treatment (compared with NSMP, HR 1.39, 95% CI 1.19 to 1.62) and overall survival (HR 2.15, 95% CI 1.77 to 2.61). In multivariable analysis, TP53mut status was associated with less favorable time to next treatment and overall survival. Frequencies of other biomarkers varied by molecular subtype. The Cancer Genome Atlas (TCGA)/Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) molecular classifier for endometrial carcinoma can be recapitulated using CGP and provides prognostic stratification even within an advanced or recurrent disease cohort. CGP for molecular subclassification could support trial design and enrollment and inform treatment escalation or selection.