David M. Gershenson

Selumetinib in women with recurrent low-grade serous carcinoma of the ovary or peritoneum: an open-label, single-arm, phase 2 study.

BACKGROUND Low-grade serous carcinoma of the ovary is chemoresistant but mutations in the MAPK pathway could be targeted to control tumour growth. We therefore assessed the safety and activity of selumetinib, an inhibitor of MEK1/2, for patients with this cancer. METHODS In this open-label, single-arm phase 2 study, women (aged ≥18 years) with recurrent low-grade serous ovarian or peritoneal carcinoma were given selumetinib (50 mg twice daily, orally) until progression. The primary endpoint was the proportion of patients who had an objective tumour response according to RECIST version 1.1, assessed for all the treated patients. Analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00551070. FINDINGS 52 patients were enrolled between Dec 17, 2007, and Nov 23, 2009. All were eligible for analyses. Eight (15%) patients had an objective response to treatment-one patient had a complete response and seven had partial responses. 34 (65%) patients had stable disease. There were no treatment-related deaths. Grade 4 toxicities were cardiac (one), pain (one), and pulmonary events (one). Grade 3 toxicities that occurred in more than one patient were gastrointestinal (13), dermatological (nine), metabolic (seven), fatigue (six), anaemia (four), pain (four), constitutional (three), and cardiac events (two). INTERPRETATION Selumetinib is well tolerated, and is active in the treatment of recurrent low-grade serous carcinoma of the ovary or peritoneum. The findings suggest that inhibitors of the MAPK pathway warrant further investigation in these patients. FUNDING National Cancer Institute.

BRAF mutation is rare in advanced-stage low-grade ovarian serous carcinomas.

Low-grade ovarian serous carcinomas are believed to arise via an adenoma-serous borderline tumor-serous carcinoma sequence. In this study, we found that advanced-stage, low-grade ovarian serous carcinomas both with and without adjacent serous borderline tumor shared similar regions of loss of heterozygosity. We then analyzed 91 ovarian tumor samples for mutations in TP53, BRAF, and KRAS. TP53 mutations were not detected in any serous borderline tumors (n = 30) or low-grade serous carcinomas (n = 43) but were found in 73% of high-grade serous carcinomas (n = 18). BRAF (n = 9) or KRAS (n = 5) mutation was detected in 47% of serous borderline tumors, but among the low-grade serous carcinomas (39 stage III, 2 stage II, and 2 stage I), only one (2%) had a BRAF mutation and eight (19%) had a KRAS mutation. The low frequency of BRAF mutations in advanced-stage, low-grade serous carcinomas, which contrasts with previous findings, suggests that aggressive, low-grade serous carcinomas are more likely derived from serous borderline tumors without BRAF mutation. In addition, advanced-stage, low-grade carcinoma patients with BRAF or KRAS mutation have a better apparent clinical outcome. However, further investigation is needed.

Ovarian low-grade serous carcinoma: A comprehensive update

Ovarian low-grade serous ovarian carcinoma (OvLGSCa) comprises a minority within the heterogeneous group of ovarian carcinomas. Despite biological differences with their high-grade serous counterparts, current treatment guidelines do not distinguish between these two entities. OvLGSCas are characterized by an indolent clinical course. They usually develop from serous tumors of low malignant potential, although they can also arise de novo. When compared with patients with ovarian high grade serous carcinoma (OvHGSCa) patients with OvLGSCa are younger and have better survival outcomes. Current clinical and treatment data available for OvLGSCa come from retrospective studies, suggesting that optimal cytoreductive surgery remains the cornerstone in treatment, whereas chemotherapy has a limited role. Molecular studies have revealed the preponderance of the RAS-RAF-MAPK signaling pathway in the pathogenesis of OvLGSCa, thereby representing an attractive therapeutic target for patients affected by this disease. Improved clinical trial designs and international collaboration are required to optimally address the unmet medical treatment needs of patients affected by this disease.

KRAS (but not BRAF) mutations in ovarian serous borderline tumour are associated with recurrent low-grade serous carcinoma

BRAF and KRAS mutations in ovarian serous borderline tumours (OSBTs) and ovarian low‐grade serous carcinomas (LGSCs) have been previously described. However, whether those OSBTs would progress to LGSCs or whether those LGSCs were developed from OSBT precursors in previous studies is unknown. Therefore, we assessed KRAS and BRAF mutations in tumour samples from 23 recurrent LGSC patients with a known initial diagnosis of OSBT. Paraffin blocks from both OSBT and LGSC samples were available for five patients, and either OSBTs or LGSCs were available for another 18 patients. Tumour cells from paraffin‐embedded tissues were dissected out for mutation analysis by conventional polymerase chain reaction (PCR) and Sanger sequencing. Tumours that appeared to have wild‐type KRAS by conventional PCR–Sanger sequencing were further analysed by full COLD (co‐amplification at lower denaturation temperature)‐PCR and deep sequencing. Full COLD‐PCR was able to enrich the amplification of mutated alleles. Deep sequencing was performed with the Ion Torrent personal genome machine (PGM). By conventional PCR–Sanger sequencing, BRAF mutation was detected only in one patient and KRAS mutations were detected in ten patients. Full COLD‐PCR deep sequencing detected low‐abundance KRAS mutations in eight additional patients. Three of the five patients with both OSBT and LGSC samples available had the same KRAS mutations detected in both OSBT and LGSC samples. The remaining two patients had only KRAS mutations detected in their LGSC samples. For patients with either OSBT or LGSC samples available, KRAS mutations were detected in seven OSBT samples and six LGSC samples. Surprisingly, patients with the KRAS G12V mutation have shorter survival times. In summary, KRAS mutations are very common in recurrent LGSC, while BRAF mutations are rare. The findings indicate that recurrent LGSC can arise from proliferation of OSBT tumour cells with or without detectable KRAS mutations. Copyright

Extreme Outlier Analysis Identifies Occult Mitogen-Activated Protein Kinase Pathway Mutations in Patients With Low-Grade Serous Ovarian Cancer

PURPOSE No effective systemic therapy exists for patients with metastatic low-grade serous (LGS) ovarian cancers. BRAF and KRAS mutations are common in serous borderline (SB) and LGS ovarian cancers, and MEK inhibition has been shown to induce tumor regression in a minority of patients; however, no correlation has been observed between mutation status and clinical response. With the goal of identifying biomarkers of sensitivity to MEK inhibitor treatment, we performed an outlier analysis of a patient who experienced a complete, durable, and ongoing (> 5 years) response to selumetinib, a non-ATP competitive MEK inhibitor. PATIENTS AND METHODS Next-generation sequencing was used to analyze this patients tumor as well as an additional 28 SB/LGS tumors. Functional characterization of an identified novel alteration of interest was performed. RESULTS Analysis of the extraordinary responders tumor identified a 15-nucleotide deletion in the negative regulatory helix of the MAP2K1 gene encoding for MEK1. Functional characterization demonstrated that this mutant induced extracellular signal-regulated kinase pathway activation, promoted anchorage-independent growth and tumor formation in mice, and retained sensitivity to selumetinib. Analysis of additional LGS/SB tumors identified mutations predicted to induce extracellular signal-regulated kinase pathway activation in 82% (23 of 28), including two patients with BRAF fusions, one of whom achieved an ongoing complete response to MEK inhibitor-based combination therapy. CONCLUSION Alterations affecting the mitogen-activated protein kinase pathway are present in the majority of patients with LGS ovarian cancer. Next-generation sequencing analysis revealed deletions and fusions that are not detected by older sequencing approaches. These findings, coupled with the observation that a subset of patients with recurrent LGS ovarian cancer experienced dramatic and durable responses to MEK inhibitor therapy, support additional clinical studies of MEK inhibitors in this disease.

Gynecologic Cancer InterGroup (GCIG) Consensus Review for Ovarian and Primary Peritoneal Low-Grade Serous Carcinomas

Abstract Low-grade serous ovarian cancer is a recently described histological subtype of ovarian cancer that is clinically and molecularly distinct from the 4 other main histological subtypes (high-grade serous, clear cell, endometrioid, and mucinous). In particular, it differs from high-grade serous ovarian cancer in that it presents at a much younger age, is more indolent, and is relatively chemoresistant. Very few clinical trials have been performed exclusively in this tumor type; and as such, specific data guiding optimal management are limited.

The Life and Times of Low-Grade Serous Carcinoma of the Ovary

For the past several years, all women with epithelial ovarian cancer have been treated identically, whether in a clinical trial or off protocol. Over the past decade, we have come to appreciate the magnitude of the heterogeneity of ovarian cancer. The development of the binary grading system for serous carcinoma was a major advance, leading to separate clinical trials for patients with this subtype, originating from the Gynecologic Oncology Groups Rare Tumor Committee. The mitogen-activated protein kinase (MAPK) pathway appears to play a prominent role in the pathogenesis of this subtype. Approximately 20% to 40% of low-grade serous carcinomas have a KRAS mutation, while BRAF mutations are rare-approximately 5%. In genomic profiling studies, these tumors appear to cluster with serous tumors of low malignant potential. Compared with high-grade serous carcinomas, low-grade serous carcinomas are also characterized by a low frequency of p53 mutations, greater expression of ER and PR, and greater expression of PAX2 and IGF-1. Primary treatment of low-grade serous carcinoma includes surgery plus platinum-based chemotherapy (either adjuvant or neoadjuvant). Clinical behavior is characterized by young age at diagnosis, relative chemoresistance, and prolonged overall survival. Current options for treatment of relapsed disease include secondary cytoreduction in selected patients, salvage chemotherapy, or hormone therapy. A recently completed trial of a MEK inhibitor for women with recurrent disease demonstrated promising activity. Future directions will include further investigations of the molecular biology and biomarker-driven clinical trials with targeted agent monotherapy and combinations.

Intratumoral heterogeneity in a minority of ovarian low-grade serous carcinomas

BackgroundOvarian low-grade serous carcinoma (LGSC) has fewer mutations than ovarian high-grade serous carcinoma (HGSC) and a less aggressive clinical course. However, an overwhelming majority of LGSC patients do not respond to conventional chemotherapy resulting in a poor long-term prognosis comparable to women diagnosed with HGSC. KRAS and BRAF mutations are common in LGSC, leading to clinical trials targeting the MAPK pathway. We assessed the stability of targetable somatic mutations over space and/or time in LGSC, with a view to inform stratified treatment strategies and clinical trial design.MethodsEleven LGSC cases with primary and recurrent paired samples were identified (stage IIB-IV). Tumor DNA was isolated from 1–4 formalin-fixed paraffin-embedded tumor blocks from both the primary and recurrence (n = 37 tumor and n = 7 normal samples). Mutational analysis was performed using the Ion Torrent AmpliSeqTM Cancer Panel, with targeted validation using Fluidigm-MiSeq, Sanger sequencing and/or Raindance Raindrop digital PCR.ResultsKRAS (3/11), BRAF (2/11) and/or NRAS (1/11) mutations were identified in five unique cases. A novel, non-synonymous mutation in SMAD4 was observed in one case. No somatic mutations were detected in the remaining six cases. In two cases with a single matched primary and recurrent sample, two KRAS hotspot mutations (G12V, G12R) were both stable over time. In three cases with multiple samplings from both the primary and recurrent surgery some mutations (NRAS Q61R, BRAF V600E, SMAD4 R361G) were stable across all samples, while others (KRAS G12V, BRAF G469V) were unstable.ConclusionsOverall, the majority of cases with detectable somatic mutations showed mutational stability over space and time while one of five cases showed both temporal and spatial mutational instability in presumed drivers of disease. Investigation of additional cases is required to confirm whether mutational heterogeneity in a minority of LGSC is a general phenomenon that should be factored into the design of clinical trials and stratified treatment for this patient population.