MEK inhibitor treatment is effective in a patient with metastatic carcinoma of the ampulla of Vater with BRAF and NRAS mutations shown by next-generation sequencing
Here, we present a case of an 84-year-old woman who developed obstructive jaundice and was diagnosed with nonoperable adenocarcinoma originating from the ampulla of Vater, a lethal disease with a median overall survival of less than a year. Her tumor was examined by next- generation sequencing, which showed BRAF and NRAS mutations. To target these mutations, a MEK inhibitor was chosen for treatment. The patient has been treated with a MEK inhibitor for the last 12 months since diagnosis, with clinical and laboratory improvement and manageable side effects. PET-computed tomography imaging has shown stable disease or improvement in the primary and metastatic lesions. This is the first case report of an ampulla of a Vater cancer patient with NRAS and BRAF mutations, identified in next-generation sequencing, and treated successfully with a MEK inhibitor.
Keywords: BRAF, carcinoma of the ampulla of Vater, MEK inhibitor, next-generation sequencing, NRAS
Introduction
Carcinoma of the ampulla of Vater (usually classified as cholangiocarcinoma) has a low probability of durable response to first-line chemotherapy and no effective subsequent lines. Understanding genetic aberrations by performing next-generation sequencing (NGS) can lead to the discovery of new targets and molecularly targeted therapies can be administered accordingly, with potential for meaningful positive outcomes.
Sequenced cholangiocarcinoma samples [1] have shown different targetable mutations. In addition, researchers have studied a range of biological therapies in cholangiocarci- noma. For example, MEK inhibitors, which have shown activity [2] in cholangiocarcinoma, prevent activation of the RAS–RAF–MEK pathway. These patients (and patients in similar series) are usually treated empirically without per- forming NGS. Treatment according to NGS can lead to a higher probability of response because the driver mutation is identified and targeted.In the case presented here, NGS was performed on a sample from a metastatic cholangiocarcinoma patient, which showed two rare but targetable mutations in BRAF (G466E) and NRAS (G12V).
BRAF G466E
When RAS is activated, it recruits RAF to the membrane for activation through phosphorylation. RAF phosphor- ylates and activates MEK, which phosphorylates and acti- vates ERK [3], which in turn leads to cell growth. In most human cancer, mutated RAF causes constitutive signaling (unrelated to RAS activation) by enhancing its ability to phosphorylate MEK [4,5]. Mutations in RAF are common in many malignancies, but are rare in pancreatic/biliary tract malignancies (reported in 0–4% of the cases) and are associated with a worse prognosis [1,6–8].
Specific BRAF mutations (such as G466E) have ‘impaired’ activity [4,9] and although they cannot directly phosphorylate MEK, they appear to retain sufficient activity to phosphorylate and activate CRAF, allowing these mutants to activate the MEK pathway indirectly [10,11]. In BRAF mutated melanoma patients treated with BRAF inhibitors, the indirect activation through CRAF can cause squamous cell carcinoma of the skin [12].
BRAF-specific tyrosine kinase inhibitors are considered to be ineffective in this case because the BRAF is already ‘impaired’. Because the MEK–ERK pathway is indirectly activated, MEK inhibitors may be used [13]. In melanoma patients [14], administration of MEK
inhibitors in addition to BRAF inhibitors effectively prevents the development of squamous cell carcinoma of the skin and adds to the effectiveness of BRAF inhibitors.
NRAS G12V
Activation of RAS signaling causes activation of the RAF–MAPK–ERK pathway and induces cell growth and survival. The G12V mutation is constitutively activated.NRAS mutations have been reported in 2% of biliary tract cancers [15,16].
Patient information
Pretreatment
An 84-year-old woman, in good general health aside from osteoporosis, developed obstructive jaundice in September 2014. A computed tomography (CT) scan showed dilated common bile duct and intrahepatic ducts with a mass in the distal common bile duct or papilla of Vater and at least two enlarged lymph nodes near the renal veins. Endoscopic retrograde choledocopancreato- graphy showed a tumor of the papilla of Vater. Biopsies were taken and a stent was inserted. Pathology showed adenocarcinoma with a papillary pattern. Because of the small amount of biopsy material, there was no specifica- tion of intestinal or ductal cell type. Because of blockage, a second stent was inserted 1 month later, in October 2014.
To further clarify the staging, a fluorine-18-fluorodeoxy- glucose (18F-FDG) PET/CT scan was carried out in October 2014, indicating a mass surrounding the ampulpatient has two sisters with the BRCA mutation, no mutation in BRCA was identified in the sample.
Treatment
On the basis of BRAF mutation, a MEK inhibitor was proposed as treatment (see below, ‘Discussion’). The MEK inhibitor trametinib was started at a full dose (2 mg daily) in November 2014.Toxicities noted included grade 2 rash, grade 3 diarrhea, grade 3 fatigue, and grade 2 peripheral edema that responded well to low-dose furosemide. These clinical side effects were well controlled by short-term dose reductions of trametinib to 1.5 mg/day. Laboratory side effects were anemia, mild hyponatremia, and hypoalbu- minemia, most probably not related to the therapy.
Gamma-glutamyl transferase decreased after starting treatment from 267 IU/l (November 2014) to 100 IU/l (June 2015) and alkaline phosphatase decreased from 349 IU/l (November 2014) to 224 IU/l (June 2015). Since then, the values have shown variability, but are generally stable.
A second 18F-FDG PET/CT scan was carried out in February 2015 (3 months after starting treatment). There was a decrease in the intensity of 18F-FDG uptake in the lymph nodes with high 18F-FDG uptake (SUVmax 19).CA 19-9 and carcinoembryonic antigen levels were nor- mal at diagnosis. Bilirubin normalized after stent inser- tion. Elevated gamma-glutamyl transferase and alkaline phosphatase were the main persistent biochemical abnormalities.
The patient was inoperable because of the extent of the disease. Chemotherapy treatment for stage IV peri- ampullary carcinoma results in a progression-free survival of 5 months (with single-agent chemotherapy) to 8 months (with chemotherapy doublet), and leads to considerable side effects including febrile neutropenia in 10% of patients and any grade 3–4 side effect in 70% of patients [17].
Therefore, upon consultation with the patient and her family, we decided to refrain from standard therapy and search for genetic alterations with clinical significance, to devise a personalized biological therapy strategy.A specimen from the tumor was sent for genomic pro- filing using NGS assay with the Illumina HiSeq 2000 platform (Foundation One; Foundation Medicine, Cambridge, Massachusetts, USA). The assay analyzes 315 cancer-related genes and selects introns from 28 genes often rearranged or altered in solid tumor cancers. The genomic analysis of the patient’s tumor showed mutations in BRAF (G466E), NRAS (G12V), and seven other mutations with no known targetable agents including mutations in TP53 and APC. Although the retroperitoneal adenopathy showed variable response in different sites with overall stable disease by RECIST. The overall sum of the short axis of four involved lymph nodes decreased from 7.4 to 6.5 cm, the intensity of 18F-FDG uptake slightly decreased (SUVmax 15), and one lymph node disappeared (Fig. 1b). New pleural fluid was observed, but without 18F-FDG uptake, and was probably because of a traumatic fall with fractured ribs on the same side.
The patient underwent a third 18F-FDG PET/CT scan in May 2015, showing again variable per-site response, with a slight decrease in 18F-FDG uptake (SUV 13) in the retroperitoneal lymph nodes and overall stable dis- ease by RECIST (the sum of the short axis of the four lymph nodes decreased to 5.9 cm). There was a new focus of abnormal uptake in a 1 cm adrenal mass (SUV 5) of unclear nature, although metastasis could not be excluded (Fig. 1).The patient is still on treatment (November 2015) with the MEK inhibitor trametinib (1.5 mg/day), 12 months after start, and remains in good clinical condition.
Discussion
Understanding genetic aberrations by NGS can lead to the discovery of new targets, and molecularly based therapies can be administered accordingly. This is especially important in tumors, such as carcinoma of the ampulla of Vater, which have a low rate of response to chemotherapy and modest survival benefit. Many of these tumors are rare and heterogenous, genetic profiling has not been carried out on a large scale, and therefore we lack understanding of the underlying mutations in most cases [18].
In a series of 28 cholangiocarcinoma patients who underwent NGS [19], 20 cases harbored at least one potentially actionable alteration, with the most common ones being FGFR2 (14%), KRAS (11%), and PTEN (11%). Our patient’s specimen showed two potentially actionable mutations: BRAF G466E and NRAS G12V.
Treatment of the patient with a MEK inhibitor targets both mutations as they both activate the RAS– RAF–MEK pathway from this point onward.
MEK inhibitors have been studied in cholangiocarci- noma patients [20]. A phase II trial [2] examined the efficacy of selumetinib, a MEK inhibitor, in 28 biliary cancer patients. In all, 12% achieved a confirmed objec- tive response; 68% achieved stable disease. The median progression-free survival was 3.7 months and the median overall survival was 9.8 months. NGS was not performed in these patients.
Trametinib, the drug chosen for this patient, is a MEK inhibitor that has been approved by the FDA for use in patients with unresectable or metastatic melanoma with BRAF V600E or V600K mutations. Trametinib is cur- rently in clinical trials in multiple tumor types including biliary tract cancer.
The use of NGS to find actionable mutations in each individual patient’s tumor can provide us with an in- depth understanding of the neoplastic process and help us select individualized treatments targeting the specific mutation or its signaling pathway. However, there are still many unanswered points on the added value of NGS in cancer patients. A specific mutation may be a cancer driver in one tumor type, but not in another tumor type; thus, identification of the mutation is no guarantee of success of treatment [21]. The NGS methodology and quality metrics are not yet standardized and have not been endorsed by professional societies. Hopefully, data from ongoing and future clinical studies will help to maximize the value of this strategy. There are tens of ongoing studies of this kind, currently registered in http:// www.clinicaltrials.gov [22]. Until then, these types of case observations are merely hypothesis generating. Furthermore, biological therapies often lead to serious side effects that need to be considered when a persona- lized treatment strategy is devised as an alternative to chemotherapy.In summary, we present a case of ampullary carcinoma treated with a prolonged duration of response to biolo- gical therapy on the basis NST-628 of NGS discovery of two actionable mutations.