Response to crizotinib observed in metastatic mediastinum lymph node from a non-small cell lung cancer patient harboring EZR–ROS1 fusion

Excerpt

In October 2010, a 73-year-old Chinese female non-smoker presented in our hospital, who had two months history of occasional dry cough. Enhanced computed tomography (CT) scan showed a 25 × 20 mm nodule in her right middle lobe of lung (Fig. 1). No pleural effusion and enlarged mediastinum lymph node (MLN) were found. Surgery was performed on her in November 2010. During the muscle-sparing thoracotomy procedure, surgeons found numerous miliary nodules in her visceral pleura of right lung. Pulmonary lobectomy of right middle lobe, systematic mediastinal lymphadenectomy and biopsy of the visceral pleura nodules were performed. Pathological results revealed the tumor was 4 × 3 × 2 cm adenocarcinoma, which was middle differentiated and infringed visceral pleura. The miliary nodules on the pleura were malignant, and metastases were found in 3A group MLN. So the pathological TNM stage was IV (T2N2M1). EGFR mutation status was detected using tumor tissue, which was kept in liquid nitrogen, while no mutation was found. One month after surgery, the patient received two courses of adjuvant chemotherapy with gemcitabine and carboplatin, which discontinued for severe vomiting. Thereafter, she only received CT scans every 3 months to evaluate the disease. In March 2013, 28 months after surgery, CT scan showed enlarged MLN (short axis = 22.09 mm) beside the superior vena cava (Fig. 2a). First-line chemotherapy to control the MLN relapse was prescribed with pemetrexed and cisplatin. After 2 courses, the MLN beside the superior vena cava was evaluated as stable disease (SD) according to standard response evaluation criteria in solid tumors (RECIST), version 1.0. Further courses of chemotherapy were discontinued due to severe gastrointestinal side effects. In August 2013, enhanced CT scan showed MLN beside the superior vena cava got remarkable enlargement (short axis = 28.86 mm) (Fig. 2b) and the patient refused re-biopsy of metastatic MLN. The presence of several gene alterations such as ALK fusion, ROS1 fusion, RET fusion, MET amplification and mutation was investigated according to the patient’s will. ROS1 rearrangement in resected primary samples was revealed in fluorescent in situ hybridization (FISH) test with formalin-fixed and paraffin-embedded (FFPE) tissue and an approach using bacterial artificial chromosome (BAC) clones corresponding to the 5′ (RP11-835I21) and 3′ (RP11-1036C2) sequences of ROS1 gene labeled by nick translation in green and red (Fig. 3). The tumor was considered to be ROS1 fusion-positive because more than 15 % of cells harbored split signals (Bergethon et al. 2012). Reverse-transcriptase polymerase chain reaction (RT-PCR) assays were performed on total RNA extracted from resected tumor samples using the primers EZR-958F (5′-GATGATGCGCGAGAAGGAGGA-3′) and ROS1-5992R (5′-ATTTGCTCATCAGATGTGCCTCCTTCAG-3′). The results showed that this rearrangement led to expression of a fusion transcript joining exon 10 of EZR to exon 34 of ROS1 (EZR–ROS1). Meanwhile, no molecular changes of other genes were found. As second-line treatment for MLN relapse, crizotinib was administered orally at a dose of 250 mg twice a day from August 2013. During the treatment period of crizotinib, the patient had fatigue (Grade 1) and nausea (Grade 1). No other severe adverse events were observed. She received enhanced CT scans in October 2013 (Fig. 2c) and January 2014 (Fig. 2d). Remarkable regression was observed: The short axis of metastatic MLN was 12.36 mm in October 2013 and was 11.10 mm in January 2014. The MLN beside the superior vena cava was evaluated as partial remission (PR). At the time of this report (10 months), the patient continued taking crizotinib with no evidence of disease progression.

…