The echinoderm microtubule-associated protein-like 4 (EML4)–anaplastic lymphoma kinase (ALK) is a recently identified fusion-type oncoprotein that exists in approximately 5% of non-small cell lung cancer (NSCLC). It has been demonstrated that NSCLC driven by EML4-ALK is strongly addicted to this fusion-type oncokinase. A clinical trial of crizotinib (PF-02341066) sponsored by Pfizer has proven this oncogene addiction in humans by demonstrating a high response rate to inhibition of ALK kinase activity. In the present study, we report on three cases harboring EML4-ALK rearrangement who were enrolled in the trial (A8081001, NCT00585195). All three patients showed favorable responses to the ALK-specific tyrosine kinase inhibitor. (Cancer Sci 2011; 102: 1602–1604)
Clinical findings in three patients treated with crizotinib are described below.
Case 1. A 30-year-old man who had never smoked presented with smoldering pneumonia in October 2008. A diagnosis of Stage IIIB (cT2N3M0) lung adenocarcinoma was made and the patient subsequently received two cycles of systemic chemotherapy with cisplatin and vindesine, with concurrent thoracic irradiation, followed by two cycles of consolidation with carboplatin and paclitaxel. This treatment regimen resulted in stable disease. The primary tumor did not have epidermal growth factor receptor (EGFR) mutations, but immunohistochemistry (IHC) was positive for anaplastic lymphoma kinase (ALK) protein using the intercalated antibody-enhanced polymer (iAEP) method with 5A4 (Abcam, Cambridge, UK) as the primary antibody (Fig. 1a).(1) Fluorescence in situ hybridization (FISH), using probes described elsewhere,(2) confirmed echinoderm microtubule-associated protein-like 4 (EML4)–ALK rearrangement (Fig. 1b). Multiplex RT-PCR(1,3) further showed that this patient’s fusion type was variant 3 (Fig. 1c). The patient was enrolled in the trial in April 2009.(4) The patient’s persistent cough disappeared within 2 weeks of initiation of oral crizotinib therapy (250 mg twice daily) and the primary tumor shrank. Although there was no change in the size of the mediastinal lymph nodes, PET CT demonstrated marked reductions in the accumulation of fluorodeoxyglucose (18F) after 12 months (Fig. 1d). Transient mild nausea and diarrhea were observed for the first 4 weeks of treatment, but were well controlled over the subsequent 19 months without any other toxicity. Follow-up MRI of the brain in November 2010 showed the appearance of asymptomatic but multiple new lesions, despite favorable control outside the central nervous system (CNS). The patient received whole-brain radiotherapy in December 2010; thereafter, crizotinib was resumed after a 4-week break. The patient is currently continuing crizotinib treatment for 24 months in total.
Case 2. A 29-year-old man who was a heavy smoker presented with progressive lumbago in May 2009. Shortly thereafter, sudden onset symmetrical leg paralysis developed. Because MRI revealed tumors in multiple segments of the thoracic and lumbar spine, emergent radiotherapy to the 10th–12th thoracic vertebrae was performed. This patient’s disease was diagnosed as Stage IV (cT2N3M1) lung adenocarcinoma with single brain and multiple bone metastases. Tests for EGFR mutations were negative and the patient was given two cycles of systemic chemotherapy with cisplatin and vinorelbine. After insertion of a cyber knife into the brain lesion, the patient was given a cycle of carboplatin and paclitaxel, resulting in stable disease. On the evidence of ALK-positive iAEP IHC (Fig. 2a) with confirmatory FISH-positive EML4-ALK rearrangement, oral crizotinib therapy (250 mg twice daily) was started in September 2009. All tumors except for the brain lesion shrank significantly and the patient was able to cease opioid within 1 month. Mild nausea, alternating diarrhea and constipation, and the persistence of light spectrum image bothered the patient for a few months and dysgeusia lasted throughout the duration of treatment, but these adverse events were not so severe as to diminish the patient’s activities of daily living. After 6 months, a chest CT showed complete regression of the thoracic lesions and bone scintigraphy showed a marked reduction in the accumulation of 88mTc (Fig. 2b). The brain lesion remained stable and other pre-existing tumors disappeared for 9 months. However, multiple new lesions appeared in the liver and crizotinib therapy was therefore discontinued. Thereafter, the patient received four cycles of carboplatin, pemetrexed, and bevacizumab and is now being followed-up with the latter two agents being used as maintenance therapy.
Case 3. A 31-year-old man who was a light smoker presented with an asymptomatic abnormal shadow on chest X-ray found as part of the annual medical checkup in August 2009. This patient’s disease was diagnosed as Stage IIIB (cT4N0M0) lung adenocarcinoma with pleural dissemination. Chemoradiotherapy with cisplatin and vinorelbine failed after one cycle. Because tests for EGFR mutations were negative, but iAEP IHC (Fig. 3a) and FISH analyses revealed his tumor to be positive for EML4-ALK, the patient was started on oral crizotinib (250 mg twice daily) in December 2009. He achieved partial response shortly thereafter and the favorable effect has lasted thus far for 17 months (Fig. 3b). The patient is currently continuing on crizotinib treatment. As for adverse effects, mild nausea and diarrhea were noted temporarily for the first 4 weeks of treatment, but persistence of vision spectrum and dysgeusia have lasted for the duration of the treatment period.
The malignant transformation of approximately 5% of non-small cell lung cancer (NSCLC), especially adenocarcinoma, is caused by EML4-ALK and it is mutually exclusive for EGFR and KRAS mutations.(3,5–7) Basic research has shown that EML4-ALK-driven NSCLC is strongly addicted to this fusion-type oncogene.(5,8–10) Crizotinib is an experimental agent that targets ALK and mesenchymal-epithelial transition (MET) kinases and it is not currently approved by any regulatory agency. Pfizer’s trial of crizotinib has demonstrated a high response rate (57%) in the ALK fusion-positive NSCLC population, indicating that these tumors have strong addiction exclusive to this oncokinase.(4) The three patients reported herein were all treated as part of the Pfizer trial after they had met the eligibility criteria and provided informed consent. All three patients showed a substantial responses to crizotinib. Although a minority of NSCLC arises from the ALK fusion-type oncokinase, most of ALK-positive NSCLC occur in younger people.(7) Thus, it is encouraging that ALK inhibitors will become available for use in the clinical setting. Moreover, crizotinib is also attractive as a potent “pain killer” because it was so effective against the pain produced by the bone metastases in Case 2 as to completely relieve the patient’s cancer-related pain.
As for safety, temporary Grade 1 nausea and diarrhea were observed in all three patients and Grade 1 constipation coexisted in Case 2. Grade 1 dysgeusia of hot taste and visual disturbances (transient persistence of vision spectrum noted on moving from the dark to the light) occurred in Cases 2 and 3. These adverse events, except for dysgeusia, were reported in the trial(4) and all were tolerable. Crizotinib did not affect liver function, renal function, or blood cell counts in the three cases reported here.
Some responders (including two cases in the present study) develop resistance to crizotinib after a certain period, similar to most responders to EGFR tyrosine kinase inhibitors. This is a serious issue not to be overlooked. Based on the occurrence (Case 1) and unresponsiveness (Case 2) of brain metastases, crizotinib may not fully penetrate from the bloodstream into the CNS at the dose given in this trial. Costa et al.(11) recently reported a similar case to Case 1 in the present study, in whom the concentration of crizotinib was much lower in the cerebrospinal fluid (CSF) than in the plasma (0.0014 vs. 0.53 mol/L, respectively). Costa et al.(11) suggested that the low CSF:plasma ratio (0.0026) implied poor blood–brain barrier penetration of crizotinib, which may explain the persistent systemic disease control with crizotinib but the concurrent appearance of brain metastases.
Furthermore, two de novo mutations in the tyrosine kinase domain of ALK cDNA (G4374A and C4493A) have been identified recently from a patient who showed resistance to crizotinib.(12) These mutations result in substitutions of cysteine to tyrosine (C→Y) and leucine to methionine (L→M) at positions corresponding to amino acids 1156 and 1196, respectively. The L1196 of ALK corresponds to threonine (T) at position T315 in ABL and T790 in EGFR, the most frequently substituted position conferring resistance to inhibitors for these kinases. Conversely, C1156Y located adjacent to the αC helix on the N-terminal side has been proposed to allosterically hinder the binding of ALK inhibitors.(12) Such resistant mutations may provide another explanation for the lack of a response of brain metastases to crizotinib. Regarding the hepatic metastases in Case 2, it is unlikely that the hepatocyte growth factor/MET pathway or MET amplification (known resistant mechanisms for EGFR inhibitors) participated in this setting because crizotinib is a dual inhibitor for both ALK and MET kinases. We must investigate the mechanisms underlying the resistance to crizotinib to develop new treatment strategies, as well as second-generation ALK inhibitors, to overcome resistance.
The authors thank the three patients for consenting to the publication of their clinical details. The authors are also grateful to Dr Yung-Jue Bang and the medical staff of Seoul National University Hospital (Seoul, Korea) for their support in the treatment of these patients.
KT has acted in an advisory role for Chugai Pharmaceutical Co., Ltd (Tokyo, Japan). The other authors report no potential conflicts of interest. None of the authors was an investigator in the trial conducted by Pfizer.