Anaplastic lymphoma kinase inhibition in non-small-cell lung cancer

Abstract

Background: Oncogenic fusion genes consisting of EML4 and anaplastic lymphoma kinase (ALK) are present in a subgroup of non-small-cell lung cancers, representing 2 to 7% of such tumors. We explored the therapeutic efficacy of inhibiting ALK in such tumors in an early-phase clinical trial of crizotinib (PF-02341066), an orally available small-molecule inhibitor of the ALK tyrosine kinase.

Methods: After screening tumor samples from approximately 1500 patients with non-small-cell lung cancer for the presence of ALK rearrangements, we identified 82 patients with advanced ALK-positive disease who were eligible for the clinical trial. Most of the patients had received previous treatment. These patients were enrolled in an expanded cohort study instituted after phase 1 dose escalation had established a recommended crizotinib dose of 250 mg twice daily in 28-day cycles. Patients were assessed for adverse events and response to therapy.

Results: Patients with ALK rearrangements tended to be younger than those without the rearrangements, and most of the patients had little or no exposure to tobacco and had adenocarcinomas. At a mean treatment duration of 6.4 months, the overall response rate was 57% (47 of 82 patients, with 46 confirmed partial responses and 1 confirmed complete response); 27 patients (33%) had stable disease. A total of 63 of 82 patients (77%) were continuing to receive crizotinib at the time of data cutoff, and the estimated probability of 6-month progression-free survival was 72%, with no median for the study reached. The drug resulted in grade 1 or 2 (mild) gastrointestinal side effects.

Conclusions: The inhibition of ALK in lung tumors with the ALK rearrangement resulted in tumor shrinkage or stable disease in most patients. (Funded by Pfizer and others; ClinicalTrials.gov number, NCT00585195.).

Figure 1. Diagnosis of an EML4-ALK–Positive Non–Small-Cell Lung Cancer in a Single Representative Patient

Panel A shows the results of a break-apart fluorescence in situ hybridization assay of tumor cells from a patient with rearrangement of the gene encoding anaplastic lymphoma kinase (ALK). The green probe hybridizes to the region immediately 5′ to ALK, and the red probe to the 3′ region. The separation of red and green probe signals (arrows) indicates a chromosomal rearrangement involving ALK. Close apposition of red and green probe signals indicates an intact wild-type copy of ALK. The probe that was used was the Vysis LSI ALK Dual Color, Break Apart Rearrangement Probe (Abbott Molecular). Panel B shows a light micrograph of the same tumor, revealing adenocarcinoma (hematoxylin and eosin). Panel C shows a representative sequence electropherogram of a reverse-transcriptase–polymerase-chain-reaction assay of EML4-ALK. The sequence of a junction between EML4 exon 6b and ALK exon 20 is shown. Panel D shows immunohistochemical analysis of ALK protein expression in tumor cells (brown) but not in adjacent normal bronchial epithelium (diaminobenzidine).

Figure 2. Response to ALK Inhibition

Panel A shows the best response of patients with ALK-positive tumors who were treated with crizotinib, as compared with pretreatment baseline. Numbers along the x axis indicate arbitrarily assigned subject numbers from 1 to 79. The bars indicate the percent change in tumor burden from baseline. Three study patients are not included in this plot: one patient was clinically assessed as having had a partial response, although the response was primarily in areas of nonmeasurable disease, so the patient was classified as having stable disease; two patients with abrupt clinical deterioration could not be assessed. Four patients had complete resolution of their target lesions but were classified as having had a partial response on the basis of stability in nontarget lesions. Eight patients had tumor shrinkage of more than 30% but were classified as having stable disease either because confirmatory scans were not available by the data-cutoff point (for five patients) or early restaging was performed at 6 weeks after crizotinib initiation (for three patients). The dashed line indicates a tumor reduction of 30% from baseline, the minimal percent decrease that constitutes a partial response, according to Response Evaluation Criteria in Solid Tumors. Panel B shows the results of CT with coronal reconstruction in a representative patient at baseline (left) and after two cycles of therapy (right). This patient had undergone previous left lower lobectomy.

Figure 3. Best Response to Crizotinib in 31 Patients with ALK-Positive Tumors, as Correlated with Clinicopathological Characteristics

Percent tumor response, treatment duration, smoking history, and selected tumor characteristics are listed in the table below the graph, with each table entry corresponding to a patient in the graph above. Patients are listed in order of increasing percentage response to crizotinib, with listed patient numbers corresponding to those in Figure 2A. Smoking history is reported in pack-years. The EML4-ALK genotype is reported as the EML4 exon that is fused to ALK, as assayed by nucleotide sequencing of RT-PCR products. U denotes undetermined for patients for whom RT-PCR assays using primers to ALK exon 20 along with EML4 exons 6, 13, and 18 produced no product. Blank fields indicate that adequate tumor samples were not available for analysis. ALK expression is reported as 0, 1+, 2+, or 3+, per convention for immunohistochemical analysis.

Figure 4. Duration of Treatment and Estimated Progression-free Survival

Panel A shows the duration of treatment for the 82 patients, with blue bars indicating patients who were continuing to receive crizotinib by data cutoff. Red bars indicate 19 patients who discontinued treatment (13 because of disease progression, 1 because of crizotinib-related adverse events, 1 because of unrelated adverse events, 2 because of death from unrelated causes, and 2 because of other reasons). Panel B shows a Kaplan–Meier curve of estimated progression-free survival, with the lighter curves above and below the Kaplan–Meier curve representing 95% Hall–Wellner confidence limits.