Mark S. Huberman

Exon 19 Deletion Mutations of Epidermal Growth Factor Receptor Are Associated with Prolonged Survival in Non–Small Cell Lung Cancer Patients Treated with Gefitinib or Erlotinib

Purpose: Somatic mutations in the epidermal growth factor receptor (EGFR) have been detected in patients with non–small cell lung cancer (NSCLC) and are associated with sensitivity to treatment with gefitinib or erlotinib. Our study explored the relationship between the two most common types of somatic EGFR mutations, exon 19 deletions and the L858R point mutation, and outcomes of patients following treatment with gefitinib or erlotinib. Experimental Design: Tumor specimens obtained before treatment with gefitinib or erlotinib were analyzed for EGFR mutations. Patients with exon 19 deletion or L858R mutations were identified. The response rate, time to progression, and overall survival were determined for the two groups. Results: We identified 36 patients with NSCLC and an EGFR mutation who were treated with gefitinib or erlotinib. Patients with an exon 19 deletion had a significantly longer overall survival compared with patients with an L858R mutation (38 versus 17 months; P = 0.04). There were also trends toward higher response rate (73% versus 50%) and improved time to progression (24 versus 10 months) for the patients with an exon 19 deletion, although these were not independently significant in a multivariate analysis. A difference in response rate for patients treated with gefitinib compared with erlotinib was also noted [18 of 23 (78%) versus 3 of 9 (33%); P = 0.04]. No obvious difference in time to progression or overall survival was noted between gefitinib- and erlotinib-treated patients. Conclusions: Patients with NSCLC and EGFR exon 19 deletions have a longer survival following treatment with gefitinib or erlotinib compared with those with the L858R mutation. Pooling of greater numbers of patients and completion of prospective trials are needed to further define the predictive and prognostic roles of different EGFR mutations with respect to treatment with gefitinib, erlotinib, and other EGFR inhibitors.

BIM mediates EGFR tyrosine kinase inhibitor-induced apoptosis in lung cancers with oncogenic EGFR mutations

Background Epidermal growth factor receptor (EGFR) mutations are present in the majority of patients with non-small cell lung cancer (NSCLC) responsive to the EGFR tyrosine kinase inhibitors (TKIs) gefitinib or erlotinib. These EGFR-dependent tumors eventually become TKI resistant, and the common secondary T790M mutation accounts for half the tumors with acquired resistance to gefitinib. However, the key proapoptotic proteins involved in TKI-induced cell death and other secondary mutations involved in resistance remain unclear. The objective of this study was to identify the mechanism of EGFR TKI-induced apoptosis and secondary resistant mutations that affect this process. Methods and Findings To study TKI-induced cell death and mechanisms of resistance, we used lung cancer cell lines (with or without EGFR mutations), Ba/F3 cells stably transfected with EGFR mutation constructs, and tumor samples from a gefitinib-resistant patient. Here we show that up-regulation of the BH3-only polypeptide BIM (also known as BCL2-like 11) correlated with gefitinib-induced apoptosis in gefitinib-sensitive EGFR-mutant lung cancer cells. The T790M mutation blocked gefitinib-induced up-regulation of BIM and apoptosis. This blockade was overcome by the irreversible TKI CL-387,785. Knockdown of BIM by small interfering RNA was able to attenuate apoptosis induced by EGFR TKIs. Furthermore, from a gefitinib-resistant patient carrying the activating L858R mutation, we identified a novel secondary resistant mutation, L747S in cis to the activating mutation, which attenuated the up-regulation of BIM and reduced apoptosis. Conclusions Our results provide evidence that BIM is involved in TKI-induced apoptosis in sensitive EGFR-mutant cells and that both attenuation of the up-regulation of BIM and resistance to gefitinib-induced apoptosis are seen in models that contain the common EGFR T790M and the novel L747S secondary resistance mutations. These findings also suggest that induction of BIM may have a role in the treatment of TKI-resistant tumors.

A Multicenter Phase II Study of Ganetespib Monotherapy in Patients with Genotypically Defined Advanced Non–Small Cell Lung Cancer

Purpose: Ganetespib is a novel inhibitor of the heat shock protein 90 (Hsp90), a chaperone protein critical to tumor growth and proliferation. In this phase II study, we evaluated the activity and tolerability of ganetespib in previously treated patients with non–small cell lung cancer (NSCLC). Experimental Design: Patients were enrolled into cohort A (mutant EGFR), B (mutant KRAS), or C (no EGFR or KRAS mutations). Patients were treated with 200 mg/m2 ganetespib by intravenous infusion once weekly for 3 weeks followed by 1 week of rest, until disease progression. The primary endpoint was progression-free survival (PFS) at 16 weeks. Secondary endpoints included objective response (ORR), duration of treatment, tolerability, median PFS, overall survival (OS), and correlative studies. Results: Ninety-nine patients with a median of 2 prior systemic therapies were enrolled; 98 were assigned to cohort A (n = 15), B (n = 17), or C (n = 66), with PFS rates at 16 weeks of 13.3%, 5.9%, and 19.7%, respectively. Four patients (4%) achieved partial response (PR); all had disease that harbored anaplastic lymphoma kinase (ALK) gene rearrangement, retrospectively detected by FISH (n = 1) or PCR-based assays (n = 3), in crizotinib-naïve patients enrolled to cohort C. Eight patients (8.1%) experienced treatment-related serious adverse events (AE); 2 of these (cardiac arrest and renal failure) resulted in death. The most common AEs were diarrhea, fatigue, nausea, and anorexia. Conclusions: Ganetespib monotherapy showed a manageable side effect profile as well as clinical activity in heavily pretreated patients with advanced NSCLCs, particularly in patients with tumors harboring ALK gene rearrangement. Clin Cancer Res; 19(11); 3068–77. ©2013 AACR.

Structural, Biochemical, and Clinical Characterization of Epidermal Growth Factor Receptor (EGFR) Exon 20 Insertion Mutations in Lung Cancer.

Crystal structure and detailed analysis of different EGFR mutants explain why some mutations in exon 20 make lung cancers resistant to EGFR inhibitors and others make them more sensitive. A Crystal Clear Cause of Drug Resistance Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are used to treat a variety of cancers, including non–small cell lung cancer. EGFR mutations have a wide range of effects on the success of TKI treatment in this cancer type, with some sensitizing the tumors to TKI inhibitors and others making them resistant to targeted therapy. For example, most of the mutations in exon 20, a relatively common mutation site, prevent cancer cells from responding to EGFR inhibitors. Here, Yasuda and co-workers determined the crystal structure of EGFR with an exon 20 mutation and used a combination of kinetic studies and structural analysis to elucidate the mechanism for these mutants’ differential sensitivity to TKIs. The findings of Yasuda et al. clarify the reasons for the drug resistance of most exon 20 mutations and show the mechanism for the rare mutation in the same exon that increases tumors’ sensitivity to treatment. In addition to explaining which of the mutants are resistant to targeted inhibition of EGFR and the reasons for this phenomenon, this work could help with the development of future therapeutics. By taking advantage of the crystal structure and detailed insights into the function of mutant EGFR, researchers may be able to design drugs that exploit the unique structural features of resistant mutants and specifically target them for treatment. Epidermal growth factor receptor (EGFR) gene mutations (G719X, exon 19 deletions/insertions, L858R, and L861Q) predict favorable responses to EGFR tyrosine kinase inhibitors (TKIs) in advanced non–small cell lung cancer (NSCLC). However, EGFR exon 20 insertion mutations (~10% of all EGFR mutations) are generally associated with insensitivity to available TKIs (gefitinib, erlotinib, and afatinib). The basis of this primary resistance is poorly understood. We studied a broad subset of exon 20 insertion mutations, comparing in vitro TKI sensitivity with responses to gefitinib and erlotinib in NSCLC patients, and found that most are resistant to EGFR TKIs. The crystal structure of a representative TKI-insensitive mutant (D770_N771insNPG) reveals an unaltered adenosine triphosphate–binding pocket, and the inserted residues form a wedge at the end of the C helix that promotes the active kinase conformation. Unlike EGFR-L858R, D770_N771insNPG activates EGFR without increasing its affinity for EGFR TKIs. Unexpectedly, we find that EGFR-A763_Y764insFQEA is highly sensitive to EGFR TKIs in vitro, and patients whose NSCLCs harbor this mutation respond to erlotinib. Analysis of the A763_Y764insFQEA mutant indicates that the inserted residues shift the register of the C helix in the N-terminal direction, altering the structure in the region that is also affected by the TKI-sensitive EGFR-L858R. Our studies reveal intricate differences between EGFR mutations, their biology, and their response to EGFR TKIs.

Effects of Erlotinib in EGFR Mutated Non-Small Cell Lung Cancers with Resistance to Gefitinib

Purpose: Most lung cancers with activating epidermal growth factor receptor (EGFR) mutations respond to gefitinib; however, resistance to this tyrosine kinase inhibitor (TKI) invariably ensues. The T790M mutation occurs in 50% and MET amplification in 20% of TKI-resistant tumors. Other secondary mutations (D761Y and L747S) are rare. Our goal was to determine the effects of erlotinib 150 mg/d in EGFR mutated patients resistant to gefitinib 250 mg/d, because the EGFR TKI erlotinib is given at a higher biologically active dose than gefitinib. Experimental Design: Retrospective review of 18 EGFR mutated (exon 19 deletions, L858R, and L861Q) patients that were given gefitinib and subsequently erlotinib. Seven patients had tumor resampling after TKI therapy and were analyzed for secondary EGFR mutations and MET amplification. Results: Most patients (14 of 18) responded to gefitinib with median progression-free survival of 11 months (95% confidence interval, 4-16). After gefitinib resistance (de novo or acquired), 78% (14 of 18) of these patients displayed progressive disease while on erlotinib with progression-free survival of 2 months (95% confidence interval, 2-3). Six of 7 resampled patients acquired the T790M mutation, and 0 of 3 had MET amplification. Only 1 gefitinib-resistant patient with the acquired L858R-L747S EGFR, which in vitro is sensitive to achievable serum concentrations of erlotinib 150 mg/d, achieved a partial response to erlotinib. Conclusions: In EGFR mutated tumors resistant to gefitinib 250 mg/d, a switch to erlotinib 150 mg/d does not lead to responses in most patients. These findings are consistent with preclinical models, because the common mechanisms of TKI resistance (T790M and MET amplification) in vitro are not inhibited by clinically achievable doses of gefitinib or erlotinib. Alternative strategies to overcome TKI resistance must be evaluated.

Brain metastases in patients with EGFR-mutated or ALK-rearranged non-small-cell lung cancers

INTRODUCTION Brain metastases (BM) are common in non-small-cell lung cancer (NSCLC). However, the baseline incidence and evolution of BM over time in oncogene-driven NSCLCs are seldom reported. In this study, we evaluated the frequency of BM in patients with epidermal growth factor receptor (EGFR)-mutated or anaplastic lymphoma kinase (ALK)-rearranged NSCLC. METHODS The presence of BM, clinicopathologic data, and tumor genotype were retrospectively compiled and analyzed from a cohort of 381 patients. RESULTS We identified 86 EGFR-mutated (90.7% with metastatic disease; 85.9% received an EGFR inhibitor) and 23 ALK-rearranged (91.3% with metastatic disease; 85.7% received an ALK inhibitor) NSCLCs. BM were present in 24.4% of EGFR-mutated and 23.8% of ALK-rearranged NSCLCs at the time of diagnosis of advanced disease. This study did not demonstrate a difference in the cumulative incidence of BM over time between the two cohorts (EGFR/ALK cohort competing risk regression [CRR] coefficient of 0.78 [95% CI 0.44-1.39], p=0.41). In still living patients with advanced EGFR-mutated NSCLC, 34.2% had BM at 1 year, 38.4% at 2 years, 46.7% at 3 years, 48.7% at 4 years, and 52.9% at 5 years. In still living patients with advanced ALK-rearranged NSCLC, 23.8% had BM at 1 year, 45.5% at 2 years, and 58.4% at 3 years. CONCLUSIONS BM are frequent in advanced EGFR-mutated or ALK-rearranged NSCLCs, with an estimated >45% of patients with CNS involvement by three years of survival with the use of targeted therapies. These data point toward the CNS as an important unmet clinical need in the evolving schema for personalized care in NSCLC.

Bevacizumab Reverses Cerebral Radiation Necrosis

A 43-year-old Chinese woman, with a 6-month history of hearing loss, was diagnosed with biopsy-proven T3, N1, M0, stage III undifferentiated nasopharyngeal carcinoma. Her initial head magnetic resonance imaging (MRI) scan showed a mass in the nasopharynx (Fig 1A, asterisk) extending into the left sphenoid sinus (Fig 1B, arrow), and there was fluid accumulation in the left mastoid process. She received cisplatin and involved-field intensity-modulated radiotherapy (IMRT) to 70 Gy, followed by an additional three cycles of cisplatin and fluorouracil. Her inferior temporal lobes received up to 68.5 Gy of radiation (Fig 1C, red isodose line). Two years later, she experienced verbal memory loss, together with fatigue and mild imbalance. Her neurological examination was notable for psychomotor slowing and deficit in immediate recall. She also had a mini–mental status examination score of 26 (from a total of 30), suggesting moderate cognitive dysfunction. A gadolinium-enhanced head MRI, taken for evaluation of her neurocognitive deficits, showed enhancement in the inferior left temporal lobe with increased fluid-attenuated inversion recovery signals in the surrounding brain parenchyma (Figs 2A and 2B). She underwent [F]fluorodeoxyglucose (FDG)–positron emission tomography and thallium–single photon emission computed tomography, and revealed no uptake of either radionuclide in the corresponding region of gadolinium enhancement. The inferior left temporal lobe did not have increased blood flow, as measured by arterial spin labeling. Because the findings suggest radiation necrosis of the brain, she was treated with 5 mg/kg of bevacizumab every other week. After four doses, the enhancement on MRI was nearly gone (Fig 3A & 3B) and her mini–mental status examination score increased to 30. Her imbalance and fatigue disappeared. These neurocognitive improvements persisted at the time of follow-up 6 months later. Temporal lobe radiation necrosis was common before the adoption of IMRT for head and neck cancer. The spectrum of this disorder ranged from edema noted as hyperintense fluid-attenuated inversion recovery, T2 signals in the temporal lobes, and hemorrhagic transformation, to necrotic cysts causing mass effect. The development of cerebral radiation necrosis from fractionated radiotherapy is a function of total dose, dose per fraction, and time from completion of radiation. The higher the total dose or dose per fraction, the sooner cerebral radiation necrosis would appear in patients. The mechanism appears to be a result of radiation damage to vascular endothelial cells, causing endothelial cell proliferation, telangiectatic vessels, and fibrinoid necrosis with accompanying perivascular exudation and edema. In experimental settings, microhemorrhages was noted in the brains of rabbits when they were treated with proton stereotaxic radiosurgery. Similarly, in the gastrointestinal tract of mice treated with 15 Gy of whole-body irradiation, radiation-induced endothelial cell apoptosis was the primary mechanism leading to stem-cell dysfunction, crypts damage, and death. The secondary stem-cell dysfunction was probably a result of damage to the vascular niche where the stem cells reside. Although the kinetics of this damage is unknown in experimental animals, patients who received radiation at 62.5 Gy or more have greater than 25% probability of radiation necrosis within 5 years. Our patient received a dose of up to 68.5 Gy in the inferior temporal lobe, making her high risk for developing radiation necrosis despite the tight conformality of IMRT-limiting scattered radiation to the temporal lobes. The gadolinium-enhancing abnormality was not FDG or thallium avid, suggesting that it was unlikely to be tumor or infection. A diagnosis of cerebral radiation necrosis was also supported by more than 2 years of delayed development of her temporal abnormality. Conventional treatment consisted of corticosteroid to limit the extent of cerebral edema and, if necessary, drainage of compressive cysts. Unfortunately, due to the unrelenting process of necrosis, patients in the past typically succumbed to complications of

Selective chemoembolization in the management of hepatic metastases in refractory colorectal carcinoma

PURPOSE: Metastatic involvement of the liver frequently determines the evolution of the clinical picture in colorectal cancer patients. We examined the efficacy and toxicity of chemoembolization in this setting, identifying prognostic factors to define patients most likely to benefit from the procedure. METHODS: Forty patients underwent chemoembolization of metastatic liver lesions from colorectal carcinoma. Selective angiography of the hepatic artery was performed to identify the feeding vessels of the metastatic lesions. The injected chemoemulsion consisted of 1,000 mg of 5-fluorouracil, 10 mg of mitomycin C, and 10 ml of ethiodized oil in a total volume of 30 ml. Gelfoam embolization then followed, until stagnation of blood flow was achieved. Patients were evaluated for response, overall survival, and toxicities. RESULTS: Overall median survival from date of first chemoembolization was ten months. Factors that predicted a longer median survival included favorable performance status (24 months), serum alkaline phosphatase and lactate dehydrogenase levels less than three times normal (24 and 12 months, respectively), and metastatic disease confined to the liver (14 months). Most patients tolerated the procedure well. The most common side effects were transient fevers, abdominal pain, and fatigue. Three patients died within one month from the procedure. CONCLUSION: This study suggests that chemoembolization of hepatic metastases in colorectal cancer should be further evaluated; it may be beneficial in patients who have failed systemic chemotherapy, have a good performance status, and have metastatic disease confined to the liver.

Erlotinib at a dose of 25 mg daily for non-small cell lung cancers with EGFR mutations.

Purpose: The tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib are effective in non-small cell lung cancers (NSCLCs) with epidermal growth factor receptor (EGFR) gene mutations. The usual clinical dose of gefitinib (250 mg/d) is only one third of its maximum tolerated dose, whereas the dose of erlotinib (150 mg/d) is at its maximum tolerated dose. In NSCLC cell lines, both TKIs have similar micromolar inhibitory concentrations. We explored whether erlotinib at 25 mg/d (trough serum concentration similar to gefitinib 250 mg/d) would be efficacious in EGFR-mutated NSCLC. Methods: To study the inhibitory concentrations of gefitinib and erlotinib, we exposed EGFR-mutated cell lines (HCC827, H3255, PC-9, and H1975) to increasing concentrations of these TKIs. Further on, we performed a retrospective evaluation of seven patients with advanced EGFR-mutated (exon 19 deletions and L858R) NSCLC that were given erlotinib at 25 mg/d as their first EGFR TKI. Results: Gefitinib and erlotinib generated similar inhibitory curves across our panel of EGFR-mutated NSCLC cell lines with overlapping mean 50% inhibitory concentration 95% confidence intervals for HCC827, PC-9, and H1975. Both drugs also displayed a high degree of correlation in mean 50% inhibitory concentration (Pearsons r = 0.99, p = 0.0417). Of the seven patients, five patients (71.5%) had partial responses to erlotinib 25 mg/d. Median progression-free survival was 17 months (95% confidence interval, 6–35 months). Toxicities were minimal, with only two (28.5%) patients having a rash and none experiencing (0%) diarrhea. Conclusions: In NSCLC cell lines, gefitinib and erlotinib have similar inhibitory profiles. In patients with NSCLC and EGFR-activating mutations, a dose of erlotinib 25 mg/d (equivalent to gefitinib 250 mg/d) leads to impressive response rates and progression-free survival similar to the growing experience with the approved doses of gefitinib (250 mg/d) and erlotinib (150 mg/d). Identifying prospectively the lowest and clinically active dose ranges of erlotinib and gefitinib will help further to personalize care for patients with tumors harboring EGFR mutations.

Compound EGFR Mutations and Response to EGFR Tyrosine Kinase Inhibitors

Background: Non–small-cell lung cancers (NSCLCs) containing EGFR mutations are exquisitely sensitive to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). This is the case of the most common EGFR mutations affecting exon 18 (G719X), 19 (inframe deletions), and 21 (L858R and L861Q). However, the frequency of compound (i.e., double or complex) EGFR mutations—where an EGFR TKI sensitizing or other mutation is identified together with a mutation of unknown clinical significance—and their pattern of response/resistance to EGFR TKIs are less well described. Methods: We analyzed the EGFR mutation pattern of 79 cases of NSCLC harboring EGFR mutations and compiled the genotype-response data for patients with NSCLCs with compound EGFR mutations treated with EGFR TKIs. Results: Of the 79 EGFR-mutated tumors identified, 11 (14%) had compound mutations. Most involved the EGFR TKI–sensitizing G719X (n = 3, plus S768I or E709A), L858R (n = 4, plus L747V, R776H, T790M, or A871G), L861Q (n = 1, plus E709V), and delL747_T751 (n = 1, plus R776H). Eight patients received an EGFR TKI: three cases with G719X plus another mutation had partial responses (PRs) to erlotinib; of three cases with L858R plus another mutation, two displayed PRs and one (with EGFR-L858R+A871G) progressive disease (PD) to erlotinib; one NSCLC with EGFR-L861Q+E709A and one with delL747_T751+R776S had PRs to EGFR TKIs. Conclusion: Compound EGFR mutations comprised 14% of all mutations identified during routine sequencing of exons 18–21 of EGFR in our cohort. Most patients with an EGFR TKI–sensitizing mutation (G719X, exon 19 deletion, L858R, and L861Q) in addition to an atypical mutation responded to EGFR TKIs. Reporting of the genotype-response pattern of NSCLCs with EGFR compound and other rare mutations, and the addition of this information to searchable databases, will be helpful to select the appropriate therapy for EGFR-mutated NSCLC.