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Indian Journal of Medical and Paediatric Oncology
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ORIGINAL ARTICLE
Year : 2019  |  Volume : 40  |  Issue : 1  |  Page : 73-78  

T790M mutation and clinical outcomes with osimertinib in patients with epidermal growth factor receptor-mutant nonsmall cell lung cancer


1 Department of Medical Oncology, Basavatarakam Indo-American Cancer Hospital and Research Institute, Hyderabad, Telangana, India
2 Department of Laboratory Medicine, Basavatarakam Indo-American Cancer Hospital and Research Institute, Hyderabad, Telangana, India
3 Department of Radiodiagnosis, Basavatarakam Indo-American Cancer Hospital and Research Institute, Hyderabad, Telangana, India

Date of Web Publication16-Apr-2019

Correspondence Address:
Rakesh Pinninti
Basavatarakam Indo-American Cancer Hospital and Research Institute, Hyderabad - 500 034, Telangana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijmpo.ijmpo_215_18

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  Abstract 

Introduction: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors TKIs) are highly effective in EGFR-mutant advanced lung cancer. The most common resistance mechanism to EGFR-TKI is the development of T790M mutation in Exon 20. Osimertinib, a highly selective EGFR-TKI, has been approved for use in patients who progress on the first-line TKI and harbor the T790M mutation. Objective: The primary objective is to prospectively study the incidence of T790M mutation in patients who progress on the first-line EGFR-TKI. Secondary objectives include clinical characteristics that predict for T790M mutation and outcomes with osimertinib. Materials and Methods: This single-center, prospective observational study included 90 patients who progressed on first-line EGFR TKI. All patients had DNA extracted from tissue re-biopsy or plasma circulating tumor DNA (re-biopsy was not feasible or inadequate). T790M mutation was detected using amplification refractory mutation system-polymerase chain reaction, and patients harboring T790M mutation were started on osimertinib (80 mg once daily) until progression or unacceptable side effects. Results: At progression, T790M mutation was detected in 47/90 patients (52.2%). On binary logistic regression model analysis, variables that were independently predictive of the development of T790M were younger age (odds ratio [OR] 4.3, 95% confidence interval [CI] 1.14–16.6, P = 0.031); nonerlotinib TKI use (OR 8.3, 95% CI 1.24–55.8, P = 0.029); and pure adenocarcinoma histology (OR 6.2, 95% CI 1.60–24.7, P = 0.008). Forty-six patients were started on osimertinib. The overall response rate and median progression-free survival were 65.21% and 12.45 months (standard deviation [SD] 1.03, 95% CI 10.41–14.48), respectively. Osimertinib was well tolerated with most toxicities being Grade 1 and 2 diarrhea and skin rash. Conclusions: In our prospective cohort, half of all patients had a T790M mutation at progression on the first-line EGFR TKI. Tissue biopsy is feasible in the majority of patients. Clinical outcomes with osimertinib were consistent with those reported.

Keywords: Epidermal growth factor receptor, liquid biopsy, lung cancer, osimertinib, re-biopsy, T790M


How to cite this article:
Jaiswal R, Pinninti R, Krishna Mohan M V, Santa A, Boyella PK, Nambaru L, Murthy SS, Chowdary K V, Rajappa S. T790M mutation and clinical outcomes with osimertinib in patients with epidermal growth factor receptor-mutant nonsmall cell lung cancer. Indian J Med Paediatr Oncol 2019;40:73-8

How to cite this URL:
Jaiswal R, Pinninti R, Krishna Mohan M V, Santa A, Boyella PK, Nambaru L, Murthy SS, Chowdary K V, Rajappa S. T790M mutation and clinical outcomes with osimertinib in patients with epidermal growth factor receptor-mutant nonsmall cell lung cancer. Indian J Med Paediatr Oncol [serial online] 2019 [cited 2019 Sep 22];40:73-8. Available from: http://www.ijmpo.org/text.asp?2019/40/1/73/256163


  Introduction Top


The discovery of targetable oncogenic driver mutations has successfully changed the outlook for subsets of advanced nonsmall lung cancer (NSCLC) patients.[1],[2] The landscape of therapies for epidermal growth factor receptor (EGFR) driver-mutant advanced NSCLC is fast evolving.[3],[4] Multiple EGFR tyrosine kinase inhibitors (EGFR-TKIs) have been proved to be superior to chemotherapy in multiple large Phase III trials and have been approved for clinical use. The average response rate to these TKIs range around 65%–75%, with a median progression-free survival (PFS) and overall survival of around 10–13 months and 22–30 months, respectively.[5],[6],[7],[8]

Despite a convincing initial tumor response to EGFR-TKIs, the emergence of resistance to these drugs is almost inevitable in most patients. Although multiple resistance mechanisms have been reported, majority (almost 60%) of patients acquire a secondary mutation of threonine-to-methionine substitution at amino acid position 790 (T790M) in exon 20, leading to clinical resistance to EGFR-TKI.[9],[10],[11],[12],[13] T790M results in steric hindrance and increased adenosine triphosphate affinity which decreases EGFR-TKI–mediated inhibition of downstream signaling leading to disease progression. Several studies have found a correlation between clinical variables and the frequency of T790M mutation, but the results are conflicting.[14],[15]

Osimertinib is a highly selective third-generation EGFR-TKI that potently inhibits mutant EGFR and T790M.[16] Recent studies have established the efficacy and safety of osimertinib in T790M-positive advanced NSCLC after progression with prior EGFR-TKI therapy, leading to its approval for this clinical indication.[17],[18] Through this study, we aim to investigate the incidence of T790M mutations in our population and explore the associations between clinical characteristics and frequency of T790M mutation and efficacy of osimertinib in NSCLC patients progressing on a first-line EGFR-TKI.


  Materials and Methods Top


Study design

This study is a prospective series of patients with EGFR mutation who progressed on the first-line TKI.

Inclusion and exclusion criteria

The study included a consecutive series of patients who would satisfy the following criteria: the presence of EGFR mutation at diagnosis, treatment with 1st- or 2nd-generation EGFR-TKIs, documented radiologic progression needing a change of therapy. Oligoprogressions were excluded. The study period was between November 2016 and May 2018.

Objectives

The primary objective of the study was to prospectively evaluate the incidence of T790M mutation in patients who progress on the first-line EGFR-TKIs. The secondary objectives were to identify clinical characteristics that were predictive for T790M mutations, objective response rate (ORR), and progression-free survival (defined as the time from the first dose until progression or death) with osimertinib therapy in T790M-positive patients.

Postprogression molecular assessment

Postprogression tumor rebiopsy was performed from a progressing site after obtaining written informed consent. Mutation analyses of EGFR gene including T790M was performed using amplification refractory mutation system-polymerase chain reaction (ARMS PCR) method. In patients in who declined a re-biopsy or in those where biopsy was not possible because of inaccessible lesion, blood sample (10 ml ethylenediaminetetraacetic acid) was screened for T790M on circulating tumor DNA (CTDNA) using Droplet Digital PCR.

Therapeutic interventions

Patients who had T790M mutation were treated with osimertinib 80 mg once daily until progression. Those who did not harbor the mutation were treated as per histology at rebiopsy. Patients with adenocarcinoma were treated with platinum doublet chemotherapy (intravenous pemetrexed at 500 mg/m2 plus either cisplatin at 75 mg/m2 or carboplatin area under the curve of five). Those with a small cell histology were treated with platinum and etoposide and radiation as per guidelines. Local radiotherapy was utilized for palliation of painful bone metastases or symptomatic brain metastasis.

Study oversight and statistical analysis

This study was conducted in accordance with the principles of the Declaration of Helsinki and the Good Clinical Practice guidelines of the International Conference on Harmonisation. The protocol was approved by the Local Human Investigations Committee. Written informed consent was obtained from all patients. Comparisons of the characteristics of the two groups were carried out using the Chi-square test and independent t-test or the Fisher's exact test utilized where appropriate. Initially, a bivariate analysis was carried out for probable predictive factors for T790M evolution. Subsequently, factors identified were analyzed independently using the stepwise method in the binary logistic regression analysis. Survival estimates were done using Kaplan–Meier method and comparison between subgroups done using the log-rank test. Two-sided values of P < 0.05 were considered statistically significant. Statistical analysis was performed using IBM SPSS version 22.0 software (New York, USA).


  Results Top


Patient characteristics

A total of 90 consecutive patients, comprising 46 men (51.1%) and 44 women (48.9%), who progressed on the first-line TKI were identified based on the inclusion criteria described. The characteristics of these 90 patients are outlined in [Table 1]. The mean age of the entire cohort was 59.1 years (range 38–87 years). Most patients had good performance score (ECOG PS 1 or 2, 78/90%–86.7%), and the majority were nonsmokers (83/90%–92.2%). Baseline driver mutations consisted of exon 19 deletions in 71.1% (64/90), L858R mutation in 23.3% (21/90) and uncommon mutations in 5.5% (5/90). Gefitinib was used in the first line in 72.2% (65/90), erlotinib in 13.3% (12/90), and afatinib in 14.4% (13/90) patients.
Table 1: Comparisons of the clinical characteristics of the two groups relative to entire cohort

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Clinical and molecular characteristics post first-line therapy progression

At progression, 47 of 90 patients (52.2%) had T790M mutation. T790M mutation was identified on repeat tissue biopsy in 82.9% (39/47) and with CTDNA in 17% (8/47). On bivariate analysis, identification of T790M at progression correlated with younger age (80 vs. 44.3% P = 0.005), smoking status (56.6 vs. 0%, nonsmokers and smokers, respectively, P = 0.004), nonerlotinib TKI use (57.7% vs. 16.7% nonerlotinib and erlotinib, respectively, P = 0.008), and pure adenocarcinoma histology at diagnosis (59.7 vs. 22.2%, P = 0.004) [Table 1]. On binary logistic regression model analysis, variables that were independently predictive of the development of T790M were younger age (odds ratio [OR] 4.3, 95% confidence interval [CI] 1.14–16.6, P = 0.031), nonerlotinib TKI use (OR 8.3, 95% CI 1.24–55.8, P = 0.029), and pure adenocarcinoma histology at diagnosis (OR 6.2, 95% CI 1.60–24.7, P = 0.008) [Table 2]. The transformation to small cell carcinoma was identified in two patients (2.2%).
Table 2: Predictive factors for the development of T790M resistance mechanism, selected by binary logistic regression analysis

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Objective response and duration of response to osimertinib in subsequent therapy

Of the 47 patients with T790M mutation, 46 patients received osimertinib as subsequent therapy. At a median follow-up of 15 months, 41.3% (19/46) patients had disease progression including death in 32.5% (13/46) patients [Table 2]. The median PFS on osimertinib was 12.45 months (standard deviation [SD] 1.03, 95% CI 10.41–14.48) [Figure 1]. The overall ORR with osimertinib was 65.21%; with complete responses in 26.08% (12/46) and partial responses in 39.13% (18/46) patients [Table 3]. There was no significant association between PFS and age, gender, performance score, smoking history, type of baseline EGFR mutation, or duration of first-line TKI. The only factor associated significantly with better PFS on osimertinib was the presence of a complete response to first-line TKI therapy (complete response [CR] vs. non-CR, not reached vs. 9.16, SD 3.2, 95% CI 2.81–15.52; P = 0.049) [Figure 2]. At a median follow-up of 15 months, 67.3% (33/46) patients were alive in osimertinib cohort. Osimertinib was well tolerated with most toxicities being Grade 1 and 2 diarrhea and skin rash. There was no therapy discontinuation related to adverse effects. There was one patient with interstitial lung disease which recovered with steroid and treatment interruptions and three cardiovascular deaths while on therapy.
Figure 1: Kaplan–Meier survival curves depicting progression-free survival, median progression-free survival on osimertinib was 12.45 months (standard deviation 1.03, 95% confidence interval 10.41–14.48)

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Table 3: Treatment outcomes

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Figure 2: Kaplan–Meier analysis of progression-free survival on osimertinib therapy with respect to response to first- line therapy (complete responses vs. noncomplete responses, not reached vs. 9.16 confidence interval 3.2 95% confidence interval 2.81–15.52; P = 0.049)

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Objective response and duration of response to chemotherapy in patients who were T790M negative

Of the 43 patients without T790M mutation at disease progression on the first-line oral TKI therapy, 35 (81.4%) patients had received chemotherapy as subsequent therapy, and 8 (18.6%) patients were considered for supportive care alone. The median PFS with chemotherapy in subsequent therapy was 5.94 months (SD 0.84, 95% CI 4.29–7.60). The overall ORR with subsequent line chemotherapy was 54.3%; with CR in 8.6% (3/35); partial responses in 45.7% (16/35); and stable disease in 20% (7/35) and progressive disease in 25.7% (9/35) patients.


  Discussion Top


In this prospective cohort of 90 patients, who had progressed on the first-line EGFR TKI, T790M mutation was detected in 52.2% of patients. The incidence of T790M mutation was similar in tissue and liquid biopsy at 50.6% and 52.9%, respectively. Younger age, nonerlotinib first-line TKI, and pure adenocarcinoma at diagnosis were predictive of T790M evolution. These factors were previously not reported to be predictive of T790M mutation. Joo et al., in their retrospective review, had shown exon 19 deletion to be predictive for T790M evolution which was not the case in our study. Previous studies have indicated a longer duration of EGFR-TKI therapy to be predictive of T790M evolution.[14] In a study by Kawamura et al., patients with postsurgery recurrence and total duration of first-line EGFR-TKI treatment more than 1 year significantly predicted for T790M mutation.[15] However, this was not a significant association in our study, but there was a trend toward T790M positivity, when the prior TKI therapy duration was between 12 and 24 months (63.4 vs. 42.9%, P = 0.052).

At progression, the biopsy was feasible in 77/90 (85%) patients. In a minority who declined a biopsy or in whom a biopsy was not technically feasible, liquid biopsy was utilized to determine T790M mutation. Although the guidelines recommend liquid biopsy followed by tissue for detection of T790M at progression, we prefer tissue rather than plasma due to logistic convenience and being cost-effective at our institute. Since ARMS-PCR for T790M on tissue is done in house, the results could be obtained within 3–4 working days which is shorter and easier than shipping sample for CTDNA analysis to an external laboratory. Moreover, CTDNA can miss up to 30% of T790M mutations mandating the need for a tissue biopsy.[19] The other advantages for tissue sampling include identifying phenotype changes and ability to test for other driver mutations. Two of our 90 patients had small cell transformation.

We believe that the reason for our high success with biopsy was because of close clinical and radiologic monitoring of patients. Although guidelines do not recommend routine radiologic monitoring, we suggest periodic imaging especially because highly effective therapy is available for patients with T790M mutation. There are instances where major progressions which can be minimally symptomatic are missed by just clinical monitoring. This can lead to rapid clinical deterioration and hence the window for biopsy and subsequent therapy being missed. Deterioration in PS can also mean that they are not candidates for chemotherapy.

The ORR (65.21%) and median PFS (12.45 months) with osimertinib were consistent with that of previously reported in the literature.[16],[17],[18],[20] The incidence of T790M mutation in our study was consistent with that reported in the literature both in Caucasians and Asians.[12],[13],[14],[21] The Indian data with osimertinib usage are sparse; ours is the only study that had systematically analyzed the clinical outcomes with osimertinib in EGFR-TKI pretreated driver mutation-positive advanced NSCLC [Table 4]. The only factor associated significantly with better PFS on osimertinib in subsequent therapy was the presence of a complete response to the first-line oral TKI therapy. Patients who received osimertinib (T790M positive) had a longer PFS compared to those who received chemotherapy (T790M negative) for subsequent therapy, reiterating the importance of testing for T790M mutation at progression. Osimertinib was well tolerated with hardly any Grade 3 or 4 adverse events and no therapy discontinuations related to toxicities.
Table 4: Indian data showing the prevalence of T790M in epidermal growth factor receptor tyrosine kinase inhibitors pretreated driver mutation positive advanced non-small lung cancer

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The strength of the study is prospective study design, high biopsy rate, and almost everyone with T790M positive received osimertinib. The drawbacks are heterogeneity in preferred agent in the first-line therapy and short follow-up period. The clinical correlates identified in this observational study for T790M evolution was unique and required validation in further studies.


  Conclusions Top


In our prospective cohort, half of all patients had a T790M mutation at progression on the first-line EGFR TKI. Tissue biopsy is feasible in majority of patients. The clinical outcomes with osimertinib were consistent with those reported.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.[23]

 
  References Top

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23.
Noronha V, Majumdar S, Joshi A, Patil V, Trivedi V, Chougule A, et al. Osimertinib in Indian patients with T790M-positive advanced nonsmall cell lung cancer. South Asian J Cancer 2017;6:143.  Back to cited text no. 23
    


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