Treatment of inoperable large cell neuroendocrine lung cancer with single agent temozolomide

Introduction

Large Cell Neuroendocrine Lung Cancer (LCNEC) is a rare and aggressive type of lung cancer. LCNEC is classified in the high-grade neuroendocrine carcinoma (NEC) subgroup of lung neuroendocrine neoplasms (NENs) together with small cell carcinoma (SCLC) [1]. Treatment of LCNEC is challenging due to the limited data and conflicting results [2,3]. For inoperable patients, no treatment regimen has been fully investigated yet. Platinum-etoposide is the most used first-line therapy in treating advanced LCNEC based on SCLC similarities [2,4]. Temozolomide (TMZ) as monotherapy or combined with capecitabine appears to have some activity in lung carcinoids, and in gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN) with Ki-67 index >20% [5–8]. This could indicate that TMZ may be efficacious in LCNEC. No published study has investigated the treatment of inoperable LCNEC with single-agent TMZ.

Methods

Thirty-seven patients were identified, and data retrospectively obtained from the patient files at the European Neuroendocrine Tumor Society (ENETS) Centre of Excellence Rigshospitalet, University of Copenhagen, from January 2016 to December 2020. During this period, neither diagnostics nor treatment of LCNEC was changed. Baseline and treatment characteristics, oncologic management, and follow-up information of consecutive patients were obtained from electronic medical records and the Danish National Pathology Database. The Danish Patient Safety Authority (ref. nr. 31-1521-453) and the Institutional Review Board approved the study protocol.

All pathological specimens had been reviewed by a team of pathologists specializing in lung and neuroendocrine neoplasms (Center of Excellence Pathologist). The diagnostic criteria were neuroendocrine (NE) morphology and at least one immunohistochemistry NE marker (chromogranin A, synaptophysin, or CD56), as defined by the WHO [1]. A mitotic count was assessed with the Ki-67 index in all patients. Standard upfront NGS analysis was present in 30 cases. The panel consisted of the most frequent hotspot mutations in the following 50 genes: ABL1, AKT1, ALK, APC, ATM, BRAF, CDH1, CDKN2A, CSF1R, CTNNB1, EGFR, ERBB2, ERBB4, EZH2, FBXW7, FGFR1, FGFR2, FGFR3, FLT3, GNA11, GNAQ, GNAS, HNF1A, HRAS, IDH1, IDH2, JAK2, JAK3, KDR, KIT, KRAS, MET, MLH1, MPL, NOTCH1, NPM1, NRAS, PDGFRA, PIK3CA, PTEN, PTPN11, RB1, RET, SMAD4, SMARCB1, SMO, SRC, STK11, TP53, and VHL.

Patients were included in the study if they had biopsy-proven LCNEC and at least one cycle of TMZ. All patients had measurable disseminated disease according to the Response Evaluation Criteria in Solid Tumors (RECIST 1.1). All patients were inoperable and previous treatment lines were allowed.

Patients received oral TMZ 200 mg/m² day 1–5 every 28 days until progression, intolerable toxicity, or death. CT scans were performed after every third treatment cycle. Patients were clinically and biochemically assessed before every treatment cycle. TMZ doses were modified according to hematologic and clinical side effects. Patients were followed until death or the end of the follow-up period (09 March 2022). Vital status was confirmed by The Danish Social Security Death Index.

Treatment outcomes were assessed as progression-free survival (PFS), overall survival (OS), disease control rate (DCR), and objective response rate (ORR). PFS was defined as the time from the starting day of TMZ treatment to the day of progression or death from any cause, whatever occurred first. OS was defined as the time from the start of treatment to death. DCR was defined as the proportion of patients with either complete response (CR), partial regression (PR), or stable disease (SD). The objective response rate (ORR) was defined as the proportion of patients with either CR or PR.

The survival probabilities were calculated and presented using the Kaplan-Meier method and compared across prognostic factors using log-rank analyses in Graph Pad Prism v. 9.

Results

Thirty-seven patients were eligible for assessment, 19 women and 18 men. The median age was 73 years (range 44–91, Q1 = 64, Q3 = 76, IQR = 12). Thirty-three patients (n = 33/37; 89%) were current or former smokers with a median of 40 pack years (range 0–80, Q1 = 30, Q3 = 50, IQR = 20). Performance status (PS) varied from 0–3, with a majority in PS 0–2 (n = 28/37; 76%). The most frequent comorbidity was hypertension (n = 16/37; 43%) followed by cardiovascular disease (n = 13/37; 35%) and chronic obstructive lung disease (n = 8/37; 22%). Fifteen (n = 15/37; 41%) patients had a history of previous other malignancy. All patients had disseminated disease. Sixteen patients (n = 16/43; 43%) had received one (n = 14) or two (n = 2) previous lines of treatment with either platinum-based (n = 14), topotecan (n = 2), or etoposide monotherapy (n = 2). No patients had received treatment with immune checkpoint inhibitors or tyrosine kinase inhibitors.

Ki-67 index was assessed in all patients but one patient with a median of 50% (range 17-100%).

Six patients (n = 6/37; 16%) had grade 3–4 toxicity during the treatment period. No patients discontinued TMZ due to adverse events and no patient died due to the TMZ treatment. All deceased patients died due to their cancer disease.

The course of the disease in terms of OS and PFS is shown for every patient in Figure 1. No patients had CR. Two patients (n = 2/37; 5%) had PR, and eight (n = 8/37; 22%) patients had SD during TMZ treatment. Seven (n = 7/37; 19%) patients were alive at the end of the follow-up period (March 09, 2022). All patients had radiologic or clinical progression before the end of the follow-up period.

Figure 1. The course of the disease in terms of length of progression free survival (PFS) and overall survival (OS) for all patients. Patients are sorted according to the length of PFS. OS is shown in the brightest color and PFS is shown in the darkest. Tumor development was assessed according to the response Evaluation criteria in Solid Tumors (RECIST 1.1) criteria, and the responses are marked in the figure. The maximum number of temozolomide cycles was 18. The total amount of days with treatment until progression is indicated for every patient at the end of the row.

The overall median PFS was 2.5 months, and the median OS was 5.5 months. Neither performance status, age, line of treatment, Ki67 index, or mutations in KRAS (8/30), STK11 (6/30), TP53 (8/30) had an impact on OS or PFS. One patient had an RB1 mutation.

The ORR was 5% (n = 2/37), and the DCR 27% (10/37). Twenty-seven patients had PD (27/37, 73%). PFS was 7.4 months in the DC group vs. 2.1 months in the group with PD (p < 0.001). OS was 16.5 months in the DC group vs. 3.9 months in the PD group (p = 0.01) (Figure 2).

Figure 2. a) Kaplan Meier curve of progression-free survival (PFS), disease control (DC) (n = 10) versus progressive disease (PD) (n = 27). b) Kaplan Meier curve of overall survival (OS), disease control (DC) versus progressive disease (PD).

Discussion

The clinicopathologic features of the patients were consistent with the known demographics of this disease. The high incidence rate of previous or concomitant cancer was expected since LCNEC is a smoke-related disease, and the patient cohort was elderly. This is consistent with previous studies showing rates of previous or concomitant cancer of 25–38% [9,10].

Treatment outcomes showed an overall median PFS of 2.5 months and a median OS of 5.5 months. This indicates a poorer survival in our cohort compared to other studies on systemic treatment of advanced LCNEC with PFS ranging from 4–6 months and OS 6–17 months [11–16]. Most patients in the previous studies were in PS 0-1 and received the first line of treatment. Our cohort included patients in PS 2–3 and with previous lines of treatment. However, we found no significant difference in PFS or OS in terms of PS, age, or line of treatment.

In the DC group, PFS and OS were significantly longer (7.4 months and 16.5 months, respectively) compared to the PD group, indicating the benefit of treatment in a subgroup who were particularly susceptible to the treatment. The duration of disease control is encouraging and indicates a possible biological difference between the DC and PD groups, thereby holding the potential for predictive biomarkers to be found. Our analyses did not reveal any characteristics to distinguish between the groups. A hopeful suggestion for the future investigation of predictive markers for TMZ-sensitivity could be the status of the MGMT (O6-methylguanine–DNA methyltransferase) DNA-repair gene. In advanced glioblastoma and melanoma patients with MGMT promoter methylation, TMZ has shown better efficacy compared to patients without methylation [17]. Conflicting results are reported in neuroendocrine neoplasms and the role of MGMT status remains investigational [18–20].

Conclusion

This study is among the first to analyze the treatment outcomes of TMZ in LCNEC patients. A subgroup of twenty-seven percent of the patients obtained DC with a marked improved PFS and OS. No apparent predictive factor for TMZ sensitivity could be identified from our dataset. Further prospective randomized trials are warranted to determine the most beneficial treatment of advanced LCNEC.

Ethical approval

This is an observational study. The Regional Scientific Ethical Committee of The Capital Region of Denmark has confirmed that no ethical approval is required.

Authors’ contribution

All authors contributed to the study's conception and design. Material preparation, data collection and analysis were performed by Annika Marie Ørting, Malene Martini Clausen, and Seppo W. Langer. The first draft of the manuscript was written by Annika Marie Ørting and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

RHP: Speaker fee: Medtronic, AMBU, Medela, and AstraZeneca. Advisory board: AstraZeneca, Roche and BMS.

SWL: Advisory board, research collaboration, speaker fee: Roche, Merck, Amgen, AbbVie, Jannsen Pharma, Boehringer-Ingelheim.

Data availability statement

Data available on request from the authors.

Additional information

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.