Response to nivolumab as an immune checkpoint inhibitor rechallenge for esophageal squamous cell carcinoma with PD-L1 amplification: a case report

Abstract

The Programmed death-ligand 1 (PD-L1) gene amplification has been proposed as a potential predictive biomarker for the efficacy of immune checkpoint inhibitors (ICIs); however, its clinical relevance in the setting of ICI rechallenge after resistance to initial ICI therapy remains unclear. We report a case of metastatic esophageal squamous cell carcinoma (ESCC) with PD-L1 gene amplification that showed a partial response (PR) to nivolumab monotherapy as an ICI rechallenge. A 61-year-old man with clinical stage III ESCC underwent curative esophagectomy followed by neoadjuvant chemotherapy. Three years after surgery, mediastinal lymph node recurrence was detected, and the patient was treated with curative chemoradiotherapy followed by maintenance anti-PD-L1 antibody therapy. During maintenance treatment, a new recurrence developed in the right supraclavicular lymph node. Despite multiple subsequent lines of chemotherapy, the disease progressed. Comprehensive genomic profiling revealed amplification of CD274 (PD-L1) with a copy number gain of 8. In addition, immunohistochemical analysis using the PD-L1 IHC 22C3 pharmDx assay demonstrated high PD-L1 expression, with a combined positive score exceeding 40. Based on these findings, nivolumab was administered as an ICI rechallenge 8.8 months after discontinuation of the initial ICI therapy. The patient achieved a PR after 3.1 months of nivolumab treatment, although disease progression was observed after 5 months. Although limited by its single-patient nature, this report suggests that PD-L1 gene amplification may represent complementary biological information associated with the efficacy of ICI rechallenge, warranting further investigation in larger cohorts.

Introduction

Immune checkpoint inhibitors (ICIs) targeting programmed death-1 (PD-1) or its ligand (PD-L1) improve survival outcomes across multiple tumor types, ¹ including esophageal squamous cell carcinoma (ESCC).^2–4 However, only a subset of patients shows a long-term clinical response to ICI therapy, as reported in a previous review. ⁵ To expand the patient population that benefits from ICI therapy, several predictive biomarkers have been proposed, including PD-L1 expression, high microsatellite instability, high tumor mutation burden (TMB), and tumor-infiltrating lymphocyte enrichment.

Comprehensive genomic profiling (CGP) assays have evolved within the framework of precision oncology, enabling the identification of actionable molecular alterations. Amplification of the PD-L1 (CD274) gene, located in the 9p24.1 region, has been detected in several tumors using CGP assays and fluorescence in situ hybridization (FISH). In a large cohort of diverse solid tumors analyzed using the FoundationOne^® CDx and Heme CGP assays, PD-L1 amplification was detected in 0.7% of patients, with high frequencies observed in head and neck squamous cell cancer (HNSCC; 3.2%), cervical cancer (2.1%), ESCC (2%), and breast cancer (1.4%).^6–8

A retrospective study was conducted on nine patients having solid tumors with PD-L1 amplification, defined as copy number gains (CNGs) ⩾6, using the FoundationOne CDx CGP assay; of these, six patients (66.7%) with glioblastoma (one), HNSCC (two), basal cell carcinoma (two), and bladder urothelial carcinoma (one) showed a remarkable response to anti-PD-1 treatment. ⁶ Recently, an exploratory phase II study showed that metastatic breast cancer with PD-L1 amplification, defined as CNGs ⩾5 and 3–4 using the CytoScan HD Array and OncoScan FFPE Assay Kits, respectively, had a high sensitivity to durvalumab (anti-PD-L1 antibody) maintenance therapy. ⁹ In addition, in a nationwide retrospective study of over 60,000 solid tumors, PD-L1 amplification was detected in 48 patients, including 3 with esophageal cancer, and was associated with favorable responses to ICIs. ¹⁰ Altogether, these studies suggest that PD-L1 amplification may be a promising predictive biomarker for the efficacy of anti-PD-1/PD-L1 antibody therapy.

Furthermore, according to previous systematic reviews, ICI readministration shows efficacy similar to that of the initial administration for several cancer types, such as melanoma or non-small-cell lung cancer (NSCLC), although these reports include cases of both initial ICI resistance (defined as rechallenge) and intolerance (defined as reintroduction).^11,12 Across studies of rechallenge with anti-PD-1 or anti-PD-L1 antibody after initial resistance to anti-PD-1 or anti-PD-L1 antibody, the ORR ranged from 12.5% to 53.8% for melanoma and from 0% to 42.9% for NSCLC, with median PFS values of 2.5–9.0 and 1.5–3.1 months, respectively. ICI rechallenge may be a feasible strategy for the treatment of selected patients, for example, those who previously achieved clinical benefit from initial ICI therapy.^11,12 Herein, we present the case of a patient with ESCC and PD-L1 amplification who was treated using nivolumab as an ICI rechallenge for lymph node metastasis.

Methods

The reporting of this case conforms to the CARE (CAse REport) guidelines. A completed CARE checklist is provided as a Supplemental File.

Case report

A 61-year-old man was diagnosed with clinical Stage III (T3N1M0; UICC, 8th edition) ESCC of the upper thoracic region. The patient’s treatment timeline is summarized in Figure 1. The patient underwent curative esophagectomy in February 2016, followed by three cycles of neoadjuvant chemotherapy with fluorouracil, cisplatin, and docetaxel. Histological examination of the resected ESCC revealed that it was pathological Stage III (T2N2M0). The pathological criterion for the effects of chemotherapy was Grade 1 tumor regression, defined as the absence of residual cancer with fibrosis extending through the esophageal wall layers. ¹³ Three years post-surgery, in April 2019, a follow-up computed tomography (CT) scan revealed recurrence of mediastinal lymph node metastasis (17 mm). The patient received two cycles of fluorouracil plus cisplatin with radiotherapy (total, 60 Gy) in a radical setting and showed a complete response (Response Evaluation Criteria in Solid Tumors, version 1.1). After chemoradiotherapy (CRT), the patient received maintenance therapy with anti-PD-L1 antibodies as part of a clinical trial for 8 months. In February 2020, during the maintenance treatment period, a CT scan showed a new recurrence site in the right supraclavicular lymph node (17 mm). As the recurrent lymph node was located within the previous radiation field, we did not repeat CRT. The patient received five cycles of fluorouracil, leucovorin, and oxaliplatin, followed by four cycles of weekly paclitaxel; however, both treatments were ineffective, with the best response being stable disease (SD). In May 2020, a CT scan showed regrowth of the right supraclavicular lymph node metastasis (39 mm). In June 2020, a FoundationOne CDx CGP assay was conducted using the surgical specimen; eight somatic variants were detected, including CD274 (PD-L1) with a CNG of 8, cyclin D1 (CCND1), fibroblast growth factor 19 (FGF19), FGF3, FGF4, Janus kinase 2 (JAK2), and PDCD1LG2 (PD-L2) amplification, and tumor protein p53 (TP53) R282G mutation (Table 1) with microsatellite stable and TMB low (6/Mb). The PD-L1 IHC 22C3 pharmDx assay results revealed that the combined positive score (CPS) for PD-L1 expression was >40% (Figure 2). From November 2020, 240 mg of nivolumab was administered every 2 weeks as an ICI rechallenge. The interval between the end of the first anti-PD-L1 antibody therapy and the beginning of nivolumab therapy as an ICI rechallenge was 8.8 months. After 1.3 months of nivolumab initiation (three cycles), the patient had SD with a 15% increase in the size of the right supraclavicular lymph node metastasis (45 mm). After 3.1 months of nivolumab initiation (seven cycles), the size of the right supraclavicular lymph node metastasis had decreased by 31% compared to that at the baseline CT (27 mm) with a PR. However, in April 2021, after 5 months of nivolumab initiation (11 cycles), a CT scan showed tumor regrowth (43 mm), indicating disease progression. Moreover, grade 1 interstitial pneumonia due to nivolumab treatment was detected, according to the Common Terminology Criteria version 5.0. The patient was shifted to the best supportive care and died in September 2021, 10.3 months after nivolumab initiation. No other nivolumab-induced toxicities were observed.

Figure 1.

Clinical course and treatment timeline of the patient with esophageal squamous cell carcinoma.

Table 1.

Cancer genomic profiling.

Amplified/deleted gene name	Chromosome position	Amplification/deletion	Copy number	Clinical significance
PD-L1 (CD274)	9p24.1	Amplification	8	Likely pathogenic
FGF19	11q13	Amplification	22	Likely pathogenic
FGF3	11q13	Amplification	22	Likely pathogenic
FGF4	11q13	Amplification	22	Likely pathogenic
JAK2	9p24.1	Amplification	8	Likely pathogenic
PDCD1LG2 (PD-L2)	9p24.1	Amplification	8	Likely pathogenic
TP53	17p13	Mutation	0	Likely pathogenic

FGF19, fibroblast growth factor 19; FGF3, fibroblast growth factor 3; FGF4, fibroblast growth factor 4; JAK2, Janus kinase 2; PDCD1LG2 (PD-L2), programmed cell death 1 ligand 2; PD-L1 (CD274), programmed death-ligand 1; TP53, tumor protein p53.

Figure 2.

Immunohistochemical analysis of PD-L1 expression in the primary tumor specimen. PD-L1 expression was assessed using the PD-L1 IHC 22C3 pharmDx assay. Both tumor cells and tumor-associated immune cells showed strong membranous staining, with a CPS (number of PD-L1-positive tumor and immune cells divided by total number of viable tumor cells × 100) >40. Original magnification ×400.

Discussion

We presented the case of a patient with metastatic ESCC and PD-L1 amplification who showed a PR to nivolumab monotherapy as an ICI rechallenge. To the best of our knowledge, this appears to be the first reported case of ICI rechallenge therapy in a patient with metastatic ESCC. This report suggests that PD-L1 amplification may be associated with sensitivity to ICI rechallenge therapy; however, this interpretation should be made cautiously, given the single-case nature of this observation.

Although the rechallenge of anti-PD-1/PD-L1 antibodies in other cancers, such as melanoma and lung cancer, was effective with tolerable toxicity, no predictive biomarker for the effectiveness of rechallenge has been identified. In this case, CGP was performed after completion of standard treatments, which revealed PD-L1 amplification. Furthermore, PD-L1 immunohistochemistry showed a high CPS (>40), which itself has been associated with favorable responses to ICIs in ESCC. On the basis of these findings, ICI rechallenge was subsequently considered. At that time, no established standard treatment options remained, which further supported consideration of ICI rechallenge. Therefore, the observed response to nivolumab rechallenge cannot be attributed solely to PD-L1 gene amplification.

In an observational study, the researchers analyzed whether PD-L1 CNGs were associated with response to nivolumab monotherapy after disease progression following standard therapy in patients with NSCLC. ¹⁴ PD-L1 amplification was defined as a PD-L1/CEP9 ratio of two or higher by FISH. The authors reported that NSCLC with PD-L1 amplification is associated with a markedly inflamed immune microenvironment. Therefore, these findings suggest that PD-L1 amplification may be a predictive biomarker for the efficacy of ICI treatment, even in cancers such as NSCLC that are highly responsive to ICIs.

However, the relationship between PD-L1 protein expression and gene amplification remains unclear. For example, in the observational study mentioned above, ⁹ 40% of patients with PD-L1 amplification (2 of 5) had low PD-L1 expression, and these two patients achieved SD and PR, respectively. In another study on NSCLC, 37% of patients (9 of 24) with PD-L1 amplification were PD-L1-negative. ¹⁵ These findings suggest that PD-L1 amplification may predict ICI efficacy independently of PD-L1 protein expression. This could be due to the fact that PD-L1 protein levels in tumor cells are influenced by various factors, especially immune reactivity and oncogenic signaling molecules. A key mechanism of PD-L1 protein upregulation is PD-L1 gene expression.^16,17 For example, in refractory classical Hodgkin’s lymphoma, whose characteristic feature is chromosome 9p24.1 amplification, ICI therapy has shown long-term response rates of approximately 60%–90%. ¹⁸ The JAK2 gene, located in the same region as the PD-L1 gene, is overexpressed when PD-L1 is amplified, enhancing PD-L1 induction. ¹⁹ PD-L1 amplification might act as an oncogenic driver alone or in cooperation with JAK2; alternatively, PD-L1 amplification may be a bystander or surrogate marker.^20,21 Altogether, PD-L1 amplification regulates tumor progression by modulating the immune environment, suggesting that amplification could provide additional predictive information beyond PD-L1 protein expression alone for predicting ICI efficacy, even when PD-L1 protein expression is low or absent.

Therefore, PD-L1 gene amplification may serve as a complementary biomarker to PD-L1 immunohistochemistry by reflecting constitutive activation of the PD-1/PD-L1 axis through genomic alteration. Although the present single case does not allow disentanglement of the individual contributions of PD-L1 protein expression and gene amplification, the coexistence of both features may have contributed to the transient but clinically meaningful response observed with nivolumab rechallenge. Further investigation is warranted to determine whether PD-L1 gene amplification can serve as complementary biological information associated with ICI rechallenge.

In addition, it should be noted that the patient received multiple lines of cytotoxic chemotherapy during the 8.8-month interval between discontinuation of the initial anti-PD-L1 antibody and nivolumab rechallenge. Cytotoxic agents are known to modulate the tumor immune microenvironment, and taxanes in particular can enhance antitumor immunity by promoting dendritic cell maturation, improving antigen presentation, suppressing regulatory T cells, and activating effector T cells,^22,23 as well as inducing immunogenic cell death that may restore sensitivity to ICI. ²² In this case, prior paclitaxel treatment may have contributed to changes in the tumor microenvironment, which could have enhanced sensitivity to nivolumab rechallenge; thus, the observed response may have been influenced not only by tumor-intrinsic factors such as PD-L1 amplification but also by treatment-induced immune modulation.

In addition, the durability of response in this case was limited, with disease progression occurring 5 months after nivolumab initiation. Although a PR was achieved, the clinical benefit was modest and transient. This pattern may reflect the early emergence of acquired resistance in the rechallenge setting, as well as the intrinsic heterogeneity of responses to ICIs in ESCC. These findings suggest that ICI rechallenge should be carefully considered in selected patients, and its clinical utility needs to be further validated in prospective studies.

This case report has several limitations. First, the CGP was performed using the primary tumor specimen obtained at the time of surgery. No re-biopsy of the recurrent lesion or liquid biopsy was conducted at the time of ICI rechallenge. Therefore, temporal and spatial tumor heterogeneity, as well as potential genomic evolution during prior treatments, could not be assessed. Second, in this case, nivolumab was administered as monotherapy without concurrent chemotherapy at the time of rechallenge. Although combination approaches with chemotherapy or radiotherapy may enhance immunogenicity and help overcome resistance in certain settings, no cytotoxic agents were combined in this case because the patient had been refractory to fluoropyrimidines, platinum, and taxanes.

In conclusion, we presented the case of a patient with ESCC and PD-L1 amplification who received nivolumab monotherapy as an ICI rechallenge for lymph node metastasis. PD-L1 amplification may represent complementary genomic information that warrants further investigation as a potential predictive biomarker for ICI rechallenge.

Supplemental Material

sj-pdf-1-tam-10.1177_17588359261451859 – Supplemental material for Response to nivolumab as an immune checkpoint inhibitor rechallenge for esophageal squamous cell carcinoma with PD-L1 amplification: a case report

Supplemental material, sj-pdf-1-tam-10.1177_17588359261451859 for Response to nivolumab as an immune checkpoint inhibitor rechallenge for esophageal squamous cell carcinoma with PD-L1 amplification: a case report by Hiroyuki Kodama, Toshiki Masuishi, Yasunobu Ishizuka, Tomoki Sakakida, Kazunori Honda, Yukiya Narita, Hiroya Taniguchi, Shigenori Kadowaki, Masashi Ando, Waki Hosoda and Kei Muro in Therapeutic Advances in Medical Oncology