Neoadjuvant chemoimmunotherapy for small cell carcinoma of the esophagus: Clinical efficacy and biomarker exploration

ABSTRACT

Background

Small cell carcinoma of the esophagus (SCCE) is a highly aggressive neuroendocrine neoplasm, accounting for only 0.6% of all malignant esophageal tumors.¹ The prognosis for SCCE remains markedly dismal, with no established treatment strategy.² Clinical management of SCCE commonly adheres to the therapeutic protocols established for small cell lung cancer (SCLC), involving thoracic radiotherapy and concurrent platinum-etoposide chemotherapy.^3,4 Although SCCE is initially responsive to these treatment regimens, the overall prognosis remains unsatisfactory.

Immune checkpoint inhibitors (ICIs) that target the programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) pathway are revolutionizing the treatment paradigm for various cancers. The ongoing IMpower133⁵ and CASPIAN studies⁶ have demonstrated the efficacy of the combination of platinum-based chemotherapy with atezolizumab or durvalumab as the first-line systemic treatment for SCLC,⁷ marking a significant milestone in SCLC therapy. In the realm of esophageal squamous cell carcinoma (ESCC), the integration of ICIs and chemotherapy has been adopted as the standard first-line treatment for advanced ESCC.⁸ The ongoing exploration of immunotherapy for ESCC has demonstrated promising short-term efficacy and safety.⁹ Notably, SCCE and SCLC share a common cellular origin and pathogenesis, characterized by the overexpression of SOX2 and the loss of Rb1.¹⁰ Thus, the effective application of ICIs in the treatment of esophageal cancer and SCLC might also present potential benefits for patients suffering from SCCE. Previous studies have revealed the presence of a suppressive tumor immune microenvironment in SCCE. Thus, inducing a “T-cell inflamed” microenvironment may increase the response rate to immunotherapy.¹¹ Currently, there is limited research on the utilization of immunotherapy for SCCE. Only sporadic reports have been published regarding the application of immunotherapy in the palliative treatment of advanced SCCE.^12–14 However, there is a notable absence of studies investigating the efficacy of neoadjuvant immunotherapy or chemoimmunotherapy in cases of limited-stage SCCE.

This study presents findings on three patients diagnosed with SCCE who received chemoimmunotherapy. Encouragingly, two patients with limited-stage disease achieved major pathological response (MPR) and complete pathological response (pCR), respectively, following neoadjuvant treatment and surgery, with sustained responses. Additionally, an investigation into the underlying mechanisms of varying responses to immunotherapy and chemotherapy in SCCE cases was conducted.

Case presentation

Case 3

A man patient in his 50s presented with a gradual onset of dysphagia over a two-month period. No significant past medical history was reported. Gastroscopic examination revealed a substantial ulcer located 25 centimeters distal to the incisors. Subsequent pathological analysis confirmed the diagnosis of SCCE. Additionally, PET-CT scans demonstrated a malignant neoplasm at the level of the upper thoracic esophagus with metabolic abnormalities pervading the entire layer. The clinical TNM stage was classified as cT3N0M0, stage II. The patient underwent two cycles of neoadjuvant immunotherapy combined with chemotherapy [Etoposide (180 mg, days 1–3) plus Cisplatin (400 mg, day 1) plus Durvalumab (1000 mg, day 3)]. Following the treatment, a subsequent PET-CT scan demonstrated a CR of the lesion. Radiographic evaluation suggested a complete metabolic response (CMR). (Figure 1) The patient then underwent surgical resection, and the post-operative pathology report indicated a pathological complete response (pCR). (Figure 1) After surgery, the patient followed one year of immune maintenance therapy.

Open in a separate window

Figure 1.

Clinical and pathological profile of the patient who achieved pCR following neoadjuvant immunotherapy combined with chemotherapy. (a) Pre-treatment PET-CT image; (b) Post-treatment PET-CT imaging evaluation; (c) Post-treatment pathological image (congestion visible in submucosal lesions, accompanied by lymphocyte infiltration, no cancer observed).

The overall survival (OS) of the SCCE case achieving PD after EP (Etoposide and Cisplatin) plus durvalumab treatment was 4.5 months. The SCCE patients achieving PR or CR after neoadjuvant chemoimmunotherapy were not progression after surgery up to now (26 months) (Figure 2a). The medium OS of patients with SCCE, encompassing those in stages I-Ⅳ, was 23 months (Figure 2b) based on the previous data from Feng Wang’s team¹⁵ and Renda Li’s team¹¹ (Table 1), which suggested that a part of SCCE patients might benefit from neoadjuvant chemoimmunotherapy.

Open in a separate window

Figure 2.

Different outcomes for SCCE cases after neoadjuvant immunotherapy combined with chemotherapy. (a) Clinical courses of three SCCE cases with neoadjuvant immunotherapy combined with chemotherapy. (b) Kaplan-Meier survival curve of the SCCE patients including stage I-IV using the previous data from Feng Wang’s team and Renda Li’s team.

Table 1.

Clinical characteristics of the SCCE cohort from the Renda Li team and Feng Wang team.

Factor	Overall (n = 101)
Gender
Male	75 (74.3%)
Female	26 (25.7%)
Age
≤60	54 (53.5%)
>60	47 (46.5%)
Smoking
Yes	53 (52.5%)
No	48 (47.5%)
Drinking
Never	62 (61.3%)
Occasional	13 (12.9%)
Regular	25 (24.8%)
Missing	1 (1.0%)
Tumor Stage
I	11 (10.9%)
II	35 (34.6%)
III	40 (39.6%)
Ⅳ	15 (14.9%)
Tumor Location
Lower-thorax	25 (24.8%)
Mid-lower-thorax	6 (5.9%)
Midthoracic	62 (61.4%)
Mid-upper-thorax	1 (1.0%)
Upper-thorax	7 (6.9%)

Open in a separate window

Efficacy of neoadjuvant chemoimmunotherapy associated with tumor infiltrating CD8⁺ T cells and PD-L1 expression

To explore different efficacy of neoadjuvant chemoimmunotherapy in the patients with SCCE, we examined protein levels of CD8, CD163, PD1 and PD-L1 using multiplex immunohistochemistry (mIHC) in the SCCE samples. As shown in Figure 3a,b, the percent of CD8⁺ T cells was sequential increase in the SCCE patients achieving PD, PR and CR. We further evaluated the impact of CD8⁺ T cell level on OS using the previous SCCE cohort from Renda Li’s team¹¹ (Table 2). The high expression group of CD8⁺ T cell demonstrated a significant survival benefit compared to the low expression group (Figure 3c).

Open in a separate window

Figure 3.

Efficacy of neoadjuvant immuno-chemotherapy associated with tumor infiltrating CD8⁺ T cells and PD-L1 expression. (a and b) Multiplex immunohistochemistry (mIHC) imaging (a) and quantitative assay (b) of the SCCE samples staining with CD8, CD163, PD1 and PD-L1 antibodies. Scale bar: 100 μm. (c) Kaplan-Meier survival analysis of the SCCE patients with low/high expression of CD8⁺ T cell using the previous SCCE cohort from Renda Li’s team. Expression of CD8⁺ T cell was calculated according to ssGSEA analysis and the SCCE cohort was divided into low/high expression groups using an optimal cutoff value of expression of CD8⁺ T cell.

The expression of PD-L1 was high in three SCCE cases, indicating that three SCCE cases might be beneficial from immunotherapy (Figure 3a,b). However, one case experienced PD and had a survival time of only 4.5 months. Of note, the infiltration of tumor CD8⁺ T cells of this case was extremely low. Thus, the combination of tumor-infiltrating CD8+ T cells and PD-L1 expression might more accurately predict efficacy of chemoimmunotherapy in SCCE. In addition, the percent of CD163⁺ M2 macrophages was similar and expression of PD1 was the low levels in three SCCE cases (Figure 3a,b).

Gene variation features in the SCCE cases

The gene variation features in two cases of small cell carcinoma of the esophagus (SCCE) achieving PR and CR were explored through whole exome sequencing (WES). Somatic TP53 mutation was identified in both SCCE cases (Figure 4a). An analysis of the landscape of the top 20 gene alterations was conducted using data from previous studies by Feng Wang’s study¹⁵ and Renda Li’s study,¹¹ revealing that 82% patients with SCCE had TP53 mutation (Figure 4b). Somatic mutations in NOTCH1 and TTN, among the top 20 variation genes, were detected in the PR and CR cases following neoadjuvant immunotherapy combined with chemotherapy, respectively (Figure 4a,b).

Open in a separate window

Figure 4.

Gene mutation features in the SCCE patients. (a) Gene mutation in two SCCE cases. (b) Landscape of top 20 gene alterations in the previous data from the Feng Wang’s team and the Renda Li’s team.

Copy number variation (CNV) analysis revealed that 445 CNV genes were detected in the SCCE case achieving PR, consisting of 62 genes with copy number loss and 383 genes with copy number gain. Conversely, only one gene with copy number loss was found in the case achieving CR (Figure 5a). To explored impact of CNV on survival, we examined changes in CNV numbers in SCCE using the Renda Li’s study cohort.¹¹ Half of the SCCE patients exhibited over 300 CNV genes (Figure 5b). However, there was no significant difference in survival analysis between SCCE groups with high and low CNV genes (Figure 5c). These results indicated that number of CNV genes might be not a major factor to influence the outcomes of two cases after neoadjuvant chemoimmunotherapy.

Open in a separate window

Figure 5.

Gene CNV features in the SCCE patients. (a) Gene CNV number in two SCCE cases. (b) Gene CNV features in the previous data from the Renda Li’s study cohort. (c) Kaplan-Meier survival analysis of the SCCE patients with low/high groups of CNV gene number using the previous SCCE cohort from Renda Li’s team. The SCCE cohort was divided into low/high groups according to the median value of CNV gene number (CNV gene number: 300).

Furthermore, additional parameters were computed based on WES data, such as tumor mutation burden (TMB), microsatellite instability (MSI), human leukocyte antigen A/B/C (HLA-A/B/C), homologous recombination deficiency (HRD), mutant allele tumor heterogeneity (MATH), and tumor neoantigen. Analysis presented in Table 3 indicates that the factor scores were comparable in the two SCCE cases, suggesting that these factors may not serve as reliable predictors of the effectiveness of neoadjuvant chemoimmunotherapy in SCCE.

Molecular subtypes of SCCE

Similar to SCLC,¹⁶ the recent study on SCCE identified two molecular subtypes (SCCE-A and SCCE-N) according to achaete-scute complex homologue 1 (ASCL1) and NeuroD1 expression.¹¹ The staining results for ASCL1 and NeuroD1 suggested that the PR SCCE case exhibited NeuroD1 positivity, while the CR case showed ASCL1 positivity (Figure 6). Previous research has indicated that patients with the SCCE-A subtype have more favorable prognoses compared to those with the SCCE-N subtype, which could potentially explain the differing outcomes observed in the two SCCE cases following neoadjuvant chemoimmunotherapy.

Open in a separate window

Figure 6.

Molecular subtype identification of two SCCE cases using mIHC staining with ASCL1 and NeuroD1 antibodies. Scale bar: 100 μm.

The materials, reagents, and detection methods are described in the Supplementary Materials.

Discussion

SCCE is a rare and highly aggressive type of esophageal cancer that often presents with metastasis at the time of diagnosis.¹⁷ While there is currently no established standard treatment for SCCE patients, chemotherapy combined with radiation therapy has been shown to improve the prognosis to some extent, as recommended by the GEP-NEC management guidelines and NCCN guidelines.^18,19 A recent study regarding locally advanced SCCE reported an overall response rate as high as 86.4% after curative chemoradiotherapy.²⁰ However, this response is not durable, as the median progression-free survival in this study was only 12.7 months.²¹ Nevertheless, with the remarkable breakthroughs of ICIs in the treatment of SCLC and ESCC, immunotherapy holds promise for changing the treatment landscape for SCCE.

In this case report, two patients with limited-stage SCCE underwent surgery after receiving neoadjuvant chemoimmunotherapy, achieving significant and sustained positive responses. They have shown no progression and have tolerated the treatment well after one year of immunotherapy. These two cases illustrate the potential benefits of neoadjuvant chemoimmunotherapy in facilitating surgical intervention in patients with SCCE. With the application of systemic therapy, researchers have found that adding local surgical resection to systemic treatment significantly improves survival.²² Although case 2 in this study achieved significant remission after treatment, pCR was not achieved. Surgical resection may have potential benefits in preventing recurrence. Additionally, both patients who underwent surgery in this study continued with one year of maintenance immunotherapy. Based on the current condition and survival status of the patients, this treatment strategy appears to be reasonable. Therefore, our treatment approach provides examples for patients with limited-stage SCCE, and further clinical trials are needed to validate the effectiveness of this treatment.

Satoshi Yamashita et al.²³ reported that the prevalence of PD-L1 positivity in SCCE was 60% at the cutoff point for CPS was set at ≥ 1. Furthermore, most patients retained expression of HLA-I, indicating that the majority of SCCE patients may derive therapeutic benefit from ICIs treatment. However, in case 1, despite high expression of PD-L1 in an advanced-stage SCCE patient, disease progression occurred after treatment, and the overall survival was just 4.5 months. It was observed that the expression of CD8⁺ T cells in this patient was extremely low. Therefore, considering the expression level of PD-L1 alone does not seem to fully predict the treatment response of SCCE. Previous studies have also shown that the combined expression of PD-L1 and CD8⁺ can effectively predict the prognosis of SCCE patients.²⁴ Similar to reports on SCLC, ICIs treatment may be beneficial for SCCE patients who have pre-activated T cells in the tumor microenvironment, especially when PD-L1 and CD8⁺ are present simultaneously.²⁵ Therefore, the combination of CD8⁺ T cell infiltration and PD-L1 expression may be an important indicator for predicting the efficacy and prognosis of SCCE patients receiving neoadjuvant chemoimmunotherapy.

These are the first reported cases of successful application of neoadjuvant chemoimmunotherapy in SCCE, which represents a significant advancement in the field of SCCE treatment. Compared to radiotherapy and chemotherapy, neoadjuvant chemoimmunotherapy appears to be the more favorable treatment strategy. Neoadjuvant chemoimmunotherapy may represent the optimal treatment approach for limited-stage SCCE in the future. The therapeutic strategy employed in this case study could potentially offer valuable insights for the current treatment.

Supplementary Material

Funding Statement

This work was supported by the Guangzhou Science and Technology Plan Projects (202206010103).

References