Next-Generation Sequencing of Synchronous Multiple Primary Lung Cancers in a Patient with Squamous Cell Carcinoma and Small Cell Lung Cancer

Introduction

Multiple primary lung cancer (MPLC) refers to the simultaneous or sequential occurrence of two or more primary malignancies in the lungs of the same patient.¹ According to the time of tumor discovery, MPLCs can be divided into < 6 months of simultaneous MPLC (sMPLC) and≥ 6 months of metachronous MPLC (mMPLC). sMPLC is a rare entity, with an incidence rate that ranges from 1% to 7%,² and the majority are of the same histologic type. The coexistence of small and non-small cell carcinoma has been reported in a small fraction of cases.^3–9 Here, We report a rare case of synchronous MPLC of different histological types [squamous cell carcinoma (SCC) and small-cell lung carcinoma (SCLC)].

Case Report

A 60-year-old man was admitted to the First Affiliated Hospital of Shihezi University School of Medicine on 25 March 2020 with a 2-month history of cough, sputum, and wheezing. He was a road worker with a 30-year history of smoking 40 cigarettes/day; he quit smoking 9 years ago. Laboratory examination revealed elevated tumor markers, including CEA (15.94 ng/mL), CA15-3 (27.37 U/mL), CA19-9 (31.19 U/mL), CA72-4 (17.07 U/mL), and cytokeratin 19 fragment (35.15 ng/mL). Autoimmune markers, including anti-SM antibodies, anti-nucleosome antibodies (AnuA), and anti-histone antibodies (AHA), were positive. Chest computed tomography (CT) revealed two solid lesions located at the lower lobes of the right lung (48 × 36 mm) and left lung (78 × 45 mm) (Figure 1), suggesting the possibility of a malignant tumor. Magnetic resonance imaging (MRI) examination of the head indicated possible brain involvement. Tumor stage was determined stage IV (T4N3M1b). The patient reported no family history of lung cancer. To determine the histological type, needle biopsies of both lesions were performed under CT guidance. Pathology examination of needle biopsy specimens and immunohistochemistry results showed that the two lesions were histologically different. The left lower lobe was SCC and was positive for P40, P63, Ki-67 (80%), and negative for CD56, Syn, cgA, TTF-1. The right lung lower lobe tumor was diagnosed as SCLC; tumor cells were positive for CD56, Syn, cgA, TTF-1, and Ki-67 (90%) and negative for P40 and P63 (Figure 2). Immunohistochemistry suggested that the tumor origins differed between the two sites, and the molecular profiles were heterogeneous. The final clinical diagnosis of this patient was sMPLC.

Figure 1 Chest CT scans (26.03.2020) were performed and images were recorded prior to any therapies. A 48 × 36 mm size lesion in the right lung lower lobe, a 78 × 45 mm size lesion in the left lung lower lobe. (A) Lung window. (B) Mediastinal window. Red arrows point to the lung tumor.

Figure 2 Immunohistochemical examination: (A) Hematoxylin and Eosin staining revealed the bottom lobe of the left lung was SCC, and it was positive for (B) P40, (C) P63, (D) Ki-67 (80%), and negative for CD56, Syn, cgA, TTF-1. (E) Hematoxylin and Eosin staining revealed the bottom lobe of the right lung was SCLC and the tumor cells were positive for (F) CD56, (G) Syn, (H) cgA, (I) TTF-1, (J) Ki-67 (90%), and negative for P40, P63.

MRI and CT detected a head mass diagnosed as a metastatic lesion and lymph node metastasis, which were contraindications for surgery. Because this patient presented with two different tumor types in the lungs, determining a treatment strategy was challenging. SCC and SCLC have huge differences in biological behavior, treatment, and prognosis. To identify treatment targets, we used NGS technology to analyze the genetic features of the primary tumor tissues from the lungs. During the waiting period, the patient received systemic chemotherapy. According to the National Comprehensive Cancer Network guidelines for small cell lung cancer, the patient received systemic chemotherapy with carboplatin and etoposide because SCLC is more malignant. After 40 days, the results of NGS were as follows (Table 1): somatic mutations: 19 (Tables 2 and 3); germline mutations: 0; tumor cell microsatellite instability detection: microsatellite stability; tumor mutation load: high tumor mutational burden (TMB-H). The NGS results suggested that the patient should receive immunotherapy with PD-1/PD-L1 inhibitors.

Table 1 Next-Generation Sequencing Technology, Detects Four Types of Mutations Among 1021 Genes Related to Tumorigenesis and Development (Including Point Mutations, Small Deletions, Copy Number Variations, and Currently Known Fusion Genes)

Table 2 Point Mutations, Small Fragments of Indel Detection Results Indel Detection Results

Table 3 Copy Coefficient Mutation Detection Results

Follow-Up

The response of the patient to chemotherapy was evaluated in accordance with the response evaluation criteria in solid tumors. Chest CT images obtained after one cycle of chemotherapy, showed a dramatic shrinkage of the right lung lower lobe tumor from 48 × 36 mm to 30 × 15 mm. The left lung lower lobe tumor also showed from 78 × 45 mm to 29.1 × 18.7 mm (Figure 3). Full-body examination and CT scan results showed no changes in the volume of the lesions in the brain. The patient refused immunotherapy and continued with the previous chemotherapy regimen. The patient remains under follow-up.

Figure 3 Chest CT scans (05.06.2020) after systemic chemotherapy with carboplatin and etoposide. Dramatic shrinkage of the right lung lower lobe tumor from 48 × 36 mm to 30 × 15 mm. Dramatic shrinkage of the left lung lower lobe lesion from 78 × 45 mm to 29.1 × 18.7 mm. (A) Lung window. (B) Mediastinal window.  Red arrows point to the lung tumor.

Discussion

In this report, we describe a rare case of synchronous MPLC with two histologically distinct pulmonary tumors, namely, SCC and SCLC in the same patient. Martini and Melamed first proposed the diagnostic criteria for MPLC.¹ However, determining whether the additional lesion represents a second primary lung cancer or an additional tumor nodule that corresponds to the dominant cancer is difficult.¹⁰ If the histological examination shows differences between two tumors, determining whether these pulmonary cancer foci are separate primary tumors is relatively easy.¹¹ Multiple pulmonary resections are indicated for patients with synchronous or metachronous lung cancer with multiple pulmonary sites of involvement.^12,13 Chen et al Indicated that sublobar resection was acceptable for patients with MPLC detected at an early stage, because it has a similar prognosis than standard resection and better pulmonary function preservation.¹⁴ However, the presence of distant metastasis is a contraindication, for surgery, and chemotherapy. Is used to slow the progression of the disease. Small and non-small cell lung cancer are very different biological entities, and the treatment options differ significantly between the two tumor types. The treatment of synchronous multiple primary small cell and non-small cell lung cancers in patients with distant metastasis remains challenging. Comprehensive genetic profiling is needed to provide complete molecular information, which can be achieved using a clinical NGS test targeting 1021 cancer-relevant genes. The tumor mutational burden (TMB) has emerged as a new biomarker for predicting the response to programmed cell death ligand-1 (PD-L1) treatment.^15–17 The TMB results of NGS in the present patient were TMB-H (Table 1), which suggests that PD-1/PD-L1 inhibitors can be used for immunotherapy. In addition, the presence of ERCC3, RAD54L, and TP53 mutations (Table 2) indicated that the patient would benefit from PD-1/PD-L1 inhibitor therapy. Therefore, immunotherapy with PD-1/PD-L1 inhibitors was recommended in the present patient. However, after consultation with the patient and his family, this treatment plan was not adopted, chemotherapy was adopted, and good results were achieved. The results of NGS showed the presence of other mutations (Table 2), which could provide new directions for future research. Although determining an effective treatment strategy is one of the many challenges associated with sMPLC, the data generated by NGS can provide information on treatment targets, thereby advancing the era of precision medicine and improving the prognosis of patients. The objective of this case report was to analyze the origin and evolution of MPLC. The results suggest that NGS is important for identifying therapeutic targets, as well as for the discovery of new potential driver genes.