# Two cases of gastric cancer with elevated serum levels of KL-6

## TL;DR

Two gastric cancer patients with elevated KL-6 levels showed tumor and biomarker response to chemotherapy, suggesting KL-6 may also act as a cancer marker.

## Contribution

Reports two rare gastric cancer cases with elevated KL-6 and demonstrates KL-6's potential as a tumor marker in metastatic gastric cancer.

## Key findings

- Elevated KL-6 levels in gastric cancer patients decreased with chemotherapy, indicating treatment response.
- KL-6 may serve as a tumor marker in metastatic gastric cancer, beyond its role in interstitial pneumonia.
- Chemotherapy response correlated with KL-6 reduction in both patients, though one later developed interstitial pneumonia.

## Abstract

The serum level of Krebs von den Lungen-6 (sKL-6) is a biomarker of interstitial pneumonia and has been reported to be elevated in patients with cancers. However, there have been few cases of gastric cancer (GC) with elevated sKL-6 that were treated by chemotherapy. We herein report two cases of GC with elevated sKL-6 that were treated with oxaliplatin plus S-1 (SOX) chemotherapy and discussed the resulting changes in sKL-6.

The first patient was a 79-year-old woman complaining of loss of appetite. Esophagogastroduodenoscopy (EGD) showed a type-3 tumor in the gastric antrum and biopsy specimens showed adenocarcinoma. Computed tomography (CT) showed multiple liver metastases. sKL-6 was elevated to 1,292 U/ml, but a CT revealed no obvious lesions of the lungs, including interstitial pneumonia. The tumor was diagnosed as GC with liver metastases and elevated sKL-6. Respiratory function data were normal. SOX therapy using oxaliplatin and S-1 was performed. After 3 courses of SOX therapy, CT showed reductions of the liver metastases as well as the primary tumor, and sKL-6 was decreased to 201 U/ml. After the 44 courses, sKL-6 was slightly elevated. Chest CT showed interstitial pneumonia and chemotherapy was stopped. The patient is still alive without any metastasis 72 months later. The second patient was a 69-year-old woman complaining of upper abdominal pain. EGD revealed a type-3 tumor in the gastric antrum showing adenocarcinoma with HER2-positive pathology. CT showed multiple node metastases around the abdominal aorta. sKL-6 was elevated to 2,239 U/ml, but a respiratory function test showed no abnormalities, and CT of the lungs showed no obvious lesions. The tumor was diagnosed as GC with distant node metastases and elevated sKL-6. The patient received SOX therapy combined with trastuzumab. After 6 courses, the size of the primary tumor and multiple node metastases were reduced, and sKL-6 was decreased to 284 U/ml.

These two cases suggest that sKL-6 may be important not only as an indicator of interstitial pneumonia in chemotherapeutic courses, but also as a tumor marker in GC patients with multiple metastases.