Two cases of superior mesenteric artery syndrome during chemotherapy in patients with lung cancer.

Superior mesenteric artery (SMA) syndrome is a rare disease, characterized by the narrowing of the third portion of the duodenum between the aorta and SMA. The cause of the stenosis is a decrease in retroperitoneal fat between the aorta and SMA. In this report, we present two cases of SMA syndrome that occurred during chemotherapy for lung cancer. The first case was a 61-year-old male treated with nanoparticle albumin-bound-paclitaxel (nab-PTX) for lung adenocarcinoma. On day 23 of the first course of nab-PTX, he was admitted to our hospital due to vomiting and weight loss of 15.6 kg in 10 months. He was diagnosed with SMA syndrome through computed tomography, and drainage was performed using a nasogastric tube. Conservative treatment was successful, and the patient was able to continue therapy with nab-PTX. The second case was a 70-year-old male with epidermal growth factor receptor (EGFR) mutation-positive non-small cell lung cancer. He was admitted to our hospital due to vomiting and dizziness while receiving treatment with pembrolizumab, as well as weight loss of 14.6 kg in 6 months. He was diagnosed with SMA syndrome using computed tomography. Conservative treatment using a nasogastric tube led to improvement, and the patient was able to continue treatment with pembrolizumab after discharge. This is the first report of SMA syndrome in patients with lung cancer undergoing chemotherapy with nab-PTX or pembrolizumab. Late diagnosis and treatment render SMA syndrome a potentially fatal disease. Vomiting and weight loss during chemotherapy are known treatment-related side effects; in patients developing these adverse effects, the presence of SMA syndrome should be suspected and managed appropriately.