Review Outlines Rare, Complicated Cases of Co-Occurring SCLC and GI Cancers

The coexistence of small cell lung cancer (SCLC) and gastrointestinal (GI) malignancies is exceedingly rare. In a new review article in Cureus, investigators outlined 6 such cases and offered insights into why the phenomenon can be so difficult to identify and treat.¹

It is not uncommon for patients with SCLC to have distant metastases in areas such as the brain, liver, bone, and adrenal glands, the authors explained. Yet, there are only scant reports of patients with SCLC who also have other primary malignancies, they said. Primary GI malignancies are particularly rare in people with SCLC, they said.²

The first challenge posed by such cases is correctly diagnosing the situation, the authors said.

“Differentiating between metastasis and a second primary tumor is often difficult, particularly in smokers with advantaged-stage SCLC who present with GI symptoms or incidental findings,” the authors said.

Once an accurate diagnosis is made, though, the next challenge is deciding on the best treatment option. The investigators noted that SCLC typically requires systematic chemotherapy, but GI tumors are often treated with surgical resection or targeted therapies.

While there have been reports of cases of co-occurring SCLC and GI malignancies, there has not yet been a systematic review that traced the clinical features, diagnostic considerations, treatments, and outcomes of such patients. They therefore decided to seek out and aggregate the available evidence in hopes of giving clinicians insights into the best routes forward in these rare cases.

The investigators searched major scientific databases in search of case reports and studies involving people with SCLC and distinct GI cancers. They eventually found 6 case reports that matched their criteria: 3 from Japan, 1 from the Czech Republic, 1 from China, and 1 from the United States. The cases were published between 1986 and 2025. Four of the cases involved male patients. Of the 5 patients for whom age was available, the range of ages went from 53 years to 80 years old. Most of the patients had histories of heavy smoking, as is common in SCLC.

The patients had a variety of GI malignancies, including gastric, duodenal, rectal, and jejunal cancers. One patient had multiple primary malignancies involving rectosigmoid adenocarcinoma, renal cell carcinoma, and prostate adenocarcinoma (in addition to SCLC), the authors said. Four of the patients had both of their cancers diagnosed at the same time; the other two had asynchronous diagnosis.

“Diagnostic processes frequently involved PET-CT and endoscopy, with some GI tumors initially misclassified as metastases,” the authors said.

The patients received a variety of therapies, including platinum-based chemotherapy, immune checkpoint inhibitors, surgery, and supportive care. In most cases SCLC was the therapeutic priority, the authors said. Their treatment outcomes were varied. One patient, for instance, received etoposide plus cisplatin (EP) for their SCLC and underwent surgery for their GI cancer. At 6 months, the patient had no recurrence. However, another patient who underwent SCLC therapy of EP plus durvalumab (Imfinzi; ) and who did not undergo surgery for the GI cancer only achieved partial remission and then died due to progression at 7 months. Overall, the authors said, survival ranged from several months to one year.

Taken as a whole, the authors’ research showed that clinicians should be vigilant for the possibility of second primary malignancies in patients with SCLC, particularly if the patients have persistent or unexplained GI symptoms. If a second primary malignancy is identified, the authors said treatment planning should be multidisciplinary and individualized. They said molecular profiling can play an important role in directing therapy and said there is evidence that GI tumors sometimes respond to SCLC directed chemotherapy. Such cases, they said, “raise essential questions about overlapping chemosensitivity and treatment polarization.”

References

1. Ohta R, Yamamoto N, Tanaka K, et al. Coexistence of small-cell lung cancer and gastrointestinal malignancies: a narrative systematic review of case reports. Cureus. 2025;17(9):e92393. doi:10.7759/cureus.92393

2. Vogt A, Schmid S, Heinimann K, et al. Multiple primary tumours: challenges and approaches, a review. ESMO Open. 2017;2(2):e000172. doi:10.1136/esmoopen-2017-000172