Effect of adjuvant chemotherapy after curative resection of colorectal cancer peritoneal metastasis

Conversion therapy with pembrolizumab for a peritoneal metastasis of rectal cancer causing hydronephrosis in a patient with Lynch syndrome

A 44-year-old woman with Lynch syndrome was referred to our hospital for treatment of recurrence of microsatellite instability-high rectal cancer. [18F]Fluorodeoxyglucose (18FDG)-positron emission tomography revealed a peritoneal metastasis with invasion to the small intestine and left ureter. The peritoneal metastasis was diagnosed initially as unresectable because of extensive invasion to the left ureter requiring nephrectomy. Hence, first-line treatment with pembrolizumab was started. After the first course of pembrolizumab, she developed hydronephrosis and a resulting urinary tract infection (UTI). A percutaneous nephrostomy was performed to control the UTI. After six courses of pembrolizumab, 18FDG-positron emission tomography showed that the peritoneal metastasis was smaller with significantly reduced 18FDG uptake, and it was then diagnosed as resectable without nephrectomy. She underwent R0 resection of the peritoneal metastasis with partial resection of the small intestine. Intraoperatively, the peritoneal metastasis showed no invasion of the left ureter, allowing its preservation. The percutaneous nephrostomy was removed postoperatively, and she has not developed any subsequent UTIs. Histopathologically, the tumor showed a pathological complete response to pembrolizumab. To the best of our knowledge, this is the first case of conversion therapy with pembrolizumab for peritoneal metastasis with hydronephrosis.

Genetic specificity study using next-generation sequencing (NGS) of peritoneal metastatic colorectal cancer compared to primary colorectal cancer

BACKGROUND

In patients with colorectal cancer, peritoneal metastases are the second most frequent metastatic lesion after liver metastases. Peritoneal metastases have a very poor prognosis, with a median survival time of 5-7 months. Currently, there is a lack of research on the genetic differences between primary colorectal cancer and peritoneal metastases. Therefore, we aimed to identify their genetic characteristics through a cancer panel test using next-generation sequencing.

OBJECTIVE

We aim to investigate the specificity of genetic variants in primary colorectal cancer and peritoneal metastases.

METHODS

We recruited patients with stage I, II, and III primary colorectal cancer and peritoneal metastases for genetic analysis using NGS. Samples were collected from patients who underwent surgery at Dankook University Hospital and consented to genetic testing. NGS was performed using a cancer panel.

RESULTS

Among 36 patients with primary cancer, TP53 gene mutation was identified the most in 25 patients (69%), followed by APC gene mutation in 19 patients (53%), and KRAS gene mutation in 17 patients (47%). In the peritoneal metastasis patient group, unlike the primary cancer patient group, KRAS gene mutations were the most common 6 patients (55%), followed by TP53 gene mutations in 4 patients (36%) and PIK3CA gene mutations in 2 patients (18%).

CONCLUSION

The small number of surgical cases of peritoneal metastases was a limitation of our sample size. Nevertheless, we identified differences in the alterations of specific genes between primary and peritoneal metastases. Acquiring additional cases and collecting more data will provide deeper insights into these cancers.