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Published on: March 14, 2019
Pathological complete response to pembrolizumab in patients with metastatic ascending colon cancer with
Tetsuro Tominaga1, Takashi Nonaka2, Akiko Fukuda2
1Department of Surgical Oncology, Nagasaki University Graduate School of Biomedical Science, 1-7-1 Sakamoto, Nagasaki, 852-8501, Japan. tetsuro.tominaga@nagasaki-u.ac.jp.
Abstract:
Pembrolizumab is a novel immune-checkpoint inhibitor used for treatment of microsatellite instability-high (MSI-H) colorectal cancer. Several studies have reported clinical complete response (CR) after treatment with pembrolizumab, but none has confirmed pathological CR. Here we provide the first description of pathological CR with R0 resection after immune-checkpoint therapy. A 45-year-old man presented at our hospital with abdominal distention and highly elevated tumor markers. Contrast-enhanced abdominal CT showed a 110 × 75 mm bulky mass with markedly swollen lymph nodes and an isolated peritoneal metastasis in the pelvic space. Biopsy revealed poorly differentiated adenocarcinoma. We diagnosed ascending colon cancer cT4aN2bM1c Stage IVc. A biopsy specimen obtained during systemic chemotherapy (FOLFOXIRI) was confirmed pathologically as MSI-H, after which the treatment was changed to pembrolizumab. The tumor markers rapidly decreased to within normal ranges after three courses of treatment. After twenty courses, CT revealed shrinkage of the main tumor, lymph node metastases, and the peritoneal metastasis, and we performed extended right hemi-colectomy with dissection of the peritoneal metastasis. No residual tumor cells were found histologically. The patient achieved pathological CR and the postoperative course was uneventful. An accurate diagnosis and appropriate follow up are crucial for obtaining sufficient therapeutic effect of pembrolizumab.
Insights
This study reports the first case of pathological complete response with R0 resection following pembrolizumab treatment for advanced colorectal cancer. This highlights the potential of immune-checkpoint inhibitors in achieving complete tumor eradication.
Area of Science:
- Oncology
- Immunotherapy
- Gastroenterology
Background:
- Pembrolizumab is an immune-checkpoint inhibitor for microsatellite instability-high (MSI-H) colorectal cancer.
- Clinical complete response (CR) has been observed, but pathological CR confirmation is lacking.
Observation:
- A 45-year-old male with Stage IVc ascending colon cancer (cT4aN2bM1c) presented with a large tumor, lymphadenopathy, and peritoneal metastasis.
- Initial chemotherapy (FOLFOXIRI) was followed by pembrolizumab due to MSI-H confirmation.
- Significant tumor marker reduction and tumor shrinkage were observed after pembrolizumab treatment.
Findings:
- The patient achieved a pathological complete response (pCR) with R0 resection after pembrolizumab therapy.
- Histological examination revealed no residual tumor cells post-surgery.
- The patient experienced an uneventful postoperative recovery.
Implications:
- This case provides the first evidence of pathological CR with R0 resection using immune-checkpoint therapy in MSI-H colorectal cancer.
- Accurate diagnosis and vigilant follow-up are critical for optimizing pembrolizumab efficacy.
- Suggests pembrolizumab as a viable option for achieving complete tumor eradication in select colorectal cancer patients.
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