Predictors and Risk Factors of Pathologic Complete Response Following Neoadjuvant Chemoradiotherapy for Rectal Cancer: A Population-Based Analysis

Does the efficacy of regorafenib differ in chemotherapy refractory metastatic colorectal cancer patients who had mucinous pathology compared to those who had non-mucinous pathology?

PURPOSE

To investigate the importance of mucinous histopathology on the assessment of tumor response in patients with metastatic colorectal cancer (mCRC) receiving regorafenib.

MATERIALS AND METHOD

All patients diagnosed with histologically confirmed mCRC in 2 oncology centers between 2013 and 2018 were retrospectively analyzed. Among 678 patients diagnosed with mCRC, 103 patients were treated with regorafenib. Ninety-four of these patients who had used at least 2 cycles of regorafenib and evaluable for treatment response were included in the analysis. Histopathologically, 18 patients with mucinous adenocarcinoma and 76 patients with nonmucinous adenocarcinoma were compared in terms of response rate and survival durations.

RESULTS

Median follow-up duration of 6 months, median age of the patients was 61 (34-77) years. While 19.1% of the patients had mucinous histology, 80.9% had nonmucinous histology. The overall response rate was significantly lower in the mucinous subgroup than the nonmucinous subgroup (5.6% vs 43.4%, respectively, P = 0.003). Similarly, both progression-free survival (3.0 vs 4.0 months, respectively, P = 0.011) and overall survival duration were shorter in the mucinous subgroup (3.0 vs 7.0 months, P = 0.016, respectively) compared with the nonmucinous subgroup.

CONCLUSION

The histological subgroup may predict tumor response in mCRC patients receiving regorafenib. Its efficacy on nonmucinous histology had significantly more favorable than mucinous subtype.

A Case with Rectal Cancer Relapses After Clinical Complete Remission Following Neoadjuvant Chemoradiotherapy

Despite advancements in diagnosis and therapy, relapse of rectal cancer after clinical complete remission (cCR) remains a frequent event. The key factors influencing the treatment strategy for the management of patients achieving cCR following neoadjuvant chemoradiotherapy (Neo-CRT) remain to be identified. We present the case of a 64-year-old man with rectal cancer. The patient was initially admitted to the hospital in September 2011 with a 3-month history of change in his stools. Following his re-hospitalization in November 2011, a biopsy specimen of the neoplasm suggested the presence of rectal adenocarcinoma; laboratory investigations also revealed elevated levels of carcinoembryonic antigens (CEA; carbohydrate antigen 199) in the serum. Subsequently, the patient received Neo-CRT, as well as symptomatic and supportive treatment. The level of serum CEA returned to normal, without signs of swollen lymph nodes in the pelvic cavity. The patient was diagnosed with rectal cancer based on the elevated level of serum CEA, colonoscopy, and contrast-enhanced magnetic resonance imaging. He relapsed 4 months after cCR following Neo-CRT and underwent laparoscopic Miles’ surgery in April 2013. The relapse may have been mainly attributed to residual tumor cells. This case report and literature review may contribute to the clinical recognition of treatment for patients with rectal cancer achieving cCR following Neo-CRT.