DNA mismatch repair (dMMR) deficiency rectal cancer is associated with excellent prognosis and pathologic response with current therapeutic options and surgical procedures, according to research published in the Journal of Clinical Oncology.
In order to establish the efficacy of novel treatment strategies for patients with dMMR rectal cancer, researchers led by Y Nancy You, MD, The University of Texas MD Anderson Cancer Center (Houston, TX), conducted a study examining the outcomes associated with different treatment modalities and the effect of clinical genetics.
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A total of 62 patients were identified as having dMMR rectal cancer who had also received multimodality therapy between 1992 and 2012. Overall and cancer-specific survival was calculated using the Kaplan-Meier method as primary endpoints.
Researchers found that MMR deficiencies were most commonly due to alterations in MSH2 (53%) or MSH6 (23%). Rates of 5-year rectal cancer-specific survival were 100% for patients with stage I and II disease, 85.1% for patients with stage III cancer, and 60% for those with stage IV disease. Further, 5 of the 11 deaths (45.5%) during follow-up were due to extracolorectal malignancies.
The rate of complete pathologic response was observed in 27.6% of patients who received fluoropyrimidine-based neoadjuvant chemoradiation and informed decisions regarding limited resection focusing on proctectomy did not compromise overall survival.
Thus, researchers concluded that personalized treatment plans may lead to better outcomes for patients with dMMR rectal cancer. Identification of dMMR should prompt germline testing, followed by lifelong surveillance for both colorectal and extracolorectal malignancies.
"Our paper provides a perfect illustration of how the power of precision medicine can be realized," said Dr You. "This new genetic understanding of dMMR provides immediate implications for telling patients how well they will do long term and for choosing the best surgical and chemotherapy options."
