The impact of mismatch repair status in colorectal cancer on the decision to treat with adjuvant chemotherapy: an Australian population-based multicenter study

He, Emily Y., Hawkins, Nicholas J., Mak, Gabriel, Roncolato, Felicia, Goldstein, David, Liauw, Winston, Clingan, Philip, Chin, Melvin and Ward, Robyn L. (2016) The impact of mismatch repair status in colorectal cancer on the decision to treat with adjuvant chemotherapy: an Australian population-based multicenter study. Oncologist, 21 5: 618-625. doi:10.1634/theoncologist.2015-0530


Author He, Emily Y.
Hawkins, Nicholas J.
Mak, Gabriel
Roncolato, Felicia
Goldstein, David
Liauw, Winston
Clingan, Philip
Chin, Melvin
Ward, Robyn L.
Title The impact of mismatch repair status in colorectal cancer on the decision to treat with adjuvant chemotherapy: an Australian population-based multicenter study
Journal name Oncologist   Check publisher's open access policy
ISSN 1549-490X
1083-7159
Publication date 2016-05
Year available 2016
Sub-type Article (original research)
DOI 10.1634/theoncologist.2015-0530
Open Access Status Not Open Access
Volume 21
Issue 5
Start page 618
End page 625
Total pages 8
Place of publication Durham, NC United States
Publisher AlphaMed Press
Collection year 2017
Language eng
Formatted abstract
Background.
Testing for mismatch repair (MMR) status in colorectal cancer (CRC) may provide useful prognostic and predictive information. We evaluated the impact of such testing on real-world practice regarding adjuvant chemotherapy for patients with resected CRC.

Patients and Methods.
A total of 175 patients with stage II and III mismatch repair-deficient (MMRD) CRC were identified from an Australian population-based study of incident CRCs. Their treatment decisions were compared with those for a cohort of 773 stage-matched patients with mismatch repair-proficient (MMRP) CRCs. The effect of MMR status, age, and pathologic characteristics on treatment decisions was determined using multiple regression analysis.

Results.
Overall, 32% of patients in stage II and 71% of patients in stage III received adjuvant chemotherapy. Among the stage II patients, those with MMRD cancer were less likely to receive chemotherapy than were MMRP cases (15% vs. 38%; p < .0001). In this group, the treatment decision was influenced by age, tumor location, and T stage. MMR status influenced the treatment decision such that its impact diminished with increasing patient age. Among patients with stage III tumors, no difference was found in the chemotherapy rates between the MMRD and MMRP cases. In this group, age was the only significant predictor of the treatment decision.

Conclusion.
The findings of this study suggest that knowledge of the MMR status of sporadic CRC influences treatment decisions for stage II patients, in an era when clear recommendations as to how these findings should influence practice are lacking.

Implications for Practice:
Microsatellite instability (MSI) is a molecular marker of defective DNA mismatch repair found in 15% of sporadic colorectal cancers. Until recently, expert guidelines on the role of MSI as a valid biomarker in the selection of stage II patients for adjuvant chemotherapy were lacking. Conducted at a time when the clinical utility of routine MSI testing was unclear, this study found that clinicians were influenced by MSI status in selecting stage II patients for chemotherapy. Furthermore, the impact of MSI on treatment decisions was greatest in younger patients and declined progressively until age 80 years, when no effect was found.
Keyword Microsatellite instability
Mismatch repair deficiency
Colorectal cancer
Adjuvant chemotherapy
Treatment decisions
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
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