Sidedness and TP53 mutations impact OS in anti-EGFR but not anti-VEGF treated mCRC - an analysis of the KRAS registry of the AGMT (Arbeitsgemeinschaft Medikamentöse Tumortherapie).

BACKGROUND

In metastatic colorectal cancer (mCRC), the localization of the primary tumour has been shown to be of prognostic as well as predictive relevance.

METHODS

With the aim to investigate clinical and molecular disease characteristics with respect to sidedness in a real-world cohort, we analyzed 161 mCRC patients included in the KRAS Registry of the Arbeitsgemeinschaft Medikamentöse Tumortherapie (AGMT) between January 2006 and October 2013.

RESULTS

Right-sided mCRC displayed a worse median overall survival (OS) in comparison to left-sided disease (18.1 months [95%-CI: 14.3-40.7] versus 32.3 months [95%-CI: 25.5-38.6]; HR: 1.63 [95%-CI: 1.13-2.84]; p = 0.013). The choice of the biological agent in front-line therapy had a statistically significant impact on median OS in patients with right-sided tumours (anti-epidermal growth factor receptor (EGFR): 10.6 months [95%-CI: 5.2-NA]; anti-vascular endothelial growth factor (VEGF): 26.2 months [95%-CI: 17.9-NA]; HR: 2.69 [95%-CI: 1.30-12.28]; p = 0.015) but not in patients with left-sided tumours (anti-EGFR: 37.0 months [95%-CI: 20.2-56.6]; anti-VEGF: 32.3 months [95%-CI: 23.6-41.1]; HR: 0.97 [95%-CI: 0.56-1.66]; p = 0.905). When evaluating molecular characteristics of tumour samples, we found a clinically meaningful trend towards an inferior OS in TP53 mutant mCRC treated with anti-EGFR based therapy compared to anti-VEGF based therapy (17.1 months [95%-CI: 8.7-NA] versus 38.3 months [95%-CI: 23.6-48.0], HR = 1.95 [95%-CI: 0.95-5.88]; p = 0.066), which was not significantly dependent on sidedness. This was not the case in patients with TP53 wild-type tumours. Therefore we evaluated the combined impact of sidedness and TP53 mutation status in the anti-EGFR treated cohort and patients with left-sided/TP53 wild-type mCRC showed the longest median OS (38.9 months) of all groups (right-sided/TP53 mutant: 12.1 months; right-sided/TP53 wild-type: 8.9 months; left-sided/TP53 mutant: 18.4 months; p = 0.020).

CONCLUSIONS

TP53 mutation and right-sidedness are associated with shorter OS in patients treated with anti-EGFR based therapy but not with anti-VEGF based therapy. The confirmation of the predictive value of TP53 mutation status in a larger cohort is warranted.