Sidedness of primary is an established prognostic factor in mCRC and recently has been shown to be an important predictive factor for patients (pts) treated with EGFR-Ab (always in combination with chemotherapy) in 1st and 2nd line settings. Limited data is available in 3rd line and beyond, where EGFR-Ab are used either as monotherapy or with chemotherapy. In Ontario, Canada, public funding of EGFR-Ab is restricted to chemorefractory disease. This study examines the impact of sidedness on overall survival (OS) in chemorefractory mCRC treated with EGFR-Ab monotherapy and combination.
This population-based retrospective cohort study used linked data from the Institute for Clinical Evaluative Sciences to evaluate mCRC pts treated in Ontario with EGFR-Ab from Jan 2006-Dec 2014. Over 99% of cases are captured via the Ontario Cancer Registry. The primary outcome was OS. Monotherapy v combination was compared by panitumumab (pani; funded only as monotherapy) v cetuximab (cet; funded only with chemotherapy) outcomes. Sidedness was determined by ICD-10 code as right (R; including transverse colon) or left (L).
Of 67117 CRC pts,1553 received EGFR-Ab for refractory mCRC (429 R, 1080 L, 44 unknown). 71% received pani. R were more commonly female, with significantly shorter time (months, m) from diagnosis to EGFR-Ab therapy (mean ± SD: 28.7 ± 18.3 v 32.8 ± 19.2; p
This large population cohort demonstrates that R sidedness is significantly predictive for survival with EGFR-Ab in refractory mCRC, consistent with findings in earlier lines of therapy. The differences are particularly seen with monotherapy. L sided cancers appear to benefit equally from monotherapy as combination.
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All authors have declared no conflicts of interest.