Presentations at the 2016 annual meeting of the American Society of Clinical Oncology (ASCO) unveiled several important and exciting findings for patients and oncologists engaged in the treatment of colorectal cancer (CRC). Novel results included the primary tumor sidedness data in CRC, as well as data from multiple immunotherapy studies for microsatellite-stable and -unstable CRC and anal cancer.
The findings that right- and left-sided CRCs differ in prognosis and drug sensitivity was made more credible by consecutive presentations of data from a phase 3 trial, a single institution’s experience, and from the SEER registry. Alan Venook, MD, presented a retrospective ad hoc analysis of CALGB/SWOG 80405,1 examining the effect of primary tumor sidedness on patient outcomes by biologic treatment subgroups. The primary study results, previously presented as a plenary session ASCO abstract in 2014, showed that overall survival (OS) of patients with KRAS wild-type metastatic CRC (mCRC) treated in the first-line setting with either bevacizumab or cetuximab combined with FOLFOX or FOLFIRI was longer than anticipated but did not differ between treatments (32.0 months for the cetuximab group vs 31.2 months for the bevacizumab group). In this year’s presentation, data from colonoscopy reports, imaging, and operative notes were analyzed to determine left- (including rectal) vs right-sided primary tumor and the effect of sidedness on survival.