Significant increase of synchronous disease in first-line metastatic colorectal cancer trials: Results of a systematic review.

Although synchronous and metachronous metastases are considered as separate entities of metastatic colorectal cancer (mCRC) with different outcomes, its proportion is reported infrequently. We compared inclusion rates and survival of synchronous versus metachronous mCRC in different types of studies investigating initial systemic therapy or surgical treatment of mCRC.