Background: Synchronous colorectal carcinomas (CRC) occur in 1–8% of patients diagnosed with CRC. This study evaluated treatment patterns and patient outcomes in synchronous CRCs compared with solitary CRC patients. Methods: All patients diagnosed with primary CRC between 2008 and 2013, who underwent elective surgery, were selected from the Netherlands Cancer Registry. Using multivariable regressions, the effects of synchronous CRC were assessed for both short-term outcomes (prolonged postoperative hospital admission, anastomotic leakage, postoperative 30-day mortality, administration of neoadjuvant or adjuvant treatment), and 5-year relative survival (RS). Results: Of 41,060 CRC patients, 1969 patients (5%) had synchronous CRC. Patients with synchronous CRC were older (mean age 71 ± 10.6 vs. 69 ± 11.4 years), more often male (61 vs. 54%), and diagnosed with more advanced tumour stage (stage III–IV 54 vs. 49%) compared with solitary CRC (all p < 0.0001). In 50% of the synchronous CRCs, an extended surgery was conducted (n = 934). Synchronous CRCs with at least one stage II–III rectal tumour less likely received neoadjuvant (chemo)radiation [78 vs. 86%; adjusted OR 0.6 (0.48–0.84)], and synchronous CRCs with at least one stage III colon tumour less likely received adjuvant chemotherapy [49 vs. 63%; adjusted OR 0.7 (0.55–0.89)]. Synchronous CRCs were independently associated with decreased survival [RS 77 vs. 71%; adjusted RER 1.1 (1.01–1.23)]. Conclusions: The incidence of synchronous CRCs in the Dutch population is 5%. Synchronous CRCs were associated with decreased survival compared with solitary CRC. The results emphasize the importance of identifying synchronous tumours, preferably before surgery to provide optimal treatment.,
Annals of Surgical Oncology
Erasmus MC: University Medical Center Rotterdam

Bos, A., Matthijsen, R. A., van Erning, F., van Oijen, M., Rutten, H., & Lemmens, V. (2017). Treatment and Outcome of Synchronous Colorectal Carcinomas: A Nationwide Study. Annals of Surgical Oncology, 1–8. doi:10.1245/s10434-017-6255-y