Impact of primary tumor location as a predictive factor in patients suffering from colorectal cancer treated with cytotoxic anticancer agents based on the collagen gel droplet-embedded drug sensitivity test

In recent studies, better clinical outcomes for patients with left-sided colon cancer (CC) compared with right-sided CC have been reported; however, in such investigations, the chemotherapy regimens included molecular-targeting agents. To the best of our knowledge, the impact of primary tumor location as a predictive factor in patients suffering from CC treated with cytotoxic anticancer agents alone has not been investigated. The aim of the present study was to determine the impact of the primary tumor location as a predictive factor of patients undergoing the following cytotoxic anticancer agent regimens: Leucovorin and fluorouracil + oxaliplatin (FOLFOX) or Leucovorin and fluorouracil + irinotecan (FOLFIRI), using the collagen gel droplet-embedded drug sensitivity test (CD-DST). Between March 2008 and April 2017, tumor specimens were obtained from 133 patients suffering from colorectal cancer (CRC) who had not received preoperative chemotherapy. CD-DST was performed and the growth inhibition rate (IR) was determined in FOLFOX and FOLFIRI regimens. The associations between tumor location and IR values for each condition were evaluated. In the present study, the prognosis of patients receiving palliative chemotherapy as well as treatment with molecularly-targeted agents was also investigated. There were no significant differences in the IRs (%) of the two regimens using CD-DST for right-sided tumors compared with left-sided tumors, including or excluding the rectum. The median survival times of patients with right CC and left CC who had received palliative chemotherapy and treatment with molecularly-targeted agents were 960 and 1,348 days, respectively. Primary tumor location did not represent a predictive factor for the efficacy of treatment with cytotoxic anticancer agent regimens using CD-DST. However, patients suffering from left-sided CC were revealed to exhibit better clinical outcomes compared with patients suffering from right-sided CC when molecularly-targeted agent regimens were administered. Therefore, the results of the present study suggested that molecularly-targeted agents rather than cytotoxic anticancer agents may result in improved clinical outcomes for patients with CRC suffering from left-sided tumors.