The Real-Life Impact of Primary Tumor Resection of Synchronous Metastatic Colorectal Cancer-From a Clinical Oncologic Point of View.

Aim: The complex medical care of synchronous metastatic colorectal (smCRC) patients requires prudent multidisciplinary planning and treatments due to various challenges caused by the primary tumor and its metastases. The role of primary tumor resection (PTR) is currently uncertain; strong arguments exist for and against it. We aimed to define its effect and find its best place in our therapeutic methodology.

Method: We performed retrospective data analysis to investigate the clinical course of 449 smCRC patients, considering treatment modalities and the location of the primary tumor and comparing the clinical results of the patients with or without PTR between 1 January 2013 and 31 December 2018 at the Institute of Oncotherapy of the University of Pécs.

Results: A total of 63.5% of the 449 smCRC patients had PTR. Comparing their data to those whose primary tumor remained intact (IPT), we observed significant differences in median progression-free survival with first-line chemotherapy (mPFS1) (301 vs. 259 days; < 0.0001; 1 y PFS 39.2% vs. 26.6%; OR 0.56 (95% CI 0.36-0.87)) and median overall survival (mOS) (760 vs. 495 days; < 0.0001; 2 y OS 52.4 vs. 26.9%; OR 0.33 (95% CI 0.33-0.53)), respectively. However, in the PTR group, the average ECOG performance status was significantly better (0.98 vs. 1.1; = 0.0456), and the use of molecularly targeted agents (MTA) (45.3 vs. 28.7%; = 0.0005) and rate of metastasis ablation (MA) (21.8 vs. 1.2%; < 0.0001) were also higher, which might explain the difference partially. Excluding the patients receiving MTA and MA from the comparison, the effect of PTR remained evident, as the mOS differences in the reduced PTR subgroup compared to the reduced IPT subgroup were still strongly significant (675 vs. 459 days; = 0.0009; 2 y OS 45.9 vs. 24.1%; OR 0.37 (95% CI 0.18-0.79). Further subgroup analysis revealed that the site of the primary tumor also had a major impact on the outcome considering only the IPT patients; shorter mOS was observed in the extrapelvic IPT subgroup in contrast with the intrapelvic IPT group (422 vs. 584 days; = 0.0026; 2 y OS 18.2 vs. 35.9%; OR 0.39 (95% CI 0.18-0.89)). Finally, as a remarkable finding, it should be emphasized that there were no differences in OS between the smCRC PTR subgroup and metachronous mCRC patients (mOS 760 vs. 710 days, = 0.7504, 2 y OS OR 0.85 (95% CI 0.58-1.26)).

Conclusions: The role of PTR in smCRC is still not professionally justified. Our survey found that most patients had benefited from PTR. Nevertheless, further prospective trials are needed to clarify the optimal treatment sequence of smCRC patients and understand this cancer disease's inherent biology.