Abstract
In clinical practice, the efficacy of chemotherapy for metastatic colorectal cancer (mCRC) is typically evaluated according to the Response Evaluation Criteria in Solid Tumours (RECIST) criteria, and an appropriate treatment plan is determined. In the case of progressive disease (PD), the components of the treatment are altered; however, PD, as defined by the RECIST criteria, includes various types of progression. While detailed consideration regarding the impact of the growth pattern of measurable target lesions on survival has been performed, the impact of the occurrence of new lesions on survival is unclear. The aim of the present study was to assess the impact of the occurrence of new lesions on the survival of patients who underwent chemotherapy for mCRC. Among the patients who received doublet chemotherapy for mCRC as a first-line treatment between 2008 and 2016, 81, who stopped the chemotherapy due to PD, were enrolled in the present study. The types of progression were classified according to the definitions of RECIST. Subsequently, the following criteria were considered: The growth of measurable target lesions, the occurrence of new lesions and the unequivocal progression of non-target disease. Furthermore, the developing patterns of new lesions were also assessed. The association between the type of progression and the survival after the failure of the first-line chemotherapy was explored. Forty (49.4%) patients only experienced growth of measurable target lesions, 41 (50.6%) of the patients had new lesions and 3 (3.7%) of the patients had unequivocal progression of non-target disease. The survival rate from the discontinuation of first-line chemotherapy in patients with new lesions was significantly worse than that in patients without new lesions (P=0.0068); however, the developing patterns of new lesions were not associated with survival. Regardless of the developing patterns of new lesions, patients who stopped chemotherapy due to new lesions had worse survival rates from the discontinuation of first-line chemotherapy compared with those who stopped chemotherapy due only to the growth of measurable target lesions. Because the occurrence of new lesions represents severe progressive disease, patients with new lesions may require more intensive chemotherapy. The type of progression may be useful information for selecting the appropriate treatment following the failure of first-line chemotherapy.