OBJECTIVES:: Access to treatment is of great importance in potentially serious diseases, such as cancer. Therefore, identifying access gaps in the Brazilian public healthcare system (SUS) could lead to the understanding of where and why they are occurring, potentially increasing the number of treated patients. The objective of the analysis was to compare the expected number of metastatic colorectal carcinoma (mCRC) patients in SUS to the effectively treated, and to measure where the major differences were occurring and how those discrepancies varied through time. METHODS:: The number of effectively treated patients who underwent first line treatment (1L) of mCRC were collected from DATASUS from 2008 to 2016. It was assumed that the patients received treatment for less than a year, considering the median progression free survival from the chemotherapy arms of main clinical trials, which resulted in the total number of patients not being cumulative through the years. Expected number of patients was calculated through an epidemiological approach, starting from the projected Brazilian population (2008-2016) all the way to the eligible population, applying the incidence of CRC, mCRC rate and patients which have access to the SUS. Results were evaluated to the whole country and states to identify where the major gaps were occurring. RESULTS:: Number of patients being treated by SUS increased in more than 166% from 2008 to 2016 (4,700 to 12,522, respectively), while the number of expected patients, based on the patient flow, increased 30% (10,097 to 13,116, 2008 and 2016, respectively). Overall, the gap between potential and expected patients is decreasing steadily, from 53% potentialy not treated, in 2008, to just 5% in 2016. States showing major gaps in 2016 were Alagoas (74%), Distrito Federal (64%) and Rio de Janeiro (56%). CONCLUSIONS:: The gap between expected mCRC patients and treated ones is decreasing steadily in the SUS.