Despite their prevalence, data on the incidence of breast and colorectal cancers by stage are scarce in the epidemiological literature. The French Network of Cancer Registries (Francim) has established a continuous surveillance system for tumor staging based on the analysis of random samples of new cases, involving 17 registries. For each registry, the samples consist of 100 cases for breast and colon cancers and 70 cases for rectal cancers (approximately 18,000 cases over 4 years). Inclusion in the sample is determined by the patient’s day and month of birth to quickly identify and investigate the cases to be included. The information required for staging is collected using a standardized procedure. The stage is coded using a common algorithm that complies with ENCR guidelines. In cases of neoadjuvant therapy, there is a change in tumor stage, and the presentation of results takes this treatment sequence into account. The results cover 6,184 breast cancers and 11,808 colon and rectal cancers. The proportion of missing data for stage is less than 5%. Between 2009 and 2012, 60% of breast cancers diagnosed in women in France were localized (locally confined or locally advanced) and 12% were advanced. Localized forms (locally confined or locally advanced) were more common in younger women. Localized forms (locally confined or locally advanced) accounted for 44% of colon cancers (48% before age 75 and 41% after). For rectal cancer, these localized forms accounted for 39% of cases among patients who underwent primary surgery and 56% among those who received neoadjuvant therapy. For both breast cancer and colorectal cancer, no change in the distribution of stages was observed over the 4-year observation period. These results demonstrate that it is possible to establish a standardized procedure for routinely collecting stage data from population-based data. The decision to collect this data from random samples proves to be appropriate. It seems important to account for the use of neoadjuvant therapy, as it is frequently administered, particularly for rectal cancers and less often for breast cancers. These data will enable the calculation of reliable survival rates by stage at diagnosis.