The effects of subsequent primary cancers on survival analyses have been an area of clinical interest. This study aimed to evaluate the effects of subsequent primaries developed after the first primary tumor on the overall survival. METHODS We analyzed data on 6179 patients who had lung, breast or prostate cancer as their first primary cancer. All patients were recorded in the Cancer Registry Unit of the Health Directorate of Antalya Province of Turkey. We analyzed the data concerning each of

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... e three first primaries. We utilised Kaplan-Meier survival analyses and log-rank test to compare the overall survival rates of patients with single primary tumors and patients with multiple primary tumors. In addition, we stratified data according to age, gender, number of primary tumors (patients with single primary, patients with multiple primaries), or disease stage of the first primary (metastatic, non-metastatic). Lastly, potential prognostic factors were separately evaluated in Cox-regression models. RESULTS We found that the overall survival of lung cancer patients with a single primary was shorter than that of patients with multiple primaries (p<0.001). It was vice versa for breast and prostate cancer patients. Multivariate analysis performed for lung cancer patients showed that male patients had a higher risk of exitus than female patients. Lung cancer patients who had metastatic disease at the time of diagnosis had a higher risk of exitus than patients who had a non-metastatic disease at the time of diagnosis (p<0.001). CONCLUSION We found that the inclusion of subsequent primary cancers in the overall survival analysis resulted in higher survival for the patients with lung cancer as their first primary tumor. On the other hand, it was associated with lower survival for patients with breast or prostate cancer as their first primary tumor.