Risk factors of developing a second malignancy following treatment of a first primary breast cancer

Background: Breast cancer is the most prevalent cancer among Iranian women,and it is the fifth cause of cancer-related death in Iran. Most studies havereported an overall excess of 20–30% chance for a second primary cancer todevelop in individuals with a first breast cancer. In this study, we aimed atevaluating different factors that might have a role in increasing the incidence ofa second malignancy after a first primary breast cancer in Iran.Patients and methods: We considered 980 breast cancer patients from threecancer research centers in Tehran, Mashhad and Isfahan from Sep 1995 till Sep2010. Among these 980 breast cancer patients, 94 (9.5%) developed a secondmalignancy. To define the control group, adjustments were made for stage andmean duration of follow up. For each patient with a secondary cancer (casegroup) controls were chosen from the remaining 886 patients. For each patientin case group, we included control patients with the same stage disease (stagesI, II or III based on TNM staging) whose follow up period was within ±6months from the case patient. Therefore, 94 case patients and 202 controlpatients were included in the study.Results and conclusion: Overall, 94 second primary neoplasms observed. Thisanalysis shows the existence of a modest excess in several neoplasms occurringafter breast cancer. Some treatment related factors, including radiotherapy ormastectomy, had statistically significant relation with development a secondarycancer. However, sub-analysis failed to prove such a relationship. Therefore,from our study, it can be concluded that the risk of developing a second canceris more dependent on genetic and environmental factors that caused the firstprimary cancer, rather than being dependent on type of treatment and otherfactors mentioned in this study.

Keywords:

Breast cancer , secondary malignancy , Iran