Risk of secondary malignancy after radiotherapy for breast cancer: long-term follow-up of Japanese patients with breast cancer

Abstract

Purpose There have been very few reports of secondary malignancies after breast cancer treatment in Asia, particularly in Japan. This study aimed to evaluate the risk of secondary malignancies after radiotherapy (RT) in Japanese breast cancer patients. Methods This single-center retrospective study included patients who underwent RT between July 1961 and September 2006 for postoperative breast cancer. A total of 702 patients with a follow-up period of more than 5 years were analyzed. All malignancies observed at more than 5 years after the start of RT were defined as secondary malignancies. To calculate the relative risk (RR) of secondary malignancies, we applied data from the National Cancer Center in Japan. Results The median observation period was 9.7 (interquartile range 7.1–18.2) years. The cumulative person-years of observation were 6879.4. The RR of contralateral breast cancer increased by 1.85-fold (95% confidence interval [CI] 1.05–3.26) among patients compared with that among the general population; however, the difference was not significant (p = 0.053). The RR of secondary malignancies other than breast cancer increased by 2.71-fold (95% CI 1.99–3.70, p < 0.001) among the patients compared with the general population. Even when only malignancies detected more than 10 years after RT were defined as secondary malignancies, the RR of secondary malignancies other than breast cancer was 1.91 (95% CI 1.33–2.73, p < 0.001). Conclusion The incidence of secondary malignancies after RT may be somewhat higher in Japanese patients with breast cancer than in the general population.

Hybrid VMAT-3DCRT as breast cancer treatment improvement tool

“…It is important to note that exposure to high and low doses of radiation 11 , can increase the risk of damage to the heart 4 and lungs 12 . Moreover the risk of second cancer induction on contralateral breast in particular for young woman must be considered like it is reported in literature 13 . Although less severe, the consequences and doses delivered to healthy mammary glands merit particular attention.…”

Association of radiotherapy for stage I–III breast cancer survivors and second primary malignant cancers: a population-based study

“…Previous studies have shown that various types of SPCs occurred after breast cancer treatment with radiation (Li et al , 2021; Xia et al , 2022; Kim et al , 2023). Therefore, SPCs were regarded as one of the RT-associated long-term side effects (Mendes et al , 2017; Xie et al ., 2019; Okonogi et al ., 2022). Though controversies still existed, some previous studies had observed independent associations of RT and SPCs in several tumor types, such as breast, esophageal and lung (Duane et al ., 2021; Zareie et al , 2022; van Barele et al ., 2023).…”