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Background and Purpose: Radiotherapy plays an essential role in early breast cancer treatment, but is also associated with an increased risk of second malignancies decades after the exposure., Materials and Methods: We systematically searched the data-bases Medline/Pubmed, Cochrane, Embase, and Cinahl, for cohort studies estimating the risk of second non-breast cancer after primary breast cancer. Every included study was to report the standardized incidence ratio [SIR] of second cancers, comparing the risk among either irradiated or unirradiated female breast cancer patients to the risk of the general female population. From each study the SIRs were extracted and then pooled using random-effects meta-analysis. SIRs were pooled as an overall estimate and according to time since breast cancer diagnosis., Results: 22 studies were eligible for inclusion, comprising 245,575 irradiated and 277,164 non-irradiated women. Irradiated patients had an overall increased risk of second non-breast cancer, with a SIR of 1.23 (95% confidence interval [CI] 1.12-1.36). For non-irradiated patients the SIR was 1.08 (95% CI, 1.03-1.13). For irradiated patients the incidence of second cancers including the lung, esophagus, thyroid and connective tissues progressively increased over time, peaking at 10-15years following breast cancer diagnosis. Summary estimates at ⩾15years after breast cancer irradiation were 1.91 for lung, 2.71 for esophagus, 3.15 for thyroid and 6.54 at ⩾10years for second sarcomas. Non-irradiated patients had no increased risk of second lung or esophagus cancer, neither overall nor over time. For non-irradiated patients' risk of second thyroid cancer (SIR 1.21) and sarcomas (SIR 1.42) were increased overall, but with no remaining risk ⩾10 after breast cancer., Conclusion: Radiotherapy for breast cancer is associated with an excess risk of second non-breast cancer, overall and in organs adjacent to the previous treatment fields. The growing number of long-term survivors after breast cancer highlights the need for an improved individualized approach toward identifying patients with an expected benefit from radiation and patients with no added radiation-benefit., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Background and Purpose: Radiotherapy for breast cancer both decreases loco-regional recurrence rates and improves overall survival. However, radiotherapy has also been associated with increased second cancer risk at exposed sites. In this meta-analysis, we estimated the risk of second non-breast cancers after radiotherapy for breast cancer., Material and Methods: The databases Medline/Pubmed, Cochrane, Embase and Cinahl were systematically searched, for cohort studies on second cancer after radiotherapy for breast cancer, from inception to August 1st 2013. Included studies were to report the relative risk (RR) of second cancers comparing irradiated female breast cancer patients to unirradiated patients. Primary endpoints were all second non-breast-cancers and second cancers of the lung, esophagus, thyroid and second sarcomas. RRs were pooled using random-effects meta-analysis., Results: Thirteen studies comprising 762,468 breast cancer patients were included in the meta-analysis. Five or more years after breast cancer diagnosis radiotherapy was significantly associated with an increased risk of second non-breast cancer RR 1.12 (95% confidence interval [CI] 1.06-1.19), second cancer of the lung RR 1.39 (95% CI 1.28-1.51), esophagus RR 1.53 (95% CI 1.01-2.31) and second sarcomas RR 2.53 (95% CI 1.74-3.70). The risk increased over time, and was highest 15 or more years after breast cancer diagnosis, for second lung RR 1.66 (95% CI 1.36-2.01) and second esophagus cancer RR 2.17 (95% CI 1.11-4.25). There was no significant association between radiotherapy and second thyroid cancer., Conclusions: Radiotherapy for breast cancer is significantly associated with increased risks of second non-breast cancer, overall and in organs adjacent to the previous treatment fields. Despite a relative small absolute risk, the growing number of long-time survivors after breast cancer warrants the need for normal tissue sparing radiotherapy techniques., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Background: Several epidemiological studies have reported increased risks of second lung cancers after breast cancer irradiation. In this study we assessed the effects of the delivered radiation dose to the lung and the risk of second primary lung cancer., Methods: We conducted a nested case-control study of second lung cancer in a population based cohort of 23,627 early breast cancer patients treated with post-operative radiotherapy from 1982 to 2007. The cohort included 151 cases diagnosed with second primary lung cancer and 443 controls. Individual dose-reconstructions were performed and the delivered dose to the center of the second lung tumor and the comparable location for the controls were estimated, based on the patient specific radiotherapy charts., Results: The median age at breast cancer diagnosis was 54 years (range 34-74). The median time from breast cancer treatment to second lung cancer diagnosis was 12 years (range 1-26 years). 91% of the cases were categorized as ever smokers vs. 40% among the controls. For patients diagnosed with a second primary lung cancer five or more years after breast cancer treatment the rate of lung cancer increased linearly with 8.5% per Gray (95% confidence interval=3.1-23.3%; p<0.001). This rate was enhanced for ever smokers with an excess rate of 17.3% per Gray (95% CI=4.5-54%; p<0.005)., Conclusions: Second lung cancer after radiotherapy for early breast cancer is associated with the delivered dose to the lung. Although the absolute risk is relative low, the growing number of long-time survivors after breast cancer treatment highlights the need for advances in normal tissue sparing radiation techniques., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Background and Purpose: To analyze the long-term risk of second primary solid non-breast cancer in a national population-based cohort of 46,176 patients treated for early breast cancer between 1982 and 2007., Patients and Methods: All patients studied were treated according to the national guidelines of the Danish Breast Cancer Cooperative Group. The risk of second primary cancers was estimated by Standardised incidence ratios (SIRs) and multivariate Cox regression models were used to estimate adjusted hazard ratios (HR) among irradiated women compared to non-irradiated. All irradiated patients were treated on linear accelerators. Second cancers were a priori categorized into two groups; radiotherapy-associated- (oesophagus, lung, heart/mediastinum, pleura, bones, and connective tissue) and non-radiotherapy-associated sites (all other cancers)., Results: 2358 second cancers had occurred during the follow-up. For the radiotherapy-associated sites the HR among irradiated women was 1.34 (95% CI 1.11-1.61) with significantly increased HRs for the time periods of 10-14 years (HR 1.55; 95% CI 1.08-2.24) and ≥ 15 years after treatment (HR 1.79; 95% CI 1.14-2.81). There was no increased risk for the non-radiotherapy-associated sites (HR 1.04; 95% CI 0.94-1.1). The estimated attributable risk related to radiotherapy for the radiotherapy-associated sites translates into one radiation-induced second cancer in every 200 women treated with radiotherapy., Conclusions: Radiotherapy treated breast cancer patients have a small but significantly excess risk of second cancers., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)