Research article
Second malignancies in breast cancer patients following radiotherapy: a study in Florence, Italy
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* Corresponding author: Wei Zhang wei.zhang@hpa.org.uk
1 Epidemiology Department, Centre for Radiation, Chemical and Environmental Hazards, HPA, Chilton, Didcot, OX11 0RQ, UK
2 Department of Clinical Physiopathology, University of Florence, viale Pieraccini 6, Florence, 50139, Italy
3 Department of Statistics "G. Parenti", University of Florence, viale Morgagni 59, Florence, 50134, Italy
4 Biostatistics Unit, ISPO Cancer Prevention and Research Institute, via Cosimo il vecchio 2, Florence, 50139, Italy
Breast Cancer Research 2011, 13:R38 doi:10.1186/bcr2860
Published: 4 April 2011Abstract
Introduction
Patients diagnosed with breast cancer are often treated with surgery followed by radiation therapy. In this paper, we evaluate the effect that radiotherapy may have had on the subsequent risk of second malignancies, including the possible influences of age at treatment and menopausal status.
Methods
In order to evaluate the long-term consequences of radiotherapy, a cohort study was conducted based on clinical records for 5,248 women treated for breast cancer in Florence (Italy), with continuous follow-up from 1965 to 1994. The Cox proportional hazards model for ungrouped survival data was used to estimate the relative risk for second cancer after radiotherapy.
Results
This study indicated an increased relative risk of all second cancers combined following radiotherapy (1.22, 95% CI: 0.88 to 1.69). The increased relative risk appeared five or more years after radiotherapy and appeared to be highest amongst women treated after the menopause (1.61, 95% CI: 1.13 to 2.29). Increased relative risks were observed specifically for leukaemia (8.13, 95% CI: 0.96 to 69.1) and other solid cancers (1.84, 95% CI: 1.06 to 3.16), excluding contralateral breast cancer. For contralateral breast cancer, no raised relative risk was observed during the period more than five years after radiotherapy.
Conclusions
The study indicated a raised risk of second malignancies associated with radiotherapy for breast cancer, particularly for women treated after the menopause.