Epidemiology

Influence of radiotherapy for the first tumor on aggressiveness of contralateral breast cancer

  1. Maria E.C. Sandberg1,†,*,
  2. Sara Alkner2,3,
  3. Mikael Hartman1,4,5,6,
  4. Sandra Eloranta1,
  5. Lisa Rydén7,8,
  6. Alexander Ploner1,
  7. Hans-Olov Adami1,9,
  8. Per Hall1,
  9. Kamila Czene1

Article first published online: 29 OCT 2012

DOI: 10.1002/ijc.27890

Issue

International Journal of Cancer

International Journal of Cancer

Volume 132, Issue 10, pages 2388–2394, 15 May 2013

Additional Information

How to Cite

Sandberg, M. E.C., Alkner, S., Hartman, M., Eloranta, S., Rydén, L., Ploner, A., Adami, H.-O., Hall, P. and Czene, K. (2013), Influence of radiotherapy for the first tumor on aggressiveness of contralateral breast cancer. Int. J. Cancer, 132: 2388–2394. doi: 10.1002/ijc.27890

Author Information

  1. 1

    Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden

  2. 2

    Department of Oncology, Clinical Sciences, Lund University, Lund, Sweden

  3. 3

    Clinic of Oncology, Skåne University Hospital, Malmö, Sweden

  4. 4

    Department of Epidemiology and Public Health and, National University of Singapore, Singapore

  5. 5

    Department of Surgery, National University of Singapore, Singapore

  6. 6

    Center for Molecular Epidemiology, National University of Singapore, Singapore

  7. 7

    Department of Surgery, Clinical Sciences, Lund University, Lund, Sweden

  8. 8

    Clinic of Surgery, Skåne University Hospital, Malmö, Sweden

  9. 9

    Department of Epidemiology, Harvard School of Public Health, Boston, MA

  1. †

    Tel: +46 8 52483985

*Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Box 281, 171 77 Stockholm, Sweden

  1. †

    Tel: +46 8 52483985

Publication History

  1. Issue published online: 28 FEB 2013
  2. Article first published online: 29 OCT 2012
  3. Accepted manuscript online: 4 OCT 2012 01:46AM EST
  4. Manuscript Accepted: 7 SEP 2012
  5. Manuscript Received: 26 MAR 2012

Funded by

  • Swedish Research Council. Grant Number: 521-2008-2728
  • Swedish Cancer Society. Grant Number: 5128-B07-01PAF

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Keywords:

  • contralateral breast cancer (CBC);
  • adjuvant radiotherapy;
  • prognosis;
  • tumor characteristics;
  • cancer epidemiology

Abstract

We aimed to investigate if characteristics of contralateral breast cancer (CBC) are influenced by adjuvant radiotherapy for the first breast cancer. Using information from population-based registers and medical records, we analyzed two cohorts comprising all women with CBC diagnosed >3 months after their first cancer (809 patients in Stockholm 1976–2005 and 750 patients in South Sweden 1977–2005). We used Poisson regression to calculate risk of distant metastasis after CBC, comparing patients treated and not treated with radiotherapy for the first cancer. Logistic regression was used to estimate odds ratio (OR) of more aggressive tumor characteristics in the second cancer, compared to the first. For patients with CBC in Stockholm with <5 years between the cancers radiotherapy for the first cancer conferred a nearly doubled risk of distant metastasis [incidence rate ratio (IRR) = 1.91; 95% confidence interval (CI): 1.27–2.88], compared to those not treated with radiotherapy. This was replicated in the South Swedish cohort [IRR = 2.12 (95% CI: 1.40–3.23)]. In Stockholm, we found an increased odds that, following radiotherapy, a second cancer was of more advanced TNM-stage [OR 2.16 (95% CI 1.13–4.11)] and higher histological grade [OR = 2.00 (95% CI 1.08–3.72)] compared to the first, for patients with CBC with <5 years between the cancers. No effect on any of the investigated outcomes was seen for patients diagnosed with CBC >5 years from the first cancer. In conclusion, patients diagnosed with CBC within 5 years had worse prognosis and more aggressive tumor characteristics of the second cancer, if they had received radiotherapy for their first cancer, compared to no radiotherapy.

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