Journal of Clinical Oncology, 2005 ASCO Annual Meeting Proceedings.
Vol 23, No 16S (June 1 Supplement), 2005: 518
© 2005 American Society of Clinical Oncology

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Abstract

The impact of adjuvant therapy on contralateral breast cancer risk and the prognostic significance of contralateral breast cancer occurrence: A population-based study

Comprehensive Cancer Ctr North, Groningen, The Netherlands; Univ Hosp, Groningen, The Netherlands; Comprehensive Cancer Ctr, Amsterdam, The Netherlands; Comprehensive Cancer Ctr South, Eindhoven, The Netherlands; Netherlands Cancer Institute, Amsterdam, The Netherlands

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Purpose: To evaluate the impact of age and adjuvant therapy on contralateral invasive breast cancer (CBC) risk and the prognostic significance of CBC. Patients and Methods: The study included 33,930 surgically treated stage I-IIIA breast cancer patients diagnosed in the Netherlands between 1988–2000. The prognostic impact of CBC was studied in a time-dependent Cox model. Results: With a median follow-up of 5.3 years, 476 CBC were diagnosed <6 months after the index cancer (synchronous) and 999 thereafter (metachronous). Older age and lobular histology increased synchronous CBC risk. The Standardized Incidence Ratio (SIR) of any CBC was 2.9 (95% Confidence Interval (95%CI) 2.7–3.1). The SIR of metachronous CBC decreased with age, from 13.4 (95%CI 9.6–18.2) for women <35 to 1.6 (95%CI 1.4–1.8) for women 60 years. The absolute excess risk of metachronous CBC was 29.9/10,000 person-years. The cumulative risk of metachronous CBC increased with about 0.5%/year, reaching 5.3% after 10 years. Adjuvant hormonal (Hazard ratio (HR) 0.54; 95%CI 0.44–0.68) and chemotherapy (HR 0.67; 95%CI 0.51–0.87) markedly decreased metachronous CBC risk. Radiotherapy was associated with a 60% increased CBC risk (95%CI 1.04–2.62) among patients <40 years. Adjusted for age and stage of the index cancer, the survival of patients with metachronous CBC was worse than for unilateral breast cancer patients (HR 1.47; 95%CI 1.33–1.63). Conclusion: Young breast cancer patients experience very high synchronous and metachronous CBC risk. Adjuvant hormonal or chemotherapy considerably reduced the risk of CBC. The occurrence of CBC adversely affects prognosis, emphasizing the necessity of long-term surveillance directed at early CBC-detection.

No significant financial relationships to disclose.

Abstract presentation from the 2005 ASCO Annual Meeting