P5-18-01: No Effect of Adjuvant Chemotherapy in Postmenopausal Patients with Invasive Lobular (Mixed) Breast Cancer.

Abstract

Abstract Background: Although the literature is clear concerning the lack of response of invasive lobular breast cancer to neoadjuvant chemotherapy, no studies exist on the effectiveness of the adjuvant use of chemotherapy in these patients, as compared to those with ductal and mixed type lobular cancer. Methods: All women with primary non-metastatic invasive ductal or (mixed type) lobular breast cancer, aged 50 to 69 years, diagnosed in the period 1995 to 2008 and treated with surgery, were selected from the Netherlands Cancer Registry and followed until January 1, 2010. Patients were divided in two groups: those who received adjuvant hormonal therapy only versus those receiving hormonal therapy in combination with adjuvant chemotherapy. Cox proportional hazards analyses were carried out to determine the impact of chemotherapy in addition to hormonal treatment, for each histological entity separately. Results: In total 19,609 patients had ductal cancer, 3,685 had pure lobular cancer and 1,391 had mixed type lobular cancer. The patient groups were comparable with respect to the use of adjuvant systemic treatment. The 10-year survival of patients with ductal cancer treated with hormonal therapy alone was 69%, compared to 74% for those treated with hormonal therapy and chemotherapy (P<.0001). For patients with lobular cancer, the 10-year survival rate was 68% after hormonal treatment alone and 66% after hormonal therapy with chemotherapy (P=.45). The hazard ratio for death among the patients with ductal cancer receiving chemotherapy in addition to hormonal treatment was 0.70 (95% CI, 0.64−0.76, p<0.0001), as compared to those receiving hormonal treatment alone. In patients with pure or mixed type lobular cancer, however, the hazard ratio's were 1.00 (95% CI, 0.82−1.21, p=0.97) and 0.98 (95% CI, 0.70−1.33, p=0.83), respectively. A statistically significant interaction was observed between the use of adjuvant chemotherapy and histological tumor type. Conclusions: Adjuvant chemotherapy confers no additional beneficial effects in postmenopausal patients with pure or mixed type lobular breast cancer receiving hormonal therapy. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-18-01.