Obesity and the outcome of young breast cancer patients in the UK: The POSH study


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Ellen Copson1, Ramsey Cutress1, Bryony Eccles1, Clarice Wong1, Tom Maishman1, Sue Gerty1, Louise Dent1, Douglas Altman2, Lorraine Durcan1, Peter Simmonds1, the POSH steering group and D.M. Eccles1
1Cancer Sciences Academic Unit and Clinical Trials Unit, Faculty of Medicine, University of Southampton, Southampton, UK, 2Centre for Statistics in Medicine, Oxford, Oxford, UK

Background

Obese patients with early breast cancer have a poorer prognosis than non-obese patients. Host factors, tumour pathology and treatment issues have been suggested as possible factors. We examined data from the multi-centre Prospective Outcomes of Sporadic and Hereditary breast cancer study to investigate this in pre-menopausal women.

Method

2956 patients aged ≤40 at breast cancer diagnosis were recruited from 126 UK hospitals between 2001 and 2007. Details of body mass index (BMI), tumour pathology and treatment were collected. Follow-up data were collected at 6 months, 12 months and then annually. Adjuvant chemotherapy prescriptions were reviewed for 85 patients treated locally.

Results

BMI data were available for 2842 (96.1%) patients: 36 (1.3%) were underweight (BMI<18.5), 1489 (52.4%) were healthy weight (18.5≤BMI<25), 784 (27.6%) were overweight (25≤BMI<30) and 533 (18.8%) were obese (BMI≥30). There was a significant difference in 8-year overall survival between BMI categories (p<0.001), with survival of obese patients (58.6%) almost 15% lower than healthy weight patients (73.3%). Median tumour size was significantly higher in obese patients than normal weight patients (26mm vs. 20mm, p<0.001). Obese patients had significantly more grade 3 tumours (63.9% vs. 58.8%, p=0.042) and node positive tumours (54.6% vs. 49.4%, p=0.040) than normal weight patients. ER negative tumours were more frequent in obese patients than normal weight patients (68.0% vs. 59.9%, p=0.001) whereas the incidence of HER 2 positive tumours was similar (28.2% vs. 27.3%, p=NS). Obese patients were significantly more likely to experience a chemotherapy dose delay than healthy weight patients (33.3% vs. 5.9%, p=0.007).

Conclusion

Obesity at diagnosis is associated with inferior survival in young breast cancer patients. Our data confirms that obesity is associated with biologically adverse tumours. Furthermore, more obese patients receive sub-optimal chemotherapy than healthy weight patients. Further studies will explore the effect of body composition on chemotherapy tolerance.