P2-12-23: How Should We Assess Tumour Size (T Stage) in Patients with Multicentric/Multifocal Breast Cancer? Results from the NCIC CTG MA.5 Randomized Trial of CEF vs. CMF in Pre-Menopausal Women with Node Positive Breast Cancer.

Abstract Background A common clinical conundrum in breast cancer management is whether pathologic T stage in women with multicentric or multifocal disease should be taken as the diameter of the largest focus or as the sum of all foci in the breast. Most staging systems, such as the American Joint Committee on Cancer (AJCC), simply use the largest tumour focus for staging. We examine here the impact of alternate methods of estimating tumour size including measures of total tumour size, volume and surface area. Methods: NCIC CTG MA.5 is a randomized trial of CEF versus CMF in pre-menopausal women with node positive breast cancer. Median follow up is 10 years. Pathologically reported patient tumour dimensions for up to 3 foci were utilized to examine the effects of tumour size on Breast-Cancer-Free-Interval (BCFI). BCFI is defined as the time from randomization until recurrence: first local invasive or DCIS, regional, distant, contralateral invasive or DCIS. Tumour size was estimated as 1) pathologic T stage as per AJCC criteria; 2) largest dimension of largest tumour focus (cm); 3) sum of largest dimension(s) of tumour foci (cm); 4) sum of surface area(s) of tumour foci (cm2), and 5) sum of volume of tumour foci (cm3). Step-wise forward unstratified Cox regression was used to assess the different effects of tumour size. Results: This study accrued 710 patients, 37% with T1 tumours, 52% with T2 tumours and 9% with T3 tumours; 61% had 1 to 3 positive lymph nodes. 59% hormone receptor positive. Higher pathologic T stage (p=0.001) and greater surface area (p=0.02) were associated with shorter BCFI, as was lymphovascular invasion (p=0.03), and # of lymph nodes involved (p<0.0001). Administration of anthracycline therapy led to significantly longer BCFI (0.003). The sum of largest tumour sizes (p=0.33) and sum of tumour volume (p=0.34) were not significantly associated with BCFI. Additionally, when the less complete locally reported tumour grade data were included, higher tumour grade was associated with shorter BCFI (p<0.0001). Conclusions: Consideration of multicentric and multifocal disease was an important adjunct to standard pathologic tumour size as was estimation of tumour surface area in this chemotherapy trial of node positive premenopausal women. However, simply adding together the diameters of tumours in patients with multicentric or multifocal disease did not add any additional prognostic information in this high risk patient population. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-23.

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