Detecting which invasive cancers at mammographic screening saves lives?(Statistical Data Included)

Abstract

Objectives--Assessment of the features of primary operable breast carcinomas arising in women known to subsequently develop metastatic disease, to show for which invasive breast cancers earlier detection by mammographic screening is potentially beneficial. These data were applied to a separate series of screen detected cancers.

Methods--Features associated with the development of metastatic disease after a previous operable breast cancer were ascertained from examination of histological sections of the initial primary carcinoma and in particular the incidence of nodal positivity and definite vascular invasion. Trends in the frequency of nodal involvement and vascular invasion according to histological grade, invasive size, and tumour type were then examined in a further group of 573 screen detected invasive cancers to predict the likelihood of development of systemic disease in these women.

Results--Of 173 women who developed metastatic disease after a previous operable breast cancer, 79 (72%) had nodal metastases and 62 (59%) had definite vascular invasion. A high proportion (84%) had either lymph node metastases or vascular invasion or both. The absence of vascular invasion and nodal involvement in invasive breast cancer indicated a low risk of subsequent development of metastatic disease. In the screen detected group, grade 1 invasive cancers [less than]20 mm in size and grade 2 and 3 cancers [less than]10 mm in size had low rates of nodal involvement and vascular invasion. There was a gradual trend to small size, lymph node negativity, and less vascular invasion when comparing screen detected ductal carcinoma of no special type, tubular mixed carcinoma, and tubular carcinoma. Cancers with a lobular component tended to be larger and more often lymph node positive than ductal and no specific type carcinomas.

Conclusions--These data suggest that identification of grade 1 cancers less than 20 mm in size and grade 2 and 3 cancers less than 10 mm in size at screening is likely to be beneficial, with a lower likelihood of developing metastatic disease from these lesions. The detection of tubular mixed carcinomas and ductal carcinomas of no specific type also appears beneficial. However the detection of tumours with lobular features at breast screening does not seem to significantly benefit the patient.

(J Med Screen 2001;8:86-90)

Keywords: detection; invasive cancers; mammography

Mammographic screening has been shown to reduce breast cancer mortality. [1-3] However breast screening detects a wide range of breast cancer ranging from low grade ductal carcinoma in situ (DCIS) to high grade invasive cancer. [4-6] It is an issue of debate which particular subgroups should be identified early to have a significant impact on breast cancer mortality. Some argue that detecting high grade DCIS prevents the development of high grade invasive cancer, [7 8] others that detecting low grade, special type invasive cancers prevents "dedifferentiation" into high grade invasive cancers with a poor prognosis. [9] Some think that detecting high grade invasive cancers less than 10 mm in size has the greatest effect. [9]

This study aimed to identify the incidence of axillary nodal metastasis and vascular invasion in primary operable invasive breast cancers in sections from the initial therapeutic surgical specimen in women who later developed metastases and who will succumb to the disease. This information would ascertain whether the absence of these factors could be used to suggest a good prognosis for screen detected invasive breast cancer. The incidence of these prognostic factors in screen detected invasive breast cancer according to histological grade and size will be shown. This may provide insights into which invasive cancers detected at mammographic screening may result in a reduction in population mortality.

Methods

A database of women who developed metastatic disease from breast cancer at our breast unit has been maintained since 1997. The subgroup of these women who developed…