Screening Mammography Is Associated with Earlier Stage Disease and Greater Eligibility for Breast Conservation in Women Aged 40 and Older with Breast Cancer

English

Reviewer: Heather Jones, MD
OncoLink
Ultima Vez Modificado: 7 de octubre del 2002

Presenter: G.M. Freedman
Presenter's Affiliation: Fox Chase Cancer Center, Philadelphia, PA, USA
Type of Session: Plenary

Background

No cancer screening test has been studied more than mammography. Yet, after more than 35 years of trials, many questions remain regarding at what age and at what interval women should be screened. Currently, screening mammography has been recommended for women aged 40 and older for early detection of breast cancer to improve survival. The purpose of this study was to confirm in a large population of patients with newly diagnosed breast cancer a positive association between screening mammography and cancer stage at presentation. This study also attempted to evaluate the impact of mammogram screening on eligibility for breast conservation.

Materials and Methods

The study population consisted of 1591 women with breast cancer seen for consultation between 7/95 and 10/01
All patients were evaluated by a multidisciplinary team that included a Radiation Oncologist, Medical Oncologist, Breast Surgeon, Diagnostic Radiologist and Pathologist.
All eligible women were age 40 or older at diagnosis, and had information regarding the number and/or frequency of mammograms prior to diagnosis of breast cancer available for review.
For each patient, a mammogram frequency index was assigned by a formula Frequency = (age - 40) / number of prior mammograms.
The patients where then categorized by this mammogram frequency index.
Group 1 (unscreened) consisted of 176 patients with no mammography prior to their time of presentation.
Group 2 (partially screened) consisted of 705 patients with a frequency index over 1 (representing mammography on average less often than annually).
Group 3 (highly screened) was 723 patients with a frequency index <= 1 (representing on average annual mammography or more often).
These three groups were compared for method of detection, pathologic T stage at diagnosis, tumor size, and eligibility for breast conservation.

Results

Mammography as the method of cancer detection was much more likely to occur in group 3 patients. The distribution of cancer detection by mammogram per group: 34% of group 1 patients, 50% of group 2 patients, and 58% of group 3 patients (p<0.0001
Group 3 patients were more likely to present with noninvasive lesions. The distribution of ductal carcinoma in situ per group: 15% of patients in group 1 presented with ductal carcinoma in situ 19% of group 2 and 24% of patients in group 3 (p=0.0085).
Group 2 and 3 patients were more likely to have T1 lesions and smaller tumor size. The distribution of T stage and tumor size per group: Stage T1 or T2 disease made up 50% of group 1 patients, 60% of patients in groups 2 and 3 (p=0.028) The size distribution per group: tumor size was <= 1 cm in 9% of group 1 patients, compared with 21-23% of group 2 and 3 (p=0.0003).
The group 2 and 3 patients were more likely to be offered breast conservation compared to mastectomy. The distribution for multidisciplinary team options per group: For group 1, the multidisciplinary team offered the option of breast-conserving surgery and radiation to 42%, but recommended treatment by mastectomy in 38%. For groups 2 and 3, 57% were eligible for breast conservation and only 28% recommended to have mastectomy. The differences in treatment recommendation were statistically significant (p=0.0021).

Author's Conclusions

Women aged 40 or older diagnosed with breast cancer with an age-adjusted mammogram frequency on average at least annually were more often diagnosed with noninvasive breast cancer than women with less frequent screening or no prior mammography. Patients with any history of mammography prior to initial diagnosis also presented with earlier stage invasive disease and smaller tumor size. Earlier stage at presentation was associated with greater eligibility for breast conservation and less frequent recommendation for mastectomy for women with prior mammogram screening. This study supports an annual interval for most often detecting the most curable stage 0 form of breast cancer and confirms the benefits of regular mammographic screening for women 40 years or older.

Clinical/Scientific Implications

More than 3.5 million women-years of observation have been recorded for women of all ages, and more than 2.7 million women-years for women aged 40 to 49 at entry from the breast cancer screening randomized clinical trials, yet many questions remain regarding at what age and at what interval women should be screened. However, there is a growing body of evidence (to which you can add this study), which demonstrates that the utilization of screening mammography results in a significant increase in the detection rate of DCIS and early stage breast cancer. The reward for early detection is the greater likelihood of breast-conserving therapy (if that is what the patient so prefers). Of special mention is the subset analysis that confirmed the positive benefit of early detection in the women aged 40 to 49.

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