Breast Cancer Screening Enables Better Treatment
Treatment of Breast Tumors Changed by Mammography Screening Programs
Feb 22, 2009
"Thirty years of experience with mammography screening: a new approach to the diagnosis and treatment of breast cancer” was a recent review paper published in the Breast Research Cancer Journal on 18 Dec 2008. It addresses the impact that modern breast cancer screening has on the diagnosis and treatment of breast cancer. The findings of Laszlo Tabar of University of Uppsala School of Medicine, Sweden and Peter Dean of University of Turku School of Medicine, Finland, can be summarized as follows:
Breast cancer screening has given physicians much more impalpable (cannot be felt by touch) than palpable (the reverse) breast cancers. Randomized controlled trials on mammography screening have demonstrated beyond doubt that
- Breast cancer death can be prevented by breast cancer screening.
- From the outset, Breast cancer is a localized rather than generalized disease.
- Although a progressive disease, Breast cancer progression can be arrested if detected and treated at a sufficiently early phase.
- What affects the final outcome more is the timing of treatment, rather than the choice of treatment offered.
- Very early (called in situ) cancers, or early (1 to 14 mm in diameter) invasive cancers are primarily a disease potentially controllable by surgery.
- If breast cancers detected at screening are treated like palpable, clinically detected cancers, there is considerable risk for over-treatment.
Value of Mammographic Prognostic Features
Despite the usually excellent prognosis of patients with small breast cancers, some women still die from them within a few years after diagnosis. Tabar and Dean have found the mammographic image to be a reliable reflection of breast structure and is of prognostic value. Five mammographic tumor features are shown to be reliable additional prognostic tools for predicting the long-term outcome of early breast cancers. (Please refer to the attached figure and link at end of article.)
The integration of mammographic tumor features into the existing TMN (Tumor-Metastasis-Node) staging system should help physicians to better distinguish between the 1 to 14 mm breast cancers with good long-term prognosis and those cases with poor prognosis. This is relevant in prescription of more specifically targeted therapy and to avoid overtreatment.
Introduction of Large Thin Section and Subgross/three-dimensional Histological Techniques
Large thin section histology, a new technique to analyze the surgical specimen, permits a more realistic 1:1 correlation with modern imaging methods, such as mammography, breast ultrasound and magnetic resonance imaging. This technique leads to a more accurate documentation of the main tumor and the surrounding tissue, which may contain additional invasive and/or in situ cancer foci and permits more accurate assessment of the margins.
Local recurrence is not a predictor of poor outcome when the primary tumour and local recurrence are both nonpalpable and have been detected by imaging.
Non-palpable Breast Cancers have Better Prognosis
Palpable breast cancers that recur locally tend to have poor survival. However, this has not been the experience with the smaller non-palpable tumors detected by screening. Randomized controlled trials show that the harm/benefit ratio of adjuvant radiotherapy increases with decreasing tumor size. Hence, it is important to define this subgroup of patients for whom radiotherapy may do more harm than good. Use of mammographic tumor features described above will play an important role in this selection.
Conclusion
Population-based mammography screening has brought about significant changes in our approach to the diagnosis and treatment of breast cancer. The spectrum of the disease has shifted from primarily palpable, advanced cancer to mainly non-palpable tumors that have a much better prognosis. The traditional emphasis on applying therapeutic regimens for advanced disease should give way to a new emphasis on less radical and tailored treatments, whenever disease progression to advanced stages has been arrested successfully through early detection and treatment.
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