Breast cancer is the most commonly diagnosed malignancy among women and, after lung cancer, the second leading cause of cancer-related deaths in North America. Yet unlike the survival rate for individuals diagnosed with lung cancer, the rate for women diagnosed with breast cancer has been rising dramatically over the past decade—to the point where breast cancer could soon lose its ranking as the second-greatest cancer killer. Nothing would delight clinicians like us more.
This improvement in overall outlook for women diagnosed with breast cancer is attributable in part to earlier detection, which results from greater awareness of, and access to, regular breast screening. But breast cancer patients are also benefiting from accelerated research that has led to a much better understanding of the disease and a wider variety of treatment choices that doctors can mix and match to tailor therapy for a particular patient. In just the past decade, it has even become possible to target drugs to specific molecules within tumors that help to drive the disease.
Breast cancer was, in fact, the first type of solid-tumor cancer to be treated with this molecular-targeting therapeutic approach, when the drug trastuzumab (Herceptin) was approved in 1998. The protein that trastuzumab was designed to attack, called HER2, promotes aggressive tumor growth. Before trastuzumab, diagnosis with a tumor that overproduces HER2 was dreaded news for patients. Now it can be one of the tumor types with the best prognosis, because doctors have an increasing number of effective weapons against HER2.
The next decade promises to be an exciting and productive time in the field of molecular-targeted cancer therapy: additional drugs currently being tested in people and animals are making it possible to go after an increasing variety of molecular tumor features that play a critical role in the initiation and survival of malignancies and in the cancers’ progression to increasingly threatening stages. Along with improvements in older therapies and supportive care, this newer generation of drugs gives doctors more options for customizing treatment to cope with a tumor’s particular suite of molecular characteristics and reflects our growing realization that breast cancer is not a single disease.
Evolving Treatment Approaches
Although the prospect of tailoring treatment to the molecular features of individual tumors is incredibly encouraging, prior advances are also contributing to the declining mortality rate for women diagnosed with breast cancer. Improved screening techniques, for instance, are definitely helping to catch and confirm more cases at an earlier stage, which is a boon, because breast cancer is highly curable if detected early. Newer imaging methods include digital mammography (which produces a clearer picture than screen-film mammography), ultrasound and magnetic resonance imaging (MRI). Women at high risk
of developing breast cancer because of family history or mutations in one of the BRCA genes are now offered annual MRI breast screening, although ultrasounds are usually reserved for following up on abnormal fi ndings in a mammogram or physical exam.
In addition, surgical approaches to tumor excision have changed over the past 20 years from radical tissue removal in women whose tumor appears confined to a small part of the breast to breast-conserving therapy. More focused radiation is also less damaging to normal tissues such as those of the heart and lungs. These changes have made treatment less destructive, with equally successful results.
Besides these refinements in the detection and local management of breast tumors, the use of systemic therapies as supplementary, or adjuvant, treatments has become more sophisticated thanks to the availability of new drugs, improvements in their delivery, and management of side effects. Such treatments aim to eradicate any malignant cells not eliminated by surgery or radiation. The approach is often warranted because even tumors that are tiny and apparently self-contained can already have quietly spawned microscopic metastases, undetectable tumors at distant sites in the body. By attacking these invisible tumors, adjuvant chemotherapy can prolong disease-free intervals and overall survival rates.