A radiation oncology perspective
Breast cancer remains the most common non-skin cancer in women in the United States. In 2010, more than 260,000 women developed breast cancer in the U.S., and breast cancer remains the second-leading cause of cancer-related deaths in women. Despite these sobering statistics, the incidence of breast cancer has decreased at the rate of 2 percent per year. In addition, death rates from breast cancer have been decreasing over the past 20 years, largely due to improved screening techniques and improved treatment. Over those years, significant advances in all forms of treatment for breast cancer including chemotherapy, surgery, radiation and anti-hormonal therapy have all contributed to these improved outcomes.
Within the field of radiation oncology, several advances have been made that have contributed not only to these improved outcomes, but also to decreasing the side effects of treatment. Radiation has long been a mainstay in the treatment of breast cancer and has clearly been shown to result not only in the reduction of recurrence rates in patients undergoing lumpectomy, but also in overall survival of women with higher-risk breast cancer.
In women with small, early-stage breast cancer, the move in radiation treatments has been toward more limited radiation. While traditionally, women receiving radiation for breast cancer after a lumpectomy have had their whole breast irradiated, the rationale behind whole breast radiation was rooted in pathologic data from 30 years ago. In these earlier studies, the surgical specimens of women who had undergone mastectomies for breast cancer were examined, and areas of cancer were found as far as 7 to 10 centimeters away from the original tumor site. This finding of cancer cells a significant distance away from the primary tumor was the basis for treating the whole breast with radiation for the subsequent decades.
However, we now know that the breast cancers that we are treating today are significantly different from the cancers in these early studies. Routine screening with mammograms and a generally higher screening rate has led to breast cancers being detected much earlier than in those early studies. With current screening techniques, after treatment, the highest-risk area for breast cancer to return after a lumpectomy is 1 to 2 centimeters away from the primary tumor site. This has led to a movement toward treating a more limited area of the breast in patients with small, early-stage breast cancers. This treatment, known as accelerated partial breast irradiation (APBI), has become increasingly used throughout the country and offers the advantage of a shorter time course of treatment and a smaller amount of normal tissue being exposed to radiation.
The risk of overall skin irritation as well as lymphedema (swelling of the arm) due to radiation is decreased with this more limited form of radiation. Although there is no large randomized trial that has yet shown equivalent cancer control rates between APBI and traditional external beam radiation treatments, individual institutional reports, as well as early reports from larger trials, seem to show similar rates of cancer control between these different forms of radiation treatment. A national randomized trial directly comparing these treatments is currently accruing and Community is proud to be a participating member of that trial.
In women with more advanced disease, particularly those with involvement of the lymph nodes under the arm who have undergone mastectomy, improved techniques of radiation delivery have resulted in a likely survival benefit of giving radiation in a larger number of women. The traditional indication for treatment in these women has been either large tumor size or a high number of lymph nodes involved with cancer, particularly those with four or more involved lymph nodes. In those patients, several large randomized trials from the 1980s showed that overall survival was improved with the addition of radiation in the post-mastectomy setting.
The radiation techniques used in those trials, however, were quite different than modern techniques used in the current-day clinic. In those studies, although there was improved survival with the use of radiation treatments, there was also an increase in cardiovascular-related events in the patients receiving radiation therapy. Recent analysis of these trials, separating out radiation delivered using older techniques compared to treatment with more modern techniques, has shown that modern radiation delivery does not result in an increased risk of cardiovascular events. In fact, re-analysis of this data has shown that improved radiation delivery may also result in improved survival rates for women with one to three lymph nodes involved with cancer, not just those with four or more lymph nodes involved. This increased used of radiation therapy in women with a smaller number of involved lymph nodes has increasingly become the standard of care in the country and may be an important part of the improved outcomes we are seeing with breast cancer treatment in general.
One additional recent change in breast cancer management involves the use of sentinel lymph node biopsies in breast cancer patients. Sentinel lymph node biopsy has become a standard of surgical management of breast cancer in patients who do not show clinical evidence of lymph node involvement prior to lumpectomy. In these patients, the lymph node flow from the breast is mapped to find the first several lymph nodes to which lymphatic drainage flows. These lymph nodes are then removed and tested to look for cancer cells. Patients who are found to be free of cancer are then spared additional surgery. However, in patients where additional cancer cells are found, standard treatment has been to proceed to a complete dissection of the lymph nodes to look for additional lymph node involvement. Sentinel lymph node biopsy has the distinct advantage of resulting in a much lower rate of lymphedema, or swelling of the arm, compared to complete lymph node dissection.
Recently, a large trial from the American College of Surgeons Oncology Group, the preeminent surgical oncology cooperative research group, showed that in patients found to have cancer involvement on sentinel lymph node biopsy, lymph node dissection may not be necessary as long as the patients continued to receive radiation therapy to the whole breast. Radiation has been a standard treatment in patients receiving lumpectomy for their breast cancer and has clearly been shown to decrease the risk of cancer recurrence at the primary tumor site. This new data indicates that radiation also decreases the risk of cancer recurrence in the lymph node region in patients with a positive sentinel lymph node biopsy and allows patients in this situation to avoid complete lymph node dissection, decreasing their risk of lymphedema.
Breast cancer treatment remains a rapidly evolving field. Within the past decade, a number of advances in treatment have resulted in continually improving outcomes and give us great reason to be optimistic in the fight against this dangerous disease.