Radiotherapy In Breast Cancer – The Need For Newer Technologies
The primary intention of cancer treatment is to achieve cure and improve survival. Another equally important intention gaining importance in recent years is to conserve the structural and functional aspects of the organ with cancer. Radiotherapy has an important role in breast cancer as it helps in the attainment of both these objectives of cancer treatment.
Does radiotherapy improve survival?
Treatment of breast cancer has been an evolving process over the years. In the early years, it was considered that only super-major surgery would be able to cure the disease. In those days, extensive surgical removal of the breast and surrounding areas was considered to be the standard of breast cancer care. However it was noticed that despite such extensive resection, three out of four patients with positive axillary nodal involvement and almost nine of ten patients with four or more involved nodes became treatment failures. The addition of local radiotherapy in those days managed to decrease the local recurrence of disease but did not show any impact on increasing survival.
Improvement in survival was attained by addition of systemic chemotherapy into the management protocol of breast cancer.
Oncologists were faced with a puzzling question: HOW COULD RADIOTHERAPY IMPROVE LOCAL CONTROL AND YET NOT IMPACT SURVIVAL IN BREAST CANCER PATIENTS? The answer was given in an elegant analysis by The Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) – the Authority in breast cancer research worldwide. The EBCTCG performed an extensive meta analysis using the raw data from every randomized prospective trial investigating post mastectomy radiation. These data included over 15,000 women. It was seen that Radiotherapy regimens were able to produce two-thirds reduction in local recurrence and also reduced annual mortality rates from breast cancer by 13.2%. But an increase in non breast cancer deaths was noticed in this analysis. This meant that the advantage being gained by radiotherapy was being offset due to complications of radiotherapy. The major cause of non breast cancer deaths was found to be heart disease meaning that radiation being delivered inadvertently to the heart was causing an increased incidence of heart disease. An important additional observation noted by this group warrants consideration – the increase in non-breast cancer deaths was noted primarily in patients for whom older radiotherapy techniques and equipment had been used without a clear distinction of treatment volume and organs at risk like the heart, lungs and the opposite breast.
Modern radiation treatments might be associated with less cardiovascular morbidity and mortality than earlier radiation techniques. Currently, a large number of centers utilize computed tomography (CT) treatment planning and shape radiation dose using 3-dimensional conformal radiotherapy and IMRT to avoid treating the underlying heart. Furthermore, integration of electron beam therapy into breast cancer radiotherapy protocols has allowed safe delivery of higher radiation doses to patients. Indeed,in a re-analysis of EBCTCG data By Dr Van de Steene’s group, it was found that post-operative radiation improved breast cancer specific as well as overall survival up to 12.4% provided modern Radiotherapy equipment and techniques were used.
Breast conservation: Importance of Radiotherapy
Another area of active development in breast cancer is the establishment of breast conservation as the standard of care in early breast cancer. The National Institutes of Health (NIH) Consensus Development Conference on the treatment of patients with early stage invasive breast carcinoma, held in June 1990, recommended breast conservation therapy for the majority of women with Stage I or II breast carcinoma. The following issues were highlighted in the conference:
· Local Control: Local control is a major goal of breast conservation treatment. The incidence of local recurrence is low in appropriately selected patients receiving optimal breast conservation treatment.
· Cosmetic Result: A goal of primary breast cancer treatment is to produce the best cosmetic result consistent with achievement of local/regional control. Optimal long-term cosmetic outcome requires integration of careful surgical excision and precise radiotherapy techniques.
· Psychosocial Factors: Women need to be educated about treatment choices in order to make an informed decision in consultation with their physicians. A variety of factors have a major influence on the choice of primary therapy. These include logistic and emotional considerations, personal financial issues, and proximity and access to appropriate medical care
· Radiation Therapy: The conference laid out Radiation Therapy Recommendations after breast conservation surgery. It was suggested that Mega voltage radiation therapy to the whole breast to a dose of 4,500 to 5,000 cGy (180 to 200 cGy per fraction) should be routinely used. Treatment planning should be done to minimize radiation exposure to lung and heart and to achieve uniform dosage to the treatment volume. Boost irradiation should be delivered by electron beam or implantation to doses of 1,000 to 1,500 cGy.
As is evident, the availability of proper radiotherapy facilities is considered as an essential prerequisite for breast conservation as providing adequate doses of radiation becomes necessary to prevent disease recurrence in the conserved breast. The use of modern techniques is essential to provide additional dose to the lumpectomy cavity which is left behind after surgical excision of tumor from the breast without overdosing critical structures like heart and lung. Image guided localization of the cavity is a must. This is done using CT scans. The boost is delivered either using electron beam therapy, 3-D Conformal Radiotherapy,Intensity Modulated Radiotherapy, Interstitial brachytherapy, or Intra-Operative radiotherapy. All these techniques underline the importance of modern techniques and equipment like Linear Accelerators with Multi-leaf collimators, Treatment Planning systems, Interstitial brachytherapy facilities and so on.
Recent developments in the field of Radiation Oncology like Image guided Radiotherapy with respiratory gating, 4-D Radiotherapy and Dynamic adaptive Radiotherapy have shown a lot of promise in further improving outcomes. Modern methods of IMRT delivery like Helical tomothetrapy have helped in achievement of near-impossible dose gradients. PET Guided target localization is another exciting area of research. Innovations like Mammosite have fueled active research into the indications and techniques of interstitial brachytherapy in breast cancer.
Another approach towards treatment of breast cancer has been Accelerated Partial breast Irradiation (APBI). Though not routinely recommended, it is gradually gaining acceptance worldwide for treatment in a defined subset of patients, although a lot of research would be needed to establish it as a standard of care.
In conclusion, Modern Radiotherapy is an essential component in the multi modality management of breast cancer as it not only supplements the treatment outcomes but also complements organ conservation and hence impacts the quality of life of patients with breast cancer.