Chest Wall Radiation Alone for Breast Cancer Patients With 1-3 Positive Lymph Nodes Treated by Mastectomy
It is currently known that post-mastectomy radiation to the chest wall and axillary/clavicular lymphatics reduces local recurrence and increases survival in patients with 4 or more positive lymph nodes or tumors larger than 5 cm. It is uncertain whether there would be any benefit to giving radiation to those with tumors smaller than 5 cm or with only 1-3 positive lymph nodes after mastectomy. This study compared mastectomy alone to mastectomy plus radiation to the chest wall only or radiation to the chest wall and clavicular area.
The 238 participants were women (ages 31-93) with primary tumors less than 5cm and 1-3 positive lymph nodes. 165 got no radiation, 73 did receive radiation (46 to the chest wall only and 27 to the chest wall & clavicular area, 15 of whom also received radiation to the axillary area). Ninety-three percent of the participants also got adjuvant therapy (35 had chemotherapy, 54 had hormonal therapy, and 133 got both).
At 10 years, the rate of local recurrence (in the area of the original mastectomy or lymph nodes) was 10.2% in the patients without radiation, while no patients developed local recurrence in the treatment group. Patients who received radiation had better disease-free survival (meaning they were alive with no sign of disease) at five years (96% vs. 85%) and at 10 years (96% vs. 75%). The improvements in local recurrence rates and disease-free survival became evident within two years following mastectomy and radiation.
Among patients who did not receive radiation, poor tumor grade was the only factor associated with an increased risk of local recurrence.
This study is clearly important in showing that patients who receive postmastectomy radiation are less likely to experience a local recurrence and have an improved disease-free survival. However, the question regarding the extent of radiation that is needed cannot be addressed here, given that no one in the radiation groups had local recurrences and the number of patients was quite small. It will be important to conduct a larger study to determine if the smaller radiation field is as effective as including the clavicular area. This smaller field could spare some women the increased risk of side effects such as lymphedema and neuropathy due to damage to the brachial nerves.
Partially funded by an unrestricted educational grant from Bristol-Myers Squibb.