Breast cancers in the geriatric population are more likely to have tumors with indolent features such as high rates of hormone receptor expression and higher rates of low grade tumors. These factors are associated with a lower risk of recurrence after breast conserving surgery without radiation. A phase III randomized trial was conducted by the Cancer Leukemia Group B (CALGB www.calgb.org) to determine if radiation therapy could be safely omitted in patients over the age of 70 with small tumors. At 10 years from surgery, 90% of patients treated with surgery and tamoxifen were without locoregional recurrence compared to 98% of patients treated with surgery, tamoxifen and radiation therapy. This result was statistically significant. There were no differences in rates of distant metastasis, overall survival or subsequent mastectomy between the two groups. This study suggests that while radiation reduces the risk of breast cancer recurrence in this population, the absolute magnitude of this risk reduction is relatively small.

On this study, the vast majority of these patients were white (91%), and had tumors smaller than 2cm (98%) that were estrogen receptor positive (97%). Patients required were to be clinically node negative before enrolling on the study. It is important to understand these selection criteria when considering omission of radiation.

There are other large data sets that have confirmed this finding. In an analysis of the SEER database, the benefit of radiotherapy was shown to diminish with patient age. Specifically, patients over the age of 75 who were pathologically node negative and had low grade disease derived no benefit from radiation. However, in patients 70-74, there remained a benefit associated with radiation therapy that was statistically significant. Furthermore, this benefit was comparable to the benefit of other well accepted medical therapies, such as antihypertensive treatment for the prevention of cardiovascular events or bisphosphonate therapy for the prevention of fracture.

Another issue to discuss with patients when considering this approach is utilization of anti-endocrine therapy. On the CALGB study, patients were required to take tamoxifen. However, it is well established that compliance with this medication is diminished outside the setting of a clinical trial. This is significant because anti-endocrine therapy reduces the risk of local recurrence. If this aspect of treatment is omitted, one might not reach the favorable outcomes seen on the CALGB study. In one series investigating this issue, as many as 50% of patients were found to be non-compliant with anti-endocrine therapy. That risk of non-compliance increased with age. Hence when considering the omission of radiation therapy, patients must be reliable and understand the importance of continuing anti-endocrine therapy.