The Value of Adding Radiation to Tamoxifen in Post-Menopausal Women with Stage I Breast Cancer: A Decision Analysis

Reviewer: Ryan Smith, MD
OncoLink
Last Modified: October 9, 2002

Presenter: R.S. Punglia
Presenter's Affiliation: Joint Center for RadiationTherapy
Type of Session: Scientific

Background

Large randomized trials have proven that radiation therapy (RT) decreases local recurrence in post-lumpectomy patients with breast cancer. However, the effect on the development of distant metastases and overall survival is less clear. The disadvantages of radiation therapy after lumpectomy includes acute effects of radiation, decrease in cosmetic outcome, rare severe toxicities, and cost. This study reports on a decision-analytic model that attempts to estimate the clinical benefits of adding radiation therapy to Tamoxifen (TAM) in post-menopausal women with receptor positive T1N0 tumors following lumpectomy.

Materials and Methods

Results were based on a decision-analytic model to calculate life expectancy, time with an intact breast, and relapse free survival (RFS) among women aged 50-80 following breast conservation therapy.
Baseline probabilities of recurrence were derived from large randomized trials (CALGB 9343, NSABP B-21, and the Ontario-British Columbia study).
Time patients at risk for recurrence was calculated out to 10 years
Other assumptions included: 5 years of Tamoxifen, no development of contralateral breast cancer, and no increased mortality from Tamoxifen

Results

The addition of RT increased the life expectancy by 7.2 months in 50 yo patients, but only 0.5 months for 80 yo patients.
Lifetime risk of dying of breast cancer for 50 yo patients was 5.3% with TAM alone vs. 2.4% with the addition of RT
Lifetime risk of dying from breast cancer for 80 yo patients was 2% with TAM alone vs. 1.2% with the addition of RT
Time with an intact breast was increased with the addition of RT in all patients, though the addition was 1.7 years in 50 yo patients vs. 0.3 years in 80 yo patients
10 year RFS in 50 yo patients was 79% with TAM alone vs. 91% with the addition of RT.
10 year RFS in 80 yo patients was 33% with TAM alone vs. 38% with the addition of RT.

Author's Conclusions

There is a benefit to radiation with all ages of patients, though this benefit decreases with increasing age
Age and patient preference should be considered when selecting treatment plans

Clinical/Scientific Implications

Findings from this study are interesting but not unexpected. Mainly because 50 year old patients have a longer life expectancy in which to develop complications from breast cancer recurrence, the benefit from radiation therapy is amplified in younger patients. Post-menopausal women with receptor positive T1N0 breast cancer have excellent survival to begin with, so the addition of RT may not result in statistically significant differences in survival. However, it is difficult to imagine that radiation therapy could decrease survival in these patients. Also, it has been definitely demonstrated that RT greatly decreases local recurrence in these patients, which translates into a lower salvage mastectomy rate. In patients undergoing breast conservation therapy for the explicit reason to save their breasts, not offering these patients radiation therapy undermines the entire rationale behind lumpectomy. In addition, with modern techniques, the acute toxicity of radiation therapy to the breast is mild with significant late effects seldom seen. Also, it should be kept in mind that this is a model, and any changes in therapy standards should be tested in actual patients in a randomized trial setting.

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