Pattern of Local Recurence After Conservative Surgery and Whole-Breast Irradiation: Implications for Partial Breast Irradiation
Reviewer: S. Jack Wei, MD
Abramson Cancer Center of the University of Pennsylvania
Last Modified: October 21, 2003
Presenter: Gary Freedman, MD
Presenter's Affiliation: Fox Chase Cancer Center
Type of Session: Scientific
The standard treatment with radiation therapy (RT) for breast conservation therapy (BCT) is whole breast irradiation. 75-85% of local recurrences occuring within 10 yrs of BCT are true local recurrences (TLR) meaning they recur within the same quadrant as the original disease. This high rate of TLR has lead to the push for partial breast irradiation (i.e. radiating only the involved quadrant). This study analyzes the 15-year pattern of local recurrence in patients undergoing BCT with whole breast irradiation.
Materials and Methods
- The outcomes of 2730 women with stage 0-II breast cancer who were treated with BCT from 1970-1998 were retrospectively reviewed.
- Patients were treated with 46 Gy to the whole breast and 99% of patients received a local breast boost.
- Patient outcomes were analyzed for TLR, elsewhere local recurrences (ELR, representing recurrences in other quadrants, the skin, or multifocal/diffuse disease), and contralateral breast recurrences (CLBR).
- Subgroup analysis was also performed to determine patterns of failure by tumor size, nodal status, age, histology, and the use of systemic therapy.
- The median follow-up was 82 months.
- 295 patients had DCIS, 1714 had T1 breast cancer, and 721 had T2 breast cancer.
- 195 total local recurrences were found: 121 TLR and 74 ELR.
- The overall rate of ipsilateral breast recurrences (IBR) at 15 yrs was 15%; there was no difference between rates of TLR (9%) and ELR (7%).
- There was a difference in time of TLR vs. ELR: At 5, 10, and 15 yrs, TLR rate was 3%, 6%, and 9% compared to ELR rate of 1%, 2%, and 7%.
- The risk of IBR (15%) at 15 years was equal to the risk of CLBR (14%).
- Overall, the rate of ELR (7%) was half that of the rate of CLBR (14%).
- On subgroup analysis, no difference was seen for patients with lobular histology or by nodal status.
- Patients with DCIS or T1a tumors, patients <40 yrs old, and patients who did not receive tamoxifen had roughly similar rates of ELR as CLBR, rather than a rate of ELR half that of CLBR seen in the general patient population.
- The addition of tamoxifen to patients <40 years old resulted in a rate of ELR roughly half that of CLBR.
- The rate of TLR was constant at 0.6%/year through 15 yrs.
- The rate of ELR was lower than TLR in the first 10 years, but increased significantly after 10 years.
- The rate of ELR was approximately half that of CLBR in all patients except those with DCIS or T1a tumors, those <40 yrs old, or those who did not receive tamoxifen.
- Because the rate of ELR remained below that of CLBR, partial breast irradiation may be feasible and further studies are warranted.
Several interesting findings are reported in this study. First, the rates of ELR remain significantly lower than the rate of CLBR. This may be due to the sterilization of microscopic foci of more diffuse disease with the use of whole breast irradiation. Secondly, certain patient populations appear to be at higher risk for ELR; these groups may be poorer candidates for partial breast irradiation, although this finding is the result of subgroup analysis with small patient numbers. Overall, this study supports the finding the local breast currences are most likely to be TLR; however, further studies need to be conducted to determine the effectiveness of partial breast irradiation as part of BCT.
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