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Poster lunch

1526 - Effect of postmastectomy radiotherapy on breast cancer with isolated tumor cells or micrometastases in regional lymph nodes: A Propensity Score Matched Analysis Using the SEER Database (98P)

Date

18 Nov 2017

Session

Poster lunch

Topics

Surgical Oncology;  Radiation Oncology;  Breast Cancer

Presenters

Wen Xia

Citation

Annals of Oncology (2017) 28 (suppl_10): x26-x34. 10.1093/annonc/mdx654

Authors

Q. Zheng, W. Xia, Q. Lu, S. Wang

Author affiliations

  • Department Of Medical Oncology, Sun Yat-sen University Cancer Center; State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, Guangzhou, People’s Republic of China, 510060 - Guangzhou/CN
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Resources

Abstract 1526

Background

Postmastectomy radiotherapy (PMRT) has been strongly considered for patients with 1-3 positive axillary nodes (ALNs). In addition, the indications for PMRT are expanding to patients with negative ALNs but have multiple high-risk recurrence factors. However, For patients with isolated tumor cells. We aimed to determine the effects of PMRT on survival of patients with ITCs or ALNs micrometastases of breast cancer.

Methods

We identified patients with ITCs or ALNs micrometastases after mastectomy from the Surveillance, Epidemiology, and End Results database from 2004 to 2014. Overall survival (OS) and breast cancer-specific mortality (BCSM) were compared among patients received PMRT or not, using propensity score-matched analyses. Cox proportional hazards models and competing-risk models were performed in OS and BCSM analyses, respectively.

Results

We identified 11,622 eligible cases. PMRT was administered to 1,728 patients. Treatment was less frequent among patients who were older, patients with high-income, and patients with right-side tumor. OS at 5 years and 10 years were 88.1% and 74.2% in PMRT group, and were 87.8% and 77.3% in non-PMRT group, respectively. Five-year and 10-year cumulative BCSM rate were 6.4% and 12.3% in PMRT group, and were 6.6% and 14.1% in non-PMRT group, respectively. OS and BCSM were unaffected by PMRT after adjusting for multiple confounders (OS, hazard ratio, 0.92; 95% CI, 0.74 to 1.16; BCSM, subhazard ratio, 0.89; 95% CI, 0.67-1.18).

Conclusions

To our knowledge, this is the largest study to date of the effect of radiotherapy on survival in breast cancer with ITCs or ALN micrometastases. In this population-based study, we do not find survival benefit of PMRT on patients with ITCs or ALN micrometastases.

Clinical trial identification

Legal entity responsible for the study

Sun Yat-sen University Cancer Center

Funding

None

Disclosure

All authors have declared no conflicts of interest.

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