Palliative Care

PV QA 3 - Poster Viewing Q&A 3

TU_29_3022 - The influence of breast cancer subtype on survival after palliative radiation for osseous metastases.

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

The influence of breast cancer subtype on survival after palliative radiation for osseous metastases.
M. K. Abdelhakiem, C. Johnstone, C. Bergom, A. D. Currey, and J. R. Robbins; Medical College of Wisconsin, Milwaukee, WI

Purpose/Objective(s): After palliative radiation therapy (RT) for bone metastases, breast cancer (BC) patients typically live longer than patients with other types of cancers. BC is often thought of as a single disease, but based on receptor status there are at least four distinct subtypes: Luminal A (LA), Luminal B (LB), Triple Negative (TN), and Her2 enriched (HER2). We hypothesize that survival following palliative RT for osseous metastases is correlated with breast cancer subtype.

Materials/Methods: We identified 4,382 patients with BC and known receptor status, who received palliative RT for osseous metastases from 2004-2013 in the National Cancer Database. Breast cancer subtype was determined using receptor status and tumor grade to categorize as LA, LB, TN, or HER2. Kaplan-Meier method with log-rank testing and multivariate Cox-regression models were used to identify factors associated with overall survival.

Results: Breast cancer subtypes were 54% LA, 33% LB, 8% TN, and 5% HER2. Median follow-up was 21 months. Over 60% received 30 Gy in 10 fractions. Over 88% received 10 or more fractions. Overall >11% stopped RT early; TN and HER2 patients were more likely to have incomplete courses. Median survival was 34 months for LA, 29 months for LB, 17 months for HER2, and 6.4 months for TN (p<0.001). On multivariate analysis, age, private insurance status, Charlson-Deyo Comorbidity score, and breast cancer subtype impacted survival (see Table).

Conclusion: Survival following palliative RT to osseous BC metastases is directly correlated with breast cancer subtype. Receptor status may be the strongest predictor for post-RT survival. Given the disparity in outcomes, physicians should consider receptor status when deciding on a palliative RT regimen for BC to avoid excessive treatment and inconvenience for poor-prognosis patients.
Category Hazard Ratio 95% confidence Interval p-value
Age 1.015 1.011-1.018 p<0.001
Private Insurance 0.722 0.609-0.856 p<0.001
Charlson-Deyo score
0 1 2 Ref. 1.197 1.680 Ref. 1.071-1.337 1.417-1.992 Ref. p=0.002 p<0.001
Breast cancer Subtype
Luminal A Luminal B Her2 Enriched Triple Negative Ref. 1.331 2.027 3.918 Ref. 1.216-1.457 1.695-2.423 3.448-4.452 Ref. p<0.001 p<0.001 p<0.001

Author Disclosure: M.K. Abdelhakiem: None. C. Johnstone: Employee; Medical College of WI. C. Bergom: None. A.D. Currey: Honoraria; Wisconsin Oncology Network. J.R. Robbins: Travel Expenses; Elekta.

Mohamed Abdelhakiem, MD, BS

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