Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_6_3375 - Use of Preoperative Radiation Therapy in Early and Advanced Stage Breast Cancer

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Use of Preoperative Radiation Therapy in Early and Advanced Stage Breast Cancer
J. L. Koenig1, M. Kozak2, A. Sabolch3, I. L. Wapnir2, K. C. Horst4, C. J. Tsai5, and E. Pollom4; 1Stanford University School of Medicine, Stanford, CA, 2Stanford University, Stanford, CA, 3Department of Radiation Oncology, Kaiser Permanente, Portland, OR, 4Department of Radiation Oncology, Stanford Cancer Institute, Stanford, CA, 5Memorial Sloan Kettering Cancer Center, Department of Radiation Oncology, New York, NY

Purpose/Objective(s): Pre-operative radiation therapy (preopRT) can potentially be used to optimize radiation (RT) targeting, enable breast-conserving surgery (BCS), and facilitate translational research in breast cancer. Using a hospital-based national cancer registry, we characterized the use of preopRT among patients with breast cancer.

Materials/Methods: We identified adult females diagnosed with non-metastatic breast cancer from 2004 to 2014 in the National Cancer Database (NCDB) who had RT and definitive surgery. PreopRT was defined as RT that started within the year prior to definitive surgery. RT was limited to external beam, dose 14 to 70Gy, and course length <10 weeks. pCR was defined using the NCDB variable based on a physician statement about response to neoadjuvant therapy in the medical record. Surgical modality was categorized as BCS or mastectomy. Logistic regression was used to determine factors associated with the use of preop- versus post-operative RT.

Results: We identified 428,903 patients with T1-3/N0-2 tumors and 17,565 patients with T4/N3 tumors, of which 902 (0.2%) and 342 (1.9%) received preopRT, respectively. Patients treated with preopRT received a median RT dose of 58.7 Gy (interquartile range [IQR] 50.0-60.4 Gy) over a median of 43 days (IQR 35-49 days). Of those who had preopRT without adjuvant RT (88%), preopRT was completed a median of 70 days (IQR 36-142 days) before surgery. Among T1-3/N0-2 patients, factors independently associated with preopRT use (p<0.05) were: younger age, black race, earlier year of diagnosis, lower comorbidity score, cT1 (vs cT2-3), cN0 (vs cN1-2), neoadjuvant chemotherapy and hormone therapy use. Among T4/N3 patients, factors similarly associated with preopRT use (p<0.05) were earlier year of diagnosis, lower comorbidity score, and neoadjuvant hormone therapy use. However, older age and more advanced tumors (cT4 vs cT1) were more likely to receive preopRT in this group. In the entire cohort, treatment at an academic institution was associated with preopRT use (OR 1.14; p=0.045). Patients with triple negative tumors (vs triple positive) were more likely to undergo preopRT (OR 1.75; p=0.003). Among T1-3/N0-2 patients who had preopRT versus postopRT, 56.4 vs 81.8% underwent BCS (p<0.001). Among T4/N3 patients who had preopRT versus postopRT, 10.2 vs 16.1% underwent BCS (p=0.004). Of the 101 T1-3/N0-2 patients who had preopRT with recorded pCR, pCR rate was 30.7%. Of the 83 T4/N3 patients who had preopRT with recorded pCR, pCR rate was 19.3%.

Conclusion: There are different clinical and sociodemographic drivers of the use of preopRT in earlier-stage compared to more advanced stage breast cancers. We await results of ongoing trials that will shed further light on the feasibility and effectiveness of this approach.

Author Disclosure: J.L. Koenig: None. M. Kozak: None. A. Sabolch: None. K.C. Horst: Employee; Stanford University. C. Tsai: None. E. Pollom: None.

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