Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_5_3366 - A Phase 2 Study of Hypofractionated Partial Breast Irradiation (HF-PBI) in Women with Early Stage Breast Cancer

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

A Phase 2 Study of Hypofractionated Partial Breast Irradiation (HF-PBI) in Women with Early Stage Breast Cancer
P. Fang1, E. Bloom2, W. A. Woodward3, M. C. Stauder4, W. Tereffe4, S. G. Chun5, P. J. Schlembach4, L. L. Mayo6, N. R. Ahmad4, I. Y. Arzu4, V. K. Reed4, G. M. Chronowski4, M. E. Delclos4, and B. D. Smith7; 1University of Texas MD Anderson Cancer Center, Houston, TX, 2The University of Texas, M.D. Anderson Cancer Center, Houston, TX, 3The University of Texas MD Anderson Cancer Center, Department of Radiation Oncology, Houston, TX, 4MD Anderson Cancer Center, Houston, TX, 5The University of Texas MD Anderson Cancer Center, Division of Radiation Oncology, Houston, TX, 6University of Texas Medical Branch Hospitals, Galveston, TX, 7MD Anderson, Houston, TX

Purpose/Objective(s): The IMPORT LOW trial demonstrated that 40 Gy in 15 daily fractions to the partial breast (hypofractionated-partial breast irradiation [HF-PBI]) yielded optimal local control and cosmetic outcomes for women 50 and older with invasive breast cancer and negative margins (≥2mm) following segmental mastectomy. To build upon these findings, we designed a prospective, single-arm trial to shorten the treatment course to 35 Gy in 10 daily fractions to the partial breast and extend entry criteria to include patients with DCIS and/or close (<2mm) surgical margins. Herein, we report the planned early toxicity analysis for the first 30 patients.

Materials/Methods: We enrolled patients age 50 and older with DCIS or ER+, node-negative invasive cancer measuring ≤ 3 cm in size and treated with segmental mastectomy. Radiation consisted of 35 Gy in 10 daily fractions to the tumor bed plus margin and could be delivered with mini-tangents, three-dimensional conformal radiation, or intensity modulated therapy. A boost of 9 Gy in 3 fractions was delivered to patients with close (<2mm) surgical margins. The primary endpoint is the proportion of patients with NCI CTCAE v.4 grade 2 or higher toxicity occurring during radiation through the 6 month post-radiation follow up visit. Study forms assessing toxicity were completed at the end of radiation treatment and at 3 weeks and 6 months after radiation. In a prior trial run by our institution, the risk of this outcome in patients treated with hypofractionated whole breast irradiation was 60%.

Results: The first 30 patients were enrolled between March 2017 to July 2017. Median age was 62 years. The primary outcome event rate was 23% (7/30). There was only one Grade 3 toxicity, a breast infection at the 3 week follow-up visit that subsequently resolved. Grade 2+ toxicities during radiation were dermatitis (n=1), breast infection (n=1), and breast pain (n=1). Grade 2+ toxicities through 6 months post-radiation were breast atrophy (n=4), fibrosis (n=2), skin induration (n=1), and fatigue (n=1).

Conclusion: Early outcomes after HF-PBI are favorable with regard to toxicity within 6 months of radiation treatment as compared to toxicity with whole breast irradiation. Continued follow-up will assess secondary outcomes including cosmetic stability and disease-specific outcomes.

Author Disclosure: P. Fang: None. E. Bloom: None. W.A. Woodward: None. M.C. Stauder: None. W. Tereffe: None. S.G. Chun: None. P.J. Schlembach: None. B.D. Smith: Employee; UT MD Anderson Cancer Center. Research Grant; Varian Medical Systems, Inc, MD Anderson Cancer Center. Consultant; Global Oncology One. I co-invented technology that MD Anderson has licensed to Oncora Medical. In the future, if MD Anderson chooses to develop a product with Oncora, MD Anderson may receive royalties from Oncora. If that occurs, MD Anderson may choose to pass along a fraction of these royalties to me. I have no direct financial relationships or agreements with Oncora.; Oncora Medical.

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