Background: Conventional WBI after lumpectomy for early-stage breast cancer decreases ipsilateral breast tumor recurrence (IBTR), yielding comparable results to mastectomy. Accelerated PBI appears effective in reducing IBTR by treating only the tumor bed area. As the majority of IBTR occur at or in the vicinity of the tumor bed, we hypothesized that PBI would be as effective as WBI in controlling IBTR. The primary aim of NSABP B-39/RTOG 0413 was to determine if PBI provides equivalent local tumor control post lumpectomy compared to WBI in pts with early-stage breast cancer. The equivalency test was based on a 50% margin of increase in the hazard ratio (HR=1.5). Secondary endpoints included: overall survival (OS), recurrence-free interval (RFI), distant disease-free interval (DDFI), and toxicity. Methods: Eligible pts had lumpectomy with histologically-free margins and 0-3 positive axillary nodes. Pts were stratified by stage, menopausal status, hormone receptor status, and intent to receive chemotherapy and then randomized to PBI or WBI. PBI was 10 fractions of 3.4-3.85 Gy, given twice daily with either brachytherapy or 3D external beam radiation. WBI was 50 Gy in 2 Gy fractions given daily with a sequential boost to the surgical cavity. Follow-up was every 6 mos for 5 yrs and then annually. All analyses were by intent-to-treat. Results: From 3-21-05 to 4-16-13, 4216 pts were randomized: 2107 PBI; 2109 WBI. 61% were postmenopausal; 81% were hormone receptor-positive; 29% intended to receive chemotherapy. Stage distribution was: DCIS, 24%; invasive pN0, 65%; invasive pN1, 10%. As of 7-31-18, median follow-up was 10.2 yrs. There were 161 IBTRs as first events: 90 PBI v 71 WBI (HR 1.22; 90%CI 0.94-1.58). Per protocol-defined margin, to declare PBI and WBI equivalent regarding IBTR risk, the 90% CI for the observed HR had to lie entirely between 0.667 and 1.5. The percent of pts IBTR-free at 10 yrs was 95.2% PBI v 95.9% WBI. A statistically significant difference in the 10-yr RFI rate favored WBI (91.9% PBI v 93.4% WBI; HR 1.32; 95%CI 1.04-1.68; p=0.02). No statistically significant differences existed between PBI and WBI in DDFI (HR 1.31; 95%CI 0.91-1.91; p=0.15), OS (HR 1.10; 95%CI 0.90-1.35; p=0.35), or DFS (HR 1.12; 95%CI 0.98-1.29; p=0.11). Grade 3 toxicity was 9.6% PBI v 7.1% WBI, and grade 4-5 toxicity was 0.5% v 0.3%, respectively. Discussion: PBI did not meet the criteria for equivalence to WBI in controlling IBTR based on the upper limit of the hazard ratio confidence interval. However, the absolute difference in 10-yr rate of IBTR was <1% (4.8% PBI v 4.1% WBI). The risk of an RFI event was statistically significantly higher for PBI compared to WBI, but the absolute difference in 10-yr RFI rate was also small (8.1% PBI v 6.6% WBI). DDFI, OS, and DFS were not statistically different for PBI v WBI. Grade 3-5 toxicities, although low, were more common for PBI than WBI. The trial population was heterogeneous, ranging from Stage 0-2 breast cancer, and outcome by risk categories are being analyzed. Support: U10CA180868, -180822, UG1CA189867. Citation Format: Vicini FA, Cecchini RS, White JR, Julian TB, Arthur DW, Rabinovitch RA, Kuske RR, Parda DS, Ganz PA, Scheier MF, Winter KA, Paik S, Kuerer HM, Vallow LA, Pierce LJ, Mamounas EP, Costantino JP, Bear HD, Germaine I, Gustafson G, Grossheim L, Petersen IA, Hudes RS, Curran, Jr. WJ, Wolmark N. Primary results of NSABP B-39/RTOG 0413 (NRG Oncology): A randomized phase III study of conventional whole breast irradiation (WBI) versus partial breast irradiation (PBI) for women with stage 0, I, or II breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr GS4-04.
Background: Adjuvant trastuzumab (H) reduces cancer recurrence and improves survival in patients (pts) with HER2-amplified or overexpressing (IHC 3+ staining intensity) IBC. Two of the landmark trials that demonstrated the efficacy of H-based eligibility on HER2 testing performed at local site laboratories were found to contain a cohort of pts without amplification or IHC overexpression on tissue submitted for central testing. These HER2-low cohorts appeared to benefit from the addition of H, and efforts at external HER2 testing validation and laboratory explorations did not negate these findings. NSABP B-47 was performed to determine if these findings would be confirmed in a large prospective randomized trial. The primary aim was to determine whether the addition of H to chemotherapy (CT) regimens of AC→WP or TC (choice per investigator discretion) would improve invasive disease-free survival (IDFS). Methods: From 2/8/2011 to 2/10/2015, 3270 women were enrolled with 1630 pts randomly assigned to Arm 1 [TC: docetaxel 75mg/m2, cyclophosphamide 600 mg/m2 every 3 weeks x 6 cycles; or AC→WP: doxorubicin 60 mg/m2 and cyclophosphamide 600 mg/m2 every 2 or 3 weeks x 4 cycles followed by paclitaxel 80 mg/m2 every week x 12], and 1640 pts to Arm 2 [same CT regimens + 12 months of H]. Pts were stratified by IHC score (1+ vs 2+), number of positive nodes (0-3, 4-9, ≥10), hormone receptor status (ER or PgR positive vs both negative), and CT (TC vs AC→WP). Overall 58.5% were ≥50 years, 57% had tumors with IHC 1+, 17.3% were ER- and PgR-, 19.9% were node negative, and 27.4% had ≥4 positive nodes. TC was the intended CT regimen for 44.2%. Results: As of 7/31/2017, the median follow-up time was 46.1 months. We observed 264 IDFS events, which triggered the definitive analysis for the primary endpoint. The addition of H to CT showed a 5-year IDFS of 89.6% compared to 89.2% for CT alone (HR 0.98; 95%CI 0.77-1.26; P=0.90). The findings did not differ by level of HER2 IHC expression, level of lymph node involvement, or hormone receptor status. 5-year point estimates for RFI were 92.0% for CT+H compared to 92.2% for CT alone (HR 0.995; 95%CI 0.75-1.32; P=0.97). 5-year estimates for DRFI were 92.7% for CT+H and 93.5% for CT alone (HR 1.10; 95%CI 0.81-1.49; P=0.55). The addition of H did not change OS significantly with 5-year point estimates of 94.8% in CT+H vs 96.2% in CT alone (HR 1.33; 95%CI 0.91-1.94; P=0.14). 4.3% of women in the CT arm experienced Grade 4 or 5 toxicities compared to 5.0% in CT+H. Conclusion: The addition of H to CT did not demonstrate a reduction in IDFS, RFI, or DRFI in women with non-overexpressing but IHC measurable HER2 IBC. This prospective study did not confirm the retrospective findings in NSABP B-31 or N9831. The threshold of HER2 expression or genetic amplification for H benefit remains unchanged. Support: NCI U10-180868, -180822, -44066, UG1-189867, and Genentech, Inc. Citation Format: Fehrenbacher L, Cecchini RS, Geyer CE, Rastogi P, Costantino JP, Atkins JN, Polikoff J, Boileau J-F, Provencher L, Stokoe C, Moore TD, Robidoux A, Borges V, Albain KS, Swain SM, Paik S, Mamounas EP, Wolmark N. NSABP B-47 (NRG oncology): Phase III randomized trial comparing adjuvant chemotherapy with adriamycin (A) and cyclophosphamide (C) → weekly paclitaxel (WP), or docetaxel (T) and C with or without a year of trastuzumab (H) in women with node-positive or high-risk node-negative invasive breast cancer (IBC) expressing HER2 staining intensity of IHC 1+ or 2+ with negative FISH (HER2-Low IBC) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS1-02.
Background: Preclinical evidence has shown that in xenograft models with estrogen receptor (ER)+/HER2+ breast cancer, signaling through the ER pathway can be enhanced in the presence of anti-HER2 treatment and lead to treatment resistance. Concurrent targeting of ER and HER2 has led to enhanced treatment efficacy and complete tumor disappearance. We hypothesized that targeting ER with endocrine therapy concurrently with chemotherapy plus dual HER2 inhibition will not be antagonistic and can overcome ER-mediated resistance and result in higher pCR as neoadjuvant treatment of ER+/HER2+ breast cancer. NRG Oncology/NSABP B-52 is a phase III, multicenter, randomized neoadjuvant therapy trial designed to determine whether the addition of estrogen deprivation to neoadjuvant therapy consisting of docetaxel, carboplatin, trastuzumab, and pertuzumab (TCHP+Est-Dep) yields a greater rate of pCR (breast and nodes) than TCHP alone. Methods: A total of 315 patients (pts) were randomly assigned between January 15, 2014 and March 17, 2016 to receive neoadjuvant therapy consisting of TCHP with or without estrogen deprivation therapy. Pts with locally advanced, hormone receptor-positive, HER2+ invasive breast cancer with no evidence of metastatic disease were eligible. Premenopausal women randomized to estrogen deprivation therapy received ovarian function suppression with goserelin (LHRH agonist) or equivalent plus an aromatase inhibitor (AI). Postmenopausal women received an AI. The determination of pCR (breast and nodes) was defined as the absence of any invasive component in the resected breast specimen and all resected lymph nodes following completion of neoadjuvant therapy. Following the intent-to-treat principle, the difference between the rates of pCR (breast and nodes) was tested using the binomial test for the difference between two proportions. The study was designed to have a statistical power of 80% to detect an increase in the pCR rate from 45% in the TCHP alone group to 60% in the TCHP+Est-Dep group. Results: The groups were balanced, with 57% clinically node positive and 50% premenopausal. Assessments for pCR were available from 308 of 315 randomized patients. The pCR (breast and nodes) for TCHP alone and TCHP+Est-Dep were 40.9% and 46.1%, respectively (p=0.36). The pCR (breast) were 44.2% and 47.4%, respectively (p=0.57). Grade 3/4 toxicities included diarrhea (23%, <1% vs 21%,0%) vomiting (8%, <1% vs 5%, 0%), and febrile neutropenia (5%, <1% vs 7%,1%) for TCHP vs TCHP plus estrogen deprivation. Conclusion: The addition of estrogen deprivation to neoadjuvant chemotherapy is not antagonistic. It improved pCR rates numerically, but the improvement was not statistically significant. The combination did not increase toxicity and may be a reasonable approach since all patients will receive endocrine therapy after neoadjuvant therapy. Correlative science studies including evaluation of residual cancer burden (RCB) and long-term outcomes will help define the role of estrogen deprivation in the treatment of HER2+ early breast cancer. Support: U10CA180868, -180822; UG1CA189867, Genentech. Citation Format: Rimawi MF, Cecchini RS, Rastogi P, Geyer, Jr CE, Fehrenbacher L, Stella PJ, Dayao Z, Rabinovitch R, Dyar SH, Flynn PJ, Baez-Diaz L, Paik S, Swain SM, Mamounas EP, Osborne CK, Wolmark N. A phase III trial evaluating pCR in patients with HR+, HER2-positive breast cancer treated with neoadjuvant docetaxel, carboplatin, trastuzumab, and pertuzumab (TCHP) +/- estrogen deprivation: NRG Oncology/NSABP B-52 [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S3-06.
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