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Johnston S, Puhalla S, Wheatley D, Ring A, Barry P, Holcombe C, Boileau JF, Provencher L, Robidoux A, Rimawi M, McIntosh SA, Shalaby I, Stein RC, Thirlwell M, Dolling D, Morden J, Snowdon C, Perry S, Cornman C, Batten LM, Jeffs LK, Dodson A, Martins V, Modi A, Osborne CK, Pogue-Geile KL, Cheang MCU, Wolmark N, Julian TB, Fisher K, MacKenzie M, Wilcox M, Huang Bartlett C, Koehler M, Dowsett M, Bliss JM, Jacobs SA. Randomized Phase II Study Evaluating Palbociclib in Addition to Letrozole as Neoadjuvant Therapy in Estrogen Receptor-Positive Early Breast Cancer: PALLET Trial. J Clin Oncol 2019; 37:178-189. [PMID: 30523750 DOI: 10.1200/jco.18.01624] [Citation(s) in RCA: 118] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
PURPOSE CDK4/6 inhibitors are used to treat estrogen receptor (ER)-positive metastatic breast cancer (BC) in combination with endocrine therapy. PALLET is a phase II randomized trial that evaluated the effects of combination palbociclib plus letrozole as neoadjuvant therapy. PATIENTS AND METHODS Postmenopausal women with ER-positive primary BC and tumors greater than or equal to 2.0 cm were randomly assigned 3:2:2:2 to letrozole (2.5 mg/d) for 14 weeks (A); letrozole for 2 weeks, then palbociclib plus letrozole to 14 weeks (B); palbociclib for 2 weeks, then palbociclib plus letrozole to 14 weeks (C); or palbociclib plus letrozole for 14 weeks. Palbociclib 125 mg/d was administered orally on a 21-days-on, 7-days-off schedule. Core-cut biopsies were taken at baseline and 2 and 14 weeks. Coprimary end points for letrozole versus palbociclib plus letrozole groups (A v B + C + D) were change in Ki-67 (protein encoded by the MKI67 gene; immunohistochemistry) between baseline and 14 weeks and clinical response (ordinal and ultrasound) after 14 weeks. Complete cell-cycle arrest was defined as Ki-67 less than or equal to 2.7%. Apoptosis was characterized by cleaved poly (ADP-ribose) polymerase. RESULTS Three hundred seven patients were recruited. Clinical response was not significantly different between palbociclib plus letrozole and letrozole groups ( P = .20; complete response + partial response, 54.3% v 49.5%), and progressive disease was 3.2% versus 5.4%, respectively. Median log-fold change in Ki-67 was greater with palbociclib plus letrozole compared with letrozole (-4.1 v -2.2; P < .001) in the 190 evaluable patients (61.9%), corresponding to a geometric mean change of -97.4% versus -88.5%. More patients on palbociclib plus letrozole achieved complete cell-cycle arrest (90% v 59%; P < .001). Median log-fold change (suppression) of cleaved poly (ADP-ribose) polymerase was greater with palbociclib plus letrozole versus letrozole (-0.80 v -0.42; P < .001). More patients had grade 3 or greater toxicity on palbociclib plus letrozole (49.8% v 17.0%; P < .001) mainly because of asymptomatic neutropenia. CONCLUSION Adding palbociclib to letrozole significantly enhanced the suppression of malignant cell proliferation (Ki-67) in primary ER-positive BC, but did not increase the clinical response rate over 14 weeks, which was possibly related to a concurrent reduction in apoptosis.
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Affiliation(s)
- Stephen Johnston
- 1 The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
| | - Shannon Puhalla
- 2 Univeristy of Pittsburgh Medical Center Cancer Center, Pittsburgh, PA
| | - Duncan Wheatley
- 3 Royal Cornwall Hospitals National Health Service Foundation Trust, Treliske, United Kingdom
| | - Alistair Ring
- 1 The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
| | - Peter Barry
- 1 The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
| | - Chris Holcombe
- 4 Royal Liverpool and Broadgreen University Hospitals National Health Service Trust, Liverpool, United Kingdom
| | | | - Louise Provencher
- 6 Centre Hospitalier Université de Quebec-Universite Laval, Quebec City, Quebec, Canada
| | - André Robidoux
- 7 Centre Hospitalier Université de Montréal, Montreal, Quebec, Canada
| | | | | | - Ibrahim Shalaby
- 10 Joe Arrington Cancer Research and Treatment Center, Lubbock, TX
| | - Robert C Stein
- 11 National Institute for Health Research University College London Hospitals Biomedical Research Centre, London, United Kingdom
- 12 University College London Hospitals National Health Service Foundation Trust, London, United Kingdom
| | | | - David Dolling
- 14 The Institute of Cancer Research, London, United Kingdom
| | - James Morden
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Claire Snowdon
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Sophie Perry
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Chester Cornman
- 15 National Surgical Adjuvant Breast and Bowel Project Foundation, Pittsburgh, PA
| | - Leona M Batten
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Lisa K Jeffs
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Andrew Dodson
- 1 The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Vera Martins
- 1 The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
| | - Arjun Modi
- 1 The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
| | | | | | | | - Norman Wolmark
- 15 National Surgical Adjuvant Breast and Bowel Project Foundation, Pittsburgh, PA
| | - Thomas B Julian
- 16 Allegheny Health Network Cancer Institute, Pittsburgh, PA
| | - Kate Fisher
- 17 International Drug Development Institute, Brussels, Belgium
| | | | - Maggie Wilcox
- 18 Independent Cancer Patients Voice, London, United Kingdom
| | | | | | - Mitch Dowsett
- 1 The Royal Marsden National Health Service Foundation Trust, London, United Kingdom
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Judith M Bliss
- 14 The Institute of Cancer Research, London, United Kingdom
| | - Samuel A Jacobs
- 15 National Surgical Adjuvant Breast and Bowel Project Foundation, Pittsburgh, PA
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