Breast (Feb 2021)

Impact of molecular subtype on 1325 early-stage breast cancer patients homogeneously treated with hypofractionated radiotherapy without boost: Should the indications for radiotherapy be more personalized?

  • Andrei Fodor,
  • Chiara Brombin,
  • Paola Mangili,
  • Fulvio Borroni,
  • Marcella Pasetti,
  • Roberta Tummineri,
  • Flavia Zerbetto,
  • Barbara Longobardi,
  • Lucia Perna,
  • Italo Dell’Oca,
  • Chiara L. Deantoni,
  • Aniko M. Deli,
  • Anna Chiara,
  • Sara Broggi,
  • Roberta Castriconi,
  • Pier Giorgio Esposito,
  • Najla Slim,
  • Paolo Passoni,
  • Simone Baroni,
  • Stefano L. Villa,
  • Paola M.V. Rancoita,
  • Claudio Fiorino,
  • Antonella Del Vecchio,
  • Giampaolo Bianchini,
  • Oreste D. Gentilini,
  • Mariaclelia S. Di Serio,
  • N.G. Di Muzio

Journal volume & issue
Vol. 55
pp. 45 – 54

Abstract

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Aim: We report molecular subtype impact on 1325 early breast cancer (BCa) patients treated with whole breast hypofractionated (WBH) adjuvant forward-planned intensity modulated radiotherapy (F-IMRT) without boost. Methods and materials: From 02/2009-05/2017 1325 patients with pTis-pT3, pNx-N1aM0 BCa who underwent breast conservation surgery were treated with WBHF-IMRT in our institute, to a total dose of 40 Gy/15 fractions, without boost. Median age: 62 (interquartile range-IQR-:51.14–70.53) years. Histology: 8% in situ carcinoma (ISC), 92% invasive tumors. Molecular subtypes (invasive tumors): 49.9% Luminal A, 33.1% Luminal B Her2 negative (−), 6.2% Luminal B Her2 positive (+), 3.6% Hormone Receptor (HR)- Her2+, 7.1% Triple negative (TNBC), and 0.2% HR+. Chemotherapy (CT) was prescribed in 28% of patients, hormonal therapy in 80.3%, monoclonal antibodies (MAb) in 86.8% of Luminal B Her2+ and 97.7% of HR- Her2+ patients. Results: Median follow up was 72.43 (IQR: 44.63–104.13) months. The 5-year Kaplan-Meier estimates of local relapse-free survival (LRFS) was 97.8%, regional-(RRFS) 98.6%, loco-regional- (LRRFS) 96.9%, distant- (DRFS) 96.6%, disease-free survival (DFS) 94.8% and overall survival (OS) 95.5%. Considering molecular subtypes, 5-year LRFS was: 99.8% for Luminal A, 96.7% for Luminal B Her2-, 94.1% for Luminal B Her2+, 87.9% for HR- Her2+, 95.1% for TNBC and 99.1% for in situ carcinoma. Conclusion: While the overall estimated probability of LR within 5 years after WBHF-IMRT without boost is good (2.2%), molecular subtypes have a strong impact, despite MAb therapy in Her2+ patients, and CT for TNBC patients, and could be used as a parameter in deciding the boost prescription.

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