방사선의학 웹진

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Abstract

Purpose 

To evaluate the effect of adjuvant radiotherapy (RT) after breast conservation surgery in different breast cancer subtypes in a large, randomized clinical trial with long-term follow-up. 

Patients and Methods 

Tumor tissue was collected from 1,003 patients with node-negative, stage I and II breast cancer who were randomly assigned in the Swedish Breast Cancer Group 91 Radiotherapy trial between 1991 and 1997 to breast conservation surgery with or without RT. Systemic adjuvant treatment was sparsely used (8%). Subtyping was performed with immunohistochemistry and in situ hybridization on tissue microarrays for 958 tumors. 

Results 

RT reduced the cumulative incidence of ipsilateral breast tumor recurrence (IBTR) as a first event within 10 years for luminal A-like tumors (19% v 9%; P = .001), luminal B-like tumors (24% v 8%; P < .001), and triple-negative tumors (21% v 6%; P = .08), but not for human epidermal growth factor receptor 2-positive (luminal and nonluminal) tumors (15% v 19%; P = .6); however, evidence of an overall difference in RT effect between subtypes was weak ( P = .21). RT reduced the rate of death from breast cancer (BCD) for triple-negative tumors (hazard ratio, 0.35; P = .06), but not for other subtypes. Death from any cause was not improved by RT in any subtype. A hypothesized clinical low-risk group did not have a low risk of IBTR without RT, and RT reduced the rate of IBTR as a first event after 10 years (20% v 6%; P = .008), but had no effect on BCD or death from any cause. 

Conclusion

Subtype was not predictive of response to RT, although, in our study, human epidermal growth factor receptor 2-positive tumors seemed to be most radioresistant, whereas triple-negative tumors had the largest effect on BCD. The effect of RT in the presumed low-risk luminal A-like tumors was excellent.

Author information​

Sjöström M1, Lundstedt D1, Hartman L1, Holmberg E1, Killander F1, Kovács A1, Malmström P1, Niméus E1, Werner Rönnerman E1, Fernö M1, Karlsson P1.

1 Martin Sjöström, Linda Hartman, Fredrika Killander, Per Malmström, Emma Niméus, and Mårten Fernö, Lund University; Martin Sjöström, Fredrika Killander, Per Malmström, and Emma Niméus, Skåne University Hospital, Lund; Dan Lundstedt, Anikó Kovács, Elisabeth Werner Rönnerman and Per Karlsson, Sahlgrenska University Hospital; Dan Lundstedt, Erik Holmberg, and Per Karlsson, University of Gothenburg; and Erik Holmberg, Regional Cancer Center West, Gothenburg, Sweden.