Retrospective evaluation of the contribution of radiotherapy to survival in breast cancer treatment with propensity score based on stage and subgroup

Abstract

Background: Breast cancer has been a disease in which treatment strategy has changed over time under the influence of different hypotheses and evidence for more than a century. We analyzed the contribution of radiotherapy to disease-free survival and overall survival by classifying according to stage, 1-3 lymph node involvement, and molecular subgroups.

Methods: Following the approval of the Institutional Review Board, records of patients with breast cancer who were admitted to University School of Medicine Departments of Radiation Oncology and Medical Oncology between July 1999 and December 2020 were reviewed. Using data propensity score matching was performed between the groups that did and did not receive radiotherapy using an optimal matching algorithm (optimum, 1:1). Disease-free survival and overall survival after propensity score matching were calculated using the Kaplan-Meier method. Univariate and multivariate Cox regression analysis was used to estimate hazard ratios.

Results: In the radiotherapy and non-radiotherapy groups, disease-free survival was 257.42 ± 5.46 (246.72- 268.13), 208,96 ± 8,15 (192,97-224,94) months respectively, (p = < 0.001), overall survival was 272,46 ± 8,68 (255,43-289,49), 219,05 ± 7,32 (204,70-233,41) months respectively (p = .002). We compared the 19 N1 patient groups who received radiotherapy with the 19 patients who did not receive radiotherapy and calculated the disease-free survival times was 202,21 ± 10,50 (181,62-222,79) and 148,82 ± 24,91 (99,99-197,65) months respectively (p = .011) and overall survival times was 200,85 ± 12,79 (175,77-225,92) and 166,90 ± 20,39 (126,93-206,82) months respectively (p = .055). We examined disease-free survival and overall survival times in both groups according to Luminal A, Luminal B, TNBC, and HER2-enriched subgroups. In the Luminal B subgroup, the disease-free survival duration in the groups receiving radiotherapy and not receiving radiotherapy was 264.83 ± 4.95 (255.13-274.54) and 187.09 ± 11.06 (165.41-208.78) months (p < .001), and overall survival times were 252.29 ± 10.54 (231.62-272.97) and 197.74 ± 9.72 (178.69-216.80) months (p = .001) respectively.

Conclusions: Thanks to studies proving that RT increases long-term survival rates in breast cancer as a result of reducing locoregional recurrence and systemic metastasis rates, it has been understood that the spectrum hypothesis is the hypothesis that most accurately describes breast cancer to date. We found that patients with Luminal B invasive breast cancer benefited significantly more from RT compared to other subgroups.

Keywords: Breast cancer; Luminal B breast cancer; Molecular subtypes radiation therapy; Propensity score; Regional nodal irradiation in breast cancer.

Fig. 1

a Comparison of DFS with radiotherapy treated breast cancer patients in which 189 breast cancer patients who did not receive radiotherapy were balanced with the propensity score by Kaplan-Meier. b Comparison of OS with radiotherapy treated breast cancer patients in which 189 breast cancer patients who did not receive radiotherapy were balanced with the propensity score by Kaplan-Meier

Fig. 2

a, b, c, d. Comparison of DFS times of Stage I, IIA, IIB, IIIA invasive breast cancer patients who did not receive RT with the patient group who received RT using the Kaplan-Meier method after propensity score balancing

Fig. 3

a, b, c, d. Comparison of OS times of Stage I, IIA, IIB, IIIA invasive breast cancer patients who did not receive RT with the patient group who received RT using the Kaplan-Meier method after propensity score balancing

Fig. 4

a Comparison of DFS times between the groups that received RT and those that did not receive RT in our series with invasive breast cancer patients with 1–3 positive lymph nodes using the Kaplan-Meier method. b Comparison of OS times between the groups that received RT and those that did not receive RT in our series with invasive breast cancer patients with 1–3 positive lymph nodes using the Kaplan-Meier method

Fig. 5

a, b, c, d. Comparison of DFS times between the RT and non-RT groups of the Luminal A, Luminal B, Triple Negative, HER2-Enriched subgroup of 189 invasive breast cancer patients in our series using the Kaplan-Meier method

Fig. 6

a, b, c, d. Comparison of OS times between the RT and non-RT groups of the Luminal A, Luminal B, Triple Negative, HER2-Enriched subgroup of 189 invasive breast cancer patients in our series using the Kaplan-Meier method