Effect of postmastectomy radiotherapy on pT1-2N1 breast cancer patients with different molecular subtypes

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

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.

Radiation therapy of breast cancer in the Nahe Breast Center: first results of an analysis in the context of health services research

BACKGROUND

The first evaluation of radiotherapy results in patients with breast cancer treated as part of a multimodal oncologic therapy in the Nahe Breast Center is presented. Analysis of the results was performed using an in-practice registry.

PATIENTS AND METHODS

From September 2016 to December 2017, 138 patients (median age 62.5 years; range 36-94 years) with breast cancer (right side, n = 67; left side, n = 71) received adjuvant radiation therapy. Of these, 103 patients received gyneco-oncologic care at the Nahe Breast Center, and 35 were referred from outside breast centers. The distribution into stages was as follows: stage I, n = 48; stage II, n = 68; stage III, n = 19; stage IV, n = 3. Neoadjuvant chemotherapy was given to 19 and adjuvant chemotherapy to 50 patients. Endocrine treatment was given to 120 patients. Both 3D conformal (n = 103) and intensity-modulated (n = 35) radiotherapy were performed with a modern linear accelerator.

RESULTS

With a median follow-up of 60 months (1-67), local recurrence occurred in 4/138 (2.9%) and distant metastasis in 8/138 (5.8%) patients; 7/138 (5.1%) patients died of their tumors during the follow-up period. The actuarial 5‑year local recurrence-free survival of all patients was 97.1%, and the actuarial 5‑year overall survival of all patients was 94.9%. We observed no grade 3 or 4 radiogenic side effects.

CONCLUSION

The results of radiotherapy for breast carcinoma at the Nahe Breast Center are comparable to published national and international results. In particular, the local recurrence rates in our study, determined absolutely and actuarially, are excellent, and demonstrate the usefulness of radiotherapy.

Influence of age as a continuous variable on the prognosis of patients with pT1-2N1 breast cancer

PURPOSE

To assess the influence of age as a continuous variable on the prognosis of pT1-2N1 breast cancer and examine its decision-making value for postmastectomy radiotherapy (PMRT).

METHODS

We retrospectively evaluated 5438 patients with pT1-2N1 breast cancer after mastectomy in 11 hospitals. A multivariable Cox proportional hazards regression model with penalized splines was used to examine the relationship between age and oncologic outcomes.

RESULTS

The median follow-up was 67.0 months. After adjustments for confounding characteristics, nonsignificant downward trend in locoregional recurrence (LRR) risk was observed with increasing age (P-non-linear association = 0.640; P-linear association = 0.078). A significant non-linear association was found between age and disease-free survival (DFS) and overall survival (OS) (P-non-linear association <0.05; P-linear association >0.05, respectively). The DFS and OS exhibited U-shaped relationships, with the hazard ratios (HRs), reaching a nadir at 50 years old. A decreased risk of LRR with PMRT vs. no PMRT (HR = 0.304, 95% CI: 0.204-0.454) was maintained in all ages. The HR of PMRT vs. no PMRT for DFS and OS gradually increased with age. In patients ≤50 years old, PMRT was independently associated with favorable LRR, DFS, and OS, all P < 0.05). In patients >50 years old, PMRT was independently associated with reduced LRR (P = 0.004), but had no effect on DFS or OS.

CONCLUSIONS

Age was an independent prognostic factor for pT1-2N1 breast cancer; PMRT provided survival benefits for patients ≤50 years old, but not for patients >50 years old.