We used SEER database to study the influence of PMRT on BCSS in T1-2N1M0 TNBC patients, and conducted subgroup analysis to find out the subgroups that could really benefit from PMRT. The study showed that T1-2N1M0 TNBC patients with three nodes positive could get BCSS improvement from radiotherapy, in which the patients with T2 tumor concomitant with three positive LNs benefit significantly.Our study provided evidence for the management of PMRT for T1-2N1M0 TNBC patients.
Currently, the management of PMRT in T1-2N1M0 breast cancer patients remains controversial. Some studies have confirmed that such patients can benefit from PMRT [13-15], while some studies have drawn the opposite conclusion [16-17].In view of the high invasiveness and early recurrence of TNBC, local radiotherapy is particularly important.A study explored the effect of PMRT on T1-2N1M0 patients according to molecular typing, and the results showed that PMRT can reduce the local recurrence rate of TNBC patients .Gabos et al. also confirmed that PMRT can reduce the local recurrence rate, especially for women with T1-2N0 TNBC subtype .However, as with other subtypes of breast cancer, current recommendations for PMRT in T1-2N1M0 TNBC patients are controversial.
Tumor size and number of axillary lymph node metastases have been proved to be closely related to recurrence and prognosis of breast cancer [20,21].In our study, tumor size and number of positive LNs were associated with BCSS.The effect of PMRT mainly depends on the comprehensive consideration of tumor size and the number of positive LNs , and secondly, it is related to other high-risk factors such as young age and positive vascular tumor thrombus.Accordingly, we not only divided the subgroup analysis according to the clinicopathological characteristics, but also performed subgroup analysis by crossed tumor size with number of positive LNs, which proved that only BCSS in T2 patients with three positive LNs could benefit from PMRT.Zhang et al. studied the effect of PMRT on the survival of T1-4N1-N3M0 patients, and the results showed that there was no difference in BCSS between PMRT and non-PMRT cohort in the T1-2N1 subgroup (P = 0.191) , which was consistent with our results, but they did not conduct further stratified analysis.Another study included 675 T1-2N1M0 TNBC patients and subgroup analysis was performed based on the number of positive lymph nodes. After a median follow-up of 37 months, PMRT was independently associated with increased OS, but there was no improvement in BCSS in any subgroup.The reason why they are inconsistent with our conclusion may be due to their shorter follow-up time and fewer cases.
Radiotherapy can not only eliminate the residual lesions and reduce the recurrence rate of the disease, but also bring a series of complications, such as arm edema, cardiopulmonary radiation damage, pneumonia and so on [25-27].We need to comprehensively consider the benefits and side effects of radiotherapy for patients, identify the subgroups that can really benefit from radiotherapy, and optimize personalized treatment strategies.Our study conducted subgroup analyses based on clinicopathological characteristics and proves that radiotherapy did not provide survival benefit for T1-2 TNBC patients with 1 or 2 positive LNs. Chen et al. also showed that T1-2 breast cancer patients with one or two positive LNs could not benefit from PMRT .It may be that the tumor load and recurrence risk of these patients are low, radiotherapy has limited significance to improve their survival, and will instead bring side effects such as arm edema and cardiopulmonary radiation damage.For these patients, we should carefully choose radiotherapy to avoid overtreatment.
Our study has some limitations. First, we did not study the recurrence rate of patients due to that SEER database lacks recurrence data.Second, HER-2 status in SEER database was only available since 2010, so our follow-up period was relatively short. Third, SEER database does not provide detailed chemo-radiotherapy protocols.