Previously, the notion that breast cancer arising in young age presents more aggressive pathological features with advanced stage and young age is associated with increased risk of recurrence acted as barriers to perform BCT in young patients 1–3. However, this concern may be unwarranted as previous studies have reported consistently equivalent survival between BCT and mastectomy 6–20. The treatment outcomes of young patients undergoing BCT have also improved, owing to better preoperative imaging work-ups and advances in adjuvant treatments 16,21,22. Based on this evidence, BCT is currently recommended as the first option whenever suitable, even in young patients 23,24.
Despite the evidence showing equivalent survival between BCT and mastectomy, young patients with breast cancer in the United States are increasingly choosing mastectomy instead of BCT 25,26. Several factors may influence this phenomenon, including living conditions that make it difficult to receive conventional radiation therapy and fear of higher risk of LR, leading to subsequent repeated surgery 17.
Patients’ fears are not vague because several studies have reported higher rates of LR in young patients treated with BCT 6,10,12,15,19,20. In this study, patients in the BCT group had a 2.5-fold higher risk of LR than those in the total mastectomy alone group and all 23 patients with isolated LR after BCT eventually underwent salvage mastectomy. The higher cumulative incidence of LR in the BCT group is supported by a recent prospectively observational cohort study (10-year LR rates of 11.7% in the BCT group vs. 4.9% in the mastectomy group, p < 0.001) 20.
Interestingly, the cumulative incidence curve in this study indicates that the risk of LR in the BCT group increased constantly over time, whereas a plateau was reached after 6 years in the total mastectomy alone group. van der Sangen et al also reported similar patterns of LR according to the primary local treatments in young women 10. Due to the continuous increase of LR in the BCT group, the difference in the incidence of LR between BCT and total mastectomy alone group will increase over time.
In this study, approximately one-third of patients with isolated LR after BCT suffered from the development of distant metastasis, even though they underwent aggressive salvage treatments. Anderson et al. also reported that of 342 patients with isolated LR after BCT, 127 (37.1%) experienced distant metastasis 27. Given the poor DMFS after aggressive salvage treatments for isolated LR in the BCT group (44.2% at 5 years), more effective novel systemic treatments should be investigated. More importantly, follow-up strategies should be improved to find suspected benign lesions with the potential to become malignant because risk factors associated with increased risk of LR after BCT were not identified.
Constantly increased incidence of LR and secondary development of distant metastasis in the BCT group can be dealt with by identifying patients with risk factors for LR and monitoring them intensively. Therefore, we investigated risk factors associated with increased risk of LR in the BCT group. However, no clinical or pathological factors were significantly associated with increased LR. Previously, a few researchers investigated to identify risk factors associated with LR after BCT and they did not find any relevant factors 10,21,22. This suggests that decisions for definitive local treatment approaches should not be solely based on clinical and/or pathological factors in young women. Further studies are warranted to examine risk factors at the molecular level.
This study had several limitations including inherent biases due to its retrospective design. The local treatment approach was determined according to the surgeons’ discretion or patients’ preference. Therefore, the distribution of some factors was not balanced. Although we adjusted for all available clinical and pathological factors, other unknown confounders might influence treatment outcomes. In addition, this study analyzes data from two institutions and it is difficult to generalize the results. However, all the details of local and systemic treatments were performed based on standard procedures.
In conclusion, patients in the BCT group exhibited approximately a 2.5-fold increased risk of LR compared with those in the mastectomy alone group. The incidence of LR increases continuously in the BCT group in contrast to the mastectomy alone group. Furthermore, one-third of patients with an isolated LR after BCT experienced distant metastasis despite of aggressive salvage mastectomy followed by systemic treatments. Although BCT had equivalent OS to total mastectomy alone and it can be recognized as the first local treatment option for young women with breast cancer, countermeasures are required to improve quality of life in patients treated with BCT through preservation of breast cosmetic outcomes. To reduce the risk of distant metastasis and to improve prognosis in patients with isolated LR after BCT, more effective systemic treatments should be investigated. Ultimately, it is more important to reduce the incidence of LR by establishing thorough long-term follow-up strategies for improved prognosis, as well as preserving cosmetic outcomes in young women undergoing BCT.