Is breast-conserving surgery after neoadjuvant therapy safe for T3–T4 breast cancer?

For decades, the standard approach to treating large, aggressive breast tumors was to remove the entire breast. This surgery, known as a mastectomy, was considered the safest way to ensure no cancer cells were left behind, especially when the tumor was too big to be removed while keeping the breast intact. However, a shift in medical strategy has occurred over the last few decades. Doctors began using powerful drug treatments before surgery to shrink tumors, a method called neoadjuvant therapy. The goal was not only to make the cancer smaller but also to see how well a specific patient's body responded to the medicine. If the drugs worked well, it opened the door for a less invasive surgery called breast-conserving surgery, where only the tumor and a small margin of healthy tissue are removed, leaving the rest of the breast in place. While this approach has become common for smaller tumors, a lingering question remained for those with very large, advanced cancers: is it truly safe to save the breast in these severe cases, or does the risk of the cancer returning remain too high?

Researchers at the University of São Paulo set out to answer this question by looking back at the medical records of hundreds of women who faced this exact dilemma. They focused on 414 women diagnosed with locally advanced breast cancer, specifically tumors that were either larger than five centimeters or had spread to the chest wall or skin. Every woman in this group received drug therapy first to shrink the cancer, and then underwent surgery. The researchers divided the group into two categories based on the final operation: those who had the entire breast removed and those who had only the tumor removed. They then followed these women for many years to see who survived and how the cancer behaved in each group.

The results of this long-term observation were striking. The women who were able to undergo breast-conserving surgery after their tumors shrank with medication had significantly better survival rates than those who had their entire breasts removed. Eight years after treatment, nearly 79 percent of the women who kept their breasts were still alive, compared to only 60 percent of the women who had mastectomies. This difference was not just a small fluctuation; it was a clear, statistically significant gap that held true even after the researchers accounted for other factors that influence survival, such as age, body weight, and the specific type of cancer. In fact, the study found that having a mastectomy was independently linked to a higher risk of death, suggesting that for these carefully selected patients, the less invasive surgery was not just a cosmetic choice but a life-extending one.

The data also revealed why this difference might exist. The women who ended up with breast-conserving surgery were more likely to have had a complete response to the drug therapy, meaning the cancer cells were completely gone by the time of surgery. They also had lower rates of the cancer returning to the same spot compared to the mastectomy group. While local recurrence happened in about a quarter of the women who kept their breasts, it occurred in nearly half of the women who had their breasts removed. This suggests that the women whose tumors responded best to the initial drugs were the ones who could safely undergo the smaller surgery, and their bodies were better equipped to handle the disease overall. The study also identified that being older, having a higher body mass index, and having a more advanced stage of cancer at the start were all factors that made survival harder, regardless of the surgery type.

Ultimately, this research challenges the old assumption that large, advanced breast tumors must always be treated with the most radical surgery. It suggests that when the cancer responds well to medication, saving the breast is not only possible but may be the safer path for survival. The findings support a more personalized approach where the decision on surgery is guided by how the tumor reacts to treatment, rather than by the size of the tumor alone. For the women in this study, the ability to keep their breast was a sign that their cancer had been tamed by the drugs, leading to a better outcome than the traditional, more extensive surgery could provide.