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.

Development of the Breast Surgical Oncology Fellowship in the United States

The surgical treatment of breast cancer has rapidly evolved over the past 50 years, progressing from Halsted's radical mastectomy to a public campaign of surgical options, aesthetic reconstruction, and patient empowerment. Sparked by the research of Dr. Bernard Fisher and the first National Surgical Adjuvant Breast and Bowel Project trial in 1971, the field of breast surgery underwent significant growth over the next several decades, enabling general surgeons to limit their practices to the breast. High surgical volumes eventually led to the development of the first formal breast surgical oncology fellowship in a large community-based hospital at Baylor University Medical Center in 1982. The establishment of the American Society of Breast Surgeons, as well as several landmark clinical trials and public campaign efforts, further contributed to the advancement of breast surgery. In 2003, the Society of Surgical Oncology (SSO), in partnership with the American Society of Breast Surgeons and the American Society of Breast Disease, approved its first fellowship training program in breast surgical oncology. Since that time, the number of American fellowship programs has increased to approximately 60 programs, focusing not only on training in breast surgery, but also in medical oncology, radiation oncology, pathology, breast imaging, and plastic and reconstructive surgery. This article focuses on the happenings in the United States that led to the transition of breast surgery from a subset of general surgery to its own specialized field.

A Short History of Bernard Fisher's Contributions to Randomized Clinical Trials

Dr. Bernard Fisher (1918-2019) was an early proponent of evidence-based medicine using the mechanism of prospective, multicenter, randomized clinical trials to test biological and clinical hypotheses. In this article, I trace how his early scientific work in striving to understand the nature of cancer metastasis through animal experiments led to a new, testable, clinical hypothesis: that surgery to remove only the tumor and a small amount of tissue around it was as effective as the more disfiguring operations that were then the standard treatment. Fisher's work with the National Surgical Adjuvant Breast and Bowel Project (NSABP) using large, randomized clinical trials to demonstrate the veracity of this hypothesis led to a new paradigm in which the emphasis was placed on how systemic therapies used at an early stage of disease could effectively eradicate breast cancer for many patients. This new therapeutic approach led to the successful development of new treatments, many of which are widely used today. Ultimately, the new paradigm led to successfully preventing breast cancer in women who were at high risk for the disease but who had not yet been diagnosed with the disease. Throughout his entire career, Fisher championed the use of large prospective, randomized clinical trials despite criticism from many in the medical community who strongly criticized his use of randomization as a mechanism for testing clinical hypotheses. The approach he and the NSABP employed is still considered to be the highest standard of evidence in conducting clinical studies.

Epidemiology of De Novo Metastatic Breast Cancer

Most cases of metastatic breast cancer (MBC) arise as a recurrence of a previously treated early breast cancer. Distinct from recurrent MBC is de novo MBC (dnMBC), which describes patients who present with distant sites of disease at initial diagnosis and is reviewed here. dnMBC represents approximately 3% to 6% of new breast cancer diagnoses in high-income countries. This incidence has not declined despite decades of widespread use of population-based mammography screening. Overrepresentation of both biologically aggressive tumors and patients negatively impacted by social determinants of health are characteristics of dnMBC. Survival has generally been superior for patients with dnMBC compared with those with recurrent MBC, although it is similar to that for patients with recurrent MBC with long disease-free intervals. Subgroups of patients with dnMBC who experience prolonged survival include those with human epidermal growth factor receptor-2-positive disease or hormone receptor-positive bone-only disease. Opportunities to decrease dnMBC presentation may include novel screening modalities suited for biologically aggressive breast tumors and improved access to health care. Recognizing that there will remain some women diagnosed with dnMBC, refining our ability to identify those likely to be long-term survivors could allow for appropriate escalation or de-escalation of care. Finally, evaluation of tumor genomics in robust sample sizes has the potential to advance our knowledge of the biology of dnMBC as an entity distinct from recurrent MBC.

Local and regional therapy considerations after preoperative therapy in patients with breast cancer

PURPOSE OF REVIEW

The starting point of neoadjuvant therapy was to use preoperative chemotherapy in order to provide surgeons and radiotherapists with the possibility of local treatment in patients with locally advanced, primary inoperable or inflammatory disease. Since then, this treatment approach has dramatically evolved and is now a standard of care in patients with high-risk early breast cancer.

RECENT FINDINGS

The role of surgery after neoadjuvant therapy is to remove residual disease in the breast and or in the lymph nodes and to provide further treatment possibilities according to pathohistologic findings at surgery.

SUMMARY

Innovative medical treatments are now being used for neoadjuvant treatment in order to reduce the extent of locoregional surgery in the breast and the axilla and also to adjust further medical treatment after neoadjuvant therapy and surgery.