Locoregional Recurrence of Breast Cancer

Having replaced lung cancer as the most common cancer globally, breast cancer today represent 1 in 8 cancer cases and a total of 2.3 million new cases in both sexes .

It Represents a quarter of all cancer cases in females, and it was the most commonly diagnosed cancer in women in 2020 , its burden has been growing in many parts of the world, particularly in transitioning countries . An estimated 685,000 women died from breast cancer in 2020, corresponding to 16% or 1 in every 6 cancer deaths in women.

In Egypt, it constitutes 33% of female cancer cases and more than 22,000 new cases diagnosed each year .

Treatment Strategies include Surgery, Chemotherapy ,Radiotherapy, Endocrinal (Hormonal) Therapy \& Biological Therapy , according to stages and molecular subtypes

A majority of breast cancer patients undergoing surgical excision will receive radiotherapy as a local treatment, which will reduce local and regional recurrence (LRR), further elevating survival.

Slightly over 50% of women with early-stage breast cancer remain disease free for at least 10 years, but recurrences continue to occur long after primary diagnosis.

Several multigene molecular assays are currently under investigation to accurately identify patients with unfavorable prognosis .However, considering the lack of cost-effectiveness of these detection approaches, they are not easily applied on a large scale, especially in less developed countries. In contrast, immunohistochemical (IHC) staining profile is a cost-effective and popular surrogate.Based on IHC staining profiles, St Gallen International Breast Cancer Conference in 2013 classified breast cancer into four subtypes: Luminal A, Luminal B, HER2-positive, and triple-negative breast cancer (TNBC). This classification system has been widely used in clinical decision-making for the systemic management of breast cancer.

This classification depend on presence or absence of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor (Her2) and Ki 67 as luminal A is positive for ER \&PR, negative for Her2 with low Ki67, luminal B is ER positive, PR \& Her2 may be positive or negative but with high Ki67, Her2 is ER \&PR negative with Her2 positive, Triple negative (TN) is ER \& PR \& Her2 negative with high Ki67, with no benefit of hormonal or anti Her2 therapy.

Few studies done showed that Luminal A and B subtypes are generally associated with lower risks of regional nodal involvement at diagnosis and tend to have a more indolent evolution as compared with the other subtypes. Several retrospective studies have shown lower rates of LRR in luminal A as compared with the other subtypes, among whom luminal B is considered as intermediate risk with rates ranging between 1.5 and 8.7% and peak incidence during the first 5 years .

For HER2-positive patients, there are two distinct periods. In studies in which patients were not treated with HER2-targeted therapy, LRR rates ranged between 4 and 15% .

More recently, trastuzumab have positively modified the natural course of this BC subtype. patients with HER2-positive tumors who underwent surgery and received trastuzumab had LRR rate of 1.7%. This finding was supported by many studies, who also showed that trastuzumab treatment resulted in a decrease in LRR by 50%. This has also been observed in small tumors HER2-positive BC study after trastuzumab .

The TNG subtype was associated with increased LRR rates, after breast conservation and mastectomy (3-17%). Moreover, after the diagnosis of an LRR, the TNG subtype is associated with a high incidence of distant metastases .