Chemotherapy

Post-operative (adjuvant) chemotherapy

In most cases, chemotherapy is started after surgery (preoperative chemotherapy). It is indicated in certain invasive cancers, where chemotherapy has been shown to decrease the risk of recurrence and increase the chances of cure. These risks are calculated according to the type of tumor, its identity card and the patient.

The decision to use chemotherapy is made on a case-by-case basis by a team composed of medical oncologists (chemotherapists), surgeons, radiotherapists, radiologists and anatomopathologists during a Multidisciplinary Consultation Meeting (MCM or Staff).

Today, there is a decrease in the indications for chemotherapy in breast cancer. It is indicated in about 40% of cases of invasive cancer. It is prescribed in three cases:

• Some hormone-sensitive but “aggressive” cancers; in this first case, chemotherapy is discussed in addition to hormone therapy.
• Triple-negative” cancers (about 10% of invasive breast cancers), i.e., without hormone receptors or HER2 overexpression;
• And cancers with HER2 overexpression (about 10% of invasive breast cancers).

Indications for postoperative (adjuvant) chemotherapy

Hormone-sensitive cancers

Almost all hormone-sensitive invasive cancers will have postoperative hormone therapy. For some, there is also a benefit to adding chemotherapy to the hormone therapy. There are measures that can be used to determine whether chemotherapy will provide additional benefit:

• It can be measured under the microscope: the size of the tumor, its grade (1-2-3), and lymph node involvement are taken into account. These measurements are made once the tumor is removed, by an anatomopathologist: they are called “morphological” parameters.
• Then there are the biological parameters: tumor proliferation, hormone receptor levels (measured from 0 to 100%: at 100%, the tumor is highly hormone-sensitive, which indicates a better prognosis) and HER2 protein overexpression.
• In cases where there is a doubt about the value of chemotherapy, more advanced tests are used, which analyze certain genes in the tumor. These “genomic” tests are a further step in the sophistication of tumor analysis: instead of looking at the tumor under a microscope, the genetic material in the nucleus of the tumor cells is analyzed. These genomic tests are numerous, for example Oncotype DX, Mammaprint, Prosigna, EndoPredict… Genomic signature is a common practice since the 2010s. The results are provided to the team 8 to 15 days later. If the test gives a low recurrence risk score, then chemotherapy can be avoided.

Triple negative cancers

These are cancers that do not express hormone receptors or HER2 (Human Epidermal growth factor Receptor 2). They represent about 10% of invasive breast cancers. The prescription of chemotherapy has been shown to improve survival in triple-negative cancers larger than 5 mm.

HER2 positive cancers

These cancers overexpress the HER2 (Human Epidermal growth factor Receptor 2) gene. They represent about 10 to 15% of invasive breast cancers. Until 2004, they were considered to have a poor prognosis. Anti-HER2 drugs were then introduced, including trastuzumab (marketed as Herceptin) and pertuzumab (marketed as Perjeta), followed by trastuzumab emtansine (Kadcyla). Like hormone therapy, these are “targeted therapies” because they have a biological target, in this case the HER2 protein. These treatments represent a considerable advance because they considerably increase cure rates. The particularity of this treatment is that it must be combined with chemotherapy, as the latter potentiates the targeted treatment.

Neoadjuvant chemotherapy

Neoadjuvant chemotherapy was originally proposed to reduce the size of large tumors to allow for conservative treatment. If the tumor shrinks under chemotherapy, instead of performing a mastectomy, only the tumor area can be removed with the breast remaining, with a cure rate identical to that of a mastectomy.

Neoadjuvant chemotherapy is also considered in another case: for certain types of cancers, in particular inflammatory, triple-negative or HER2-positive, it is increasingly common to propose chemotherapy before surgery.