Why we need to move away from one size fits all approach to breast cancer treatment

Dr Dinesh Shet, Associate Professor at the Father Muller Medical College, Mangalore explains how increasing levels of personalisation helps avoid under or over treatment of breast cancer

Most newly diagnosed breast cancer patients want to get treated fast and are not able to invest time in understanding that treatments can be personalised to suit the exact needs of a breast cancer patient. This can lead to over or under treatment, whereas today we are in the era of personalised medicine which demands a shift away from a one size fits all approach.

To better understand personalisation of treatment one needs to first understand the different stages in which breast cancer treatment is divided. Post the diagnosis, surgery is done to remove the cancerous cells from the body. In a few instances, chemotherapy is offered before the surgery to reduce the size of the tumour, otherwise it is given once the surgery is over. Cycles of radiation are planned in some cases followed by an extended course of hormone therapy if the patient is hormone-receptor positive. Now these are the basic treatment protocols which have been put in place for treatment of breast cancer patients. When personalisation kicks in, there are specific questions which get asked based on size of the tumour and few other parameters. Answers to each of these questions determines whether a treatment protocol is required by a specific patient and if yes which form of treatment should be administered. This level of personalisation helps avoid over treatment of breast cancer. For example, if the size of the tumour is small, a patient can choose to get only a part of the breast removed (lumpectomy) over getting the complete breast removed (a mastectomy). This kind of breast conservation surgery helps the patient to have a better quality of life.

With systemic treatment administration, what started as a one size fits all approach is currently customised according to each breast cancer subtype. Furthermore, treatment should be tailored to the patient by considering anatomic and biological risk. Once surgery is completed, routine IHC testing is done to check the hormone receptor and HER2 status of the patient. In cases where the patient is HER2-positive or triple negative, chemotherapy is the next leg of treatment which could be offered to her. Today certain targeted treatments are also available to treat these subtypes. Trastuzumab has been the gold standard for treating HER2 positive breast cancer patient. It works by targeting the HER2 receptor, preventing cancer growth and has significantly improved survival in patients who have HER2 enriched cancers. However, many patients in advanced stages still relapse despite getting chemotherapy and trastuzumab. Today, we have newer monoclonal antibodies (pertuzumab , ado-trastuzumab emtansine) which have shown promise to further make treatment of HER2+ breast cancer a much efficient process.

Until recently the backbone of therapy against triple negative has been adjuvant chemotherapy. However, new research suggests that even within triple-negative breast cancer, there are many subtypes and we have been seeing encouraging clinical activity from molecularly targeted approaches. Recently, we have seen 3 newly approved targeted therapies for triple negative cancer. PARP inhibitors olaparib and talazoparib which have shown potential in treating ovarian cancer can now be used to treat patients who have germline mutations in their BRCA genes. Most recently the checkpoint inhibitor, atezolizumab in combination with nab-paclitaxel for programmed death-ligand 1 (PD-L1+) has been approved to treat advanced triple negative cancer.

In case the patient is hormone receptor-positive and HER2-negative and also detected in early stage, they may or may not require chemotherapy. The downside of chemotherapy is the side effects that it produces in the patients. There are also multiple studies which have suggested that just 15 per cent to 20 per cent of hormone positive and HER2-negative patients actually benefit from chemotherapy while rest are subjected to over treatment in case of breast cancer. All this further warrant personalisation where the question that needs to be asked is if a specific patient needs chemotherapy or not.

The advancement in science has presented us to an opportunity to get clear answers to this question and avoid any kind of trial and error while administering treatment. There are tests called prognostic tests which helps to let us understand if a particular patient is low risk or high risk for cancer recurrence. Low risk patients can avoid treatment through chemotherapy thus avoiding the side effects that it causes. Today we have a test available in India also called CanAssist Breast, that is specifically validated on Indian patients. It is an affordable test and has been used by many patients. A test like this improves the treatment experience and helps improve the overall quality of life. Without such prognostic tests, the majority of breast cancer patients in India would end up getting unnecessary chemotherapy, despite having good survival outcomes on just oral hormone therapy.

Today personalisation is driving the treatment of breast cancer and making a huge difference in patient outcomes. Survival rates have improved because of the better understanding of the disease. As oncologists our hope is that we keep getting more and more tools in our arsenal to treat every patient effectively.