One third of patients diagnosed with HER2 breast cancer can be successfully treated without chemotherapy, according to an international clinical trial led from Spain presented at the American Society for Medical Oncology (ASCO) congress held in In Chicago.
The study is part of the trend in oncology to increasingly take into account the quality of life of people with cancer without compromising the chances of long-term survival, a field in which breast cancer is pioneering.
“The goal of survival is not negotiable. A higher quality of life at the cost of reduced efficacy would not be acceptable. But now we have therapies that we did not have a few years ago and that in some cases can be alternatives to chemotherapy”, says Javier Cortés, director of the International Breast Cancer Center in Barcelona and Madrid, who yesterday presented the results of the study at the congress of Chicago.
The study has focused on HER2 tumors, which represent between 15% and 20% of all cases of breast cancer and which are characterized by the fact that the tumor cells have a large number of HER2 receptors. When these receptors are activated, they send the cell nucleus the order to multiply, which favors the growth of tumors. But today there are antibodies that block HER2 receptors and thus stop the proliferation of tumor cells.
These antibodies were introduced as an adjunct to chemotherapy and are now routinely used in the treatment of HER2 cancers. Its high efficacy “led us to think that perhaps we are administering more treatment than would be necessary to some patients, and that perhaps in some cases we could achieve the same efficacy without chemotherapy,” says Antonio Llombart-Cussac, head of the oncology service. doctor at the Arnau de Vilanova Hospital in Valencia, who has directed the investigation together with Javier Cortés.
In the clinical trial, which began in 2017, 356 patients from seven European countries have participated. All had been diagnosed before metastasis had occurred and therefore at a time when the cancer was potentially curable.
Twenty percent were treated with chemotherapy before and after surgery as indicated by clinical practice guidelines for HER2 breast cancer. The other 80% were treated with two HER2 antibodies but no chemotherapy, with the prospect of adding chemotherapy later if the antibodies were not sufficient. In cases where their tumors had hormone receptors, they also received hormone therapy. This clinical trial design was chosen to be able to compare outcomes between patients treated with antibodies and those treated with chemotherapy alone.
Among the 285 treated with antibodies, 227 (80%) initially responded to treatment, as confirmed by PET imaging. Later, when performing the surgery, it was observed that tumor cells remained in 141 patients (49% of all those treated with antibodies), so they were administered chemotherapy. The other 86 (30%) had a complete pathologic response, meaning no trace of tumor remained after antibody treatment.
After three years of follow-up, no metastases have been recorded among patients treated without chemotherapy, according to the results presented at the Chicago congress. Only one has suffered a localized recurrence, which has been treated and has a good prognosis.
65% of patients treated with chemotherapy alone have experienced serious adverse events during treatment, compared to 13% of patients treated without chemotherapy.
“These results show that we can start the treatment of all HER2 patients without chemotherapy, and add it later only in cases where it is necessary, without affecting their prospects for a cureâ€, says Javier Cortés.
This trend to de-escalate chemotherapy – the expression used by oncologists – has already started with HR /HER2 breast cancers, which represent around 70% of all cases of the disease. In patients in whom the prognosis at the time of diagnosis is good, treatment is now limited in many cases to surgery and hormonal therapy.
Regarding triple-negative breast cancer, which represents around 15% of cases, there are ongoing projects to assess whether immunotherapies and innovative ADC drugs make it possible to reduce the use of chemotherapy in the future, reports Cortés.
Other tumors in which chemotherapy de-escalation treatments are being investigated include, among others, lung, head and neck, and melanoma.
“As more treatment options become available, we can aim to increase efficacy and reduce side effects on an individual basis for each patient,†says the oncologist. “Chemotherapy is still necessary in many cases, but there are others where we can reduce it and even eliminate it.”
Transparency statement: La Vanguardia attends the American Society of Clinical Oncology congress in Chicago invited by Novartis
