Contrary to what many oncologists believe, patients with metastatic breast cancer live longer on average if their chemotherapy is continued after their cancer is brought under control, a new meta-analysis shows.
The new results, presented at the 35th Congress of the European Society for Medical Oncology (ESMO), address an important area of debate in cancer treatment.
"In metastatic breast cancer there is substantial controversy over how long chemotherapy should be continued, in the absence of significant toxicity, after the achievement of disease control," said Dr Alessandra Gennari from Galliera Hospital in Genova, Italy.
In practice, the number of chemotherapy cycles patients are given tends to be based on their response to treatment, how well their symptoms improve, and how much toxicity they experience from the treatment, she said. "Our study addressed the question of whether prolonging chemotherapy after disease response or stabilization is associated with a prolongation of survival and time to progression."
The researchers identified 11 randomized studies that had compared longer and shorter durations of chemotherapy in a total of 2269 patients with metastatic breast cancer.
Overall, longer chemotherapy duration was associated with a 34% reduction in the rate of disease progression, where progression is defined as a significant increase in the size of metastatic lesions and/or the appearance of new metastatic lesions.
The analysis also showed that longer chemotherapy durations were associated with a 9% reduction in the rate of death during the course of the studies.
The results justify a policy of prolonging chemotherapy until disease progression or unacceptable toxicity in metastatic breast cancer, Dr Gennari said. Moreover, these results raise several questions that could be addressed in future trials, the most important being the combination of chemotherapeutic agents and new targeted agents in prolonged treatments.
"The take-home message is that despite what many oncologists believe, prolongation of chemotherapy in metastatic breast cancer after the achievement of disease control affects the history of the disease and, in the presence of acceptable toxicity, may be considered routinely."
"This meta-analysis addresses an extremely important topic," commented Dr Monica Castiglione from University Hospital Geneva, Switzerland. "The duration of first-line chemotherapy in breast cancer is a matter of debate and most oncologists would consider stopping chemotherapy when the disease is controlled, and continuing with endocrine therapy in case of hormone-sensitive disease. For patients with negative hormone receptors this possibility is not available, making the question of duration of chemotherapy even more important."
It would be valuable to have additional data on how continuation of chemotherapy affects different subgroups of patients such as those whose tumors are hormone-receptor positive and negative, Dr Castiglione said.