Current concepts for chronochemotherapy of cancer

In this article, a survey on the concepts and scientific basis for applying chemotherapy against malignant tumors on a circadian schedule is given. The idea is to give the cytostatic drugs at times of the day when optimal effect on the tumor is achieved, but at the same time causing minimal toxic side effects. Following a brief description of the complexity of cancer tissue, some aspects of the present status of cancer chemotherapy in general are reviewed. Applications of chronobiology in cancer treatment are then surveyed together with possibilities to increase cytostatic doses and reduce side effects. When optimal tumor cell kill is achieved, the next step is to address the circadian aspects of normal organs, including the proliferative behavior of tissues with rapid cell renewal. Finally, the question of how regulatory mechanisms responsible for normal circadian rhythms can be interfered with is addressed. Cancer chronochemotherapy today combined with modern infusional technology is a promising field for improving cancer treatment in general and reducing side effects and is expected to make important progress in the near future.