High-dose hyperfractionated accelerated radiotherapy in non-small cell lung cancer.

The observation that improved local tumour control also results in increased survival rates, even in a disease such as non-small cell lung cancer (NSCLC), has fuelled the interest in strategies aimed at local tumour eradication. It has been demonstrated that a clear dose-response relationship exists for radiotherapy, i.e. higher doses of radiation lead to increased local tumour control. However, prolongation of the overall treatment time beyond 4-5 weeks renders radiotherapy less effective because of increased proliferation of tumour cells. It is therefore of interest to deliver as high doses as possible in short overall treatment times. An extreme example of this strategy is stereotactic body radiotherapy (SBRT), where a few large radiation doses, equalling very high biological doses, delivered in a short overall treatment time has resulted in at least 90 % tumour control in stage I NSCLC. However, when large volumes or critical normal structures such as the main bronchi are in the high-dose radiation volumes, more extensive fractionation schedules have been used, such as 70 Gy in 35 daily fractions of 2 Gy. As the overall treatment time than exceeds 4-5 weeks, hyperfractionated radiotherapy schedules have been introduced, which all delivered 2-3 relatively small fractions per day to total doses that are similar to the so-called standard regimen. Several randomized phase III trials and a meta-analysis based on individual patient data have demonstrated a superior 5-year survival with this strategy, without increased side effects. Our group has also shown that individualised hyperfractionated accelerated radiotherapy (INDAR) makes treatment with curative intent even in patients with large tumour volumes possible with few important side effects. Early results of INDAR with concurrent chemotherapy or with cetuximab are promising.