DNA Repair

Cellular chromosomal DNA is the principal target through which ionising radiation exerts it diverse biological effects. This chapter summarises the relevant DNA damage signalling and repair pathways used by normal and tumour cells in response to irradiation. Strategies for tumour radiosensitisation are reviewed which exploit tumour-specific DNA repair deficiencies or signalling pathway addictions, with a special focus on growth factor signalling, PARP, cancer stem cells, cell cycle checkpoints and DNA replication. This chapter concludes with a discussion of DNA repair-related candidate biomarkers of tumour response which are of crucial importance for implementing precision medicine in radiation oncology.

Concurrent therapy with taxane versus non-taxane containing regimens in locally advanced squamous cell carcinomas of the head and neck (SCCHN): a systematic review

BACKGROUND

Platinum compounds remain the most widely utilized systemic agents in combination with radiation for treating SCCHN in the concurrent setting. Despite recent interest in using taxanes in this setting, there is a lack of randomized clinical trials to support this approach. We conducted a systematic review of published clinical trials of taxane-containing versus standard non-taxane-based regimens used in definitive treatment of SCCHN.

METHODS

Trials published between 1994 and 2012 were identified by an electronic search of public databases (MEDLINE, EMBASE, Cochrane library). All prospective studies were independently identified by two authors for inclusion. Studies were excluded if induction therapy was part of the regimen or if targeted agents were used. Trials using cisplatin- or carboplatin-based regimens and paclitaxel or docetaxel were included. Demographic data, treatment response, locoregional failure free rate (LFFR), progression-free and overall survival (PFS, OS) and toxicities were extracted and analyzed using Comprehensive Meta Analysis software (Version 2.0). Outcome data were pooled and reported as weighted response rate (RR), PFS and OS.

RESULTS

A total of 790 studies were retrieved and 42 studies with 3120 patients were included: 804 patients were treated with taxanes (80% males, median age 57years) and 2316 with non-taxanes (86% males, median age 56years). Progression free survival was not different between the two groups. Weighted median survival was compared from those studies that reported these data; taxanes=36.7months (N=197) versus non-taxanes=25months (N=503), P<0.001. Toxicity (grade 3 and above) was higher in non-taxane containing trials.

CONCLUSIONS

The improved overall survival observed supports the choice of taxane-based regimens in the concurrent setting but may also reflect the predominance of single arm multi-agent phase II trials in the taxane arm. Our findings urge the need for better standardization of taxane-based regimens.