Neoadjuvant radiotherapy combined with capecitabine and sorafenib in patients with advanced KRAS-mutated rectal cancer: A phase I/II trial (SAKK 41/08).

BACKGROUND: KRAS mutation occurs in ∼40% of locally advanced rectal cancers (LARCs). The multitarget tyrosine kinase inhibitor sorafenib has radiosensitising effects and might improve outcomes for standard preoperative chemoradiotherapy in patients with KRAS-mutated LARC. METHODS: Adult patients with KRAS-mutated T3/4 and/or N1/2M0 LARC were included in this phase I/II study. The phase I dose-escalation study of capecitabine plus sorafenib and radiotherapy was followed by a phase II study assessing efficacy and safety. Primary end-points were to: establish the maximum tolerated dose of the regimen in phase I; determine the pathologic complete response (pCR) rate in phase II defined as Dworak regression grade 3 and 4. RESULTS: Fifty-four patients were treated at 18 centres in Switzerland and Hungary; 40 patients were included in the single-arm phase II study. Recommended doses from phase I comprised radiotherapy (45 Gy in 25 fractions over 5 weeks) with capecitabine 825 mg/m2 twice daily × 33 plus sorafenib 400 mg/d. Median daily dose intensity in phase II was radiotherapy 100%, capecitabine 98.6%, and sorafenib 100%. The pCR rate (Dworak 3/4) was 60% (95% CI, 43.3-75.1%) by central independent pathologic review. Sphincter preservation was achieved in 89.5%, R0 resection in 94.7%, and downstaging in 81.6%. The most common grade 3 toxicities during phase II included diarrhoea (15.0%), skin toxicity outside radiotherapy field (12.5%), pain (7.5%), skin toxicity in radiotherapy field, proctitis, fatigue and cardiac ischaemia (each 5%). CONCLUSIONS: Combining sorafenib and standard chemoradiotherapy with capecitabine is highly active in patients with KRAS-mutated LARC with acceptable toxicity and deserves further investigation. www.clinicaltrials.gov: NCT00869570.

Using state variables to model the response of tumour cells to radiation and heat: a novel multi-hit-repair approach.

In order to overcome the limitations of the linear-quadratic model and include synergistic effects of heat and radiation, a novel radiobiological model is proposed. The model is based on a chain of cell populations which are characterized by the number of radiation induced damages (hits). Cells can shift downward along the chain by collecting hits and upward by a repair process. The repair process is governed by a repair probability which depends upon state variables used for a simplistic description of the impact of heat and radiation upon repair proteins. Based on the parameters used, populations up to 4-5 hits are relevant for the calculation of the survival. The model describes intuitively the mathematical behaviour of apoptotic and nonapoptotic cell death. Linear-quadratic-linear behaviour of the logarithmic cell survival, fractionation, and (with one exception) the dose rate dependencies are described correctly. The model covers the time gap dependence of the synergistic cell killing due to combined application of heat and radiation, but further validation of the proposed approach based on experimental data is needed. However, the model offers a work bench for testing different biological concepts of damage induction, repair, and statistical approaches for calculating the variables of state.