Published in:
Open Access 01-12-2012 | Research
Correlation between egfr expression and accelerated proliferation during radiotherapy of head and neck squamous cell carcinoma
Published in: Radiation Oncology | Issue 1/2012
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Purpose
To investigate the correlation between the expression of Epidermal Growth Factor receptor (EGFr) and the reduction of the effective doubling time (T
D
) during radiotherapy treatment and also to determine the dose per fraction to be taken into account when the overall treatment time (OTT) is reduced in accelerated radiotherapy of head and neck squamous cell carcinoma (HNSCC).
Methods
A survey of the published papers comparing 3-years of local regional control rate (LCR) for a total of 2162 patients treated with conventional and accelerated radiotherapy and with a pretreatment assessment of EGFr expression, was made. Different values of T
D
were obtained by a model incorporating the overall time corrected biologically effective dose (BED) and a 3-year clinical LCR for high and low EGFr groups of patients (HEGFr and LEGFr), respectively. By obtaining the T
D
from the above analysis and the sub-sites’ potential doubling time (T
pot
) from flow cytometry and immunohistochemical methods, we were able to estimate the average T
D
for each sub-site included in the analysis. Moreover, the dose that would be required to offset the modified proliferation occurring in one day (D
prolif
), was estimated.
Results
The averages of T
D
were 77 (27-90)95% days in LEGFr and 8.8 (7.3-11.0)95% days in HEGFr, if an onset of accelerated proliferation T
K
at day 21 was assumed. The correspondent HEGFr sub-sites’ T
D
were 5.9 (6.6), 5.9 (6.6), 4.6 (6.1), 14.3 (12.9) days, with respect to literature immunohistochemical (flow cytometry) data of T
pot
for Oral-Cavity, Oro-pharynx, Hypo-pharynx, and Larynx respectively. The D
prolif
for the HEGFr groups were 0.33 (0.29), 0.33 (0.29), 0.42 (0.31), 0.14 (0.15) Gy/day if α = 0.3 Gy-1 and α/β = 10 Gy were assumed.
Conclusions
A higher expression of the EGFr leads to enhanced proliferation. This study allowed to quantify the extent of the effect which EGFr expression has in terms of reduced T
D
and D
prolif
for each head and neck sub-site.