Despite significant progress over the past decade, the loco-regional control and survival rates of 50-60% for patients with locally-advanced oropharyngeal (OP) head and neck squamous cell carcinomas (HNSCC) with radiotherapy (RT) alone leave room for improvement  considering the limited options for salvage treatment after failure of the initial therapy. Current standards of RT have been re-defined by the RTOG- 9003 trial, comparing standard fractionation (SF) of 70 Gy, delivered in 35 fractions over 47 treatment days, with three different altered fractionation RT regimens; of the latter, both pure hyperfractination (HFX) and accelerated fractionation with concomitant boost (AFX CB) produced superior outcomes . This RTOG trial produced important clinical evidence for the benefit of radiation dose intensification and shortening of the overall treatment time which had been demonstrated by other trial results and institutional experiences [2, 3, 21, 23, 24, 38, 40]. However, most approaches of dose intensification to the gross tumor volume (GTV) by three-dimensional conformal radiotherapy (3D-CRT) techniques require twice-daily irradiation. This has the disadvantages of reduced biological effectiveness of the cumulative nominal daily doses, and includes the need for repeated irradiation of normal and other target tissues overlying gross tumor.
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