Improved Normal Tissue Sparing in Head and Neck Radiotherapy Using Biological Cost Function Based-IMRT

Abstract

Intensity-modulated radiotherapy (IMRT) has reduced the impact of acute and late toxicities associated with head and neck radiotherapy. Treatment planning system (TPS) advances in biological cost function based optimization (BBO) and improved segmentation techniques have increased organ at risk (OAR) sparing compared to conventional dose-based optimization (DBO). A planning study was undertaken to compare OAR avoidance in DBO and BBO treatment planning. Simultaneous integrated boost treatment plans were produced for 10 head and neck patients using both planning systems. Plans were compared for tar get coverage and OAR avoidance. Comparisons were made using the BBO TPS Monte Carlo dose engine to eliminate differences due to inherent algorithms.Target coverage (V95%) was maintained for both solutions. BBO produced lower OAR doses, with statistically significant improvement to left (12.3%, p 5 0.005) and right parotid mean dose (16.9%, p 5 0.004), larynx V50 Gy (71.0%, p 5 0.005), spinal cord (21.9%, p , 0.001) and brain stem dose maximums (31.5%, p 5 0.002). This study observed improved OAR avoidance with BBO planning. Further investigations will be undertaken to review any clinical benefit of this improved planned dosimetry.

Direct use of multivariable normal tissue complication probability models in treatment plan optimisation for individualised head and neck cancer radiotherapy produces clinically acceptable treatment plans

“…The emergence of the gEUD-based objectives for planning optimisation was a first practical step in the transition of dose-volume-based to model-based optimisations. Several research groups demonstrated that gEUD criteria for normal tissues improved critical structure sparing in HNC cases, compared to physical dose-volume-based objectives [12,14,15]. However, gEUD objectives remain in the dose domain and do not necessarily correlate linearly with clinical outcome, which is in contrast to direct application of NTCP-models in the optimisation process.…”

“…Currently, the gEUD formalism is the most frequently used biologically motivated OF in commercial treatment planning systems (TPS) [11]. Several studies demonstrated successful application of gEUDbased OFs for normal tissue sparing [12][13][14][15][16][17][18]. However, application of gEUD-based OFs to the PTVs can result in undesirable hotspots when no additional gEUD-based objective with a positive volume effect parameter to control the overdosage is added [17].…”

Estimation of the effects of normal tissue sparing using equivalent uniform dose-based optimization

“…The same has been demonstrated by several authors. [ 6 7 8 ] Further, EUD-based cost functions are insensitive to hot spots inside the tumor which leads to highly inhomogeneous target dose, if used alone. [ 2 ] In clinical practice, a physical cost function (DV-based) is added with EUD cost function to achieve homogenous dose distribution inside the tumor by accepting higher OAR dose.…”

Clinical and dosimetric risk stratification for patients at high-risk of feeding tube use during definitive IMRT for head and neck cancer

“…Treatment was delivered five fractions per week over six to seven weeks. Target coverage and dose volume constraint goals are listed in Table 1 [25]. Medically fit patients were considered for concurrent systemic therapy based on disease stage and comorbidities.…”