Evaluation of Modern Radiotherapy Techniques in Treatment of Cancer Prostate

Abstract

Purpose: The aim of this study is to establish a procedure to allow evaluating physically and biologically a 3DCRT, IMRT and RapidArc treatment plans in radiotherapy of cancer prostate.

Material and Methods: In an attempt to launch a model to evaluate treatment plans in advanced radiotherapy, we have studied some common evaluation indices. In physical evaluation, we studied dose homogeneity indices (MHI and HI), target coverage and conformity indices (PITV, TCI, CI, and CN), dose gradient (GI and GM) and an index for overall plan quality factor (QF). In Biological evaluation we studied TCP and NTCP for tumor and critical structures, and P+ for free complication tumor control. Evaluation has been performed for six plans, four RapidArc plans, one IMRT and one 3DCRT plan.

Results: In physical evaluation, HI and MHI values indicated that 3DCRT has the best dose homogeneity. Calculated values of PITV, TCI, CI, and CN showed that both IMRT and RapidArc produce better dose conformity than 3DCRT. GM and GI values displayed that, RapidArc gives better dose gradient than IMRT and 3DCRT. So, none of these physical evaluation indices allowed ranking the plans. Calculating QF index allowed ranking the plans. The QF value of RapidArc plans gave the highest values. In Biological evaluation, in spite of the clear difference in NTCP values of OARs, the TCP values were almost equal. So P+ was calculated to integrate both of TCP and NTCP in one index. RapidArc plans with avoidance of both bladder and rectum had the highest P+ values.

Conclusion: Physical evaluation of treatment plan can't be achieved by calculating dose homogeneity, dose conformity, or dose gradient alone. This issue can be solved by calculating treatment plan quality factor. In biological evaluation of treatment plan, outcome can be estimated by calculating P+ rather than calculating TCP and NTCP alone.