Three-dimensional conformal radiation therapy: evidence-based treatment of prostate cancer

A randomized trial (Irish clinical oncology research group 97-01) comparing short versus protracted neoadjuvant hormonal therapy before radiotherapy for localized prostate cancer

PURPOSE

To examine the long-term outcomes of a randomized trial comparing short (4 months; Arm 1) and long (8 months; Arm 2) neoadjuvant hormonal therapy before radiotherapy for localized prostate cancer.

METHODS AND MATERIALS

Between 1997 and 2001, 276 patients were enrolled and the data from 261 were analyzed. The stratification risk factors were prostate-specific antigen level >20 ng/mL, Gleason score≥7, and Stage T3 or more. The intermediate-risk stratum had one factor and the high-risk stratum had two or more. Staging was done from the bone scan and computed tomography findings. The primary endpoint was biochemical failure-free survival.

RESULTS

The median follow-up was 102 months. The overall survival, biochemical failure-free survival. and prostate cancer-specific survival did not differ significantly between the two treatment arms, overall or at 5 years. The cumulative probability of overall survival at 5 years was 90% (range, 87-92%) in Arm 1 and 83% (range, 80-86%) in Arm 2. The biochemical failure-free survival rate at 5 years was 66% (range, 62-71%) in Arm 1 and 63% (range, 58-67%) in Arm 2.

CONCLUSION

No statistically significant difference was found in biochemical failure-free survival between 4 months and 8 months of neoadjuvant hormonal therapy before radiotherapy for localized prostate cancer.

A treatment planning comparison of combined photon-proton beams versus proton beams-only for the treatment of skull base tumors

PURPOSE

To compare treatment planning between combined photon-proton planning (CP) and proton planning (PP) for skull base tumors, so as to assess the potential limitations of CP for these tumors.

METHODS AND MATERIALS

Plans for 10 patients were computed for both CP and PP. Prescribed dose was 67 cobalt Gray equivalent (CGE) for PP; 45 Gy (photons) and 22 CGE (protons) for CP. Dose-volume histograms (DVHs) were calculated for gross target volume (GTV), clinical target volume (CTV), normal tissues (NT), and organs at risk (OARs) for each plan. Results were analyzed using DVH parameters, inhomogeneity coefficient (IC), and conformity index (CI).

RESULTS

Mean doses delivered to the GTVs and CTVs with CP (65.0 and 61.7 CGE) and PP (65.3 and 62.2 Gy CGE) were not significantly different (p > 0.1 and p = 0.72). However, the dose inhomogeneity was drastically increased with CP, with a mean significant incremental IC value of 10.5% and CP of 6.8%, for both the GTV (p = 0.01) and CTV (p = 0.04), respectively. The CI(80%) values for the GTV and CTV were significantly higher with PP compared with CP. Compared with CP, the use of protons only led to a significant reduction of NT and OAR irradiation, in the intermediate-to-low dose (< or =80% isodose line) range.

CONCLUSIONS

These results suggest that the use of CP results in levels of target dose conformation similar to those with PP. Use of PP significantly reduced the tumor dose inhomogeneity and the delivered intermediate-to-low dose to NT and OARs, leading us to conclude that this treatment is mainly appropriate for tumors in children.

An integrated two-level hierarchical system for decision making in radiation therapy based on fuzzy cognitive maps

The radiation therapy decision-making is a complex process that has to take into consideration a variety of interrelated functions. Many fuzzy factors that must be considered in the calculation of the appropriate dose increase the complexity of the decision-making problem. A novel approach introduces fuzzy cognitive maps (FCMs) as the computational modeling method, which tackles the complexity and allows the analysis and simulation of the clinical radiation procedure. Specifically this approach is used to determine the success of radiation therapy process estimating the final dose delivered to the target volume, based on the soft computing technique of FCMs. Furthermore a two-level integrated hierarchical structure is proposed to supervise and evaluate the radiotherapy process prior to treatment execution. The supervisor determines the treatment variables of cancer therapy and the acceptance level of final radiation dose to the target volume. Two clinical case studies are used to test the proposed methodology and evaluate the simulation results. The usefulness of this two-level hierarchical structure discussed and future research directions are suggested for the clinical use of this methodology.