ESTRO 2024 - Abstract Book

S3520

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

TCP enhancement was 4%, observed in the IMPT plans. Patients exhibiting larger IPL volumes gain the greatest advantage from heterogeneous dose escalation to the IPL. The Pearson correlation coefficients, between planned dose and tumour cell numbers for heterogeneous boost plans, was significantly higher than for homogeneous boost plans (Wilcoxon signed-rank test, P value = 0.004), indicating that volumes housing greater tumor cell numbers received elevated doses in the heterogeneous boost plans. Among all modalities, IMPT demonstrated the best sparing for the rectum and bladder, with approximately 20% and 80% of bladder and rectum volume planned to receive ~0 Gy doses in IMPT plans.

Figure 1 The employed prescriptions, resulting planned dose distributions, and TCP distributions for CyberKnife treatment plans of the patient with the largest IPL volume. In the prescription plots, the prescribed doses for the relevant structures are indicated in the upper right corner. Adjacent to the dose or TCP distribution for the entire prostate, the corresponding distribution for IPL is delineated on the right side.

Conclusion:

A methodology for a structure-based dose prescription was developed to achieve a heterogenous IPL boost. Among the 30 plans generated for 5 treatment modalities and 3 patients, without violating any dose constraints, the feasibility of applying homogeneous and heterogeneous IPL boosts was established. For more than 50% of plans produced for a heterogeneous IPL boost, a non-significant TCP increase could be achieved relative to plans produced for a homogeneous DIL boost. The heterogeneous DIL boost using a structure-based prescription was more likely to achieve TCP improvements for a patient with a large DIL volume (>4.63 cc), enabling higher doses to be planned to volumes housing greater tumor cell numbers.