Salvage radiotherapy for prostate cancer

Figures & data

Figure 1. TCP and NTCP models using baseline parameters. The optimal SRT dose in this scenario is 66 Gy. This provides a 61% chance of tumor control, 5% chance of severe toxicity and a 58% chance of “success” (tumor control without toxicity).

Figure 2. TCP and NTCP models using baseline parameters, except TCD50 is increased from 74 Gy to 80 Gy. The optimal SRT dose in this scenario is 70 Gy. This provides a 65% chance of tumor control, 3% chance of severe toxicity and a 63% chance of “success.”

Figure 3. TCP and NTCP models using baseline parameters, except K is increased from 0.70 to 0.85. The optimal SRT dose in this scenario is 66 Gy. This provides a 75% chance of tumor control, 5% chance of severe toxicity and a 71% chance of “success.”

Figure 4. (A) TCP and NTCP models using baseline parameters and mildly hypofractionated SRT schedules (2.5 Gy per fraction). The optimal SRT dose in this scenario 60 Gy (gray boxes). This provides a 64% chance of tumor control, a 5% chance of severe toxicity and a 60% chance of “success.” (B) TCP and NTCP models using baseline parameters and 5-fraction SRT schedules. The optimal SRT dose this scenario is 32.5 Gy (6.5 Gy x 5, gray boxes). This provides a 67% chance of tumor control, a 1% chance of severe toxicity and a 66% chance of “success.”

Table 1. Summary of modeling results and possible clinical correlates

Model Adjustment	Effects	Possible Clinical Correlates	Current Status
↑ TD50 (decreasing toxicity)	↑ optimal SRT dose ↑ TCP ↓ NTCP	IGRT	Used by some clinicians
		IMRT	Used by some clinicians
		Radioprotective agents	Under investigation
↑ α (tumor cell radiosensitization)	↓ optimal SRT dose ↑ TCP ↓ NTCP	Concurrent systemic therapy	Under investigation
↑ K (increasing achievable cure rate using SRT)	↑↑ TCP	Improved staging before SRT	Under investigation
		Systemic therapy	Under investigation
↑ SRT fraction size	↓ optimal SRT dose ↑ TCP ↓ NTCP	Hypofractionated SRT	Under investigation