The HYP-RT Hypoxic Tumour Radiotherapy Algorithm and Accelerated Repopulation Dose per Fraction Study

Table 3

A list of model parameters used in the fractionated radiotherapy algorithm.

Parameter	Default	References	Comments
Accelerated repopulation (AR)—time of onset after initialisation during RT (weeks)	No onset	[8, 10–12, 25, 53–55]	The number of weeks into RT that AR is onset, 2–4 weeks observed in literature; however 0 week onset has been made possible for modelling microscopic response in a small tumour system.
Reoxygenation (ROx)—time of onset after initialisation during RT (weeks)	No onset	N/A	An extremely variable parameter and open to user input.
Time of ROx after a particular RT fraction (weeks)	4 hours	[44]
AR boost factor	×10	[23, 25, 40]	The factor applied to increase the symmetrical stem cell division probability during AR.
ROx-induced incremental increases in pO2 (mmHg)	3 mmHg	N/A	The pO2 increment size during randomised reoxygenation after an RT fraction (linearly SF dependent), set to obtain full oxygenation by ~1 to 2 mm tumour diameter.
ROx percentage of the very low oxygenated cell population (%)	60%	N/A	The percentage of hypoxia-induced quiescent cells brought back into the cell cycle upon ROx after an RT fraction (linearly SF dependent), set to obtain full oxygenation when the tumour has reduced to 10^5 to 10^6 cells (from 10^8 initial cells).
Alpha (LQ model) Gy^−1	0.3	[56, 57]	Used in SF calculations (linear quadratic equation).
Beta (LQ model) Gy^−2	0.03		Used in SF calculations (linear quadratic equation).
Noncycling cell radiosensitivity compared to oxic cycling cells	0.5	[58, 59]	Factor for the decreased radiosensitivity of noncycling cells, based on the likely increase in resistance of cells in resting phase (transit cells and stems cells however assumed to be equally radiosensitive in tumour cells).