Table 2.

Results for model fits

Model with dose only
$${\mathit{TRP}}_{\mathit{TRG}\le i}=\frac{exp(b_{0,i}+b_1\mathit{EQD}2)}{1+exp(b_{0,i}+b_1\mathit{EQD}2)}$$
Actual dose delivered		Intention To Treat
b0,TRG1:	−3.928 (−5.787;−2.181)	b0,TRG1:	−3.511 (−5.417;−1.621)
b0,TRG2:	−3.079 (−4.865;−1.392)	b0,TRG2:	−2.671 (−4.501;−0.814)
b0,TRG3:	0.085 (−1.591;1.693)	b0,TRG3:	0.451 (−1.282;2.153)
b1:	0.0427 (0.0153;0.0712)	b1:	0.0358 (0.0060;0.0648)

Model with dose, tumour size and N-category
$${\mathit{TRP}}_{\mathit{TRG}\le i}=\frac{exp(b_{0,i}+b_1\mathit{EQD}2+b_{\mathit{tumour}-\mathit{size}}{Y}_{\mathit{vol}}+b_{N-\mathit{stage}}{Y}_{N-\mathit{stage}})}{1+exp(b_{0,i}+b_1\mathit{EQD}2+b_{\mathit{tumour}-\mathit{size}}{Y}_{\mathit{vol}}+b_{N-\mathit{stage}}{Y}_{N-\mathit{stage}})}$$
Actual dose delivered		Intention To Treat
b0,TRG1:	−2.634 (−4.836;0.600)	b0,TRG1:	−2.106 (−4.400;0.060)
b0,TRG2:	−1.762 (−3.903;0.246)	b0,TRG2:	−1.240 (−3.514;0.856)
b0,TRG3:	1.463 (−0.641;3.404)	b0,TRG3:	1.949 (−0.281;3.979)
b1:	0.0349 (0.0060;0.0641)	b1:	0.0268 (−0.0039;0.0580)
btumour-size:	−0.0058 (−0.0132;0.0008)	btumour-size:	−0.0061 (−0.0134;0.0008)
bN-category:	−0.6252 (−1.3399;0.1449)	bN-category:	−0.6580 (−1.3920;0.1106)

TRP_TRG≤i is the probability of tumour regression of at least grade TRGi. EQD2 is the equivalent average dose to the tumour in 2 Gy fractions. Y_vol is the pre-treatment tumour volume, as estimated from the tumour length and diameter on the pre-treatment MRI scan and assuming cylindrical symmetry. Y_N-category is 0 for clinical N0 patients and 1 for N1-2 patients. The b₁ coefficient has the unit of [Gy⁻¹], the b_tumour-size coefficient the unit of [cm⁻³]. All other coefficients are dimensionless.