Can the probability of radiation esophagitis be reduced without compromising lung tumor control: A radiobiological modeling study

Figures & data

Figure 1. Dose-volume histogram (DVH) for three plans for Patient 2. Mean esophageal dose (esophagus contoured with 4D information, Eso) is reduced from an average of 29.0 Gy in the non-sparing plan to 23.5 Gy and 15.8 Gy for the controlled sparing and extreme sparing plans, respectively. The largest dose reduction takes place in the overlapping area (Eso&PTV). DVH for total lung-PTV (TL) and contralateral lung (CL) are also shown. Squares: reference plan, triangles: extreme sparing plan, dots: controlled sparing plan.

Table I. Dosimetric parameters of planning target volume and lung for controlled esophagus sparing and non-sparing plans.

	Mean PTV dose (Gy)		PTV V95% (%)		Max PTV dose (Gy)		TCP (%)		EUD-5 (Gy)		EUD-20 (Gy)		CL-V5 (%)		TL-V20 (%)
Case	NS	S	NS	S	NS	S	NS	S	NS	S	NS	S	NS	S	NS	S
1	61.6	61.6	96.0	90.0	68.5	72.9	72	72	61.3	60.9	59.4	57.8	26.3	32.9	14.6	15.1
2	62.7	62.6	95.0	93.5	72.8	73.2	74	74	62.1	61.9	59.6	58.2	36.8	38.6	24.0	24.1
3	62.3	62.1	99.2	96.6	70.2	69.1	74	73	62.1	61.8	61.6	60.2	14.8	17.6	9.8	10.3
4	60.9	61.1	95.8	92.9	69.5	71.8	72	72	60.6	60.7	59.6	59.0	29.3	35.1	26.3	28.2
5	62.2	61.7	95.1	90.2	69.6	70.3	73	72	61.8	61.1	60.3	58.9	49.4	49.8	27.8	28.0
6	62.1	62.5	98.8	93.9	69.8	71.4	73	74	61.9	62.0	61.3	59.8	35.5	42.6	25.9	27.7
7	61.8	60.9	97.8	86.7	68.0	71.1	72	71	61.5	60.1	60.7	56.4	26.5	36.9	20.9	24.0
8	62.5	61.9	95.0	88.4	74.0	72.7	73	73	62.0	61.1	60.2	58.3	39.2	43.1	30.2	30.3
9	62.3	62.4	95.0	93.7	71.6	71.1	73	73	61.8	61.8	59.4	59.1	27.5	29.8	19.3	19.7
10	61.3	61.3	95.0	93.7	70.3	69.3	71	72	60.9	60.9	59.4	59.1	15.8	17.2	21.4	21.2
Mean	62.0	61.8	96.3	92.0	70.4	71.3	73	73	61.6	61.2	60.2	58.7	30.1	34.4	22.0	22.9
SD	0.6	0.6	1.7	3.0	1.9	1.4	0.8	0.9	0.5	0.6	0.8	1.1	10.6	10.6	6.2	6.4
p	0.26		<0.01		0.29		0.16		0.02		<0.01		<0.01		0.01

CL, contralateral lung; CL-V5, volume of the contralateral lung receiving at least 5 Gy; EUD, equivalent uniform dose; EUD-5, EUD for ‘a’ value of -5; EUD-20, EUD for ‘a’ value of -20; max, maximum; NS, non-sparing; p, p-value; PTV, planning target volume; PTV V95%, the volume of the PTV receiving at least 95% of the prescribed dose; S, sparing; SD, standard deviation; TCP, tumor control probability; TL-V20, volume of total lung receiving at least 20 Gy.

Table II. Dosimetric parameters of the esophagus for controlled esophagus sparing and non-sparing treatment plans.

	V30 (%)		V40 (%)		V50 (%)		Mean dose (Gy)		NTCP Huang CCRT (%)		NTCP Huang RT (%)		NTCP Chapet (%)
Case	NS	S	NS	S	NS	S	NS	S	NS	S	NS	S	NS	S
1	46.6	35.1	43.2	29.4	40.1	18.7	29.4	20.7	60	45	25	15	28	11
2	34.6	28.5	24.3	17.9	15.9	8.6	23.7	20.6	50	45	18	15	13	8
3	29.7	20.7	23.0	16.1	18.2	12.0	19.6	16.0	43	37	14	12	12	6
4	39.4	30.6	31.2	20.6	22.4	14.6	26.8	21.8	55	47	22	16	18	9
5	52.6	48.5	52.0	35.0	51.2	26.3	32.1	25.0	64	52	28	20	34	16
6	57.3	47.9	48.3	36.0	38.7	27.1	36.6	30.8	71	62	35	27	31	19
7	80.9	73.1	75.2	59.2	68.1	33.6	48.8	38.3	85	73	56	38	55	29
8	46.8	45.1	43.5	41.6	40.3	37.8	33.1	29.2	66	59	30	25	31	20
9	38.8	30.5	30.0	18.0	21.4	6.3	22.4	18.3	48	41	17	13	14	7
10	24.5	13.0	16.7	3.6	6.8	0.7	17.1	13.9	39	34	12	10	6	3
Mean	45.1	37.3	38.7	27.7	32.3	18.6	29.0	23.5	58	50	26	19	24	13
SD	16.1	17.1	17.4	15.9	18.7	12.3	9.3	7.5	14.0	12.3	12.8	8.4	14.4	8.1
p	<0.01		<0.01		<0.01		<0.01		<0.01		<0.01		<0.01

CCRT, concurrent chemo-radiotherapy; NS, non-sparing; NTCP, normal tissue complication probability; NTCP Chapet, estimated rates of NTCP by the Chapet parameters; NTCP Huang, estimated rates of NTCP by the Huang parameters; p, p-value; RT, radiotherapy; S, sparing; Vx, volume of the esophagus contoured with 4D information receiving at least xGy, with ‘x’, 30, 40 or 50.