Integrated peripheral boost in preoperative radiotherapy for the locally most advanced non-resectable rectal cancer patients

Figures & data

Table I. Patient characteristics.

Patient no	Gender	Age	Overgrowth	Tumour level (cm)*	GTV** (cm^3)	cTN-stage***
1	Male	63	S1	5.5	288	cT4aN0
2	Male	53	left pelvic side wall	5.5	101	cT4aN2
3	Male	55	left pelvic side wall	7.5	150	cT4aN1
4	Male	73	left pelvic side wall	7.5	396	cT4aN2
5	Male	75	S2 + right pelvic side wall	0	748	cT4aN2
6	Female	52	left pelvic side wall	4.5	85	cT4aN2
7	Male	63	S2	3	212	cT4aN2

*Distance from anal verge

**Gross tumour volume

***According to AJCC TNM5

Figure 1. Beam orientation in proton plan (top) and starting angles for photon arcs (bottom) for patient no. 3.

Table II. Planning target volume (PTV) coverage and doses (VMAT stands for photon plan and P+ stands for proton plan).

		Patient no. 1		Patient no. 2		Patient no. 3		Patient no. 4		Patient no. 5		Patient no. 6		Patient no. 7
PTV		VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+
PTV-boost	Volume (cm^3)	67		46		43		49		114/62*		28		37
	D99% (Gy)	60.3	60.4	60.0	60.8	60.5	60.9	60.3	61.3	59.7/60.6	60.4/60.9	60.7	61.2	60.8	61.9
	D1% (Gy)	63.5	63.2	63.4	63.1	63.4	63.2	63.2	63.0	60.2/61.3	61.1/61.5	63.2	62.9	63.2	63.1
	Average (Gy)	62.4	62.4	62.4	62.4	62.4	62.5	62.4	62.5	64.3/63.9	63.1/63.0	62.5	62.4	62.5	62.5
	V95 Gy (%)	99.9	100	99.7	100	99.9	100	99.9	100	99.6/100	99.9/100	100	100	99.8	100
	CI95	1.56	1.43	1.51	1.42	1.64	1.44	1.95	1.68	1.67	1.97	1.78	1.52	1.86	1.98
PTV-tumour	Volume (cm^3)	860		453		652		1210		2085		517		816
	D99% (Gy)	48.2	49.8	49.1	48.7	48.4	48.6	48.8	49.6	17.9	8.8	48.4	48.6	48.8	48.4
	D1% (Gy)	63.0	62.8	63.1	62.8	63.0	62.9	62.9	62.6	49.6	50.1	62.9	62.7	62.8	62.7
	Average (Gy)	53.3	53.0	54.3	53.3	52.9	52.3	52.8	52.5	63.5	63.2	53.0	52.6	53.0	52.1
	V95 Gy (%)	99.7	100	100	99.8	99.9	99.9	99.9	100	99.8	99.9	99.9	99.9	100	99.8
	CI95	1.27	1.39	1.81	1.53	1.43	1.41	1.25	1.27	1.44	1.34	1.58	1.39	1.21	1.20
PTV-regional	Volume (cm^3)	1347		1230		1374		1602		2828		1206		1056
	D99% (Gy)	44.2	45.5	44.4	45.1	44.3	44.2	44.5	45.6	27.1	6.2	44.2	44.9	44.6	45.3
	D1% (Gy)	62.9	62.8	62.9	62.7	62.7	62.7	62.8	62.6	45.3	46.1	62.7	62.6	62.8	62.6
	Average (Gy)	51.0	50.8	49.8	49.2	49.9	49.5	51.5	51.3	63.3	63.1	49.5	49.3	51.7	50.9
	V95 Gy (%)	99.9	100	100	100	100	99.6	99.9	100	99.6	100	100	100	100	100
	CI95	1.27	1.43	1.34	1.40	1.28	1.40	1.26	1.33	1.39	1.37	1.36	1.37	1.31	1.37

*Patient no. 5 has two boost regions.

**Conformity index 95% (CI95) is defined as the volume within the 95% isodose divided by the target volume.

Table III. Organs at risk (OAR) volumes and doses (VMAT stands for photon plan and P+ stands for proton plan).

		Patient no. 1		Patient no. 2		Patient no. 3		Patient no. 4		Patient no. 5		Patient no. 6		Patient no. 7
OAR		VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+	VMAT	P+
Intestinal cavity	Volume (cm^3)	1125		953		875		935		1157		732		615
	Cavity in PTV	144		82		100		162		516		111		83
	Average (Gy)	29.2	14.3	22.0	8.8	28.9	12.8	34.6	21.2	39.3	34.8	34.2	18.2	29.6	14.7
	D50% (Gy)	26.6	1.5	19.9	0.0	26.7	0.6	34.1	11.8	46.6	45.9	34.6	6.9	26.8	1.6
	D1% (Gy)	52.1	51.2	47.8	46.9	50.7	50.5	56.5	55.7	53.3	51.2	51.9	50.1	52.8	51.0
Bladder	Volume (cm^3)	95		506		206		76		141		177		59
	Bladder in PTV	42		64		8		53		57		31		15
	Average (Gy)	43.5	37.2	36.0	15.8	35.0	12.6	50.6	50.2	48.7	40.8	40.4	23.6	40.2	29.5
	D50% (Gy)	47.7	47.9	34.0	2.0	33.3	1.3	51.4	51.0	49.6	49.4	41.7	18.9	42.4	39.7
	D1% (Gy)	53.2	52.7	51.8	52.3	49.9	50.6	54.6	52.5	56.3	54.4	52.5	53.1	52.6	52.0
Femoral Head (Left)	Volume (cm^3)	169		173		147		185		185		109		76
	Average (Gy)	22.3	2.5	22.2	2.8	19.8	3.5	15.5	2.5	27.8	3.9	20.2	4.2	25.5	5.1
	D50% (Gy)	20.5	0.0	24.4	0.0	17.9	0.0	12.6	0.0	28.6	0.0	19.2	0.0	25.3	0.2
	D1% (Gy)	37.9	31.5	39.5	34.6	40.4	40.0	37.7	24.6	35.8	34.5	34.8	36.9	37.8	40.5
Femoral Head (Right)	Volume (cm^3)	175		167		153		197		216		114		97
	Average (Gy)	15.4	2.8	17.1	2.6	18.2	1.7	11.9	0.2	25.6	20.1	17.0	2.1	20.7	3.5
	D50% (Gy)	12.6	0.0	16.5	0.0	15.7	0.0	9.8	0.0	24.6	18.5	14.0	0.0	21.4	0.0
	D1% (Gy)	37.9	38.7	34.9	35.3	34.7	29.9	28.2	4.2	48.5	41.1	36.2	32.1	36.1	35.9
Nerve roots L5-S2	Volume (cm^3)	27		25		33		44		30		31		33
	Average (Gy)	25.1	28.4	29.0	33.3	24.5	27.3	20.3	23.5	23.8	28.6	20.6	23.5	27.3	31.5
	D50% (Gy)	28.8	36.1	32.0	36.7	30.0	36.3	17.1	29.6	27.3	38.1	19.5	29.8	26.9	35.6
	D1% (Gy)	59.8	59.3	47.4	47.5	47.0	46.4	46.8	47.0	57.8	53.6	46.6	46.5	60.9	61.7
Sacrum	Volume (cm^3)	376		243		286		315		417		139		213
	Average (Gy)	41.9	45.5	40.5	41.6	38.0	41.6	34.6	37.8	39.9	43.6	34.8	36.5	41.6	44.3
	D50% (Gy)	42.1	44.6	41.2	42.7	39.2	42.4	38.3	41.4	41.1	44.0	37.7	38.9	42.3	44.7
	D1% (Gy)	62.9	62.8	52.9	52.5	48.9	49.1	51.7	51.8	63.1	62.7	50.7	51.9	62.8	62.7
Body	Volume (cm^3)	14958		18989		24260		15545		15989		21345		11448
	Average (Gy)	17.7	11.2	16.1	9.1	13.8	7.4	16.5	11.3	25.2	18.8	13.9	7.8	19.7	12.0
	D50% (Gy)	14.9	0.1	12.9	0.1	10.3	0.0	11.1	0.1	23.7	8.9	9.7	0.0	17.1	0.2
	D1% (Gy)	57.0	55.4	53.9	52.3	52.7	51.8	56.3	54.7	61.5	62.3	52.4	52.1	56.2	55.2

Figure 2. Dose volume histogram (DVH) for intestinal cavity for protons (top) and photons (bottom) with critical volumes recommended by Fiorino et al. (18) and Roeske et al. (30) mapped.

Figure 3. Dose volume histogram (DVH) for intestinal cavity showing mean values for patient 3 and 6, critical volumes recommended by Fiorino et al. (18) and Roeske et al. (30) mapped.

Figure 4. Differences in target coverage – intestinal gas influence in patient no 3. Photon plan to the left and proton plan to the right. Upper row: Dose distribution in the planning CT with gas present. Lower row: Dose distribution when gas is replaced by water in 25 of 25 fractions. It is the distance the protons have to cross in the gas cavity that is important for the robustness of the proton plan.