Adaptive brachytherapy of cervical cancer, comparison of conventional point A and CT based individual treatment planning

Figures & data

Figure 1. Delineation of volumes of interest in CT images in FIGO stage IIIB cervical cancer, second brachytherapy fraction. Left: Axial view. Right: Sagittal view.

Table I. Patient, tumor and treatment characteristics.

Characteristics		Median	Range	Total (n)
Eligible patients				19
Age (years)		56	27–87	19
Histologic type	Squamous cell carcinoma			17
	Adenocarcinoma			1
	Adenosqamous carcinoma			1
FIGO stage	IBI			2
	IBII			2
	IIA			2
	IIB			4
	IIIB			8
	IV			1
Largest tumour diameter on MRI at diagnosis (cm)		6.4	2.4–11.7	19
Enlarged lymph nodes at diagnosis	Yes			10
	No			9
Weekly cisplatin				10
Prescription EBRT dose (Gy)			3 Gy × 10 2 Gy × 25 1.8 Gy × 25	1 12 6
Prescription EBRT boost to enlarged lymph nodes dose (Gy)			2 Gy × 3 2 Gy × 5	7 1
Prescription brachytherapy dose (Gy)			4.2 Gy × 5 5 Gy × 4 5 Gy × 2	2 16 1
Delivered treatment*		Mean	Range
Point A (A1 + A2)/2 EQD2Gy (Gy)		73 ± 3	67–79	18
TRAK (cGy)		1.6 ± 0.2	1.2–1.9	18
V^Ext100 (cm^3)		88 ± 17	65–131	18
Bladder D2cc EQD2Gy (Gy)		81 ± 9	68–102	18
Rectum D2cc EQD2Gy (Gy)		61 ± 7	50–69	18
Sigmoid D2cc EQD2Gy (Gy)		64 ± 7	50–71	18

*Pooled data for total dose to point A and doses to the OARs are presented for the 18 patients receiving curative treatment regimens. One patient receiving 3 Gy × 10 for the external treatment and only two brachytherapy fractions is omitted. Total reference air kerma (TRAK) for the total brachytherapy treatment is shown. 57 of the 72 delivered fractions are individually planned.

Figure 2. Target coverage against volume of CTV (linear regressions) for optimized plans (—) and standard (– –) plans. The individual fractions are shown for standard plans below OAR limits (○), or with bladder (▴), rectum (•) or sigmoid (♦) exceeding tolerance limits.

Table II. Mean values of dose and volume data for optimized and standard treatment plans.

		Optimized			Standard
		Entire group	CTV<70 cm^3	CTV>140 cm^3	Entire group	CTV<70 cm^3	CTV>140 cm^3
Number of plans		72	15	17	72	15	17	p-value
CTV	D90 (Gy)	65.8 ± 5.1			62.5 ± 3.7			0.00
			68.7 ± 4.8			64.6 ± 4.4		0.01
				62.5 ± 5.8			58.5 ± 3.3	0.00
	Vtot (cm^3)	114 ± 47			114 ± 47
			63 ± 7			63 ± 7
				180 ± 37			180 ± 37
	V100 (cm^3)	76 ± 26			62 ± 13			0.00
			48 ± 6			45 ± 5		0.13
				105 ± 27			74 ± 8	0.00
	V130 (cm^3)	53 ± 18			44 ± 8			0.00
			35 ± 5			36±4		0.42
				72 ± 21			49 ± 5	0.00
	V200 (cm^3)	23 ± 8			21±3			0.16
			16 ± 3			20 ± 3		0.01
				32 ± 10			23±2	0.00
	V400 (cm^3)	5.6 ± 2.4			5.8± 0.9			0.09
			3.6 ± 0.9			5.4 ± 0.9		0.00
				8.4 ± 2.9			6.4 ± 0.7	0.01
External	V100 (cm^3)	105 ± 33			81 ± 13			0.00
			73 ± 11			74 ± 12		0.65
				136 ± 37			86 ± 11	0.00
	V200(cm^3)	25 ± 9			23 ± 4			0.05
			17 ± 4			21 ± 4		0.02
				35 ± 10			24 ± 3	0.00
Indices	TC	0.70±0.13			0.59±0.13			0.00
			0.78 ± 0.09			0.73 ± 0.09		0.11
				0.60 ± 0.14			0.43 ± 0.08	0.00
	CI	0.72 ± 0.08			0.76 ± 0.12			0.00
			0.66 ± 0.07			0.62 ± 0.08		0.08
				0.78 ± 0.05			0.87 ± 0.05	0.00
	COIN	0.50 ± 0.09			0.44 ± 0.08			0.00
			0.51 ± 0.08			0.45 ± 0.04		0.00
				0.46 ± 0.09			0.37 ± 0.07	0.00
Point A	(A1+A2)/2(Gy)	75.7 ± 7.4			73.7 ± 2.0			0.32
			70.5 ± 3.1			73.7 ± 2.0		0.02
				81.3 ± 10.9			74.3± 1.3	0.01
Bladder	D2cc (Gy)	85.2 ± 3.4			81.0 ± 7.9			0.09
			86.3 ± 3.5			90.8± 6.5		0.07
				84.1 ± 3.4			77.0 ± 8.9	0.02
Rectum	D2cc (Gy)	65.9± 3.8			60.4 ± 3.9			0.00
			65.1 ± 4.9			63.7 ± 7.9		0.09
				66.6 ± 4.4			60.4 ± 3.5	0.00
Sigmoid	D2cc (Gy)	66.6 ± 4.4			65.1 ± 4.9			0.21
			64.4 ± 4.3			66.6± 6.1		0.08
				69.8 ± 4.6			65.9 ± 4.9	0.01

Dose data are presented as EQD_2Gy for total treatment calculated as if each brachytherapy fraction was given equally four times in addition to external radiation (2 Gy × 25 = 50 Gy) using σ/β =10 for tumor and σ/β = 3 for OARs. Data (with standard deviations) are presented for the entire group and for subgroups of the smallest and largest target volumes. P-values for comparable data are listed, and statistic significant differences in comparable data are shown in bold.

Figure 3. Optimized plans: EQD_2Gy for CTV D₉₀ plotted against dose to point A for different ranges of CTV sizes. CTV < 70 cm³ (- - ○), 70 cm³ < CTV < 140 cm³ (- - x), CTV > 140 cm³ (— ▴). The data are presented for total treatment calculated as if each brachytherapy fraction was given equally four times in addition to standard external radiation (2 Gy × 25) using σ/β = 10 for tumor.