Journal of ISSN: 2373-633XJCPCR

Cancer Prevention & Current Research
Proceeding
Volume 4 Issue 5 - 2016
Image-Guided Radiotherapy Treatment Using Daily versus Weekly Cone Beam CT for Intensity Modulated Radiotherapy of Prostate
SM Soaida1, Z Mulla2, ME EL Sayed3, OY Soliman3 and AS AL Hebshi2
1Department of Clinical Oncology, Cairo University, Egypt
2Department of Radiation Oncology, King Faisal Specialist Hospital and Research Center, Saudi Arabia
3Department of Radiotherapy and Nuclear Medicine, National Cancer Institute, Egypt
Received: April 07, 2016 | Published: May 04, 2016
*Corresponding author: SM Soaida, Cairo University Faculty of Medicine, Department of Clinical Oncology, NEMROCK, Cairo, Egypt, Tel: +201005030002; Email:
Citation: Soaida SM, Mulla Z, Sayed ME EL, Soliman OY, Hebshi AS AL (2016) Image-Guided Radiotherapy Treatment Using Daily versus Weekly Cone Beam CT for Intensity Modulated Radiotherapy of Prostate. J Cancer Prev Curr Res 4(5): 00137. DOI: 10.15406/jcpcr.2016.04.00137

Introduction

IMRT has become a main line of definitive treatment of Prostate cancer in localized cases as it allows delivery of higher doses to target volumes while sparing normal tissues which was shown to offer better biochemical failure‐free survival [1‐2].

Proper Positioning and daily setup are an essential step in the proper treatment of IMRT patents to ensure that the main goal of IMRT is achieved, which is higher doses to target volumes while sparing surrounding normal tissues for best local control and least side effects. Adequate PTV is essential to cover both inter and intra fractional variations in patents position [3].

CBCT is a new applicable and successful technique for better patents setup and positioning verification [4‐10].

Aim of the work

To compare the daily cone beam CT (DCBCT) with weekly CBCT (WCBCT) as a verification method for delivery of the treatment by intensity modulated radiotherapy (IMRT), for patients with prostate cancer.

Patients and Methods

We retrospectively reviewed the readings of CBCT images of 24 patients with prostate cancer treated with IMRT from January 2012 to February 2015. All images obtained from the 24 patients were divided into three pools: unclassified, daily and weekly CBCT images. For each image, data collected included the size in millimeters of the shifts measured in the 6 directions of the 3 axes: medial‐lateral (ML), superior‐inferior (SI) and anterior‐posterior (AP). In all 6 directions’ measurements, the presence of a significant shift was assumed for an absolute value >0.4cm. The proportion of significant shifts was compared between DCBCT and WCBCT images In addition; means (SD) of absolute shifts were compared between DCBCT and WCBCT.

Furthermore, we assessed the fitness of our planning target volume (PTV) that uses a 1 cm margin all around the prostate, except 0.6 cm in the posterior direction. We compared the proportion of readings within the PTV in DCBCT versus WCBCT images.

Statistical analysis was performed using SPSS, version 16.0 for Windows (SPSS Inc., Chicago, IL, USA). Comparisons of means were carried out on continuous variables using independent t‐test; while comparisons of proportions were carried out on categorical variables using Pearson’s Chi‐square test or Fisher’s exact test, as appropriate. The null hypothesis was rejected for a p‐value <0.05.

Results

Total number of images = 502: 306 (60.9%) daily; 61 (12.1%) weekly; 135 (26.9%) unclassified. Comparisons between DCBCT versus WCBCT images showed that Weekly images exhibited significantly smaller (0.23 ± 0.19) mean ±SD absolute shift in the median‐lateral axis, as compared with daily images (0.31 ±0.30), (p=0.043). However, no difference in the mean ±SD absolute shift was observed in the superior‐inferior (p=0.167) or the anterior‐posterior (p=0.531) axes (Table 1).

Parameter

Unclassifie (n=135)

Daily (n=306)

Weekly (n=61)

p-value

Mean

SD

Mean

SD

Mean

SD

Raw Shift Values

Med-Lat

0.02

0.44

-0.06

0.43

0.02

0.3

0.174

Sup-Inf

-0.16

0.41

-0.14

0.44

-0.02

0.38

.048*

Ant-Post

0.02

0.37

0.04

0.34

0.03

0.31

0.766

Absolute Shift Values

Med-Lat

0.32

0.3

0.31

0.3

0.23

0.19

.043*

Sup-Inf

0.33

0.3

0.35

0.31

0.29

0.24

0.167

Ant-Post

0.25

0.27

0.25

0.24

0.22

0.21

0.531

Table 1: Comparisons between DCBCT versus WCBCT images showed that Weekly images exhibited significantly.
*Statistically significant (independent t-test, p-value<0.05); §not included in the comparative analysis.

Weekly images are more likely to be non‐shifted (21.3%) than daily ones (13.1%); but the results are not statistically significant (p=0.84). Moreover, there are more (44.3% versus 38.8%) right‐shifted images and less (34.4% versus 48.4%) left‐shifted images in weekly versus daily group, respectively (Table 2).

Parameter

Value

Daily (n=306)

Weekly (n=61)

p-value

Freq

%

Freq.

%

Shift Direction

Med-Lat

No shift

40

13.1

13

21.3

0.084

Right shift

118

38.6

27

44.3

Left shift

148

48.4

21

34.4

Sup-Inf

No shift

33

10.8

10

16.4

0.057

Inferior shift

92

30.1

25

41

Superior shift

181

59.2

26

42.6

Ant-Post

No shift

65

21.2

14

23

0.954

Posterior shift

140

45.8

27

44.3

Anterior Shift

101

33.3

20

32.8

Shift Significance (≥0.40cm)

Med-Lat

97

31.7

14

23

0.174

Sup-Inf

104

34

19

31.1

0.668

Ant-Post

79

25.8

12

19.7

0.31

Beyond Margin (shift >1.00cm in all directions; and > 0.60cm in posterior direction)

Med-Lat

10

3.3

0

0

.380 §

Sup-Inf

10

3.3

0

0

.380 §

Ant-Post

13

4.2

2

3.3

1.000 §

Table 2: Shift significance values both anterior‐posterior and § p-value calculated using Fisher’s exact test.

Shift significance

Daily images are more likely to exhibit significant (≥0.40cm) shifts in both median‐lateral (31.7% versus 23.0%, p=0.174) and anterior‐posterior (25.8% versus 19.7%, p=0.310) axes, respectively; however, results are not statistically significant (Table 2).

Margin respect assessment

Surprisingly, although not statistically significant, 100% of weekly images versus 96.7% of daily images were

with margin, in both median‐lateral (p=0.380) and superior‐inferior axes (p=0.380) (Table 2).

Conclusion

Daily CBCT did not show superior accuracy as compared to weekly CBCT, in patients with prostate cancer treated with IMRT. Consequently, weekly CBCT appears to be a safe alternative, especially recommended in departments with over‐request. As per the direction, the use of a 6‐to‐10 mm margin in the PTV was found to be adequate to cover shifts in all directions in both Daily and Weekly analysis.

References

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