Original papers
2012, Vol. 14, no. 1, 19-23Abstract
Aim: To assess the changes in the angiogenic status of rectal cancer before and after preoperative radiotherapy (RT) using endosonography (ES).
Material and methods: Fifty-four patients with rectal cancer were examined by ES before and 6-7 weeks after preopera- tive RT and . The tumour size, stage, echostructure and vascularization before and after RT were compared. Tumour vasculari- zation was determined by qualitative power Doppler and by computer-assisted method.
Results: Compared to the histological data, ES restaging after RT was accurate in 65% of the cases for the T parameter and in 83% for the N parameter (TNM tumour classification). The histological data compared with the initial ES examination revealed downstaging in relation to the T parameter in 33% and for the N stage in 24% of the cases. The tumour structure fol- lowing RT became hyperechogenic in 89% of tumours and remained hypoechogenic in 11% of tumours. Power Doppler found a reduction in tumour vascularization after RT in 61% of the tumours. The PDVI before RT was 10.7±5.8% and 6.3±4.6% after RT (р<0.05). A strong correlation between the qualitative assessment of the vascularization and PDVI was found (r=0.536, p<0.001). The vascularization reduction after RT was found to be a protective factor which decreased the death risk by about 86 % (ОR=0.14, р=0.001).
Conclusions: Endorectal Doppler sonographic findings are promising in the evaluation of tumour vascularization in pa- tients with rectal cancer. The qualitative and quantitative digital assessment of the vascularization gives supplementary infor- mation about the patients’ prognosis.
Keywords: rectal cancer, radiotherapy, endosonography, power Doppler
Endosonographic assessment of rectal cancer after neoadjuvant radiotherapy.
Ludmila Tanova Tankova
1, Plamen Ivanov Penchev
1, Daniel Kovatchki
2, Georgi Stoilov
3, Tatiana Hadjieva
41 Clinical Center of Gastroenterology, Clinic of Gastroenterology, University Hospital “Queen Joanna”, Sofia, Bulgaria
2 Center for assisted reproduction „Goldenes Kreuz”, Vienna, Austria
3 Institute of Mechanics, Bulgarian Academy of Sciences, Sofia, Bulgaria
4 Radiotherapy Department, University Hospital “Queen Joanna”, Sofia, Bulgaria
Received 30.09.2011 Accepted 20.11.2011 Med Ultrason
2012, Vol. 14, No 1, 19-23
Corresponding author: Plamen Ivanov Penchev
University Hospital “Queen Joanna”, 8 Belo more str,
1527 Sofia, Bulgaria tel: +359 2 9432519;
fax: +359 2 9432103 Emal: [email protected]
Introduction
Endosonography (ES) is recognized to be the most reli- able method for rectal cancer staging and selection of pa- tients suitable for neoadjuvant treatment. However, little is known about endosonographic findings after radiotherapy (RT) and about changes in rectal cancer vascularization after
RT. The published papers on postradiation ES findings are still inconclusive [1-7]. Postradiation tissue changes such as edema, inflammation, necrosis, and fibrosis may blur the image of the layers of the rectal wall and thus complicate the endosonographic interpretation of the residual tumour.
Although the extent of angiogenesis is considered to be an important prognostic factor for colorectal carcino- ma, there are still few studies concerning the changes in angiogenesis due to RT [8]. Several studies have suggest- ed that color Doppler ultrasonography may provide reli- able preoperative assessment of the tumour angiogenesis and also prognostic informations for patients with can- cer [9,10]. The aim of the study was to evaluate by en- dosonograhy the changes of the structure and angiogenic status of rectal cancer after preoperative radiotherapy.
Fig 1. a) Rectal cancer- power Doppler endosonography; b) and c) Power Doppler Vascularization Index determination.
We tried to answer the following questions:
1. How does radiotherapy alter the endosonographic image of rectal cancer?
2. Can ES pulse and power Doppler detect the vascu- lar changes caused by RT?
3. Does the data from qualitative Doppler assess- ment correlate with computer-assisted power Doppler evaluation of tumour vascularization?
4. Could the angiogenesis activity, determined by ES performed before and after RT, be considered as prognos- tic and/or predictive indicators?
Material and methods
Fifty-four patients (20 female, 34 males), mean age 58±13 years (range: 27-73 years) with histological con- firmed rectal cancer underwent preoperative RT. Accord- ing to TNM classification the patients were in the second (19 patients) and in the third clinical stage (35 patients).
All patients were examined prior RT with Toshiba, Nemio SSA 550A, Japan apparatus with a biplane con- vex transversal and еnd-fire scanning probe PVM-740RT (5.0/7.5/10 MHz/144°) capable of pulse color and power Doppler. Irradiation was given in a dose of 50Gy/5 weeks with 2Gy fraction treating 5 days/week using three- or four- field-technique. Surgical resection was performed within seven – eight weeks after RT. The ES was repeated one week before operation. The patients were followed up after surgery for a mean period of 30.4±17.6 months.
In the follow up period, 6 of the patients developed liver metastases, one developed metastatic paraaortic lymph nodes, 2 patients had local recurrence, and 5 patients died due to postoperative complications.
The patients were prepared by small enema two hours before ES. The examination was performed with the pa- tient in a left lateral position. The probe was inserted 12- 15 cm and then was pulled out to the tumour level. Three females were evaluated by endovaginal ultrasonography due to the rectum stenosis.
We compared the tumour size, stage, echostructure and vascularization before and after RT. The analysis of the tu- mour response was based on the downstaging of the T and N stages achieved by comparing the pretreatment endorec- tal ultrasound and the resection histology statement. The sonographic structure of the ultrasound image of the tumour was defined as hypoechogenic, hyperechogenic or mixed.
The rectal cancer staging was based upon the level of invasion of the tumor into the rectal wall, corresponding to the T parameter of the TNM classification. We defined the N parameter either as N0- if no nodes involved were presented or as N1 – if metastatic nodes were identified.
In the case of N1 stage hypoechoic round or oval-shaped masses were found in the mesorectal fat. Since the prom- inent vessels were also hypoechoic and could mimic a node, endorectal Doppler evaluation was used.
Pulse color (cut-off wall filter: 50-100Hz; pulse rep- etition frequency: 4kHz) and power Doppler US were used to estimate tumour vascularisation. Power Doppler settings were set to detect low velocity flow without arti- facts. Tumour vascularization was determined by ES by subjective assessment and by computer-assisted method.
The following classification was used: poor vascularity – absent or isolated color signals; abundant vasculariza- tion – plenty of chaotic vessels in the periphery and/or the central part of the tumour. The tumour vasculariza- tion after RT was described as more or less abundant or unchanged comparing with the status before RT.
The power Doppler was used for the digital assess- ment of tumour vascularization. The color window was set to include the whole tumour on the screen. After- wards, three tumour slices with maximal color signal numbers were chosen. The tumour image was traced with the pointer, followed by a computer-assisted calculation of the percentage ratio of the colored pixels number with- in a delineated tumour section to the number oftotal pix- els in that specific tumour section (fig 1). The term Power Doppler Vascularization Index (PDVI) was introduced, showing the mean of the three consecutive results.
The data was entered and processed with the statistical package SPSS for Windows version 17. The degree of sig- nificance, for which the zero hypotheses was rejected, was chosen as p<0.05. The following methods were used: De- scriptive analysis; Variation analysis; Student’s t-test; Single factor dispersion analysis (ANOVA) – parametric method to test hypotheses for differences between several independent subsets; Mann-Whitney non-parametric test – to test hypoth- eses for differences between two independent subsets.
The study was approved by the Regional Ethic Com- mittee in the University Hospital „Queen Joanna”, Sofia.
All patients received information and gave written in- formed consent before enrollment in the study.
Results
The mean transversal diameter of the rectal tumours be- fore RT established by ES was 39mm±11mm (between 14 to 55 mm). After RT, a significant reduction in the tumours transversal size of 41 % was found (23±6 mm, between 13 to 35 mm) (р<0.001). The reduction in the longitudi- nal size of the tumours was less pronounced. The average distance of the lesions from the inner anal sphincter was increased by 5%, without being statistically significant:
from 58±18mm before RT to 61±16mm after RT (p=0.16).
Compared to the histological data, endosonographic restaging after RT was accurate in 35/54 cases (65%) for the T parameter and in 45/54 cases (83%) for the N stage.
A comparison of the histological data with the initial en- dosonographic examination showed a downstaging in re- lation to the T parameter in 18/54 (33%) cases. For the N parameter, there was a downstaging in 13/54 (24%) cases.
Before RT, the ES structure of the rectal tumours was hypoechogenic in 40 cases (74%) and mixed (het- erogeneous) in 14 patients (26%). After RT the tumour echostructure was hyperechogenic in 89% of the cases (highly inhomogeneous – in 40 tumours and discrete homogeneous – in 8 cases). In only 6 cases (11%) the echostructure remained unchanged hypoechogenic.
Doppler examination prior to the RT established a poor vascularization in 28 tumours (52%), (9 of the pa- tients being in the second stage and 19 in the third stage) and abundant vascularization in the rest of 26 tumours (48%) (fig 2). In 33 out of 54 cases (61%), there was a re- duction of the vascular signals after RT (fig 3), 7 of these cases with absence of the tumour vascularization. In the remaining 21 cases (39%), no reduction of the tumour vascularization was found.
The mean PDVI before RT was 10.72%±5.8% (be- tween 0% to 27.3%) and after RT was 6.29%±4.6% (be- tween 0% to 14%) with a statistically significant differ- ence (р<0.05). There was a strong correlation between
the visual subjective assessment of the vascularization and the computer-assisted quantification of color pixels (r=0.536, p<0.001).
We found a statistically significant relationship be- tween the decrease in the vascularization after RT and the clinical outcome. The proportion of patients who were alive during the follow-up period was significantly higher in cases of tumour vascularization reduction after RT compared to patients without vascularization reduc- tion (table I). The vascularization reduction after RT is a protective factor which decreases the death risk by about 86 % (ОR=0.14, р=0.001).
Fig 2. Pulse color Doppler endosonography of rectal cancer (high PSV – 47.6 cm/s; low RI – 0.65).
Fig 3. a) Color Pulse Doppler endosonography before RT: abundant vascularization with high Peak Systolic Velocity - 45.2 cm/sec and Resistance Index – 0.64; b) The same patient after RT with reduced vascularisation.
Table I. Relationship between reduction of vascularization after RT and clinical outcomes in patients with rectal cancer
Variable
Reduction of the vascularization p
No Yes
n % n %
Clinical outcome
Dead 12 52.4 4 12.1
0.001
Alive 9 42.9 29 87.9
The neoadjuvant RT yielded good local control – lo- cal recidives were observed in only 3.7% (2/54) of the patients. We established that the mean overall survival of the patients with vascularization reduction after RT was three months longer (without statistical significance) than that of patients without changes in the vascular sta- tus (table II).
Discussion
In the last decade ES has been recognized as a widely applied and accurate method for T and N staging of the rectal cancer [11,12]. However, there are still debates about the accuracy, sensitivity and specificity of the method after preoperative RT. Studies on postradiation endosonographic images are still insufficient [1-7,13].
The accuracy of ES is 47-62% for T parameter and is better for the N parameter (58-80%) [1,3,5-7].
According to our results the accuracy of endosono- graphic restaging after radiotherapy was lower for assess- ment of T criterion and higher for N parameter. To obtain high sensitivity and high specificity, the ES-guided fine needle aspiration biopsy may be helpful [11]. Perhaps the application of Doppler in our series facilitates the verifi- cation of lymph nodes and reduces the possibility of mis- interpretation of blood vessels in a cut for lymph nodes.
The preoperative RT changed considerably the initial ES findings. In general, tumour ES structure after RT was hyperechogenic as have reported other authors [2,13].
Gaviolli et al [2] registered restoration of rectal wall layers in cases of complete response. They defined pos- tradiation fibrosis as the morphological essence of en- dosonographic images. We had a similar case, where the rectal wall layers became visible after RT (fig 4).
ES is proven to be the most exact method for rectal cancer staging, but less attention has been paid to the ES pulse color and power Doppler evaluation [13-18,20].
The conventional method for angiogenesis quantification
requires tumor biopsy for specific immunohistochemical or molecular biological tests. Doppler ultrasonography is a noninvasive method for angiogenesis evaluation. The colorDoppler signals detected within the tumour repre- sent the larger vessels(approximately 100 µm or more in diameter), possibly intratumouralarterioles, venules, and arteriole-venule shunts. Due to the higher sensitivity in detecting the slow flows Power Doppler is a suitable technique for the tumour vessels depicting.
We hypothesized that the amountof detected supply- ing intratumoural arterioles and draining venules corre- lates positively with the degree of the tumour microv- ascularization. Thus, the PDVI can reflectthe extent of global neovascularization of a tumour. In our previous study we found a strong correlation between PDVI and the conventional indicator of tumour angiogenic activity – microvessel density assessed immunohistochemically using a monoclonal antibody against CD31 (r = 0.438, p = 0.002) [19]. Due to the subjectivity in the visual as- sessment of the degree of vascularization, we applied the digital assessment of tumour vascularization by calculat- ing PDVI.
Barbaro et al [20] examining tumour response to chemoradiotherapy by endorectal Doppler ultrasound, noted significantly higher rates of response in tumours that were more extensively vascularized and had less vascular resistance . In the present study the vasculariza- tion reduction after a long course of preoperative RT was a predictor of a favourable clinical outcome.
The time from RT to the second ES is of great im- portance, particularly for the degree of vascularization and tumour echogenicity. We performed the second ES more than 30 days after RT and we observed significant decreasing of tumour size; in 89% we found increased tumour echogenicity and in 61% reduced tumour vascu- larization probably due to vasculitis obliterans.
The present study had several limitations: the opera- tor dependency of the Endoechographic method; most Table II. Mean overall survival and 95% confidence interval
according to the vascularization status after RT Vascularization
after RT n Mean overall survival
(months) 95% CI Without alterations 21 36.92* 5.97 25.22 Reduced tumour
vascularization 33 39.98* 2.93 34.24
* There was no significant differences p > 0.05 Fig 4. Endosonography before (a) and after RT (b). After RT the tumour size is reduced and the wall layers could be identified (blue arrow). Lymph nodes were detectable only before RT (red аrrow)
of the patients were in the third clinical stage due to the selection for radiotherapy; the detection of the larger ves- sels by means of colorDoppler.
Conclusion
Our study showed that the long course of preopera- tive RT decreased the vascularization and increased the echogenicity of rectal cancer.
Endorectal Doppler sonographic findings are prom- ising in the evaluation of the tumour vascularity, its predictive and prognostic values, but larger studies are required to validate the benefit from this method. In the future contrast enhanced endo-ultrasound might offer more precise information regarding changes in tumour vascularity after RT.
Conflict of interest: none
References
1. Bernini A, Deen KI, Madoff RD, Wong WD. Preoperative ad- juvant radiation with chemotherapy for rectal cancer: its impact on stage of disease and the role of endorectal ultrasound. Ann Surg Oncol 1996; 3: 131-135.
2. Gavioli M, Bagni A, Piccagli I, Fundaro S, Natalini G. Useful- ness of endorectal ultrasound after preoperative radiotherapy in rectal cancer: comparison between sonographic and histopatho- logic changes. Dis Colon Rectum 2000; 43: 1075-1083.
3. Kahn H, Alexander A, Rakinic J, Nagle D, Fry R. Preopera- tive staging of irradiated rectal cancers using digital rectal ex- amination, computed tomography, endorectal ultrasound, and magnetic resonance imaging does not accurately predict T0,N0 pathology. Dis Colon Rectum 1997; 40: 140–144.
4. Maor Y, Nadler M, Barshack I, et al. Endoscopic ultrasound staging of rectal cancer: diagnostic value before and following chemoradiation. J Gastroenterol Hepatol 2006; 21: 454–458.
5. Rau B, Hünerbein M, Barth C, et al. Accuracy of endorectal ultrasound after preoperative radiochemotherapy in locally ad- vanced rectal cancer. Surg Endosc 1999; 13: 980–984.
6. Vanagunas A, Lin DE, Stryker SJ. Accuracy of endoscopic ultrasound for restaging rectal cancer following neoadjuvant chemoradiation therapy. Am J Gastroenterol 2004; 99: 109–
112.
7. Williamson PR, Hellinger MD, Larach SW, Ferrara A. Endorec- tal ultrasound of T3 and T4 rectal cancers after preoperative chemoradiation. Dis Colon Rectum 1996; 39: 45–49.
8. Baeten CI, Castermans K, Lammering G, et al. Effects of ra- diotherapy and chemotherapy on angiogenesis and leukocyte infiltration in rectal cancer. Int J Radiat Oncol Biol Phys 2006;
66: 1219-1227.
9. Chen CN, Cheng YM, Lin MT, Hsieh FJ, Lee PH, Chang KJ.
Association of color Doppler vascularity index and microvessel density with survival in patients with gastric cancer. Ann Surg 2002; 235: 512-518.
10. Ogura O, Takebayashi Y, Sameshima T, et al. Preoperative as- sessment of vascularity by color Doppler ultrasonography in human rectal carcinoma. Dis Colon Rectum 2001; 44: 538-546.
11. Edelman BR, Weiser MR. Endorectal ultrasound: its role in the diagnosis and treatment of rectal cancer. Clin Colon Rectal Surg 2008; 21: 167-177.
12. Harewood GC. Assessment of publication bias in the reporting of EUS performance in staging rectal cancer. Am J Gastroen- terol 2005; 100: 808-816.
13. Glaser F, Kuntz C, Schlag P, Herfarth C. Endorectal ultrasound for control of preoperative radiotherapy of rectal cancer. Ann Surg 1993; 217: 64-71.
14. Alexander AA, Palazzo JP, Ahmad NR, Liu JB, Forsberg F, Marks J. Endosonographic and color Doppler flow imaging alterations observed within irradiate rectal cancer. Int J Radiat Oncol Biol Phys 1996; 35: 369-375.
15. Heneghan JP, Salem RR, Lange RC, Taylor KJ, Hammers LW.
Transrectal sonography in staging rectal carcinoma: The role of gray-scale, color-flow, and Doppler imaging analysis. AJR Am J Roentgenol 1997; 169: 1247–1252.
16. Lassau N, Paturel-Asselin C, Guinebretiere JM, et al. New he- modynamic approach to angiogenesis: color and pulsed Dop- pler ultrasonography. Invest Radiol 1999; 34: 194-198.
17. Sudakoff GS, Gasparaitis A, Michelassi F, Hurst R, Hoffmann K, Hackworth C. Endorectal color Doppler imaging of primary and recurrent rectal wall tumours: Preliminary experience. AJR Am J Roentgenol 1996; 166: 55–61.
18. Mcdonald DM, Choyke PL. Imaging of angiogenesis: from mi- croscope to clinic. Nat Med 2003; 9: 713-725.
19. Tankova L, Stoilov G, Kovatchki D, Gegova A, Kalinov K, Hadjiolov N, Terziev I. Comparative evaluation of angiogen- esis in rectal cancer using Doppler ultrasound and immunohis- tochemical assessment. Compt Rend Acad Bulg Sci 2010; 63:
163-166.
20. Barbaro B, Valentini V, Coco C, et al.Tumour vascularity evalu- ated by transrectal color Doppler US in predicting therapy out- come for low-lying rectal cancer. Int J Radiat Oncol Biol Phys 2005; 63: 1304–1308.
