The total sample size in this study is 35.
1. Age distribution:
The details of age distribution of the cases in this study are shown in the Table I and Chart I.
Age in years
|
No. of cases (%)
|
40-49
|
9 (25)
|
50-59
|
16 (46)
|
≥ 60
|
10 (29)
|
Total
|
35 (100)
|
2. Gender distribution:
The distribution of gender in this study are shown in the Table II and Chart II.
Gender
|
No. of cases (%)
|
Male
|
21 (60 )
|
Female
|
14 (40)
|
Total
|
35 (100)
|
3. Risk factors
The various risk factors associated with head and neck cancers are smoking, alcoholism, tobacco products, and the genetic predisposition. The risk factors found among the patients in this study were smoking, alcohol, tobacco chewing.
The details of the distribution of the cases in relation to the number of risk factors is shown in the Table IV.
Sub-group
|
No. of risk factors
|
Total no cases
|
1
|
2
|
3
|
No risk factors
|
Complete tumour regression
|
3
|
9
|
1
|
1
|
14
|
Residual tumour
|
10
|
5
|
4
|
2
|
21
|
Total
|
13
|
14
|
5
|
3
|
35
|
Baseline DNA damage
4. Age and Baseline DNA damage:
Comet parameters of total comet length, head diameter, percentage of DNA in head, tail length and percentage of DNA in tail were recorded in all the age groups. The comet parameters of the baseline sample (before radiotherapy) among the various age groups are shown in the Table V.
Comet Parameters
|
Mean ± SD
|
p value
|
40 – 49
Years
|
50 – 59
Years
|
>60 years
|
Comet length (μm)
|
76.6±31.3
|
55.3±29.2
|
54.5±25.5
|
0.125
|
Head diameter(μm)
|
59.4±25
|
46.5±23.6
|
40.2±16.2
|
0.018
|
% of DNA in head
|
87.1±5.9
|
87.5±5.4
|
83.2±8.2
|
0.242
|
Tail length (μm)
|
17.8±16.4
|
9.7±10.1
|
15±13.6
|
0.082
|
% of DNA in tail
|
12.9±5.9
|
12.6±5.4
|
16.8±8.2
|
0.252
|
5. Risk factors and basal DNA damage:
The comet parameters of the baseline sample in relation to the risk factors are shown in the Table VI and the Chart V.
Comet Parameters
|
Mean ± SD
|
p value
|
Risk factors <1
|
Risk factors >1
|
Comet length (μm)
|
66.9±31.7
|
55.2±27.1
|
0.172
|
Head diameter(μm)
|
53.3±24.5
|
43.6±20.7
|
0.279
|
% of DNA in head
|
87.5±7.7
|
85.1±5.3
|
0.292
|
Tail length (μm)
|
14.4±14
|
12.3±12.5
|
0.317
|
% of DNA in tail
|
12.5±7.7
|
15.0±5.3
|
0.273
|
DNA damage after radiotherapy in patients with complete regression of tumor
The comet parameters within the patients having complete regression of tumor is shown in the Table VIII.
Comet Parameters
|
Mediam (IQR)
|
p value
|
Complete tumour regression
|
Residual tumour
|
Comet length (μm)
|
45.3(38.6-77.8)
|
56.4(35.2-84.9)
|
0.840
|
Head diameter(μm)
|
40.2(37.6-55.6)
|
37.5(27.9-66.6)
|
0.329
|
% of DNA in head
(mean ± SD)
|
86.8±5.5
|
85.7±7.1
|
0.613
|
Tail length (μm)
|
6.5(3.0-14.1)
|
7.9(3.7-23.0)
|
0.400
|
% of DNA in tail
(mean ± SD)
|
13.3±5.5
|
14.2±7.2
|
0.652
|
a) Comet Length
Comparison of comet length parameter of all the five samples in patients with complete regression of tumour is shown in Table IX and Chart VII.
Comet Parameters
|
Mediam (IQR)
|
Baseline
|
Post – RT1
|
Post – RT2
|
Post – RT3
|
Follow - Up
|
Comet Length
(μm)
|
45.3
(38.6-77.8)
|
114.5
(107.4-54.3)
|
116.5
(107.5- 146)
|
116.9
(106.4 - 152.3)
|
67.9
(54.5-82.6)
|
p<0.05
|
Baseline vs Post-RT1
Post-RT3 vs Follow-up
|
p>0.05
|
Post-RT1 vs Post-RT2
Post-RT2 vs Post-RT3
|
The comet length parameter of post-RT sample [114.5(107.4-154.3) μm] is increased when compared to baseline sample [45.3(38.6-77.8) μm] with a p value less than 0.05.
There is a progressive increase in the comet length parameter of post-RT samples 1, 2 and 3, though it is statistically insignificant.
The comet length parameter of follow-up sample [67.9(54.5-82.6) μm] is decreased when compared to post-RT sample 3 [116.9(106.4-152.3) μm] with a p value less than 0.05.
B) Head Diameter
Comparison of head diameter parameter of all the five samples in patients with complete regression of tumour is shown in Table X and Chart VIII.
Comet Parameters
|
Mediam (IQR)
|
Baseline
|
Post – RT1
|
Post – RT2
|
Post – RT3
|
Follow - Up
|
Head diameter
(μm)
|
40.2
(37.6-55.6)
|
66.0
(54.7-81.9)
|
65.3
(54.0-73.5)
|
62.2
(51.6-85.7)
|
56.6
(39.3-61.5)
)
|
p<0.05
|
Baseline vs Post-RT1
Post-RT3 vs Follow-up
|
p>0.05
|
Post-RT1 vs Post-RT2
Post-RT2 vs Post-RT3
|
The head diameter parameter of post-RT sample 1 [66.0(54.7-81.9) μm] is increased when compared to baseline sample [40.2(37.6-55.6) μm] with a p value less than 0.05.
There is a progressive decrease in the head diameter parameter of post-RT samples 1, 2 and 3, though it is statistically insignificant.
The head diameter parameter of follow-up sample [56.6(39.3-61.5) μm] is decreased when compared to post-RT sample 3 [62.2(51.6-85.7) μm] with a p value less than 0.05.
C) Percentage of DNA in head
Comparison of % of DNA in head parameter of all the five samples in patients with complete regression of tumour is shown in Table XI and Chart IX
Comet Parameters
|
Mediam (IQR)
|
Baseline
|
Post – RT1
|
Post – RT2
|
Post – RT3
|
Follow - Up
|
% of DNA in head
|
86.8±5.5
|
79.6±7.8
|
75.0±10.4
|
73.2±10.3
|
84.2±6.7
|
p<0.05
|
Baseline vs Post-RT1
Post-RT3 vs Follow-up
|
p>0.05
|
Post-RT1 vs Post-RT2
Post-RT2 vs Post-RT3
|
The percentage of DNA in head parameter of post-RT sample 1 (79.6 ± 7.8) is decreased when compared to baseline sample (86.8 ± 5.5) with a p value less than 0.05.
There is a progressive decrease in the percentage of DNA in head parameter of post-RT samples 1, 2 and 3, though it is statistically insignificant.
The percentage of DNA in head parameter of follow-up sample (84.2 ± 6.7) is increased when compared to post-RT sample 3 (73.2 ± 10.3) with a p value less than 0.05.
D) Tail length
Comparison of tail length parameter of all the five samples in patients with complete regression of tumour is shown in Table XII and Chart X.
Comet Parameters
|
Mediam (IQR)
|
Baseline
|
Post – RT1
|
Post – RT2
|
Post – RT3
|
Follow - Up
|
Tail length (μm)
|
6.4
(3.0-14.1)
|
46.9
(41.1-76.0)
|
57.13
(44.6-67.3)
|
52.8
(45.5-73.4)
|
18.0
(10.8-26.0)
|
p<0.05
|
Baseline vs Post-RT1
Post-RT3 vs Follow-up
|
p>0.05
|
Post-RT1 vs Post-RT2
Post-RT2 vs Post-RT3
|
The tail length parameter of post-RT sample 1 [46.9(41.1-76.0) μm] is increased when compared to baseline sample [6.4(3.0-14.1) μm] with a p value less than 0.05.
There is no progressive increase in the tail length parameter of post-RT samples 1,2 and 3
The tail length parameter of follow-up sample [18.0(10.8-26.0) μm] is decreased when compared to post-RT sample 3 [52.8(45.5-73.4) μm] with a p value less than 0.05.
E) Percentage of DNA in tail
Comparison of percentage of DNA in tail parameter of all the five samples in patients with complete regression of tumour is shown in Table XIII and Chart XI
Comet Parameters
|
Mean ± SD
|
Baseline
|
Post – RT1
|
Post – RT2
|
Post – RT3
|
Follow - Up
|
% of DNA in tail
|
13.3±5.5
|
22.7±11.0
|
25.7±10.2
|
27.8±10.5
|
15.8±6.7
|
p<0.05
|
Baseline vs Post-RT1
Post-RT3 vs Follow-up
|
p>0.05
|
Post-RT1 vs Post-RT2
Post-RT2 vs Post-RT3
|
The percentage of DNA in tail parameter of post-RT sample 1 (22.7±11.0) is increased when compared to baseline sample (13.3±5.5) with a p value less than 0.05.
There is a progressive increase in the percentage of DNA in tail parameter of post-RT samples 1, 2 and 3, though it is statistically insignificant.
The percentage of DNA in head parameter of follow-up sample (15.8±6.7) is decreased when compared to post-RT sample 3 (27.8±10.5) with a p value less than 0.05.
Repair analysis and risk factors in complete tumour regression patients
Smoking
Comet parameters were compared in relation to smoking status among the patients with complete regression of tumour for repair analysis of DNA and the results are shown in the Table XX.
Comet parameters
|
smoking
|
Mean ± SD
|
p value
|
Baseline
|
Follow-up
|
Comet
length(μm)
|
Yes
|
52.1±25.0
|
69.4±24.9
|
>0.05
|
No
|
75.9±36.7
|
74.8±10.1
|
Head
diameter(μm)
|
Yes
|
46.3±23.9
|
57.3±24.2
|
No
|
59.3±28.0
|
49.8±12
|
% DNA in head
|
Yes
|
85.5±4.4
|
84.9±7.5
|
No
|
89.3±7.0
|
82.9±5.5
|
Tail length(μm)
|
Yes
|
6.7±3.9
|
13.3±8.6
|
No
|
17.5±17.9
|
24.5±2.3
|
% DNA in tail
|
Yes
|
14.7±4.3
|
15±7.5
|
No
|
10.7±7.0
|
17.1±5.5
|
No significant difference in repair analysis of DNA was observed between smokers and non-smokers in patients with complete regression of tumor.
Alcoholic status
Comet parameters were compared in relation to alcoholic status among the patients with complete regression of tumour for repair analysis of DNA and the results are shown in the Table XXI.
Comet parameters
|
Alcoholic status
|
Median ± IQR
|
p value
|
Baseline
|
Follow-up
|
Comet
length(μm)
|
Yes
|
59.2±38.0
|
69.8±9.6
|
>0.05
|
No
|
61.1±29.6
|
71.9±23.9
|
Head
diameter(μm)
|
Yes
|
55.1±35.3
|
54.0±14.6
|
No
|
49.3±22.2
|
54.8±23.1
|
% DNA in head
|
Yes
|
87.0±4.6
|
84.6±5.5
|
No
|
86.8±6.1
|
84.0±7.5
|
Tail length(μm)
|
Yes
|
5.7±3.7
|
16.8±9.4
|
No
|
12.5±13.4
|
17.8±9.4
|
% DNA in tail
|
Yes
|
13.0±4.6
|
15.4±5.5
|
No
|
13.4±6.1
|
15.9±7.4
|
No significant difference in repair analysis of DNA was observed between alcoholics and others in patients with complete tumor regression
Tobacco chewing status
Comet parameters were compared in relation to tobacco chewing status among the patients with complete regression of tumour for repair analysis and the results are shown in the Table XXII
Comet parameters
|
Tobacco chewing
|
Median ± IQR
|
p value
|
Baseline
|
Follow-up
|
Comet
length(μm)
|
Yes
|
53.1±23.4
|
70.3±22.5
|
>0.05
|
No
|
87.9±44
|
75.3±82.5
|
Head
diameter(μm)
|
Yes
|
45.9±20.6
|
54.0±22.3
|
No
|
69.5±36.6
|
56.9±14.7
|
% DNA in head
|
Yes
|
87.1±5.8
|
84.6±7.4
|
No
|
86.0±5.3
|
83.0±3.8
|
Tail length(μm)
|
Yes
|
8.0±6.8
|
17.2±10.1
|
No
|
19.9±12.2
|
18.8±4.4
|
% DNA in tail
|
Yes
|
13.1±5.8
|
15.4±7.4
|
No
|
14.0±5.3
|
17.0±3.8
|
No significant difference in repair analysis of DNA was observed between tobacco users and others in patients with complete regression of tumor