Population statistics
At baseline, 42 patients displayed at least 1 TL. A set of 88 TLs was distributed per disease location as follows: lung (31% n = 27), breast (26% n = 23), liver (23%, n = 20), lymph nodes (17% n = 15) and miscellaneous (3%; n = 3). Miscellaneous locations (skin and mediastinal lesions) were excluded as they were underrepresented. Therefore, 85 TLs were classified into 4 major groups by location (Table 2). To be noted that 22 patients had no visible primary breast tumors on CT due to previous trastuzumab treatment or because their tumors were visible only on mammography.
Table 2
Proportion of tumors at each disease location at baseline
|
Varlitinib + Capecitabine
|
Lapatinib + Capecitabine
|
p valuea
|
|
Number of Tumors
|
%
|
Number of Tumors
|
%
|
Breast
|
12
|
35.3
|
11
|
21.6
|
0.16
|
Lung
|
7
|
20.6
|
20
|
39.2
|
0.07
|
Liver
|
9
|
26.5
|
11
|
21.6
|
0.6
|
Lymph node
|
6
|
16.6
|
9
|
17.6
|
1.0
|
Total
|
34
|
100
|
51
|
100
|
|
a p value corresponding to statistical significance of the inter‑arm difference of proportion of tumor numbers, calculated using a two-sided Chi-square test.
At Week 12, 35 patients remained in the study (14 and 21 patients in the VC and LC arms, respectively) (Table 3) and 74 tumors were measured.
Table 3
Tumor burden changes from baseline to Week 12
|
VC
(tumor diameter)
|
LC
(tumor diameter)
|
VC
(tumor volume)
|
LC
(tumor volume)
|
Number of evaluable patients
|
14
|
21
|
14
|
21
|
Mean change in tumor burdena
|
-40.03%
|
-21.19%
|
-64.15%
|
-25.59%
|
p valueb
|
0.086
|
0.13
|
LC = Lapatinib + Capecitabine; VC = Varlitinib + Capecitabine.
a Tumor burden computed as per Response Evaluation Criteria in Solid Tumor, by summing the size of up to 5 target tumors independent of tumor location, considering not more than 2 tumors per location.
b p value corresponding to statistical significance of inter-arm difference in mean changes in tumor burden (Wilcoxon rank test).
Distributions of tumor size at baseline per tumor location in both treatment arms are displayed in Fig. 2 for both QIBs.
At baseline, there was no significant difference between the treatment arms in the proportion of tumors (p = 0.27), though there was a greater proportion of lung tumors in the LC arm versus the VC arm (p = 0.07) (Table 2). When considering either QIB, the mean size of breast tumors was significantly larger than that of tumors at the other locations (p < 0.002).
Inter-arm comparison of the responses
Tumor burden changes, in both treatment arms, are presented in Table 3. Waterfall plots of patient responses (LAD and volume) are displayed in Figs. 3; changes of tumor burden stratified per tumor location are in Figs. 4.
There were significant reductions in breast tumor burden in the VC arm compared to the LC arm (p = 0.002 for LAD, p < 0.001 for volume in favor of VC arm). No significant interarm differences were noted for other TLs. Table 4 summarizes the mean tumor response with tumors considered independently from patients and grouped by location. Putting all tumors together without distinction from disease location and patient, a test of interarm difference of the response yielded p = 0.02 for tumor LAD and p = 0.015 for tumor volume. There was no significant relationship between the response and baseline tumor size by LAD or volume.
Table 4
Mean proportional change (%) in diameter and volume of tumors considered independent of patients and grouped by disease locations
|
Varlitinib + Capecitabine
|
Lapatinib + Capecitabine
|
p valuea
|
Diameter (%)
|
Volume (%)
|
Diameter (%)
|
Volume (%)
|
Diameter
|
Volume
|
Breast
|
-50.19
|
-85.06
|
-16.15
|
-30.90
|
0.001
|
< 0.001
|
Lung
|
-29.96
|
-56.31
|
-12.17
|
16.68
|
0.11
|
0.14
|
Liver
|
-8.64
|
7.24
|
-21.55
|
-44.71
|
0.80
|
0.40
|
Lymph node
|
-46.15
|
-71.7
|
-31.86
|
-46.48
|
0.82
|
0.59
|
a p value corresponding to significance of the inter‑arm comparison of the proportional change according to diameter and volume of tumors (Wilcoxon rank test).
Intra-arm comparison of the responses
Tables 5 and 6 summarizes, for tumor diameter and volume respectively, the difference of responses between the different pairs of tumor locations.
Table 5
Intra-arm comparison of change in tumor diameter change at different tumor locations from baseline to Week 12
Mean proportional change in tumor diameter
|
Varlitinib + Capecitabine
|
Lapatinib + Capecitabine
|
Difference [95% CIs] (%)
|
p valuea
|
Difference [95% CIs] (%)
|
p valuea
|
Liver-breast
|
49.96 [-8.31; 108.29]
|
0.11
|
-10.08 [-70.42; 50.25]
|
0.97
|
Lung-breast
|
19.89 [-38.41; 78.19]
|
0.77
|
-1.76 [-52.75; 49.23]
|
0.99
|
Lymph Node-breast
|
6.33 [-51.96; 64.63]
|
0.99
|
-16.01 [-79.70; 47.67]
|
0.90
|
Lung-liver
|
-30.09 [-98.69; 38.51]
|
0.61
|
8.32 [-47.53; 64.18]
|
0.98
|
Lymph node-liver
|
-43.65 [-112.26; 24.95]
|
0.30
|
-5.93 [-73.58; 61.71]
|
0.99
|
Lymph node-lung
|
-13.56 [-82.16; 55.03]
|
0.94
|
-14.25 [-73.72; 45.21]
|
0.91
|
CI = Confidence interval.
a p value corresponding to the test of a significant difference in the responses between the tumor locations (Test of Tukey Honest Significant Differences).
Table 6
Intra-arm comparison of change in tumor volume at different tumor locations from baseline to Week 12
Mean proportional change in volume
|
Varlitinib + Capecitabine
|
Lapatinib + Capecitabine
|
Difference [95% CIs] (%)
|
p valuea
|
Difference [95% CIs] (%)
|
p valuea
|
Liver-breast
|
107.49 [26.34; 188.64]
|
0.007
|
-21.09 [-126.18; 83.98]
|
0.94
|
Lung-breast
|
30.49 [-50.67; 111.64]
|
0.71
|
42.11 [-48.31; 132.52]
|
0.58
|
Lymph Node-breast
|
14.47 [-66. 68; 95.62]
|
0.96
|
-17.16 [-128.08; 93.77]
|
0.97
|
Lung-liver
|
-77.00 [-172.49; 18.49]
|
0.14
|
63.20 [-35.55; 161.96]
|
0.32
|
Lymph node-liver
|
-93.02 [-188.51; 2.47]
|
0.057
|
3.94 [-113.88; 121.77]
|
0.99
|
Lymph Node-lung
|
-16.01 [ -111.51; 79.48]
|
0.96
|
-59.26 [-164.21; 45.69]
|
0.42
|
CI = Confidence interval.
a p value of the test of a significant difference in the responses between the tumor locations (Test of Tukey Honest Significant Differences).
For changes in tumor diameter (Table 5), explained variabilities per tumor location, patient and patient:tumor interaction were 22%, 5% and 16%, respectively, in the VC arm, and 2%, 0.5% and 30%, respectively, in the LC arm.
For changes in tumor volume (Table 6), explained variabilities per tumor location, patient and patient:tumor interaction were 36%, 10% and 4%, respectively, in the VC arm, and 13%, 1% and 23%, respectively, in the LC arm.
Model design
We applied our model using the distribution of tumor location (Table 2) and the average response by tumor location (independent tumors) in Table 5 and Table 6. Thus, we modeled the response to treatment for the VC and LC arms respectively in Eqs. 1 and 2 (using LAD) and respectively in Eqs. 3 and 4 (using volume).
LAD
1/28 * (11* -50.19% + 5* -29.96% + 6 * -8.64% + 6*-46.15%) = -36.8% Eq. 1
1/46 * (11* -16.15% + 18* -12.17% + 11 * -21.55% + 6*-31.86%) = -17.9% Eq. 2
Volume
1/28 * (11* -85.06% + 5* -56.31% + 6 * 7.23% + 6*-71.7%) = -57.3% Eq. 3
1/46 * (11* -30.90% + 18* 16.68% + 11 * -44.71% + 6*-46.48%) =-17.6% Eq. 4
a test for a significant difference in inter-arm responses yielded p = 0.07 (using LAD), and p < 0.001 (using volume) both in favor of VC arm.
Sensitivity analysis
The inter-arm comparison of the stratified responses yielded p = 0.015 (using LAD) and p = 0.03 (using volume) after removing outliers at Week 12 (n = 6 for tumor diameter, n = 3 for tumor volume) (supplementary Table I.1). When considering each tumor independently from patients, interarm comparison yielded p < 0.007 (for tumor diameter) and p = 0.016 (for tumor volume) after removing outliers (n = 7 for tumor diameter, n = 4 for tumor volume). Intra-arm comparisons of the stratified responses by disease location are summarized in supplementary Tables I.2 and I.3.
Equations 1.1 to 1.4 (electronic supplementary material [ESM]) obtained following data adjustment at Week 12 with balancing of tumors at each disease location were comparable to equations 1 to 4. A test for a significant difference in inter-arm responses yielded p = 0.17 (tumor diameter) and p = 0.003 (tumor volume).
Equations 1.5 to 1.8 (electronic supplementary material [ESM]) obtained in computing stratified change of tumor burden, balancing numbers of patients having tumor at the same location, were comparable to equations 1 to 4. A test for a significant difference in inter-arm responses yielded p = 0.26 for tumor diameter and p = 0.11 for tumor volume in favor of VC arm.