General characteristics
Ten patients, all of whom were men, were enrolled in the study between August 2013 and September 2016. The patients’ characteristics are presented in Table 2. The median patient age was 47.5 (range, 33–61). The site of disease was the hypopharynx–oropharynx in two patients, the buccal space in two patients, and the tongue in two patients. Four patient developed distant metastases, and six had localized progression. All patients were cisplatin-refractory. Five patients (Patient Nos. 1–5) experienced progression despite receiving a cetuximab-containing regimen. Nine patients were refractory to concurrent chemoradiotherapy (Patient Nos. 1–6 and 8–10). No patients had received immune checkpoint inhibitors at the time of study enrollment.
Table 2. Patients’ demographic data
Patient no.
|
Age (years)
|
Site
|
Previous lines of treatment
|
Recurrence
type
|
Cisplatin failure
|
Treatment
schedule
|
Best response
|
PFS (months)
|
1
|
47
|
Buccal space
|
3
|
local
|
Yes
|
R then CT
|
SD
|
6.3
|
2
|
38
|
Buccal space
|
3
|
local
|
Yes
|
R then CT
|
PD
|
1.9
|
3
|
49
|
Hypopharynx
|
3
|
local
|
Yes
|
R then CT
|
PD
|
1.1
|
4
|
49
|
Hypopharynx
|
3
|
Local +distant
|
Yes
|
R then CT
|
PD
|
1.9
|
5
|
39
|
Tongue
|
2
|
Local
|
Yes
|
R plus CT
|
PR
|
7.0
|
6
|
58
|
Hypopharynx
|
2
|
Distant
|
Yes
|
R plus CT
|
CR
|
6.2
|
7
|
61
|
Hypopharynx
|
1
|
Distant
|
Yes
|
R plus CT
|
PD
|
1.6
|
8
|
33
|
Tongue
|
3
|
Local
|
Yes
|
R plus CT
|
PD
|
0.7
|
9
|
48
|
Oropharynx
|
2
|
Distant
|
Yes
|
R plus CT
|
PR
|
7.1
|
10
|
45
|
Oropharynx
|
2
|
Local
|
Yes
|
R plus CT
|
SD
|
3.0
|
PFS, progression-free survival; R, rituximab; CT chemotherapy; SD, stable disease; PD, progressive disease; PR, partial response; CR, complete response
Feasibility evaluation
The first four patients (Patient Nos. 1–4) were treated using protocol 1. Three of these patients completed all evaluations after treatment, and the remaining patient (Patient No. 4) could not undergo CT because of upper airway compression secondary to disease progression. Patient No. 5 initially received rituximab 1000 mg on day −14. However, his tongue pain worsened, and an episode of tumor bleeding occurred 3 days later. After suspecting disease progression, salvage chemotherapy with gemcitabine and cisplatin was administered. The tumor bleeding subsided, and his tongue pain improved obviously. Following discussions with the local IRB, we amended the protocol to include the co-administration of rituximab with gemcitabine/cisplatin every 3 weeks (protocol 2). Finally, six patients, including Patient No. 5, were treated using protocol 2. No unexpected adverse effects were observed in patients treated using protocol 2, and all patients could be evaluated 1 week after rituximab administration.
The other adverse events during treatment are presented in Table 3. Most patients had grade 1–2 side effects, but two patients each had grade 3–4 nausea and grade 3–4 oral mucositis. The grade 3–4 hematologic side effects included grade 3–4 neutropenia in three patients, grade 3–4 anemia in two patients, and febrile neutropenia in two patients.
Table 3. Adverse events graded using NCI-CTCAE version 4.03
NICIC CTG grade
|
Grade 1–2
|
Grade 3–4
|
During induction chemotherapy (n = 10)
|
Anemia
|
5
|
1
|
Neutropenia
|
5
|
3
|
Thrombocytopenia
|
1
|
0
|
Alopecia
|
3
|
|
Mucositis/stomatitis
|
3
|
1
|
Febrile neutropenia
|
2
|
Nausea
|
5
|
2
|
Vomiting
|
1
|
0
|
Fatigue
|
7
|
1
|
Peripheral neuropathy
|
2
|
0
|
Response evaluation
In protocol 1, three patients experienced disease progression, and one patient had a best response of stable disease (Patient No. 1). In protocol 2, three patients responded to treatment, including one complete response (Patient No. 6) and two partial responses (Patient Nos. 5 and 9). Two patients experienced disease progression, and the remaining patient had stable disease. Among the five patients experiencing clinical benefits (including complete responses, partial responses, and stable disease), the median duration of response was 6 months (range, 3–7.1). The waterflow plot of the patients’ best responses is presented in Fig. 1. The representative CT findings of one responder (Patient No. 5) before and after treatment are presented in Fig. 2.
Because we observed rapid disease progression in Patient No. 5 shortly after the administration of rituximab, we questioned whether B cell depletion using rituximab monotherapy could cause HPD. We used TGKR to evaluate tumor growth rates in patients with disease progression [14]. TGKR could be evaluated in three patients treated using protocol 1 (Patient Nos. 2–4). All three patients experienced HPD, as presented in Fig. 3. Regarding patients treated using protocol 2 who experienced disease progression (Patient Nos. 7–8), Patient No. 8 could not undergo CT after disease progression because superior vena cava syndrome prevented him from adopting the supine position during the examination. Therefore, we only evaluated TGFR in Patient No. 7, and no evidence of HPD was detected, as illustrated in Fig. 3.
Immune cell evaluation
We investigated the changes of immune cell counts in peripheral blood. We found B cells were significantly depleted in all patients after rituximab administration (p = 0.013). We examined the counts of B cells (CD19+CD20+), cytotoxic T cells (CD3+CD8+), helper T cells (CD3+CD4+), regulatory T cells (CD3+CD4+CD25+CD127−), classical monocytes (CD14+CD16−), non-classical monocytes (CD14−CD16+), and intermediate monocytes (CD14+CD16+) to analyze whether the immune cell counts in peripheral blood were correlated with treatment responses. The results demonstrated that responders had a significantly higher ratio of cytotoxic T cells/regulatory T cells in peripheral blood before rituximab treatment than non-responders (p = 0.017) (Fig. 4). No differences were detected in the counts of other immune cells between responders and non-responders.