Long-term outcomes following stereotactic body radiotherapy boost for oropharyngeal squamous cell carcinoma

Figures & data

Table 1. Baseline characteristics of the study population (n = 195).

	Value*
Age (years)	61 (34–86)
Gender
Male	122 (63%)
Female	73 (37%)
ECOG performance status
0	151 (77%)
1	44 (23%)
Smoking >10 pack-years	147 (75%)
Smoker at diagnosis	103 (53%)
Current or previous alcohol abuse	59 (30%)
CCI
0	54 (28%)
1	44 (23%)
≥2	97 (50%)
Baseline BMI
>22	152 (78%)
≤ 22	43 (22%)
Tooth extraction prior to RT	64 (33%)
T stage classification
T1	39 (20%)
T2	136 (70%)
T3	20 (10%)
N Stage classification
N0	91 (47%)
N1	32 (16%)
N2a	15 (8%)
N2b	49 (25%)
N2c	8 (4%)
Stage grouping (AJCC 7th Edition)
Stage I	11 (5.6%)
Stage II	68 (34.9%)
Stage III	44 (22.6%)
Stage IVa	72 (36.9%)
Oropharynx subsite
Base of tongue	35 (18%)
Soft palate	23 (12%)
Tonsil	113 (58%)
Oropharynx wall	11 (6%)
Other	13 (7%)
P16 status
Positive	63 (32%)
Negative	30 (15%)
Unknown	102 (52%)
Concurrent systemic treatment
Cisplatin	10 (5%)
Cetuximab	2 (1%)
Accelerated radiotherapy	192 (99%)
Neck dissection	101 (52%)
Unilateral neck radiotherapy	82 (42%)

Abbreviations: CCI: Charlson Comorbidity Index; ECOG: Eastern Cooperative Oncology Group.

*Median and range are provided for continuous variables while n and percent are provided for categorical variables.

Three patients with lymph node metastases did not undergo neck dissection due to advanced age and inclusion of the involved lymph node in the SBRT boost (n = 1), complete excision of the lymph node with excisional biopsy (n = 1), and involvement of a retropharyngeal lymph node which was included in the SBRT boost (n = 1).

Figure 1. Kaplan-Meier plots showing freedom from locoregional progression, freedom from any progression, disease-specific survival, overall survival, and disease-free survival.

Figure 2. Kaplan-Meier plots showing cumulative incidence of late grade ≥3 toxicity in 182 patients.

Figure 3. Kaplan-Meier plots showing cumulative incidence of specific late grade ≥3 toxicity in 182 patients.

Table 2. Distribution of maximum toxicity scores in 182 evaluated patients (crude numbers).

Endpoint	Grade 3 n (%)	Grade 4 n (%)	Grade 5 n (%)
Overall max score	39* (21.4%)	6 (3.2%)	2 (1.1%)
Mucosal ulcer/soft tissue necrosis	28 (15.4%)	1 (0.5%)	1 (0.5%)
Dysphagia	15 (9.0%)	0	0
Weight loss	7 (3.8%)	0	0
Osteoradionecrosis	3 (1.6%)	5 (2.7%)	1 (0.5%)
Trismus	4 (2.2%)	0	0
Aspiration	1 (0.5%)	0	0
Xerostomia	0	0	0

*Including 12 patients with 2 or more grade 3 events.

Table 3. Prognostic factors for grade ≥3 late toxicity.

	Univariable			Multivariable
	HR	95% CI	p	HR	95% CI	p
Sex (male vs. female)	0.61	0.34–1.08	.089
Age (>65 vs. ≤65)	1.05	0.56–1.97	.9
ECOG (1 vs. 0)	1.00	0.49–2.08	1.0
Pack years (>10 vs. ≤10)	1.93	0.86–4.29	.11
Smoker at diagnosis (yes vs. no)	2.84	1.47–5.49	.002	2.91	1.51–5.51	.001
History of alcohol abuse (yes vs. no)	1.37	0.75–2.51	.3
CCI (≥ 2 vs. < 2)	1.84	1.02–3.31	.042	1.90	1.06–3.43	.032
BMI at start of RT (≤22 vs. >22)	1.67	0.89–3.11	.11
Tumor subsite tonsil (vs other)	1.17	0.65–2.11	.6
Tumor subsite BOT (vs other)	0.42	0.15–1.17	.095
T stage (T3 vs. T1–T2)	1.49	0.63–3.50	.4
Bilateral vs. unilateral neck RT	1.09	0.61–1.95	.8
Tooth extraction prior to RT	1.09	0.60–2.00	.8

BMI: body mass index; BOT: base of tongue; CCI: Charlson Comorbidity Index; CI: confidence interval; ECOG: Eastern Cooperative Oncology Group; HR: hazard ratio; RT: radiotherapy. Bold values indicate statistical significance (p<0.05).