Treatment of oropharyngeal squamous cell carcinoma with external beam radiation combined with interstitial brachytherapy

Tolerance limit of external beam radiotherapy combined with low-dose rate brachytherapy in normal rabbit tissue

BACKGROUND

Dosage-optimized multimodal radiotherapies that are safe for head and neck cancer patients are desirable. In this study, we investigated tissue tolerance to varying doses of external beam radiotherapy (EBRT) combined with low-dose rate brachytherapy in the neck of a rabbit model.

METHODS

Twenty rabbits were used in the four test groups (five each) with iodine-125 seeds implanted in the neck treated with EBRT in four doses at 50, 40, 30 and 20 Gy each. Twelve rabbits for three control groups (four each). Three months after implantation, all rabbits were euthanized, and target tissues were collected. Analyses included seed implantation assessment, histopathological evaluation, immunohistochemistry staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, electron microscopy and statistics with the SPSS software.

RESULTS

Five rabbits died in the four test groups, and three rabbits died in the three control groups (one per group), which showed no significant difference by survival analysis. The calculated minimum peripheral dose was 17.6 Gy, the maximum dose near the seed was 1812.5 Gy, the D90 was 34.5 Gy and the mean dose was 124.5 Gy. In all groups that received radiation, apoptosis occurred primarily in the esophageal mucosa and corresponded to the dose of radiation; a higher dose caused a greater apoptosis, with significant difference between groups (P < 0.05). Electron microscopy of carotid arteries revealed that endothelial cells were swollen and some were shed from basement membrane, but no other noticeable tissue damages.

CONCLUSIONS

Limited EBRT at maximal dose (50 Gy) combined with the brachytherapy interstitially applied to the neck was tolerated well in the rabbit model.

Dose Escalation of Oropharyngeal Cancer: Long-Time Follow-Up and Side Effects

Previous studies on dose-escalated radiotherapy in head and neck cancer have shown mixed results, and it is not established which patients would benefit from dose escalation. Further, while dose escalation does not appear to increase late toxicity, this needs to be confirmed with longer follow-up. In this study, we analysed treatment outcome and toxicity in 215 patients with oropharyngeal cancer treated with dose-escalated radiotherapy (>72 Gy, EQD2, α/β = 10 Gy, boost by brachytherapy or simultaneous integrated boost) and a matched cohort of 215 patients treated with standard dose external-beam radiotherapy (68 Gy) between 2011 and 2018 at our institution. The 5-year overall survival (OS) was 77.8% (72.4-83.6) and 73.7% (67.8-80.1) in the dose-escalated and standard dose group, respectively (p = 0.24). Median follow-up was 78.1 (49.2-98.4) and 60.2 (38.9-89.4) months in the dose-escalated and standard dose groups, respectively. Grade ≥3 osteoradionecrosis (ORN) and late dysphagia were more common in the dose-escalated group compared to the standard dose group, with 19 (8.8%) vs. 4 (1.9%) patients developing grade ≥3 ORN (p = 0.001), and 39 (18.1%) vs. 21 (9.8%) patients developing grade ≥3 dysphagia (p = 0.01). No predictive factors to help select patients for dose-escalated radiotherapy were found. However, the remarkably good OS in the dose-escalated cohort, despite a predominance of advanced tumour stages, encourages further attempts to identify such factors.

Dose escalation in oropharyngeal cancer: a comparison of simultaneous integrated boost and brachytherapy boost

BACKGROUND

Local recurrence is the most common pattern of failure in head and neck cancer. It can therefore be hypothesised that some of these patients would benefit from an intensified local treatment, such as radiation dose escalation of the primary tumour. This study compares treatment and toxicity outcomes from two different boost modalities in oropharyngeal cancer: simultaneous integrated boost (SIB) and brachytherapy boost.

METHODS

Two hundred and forty-four consecutive patients treated with > 72 Gy for oropharyngeal squamous cell carcinoma between 2011 and 2018 at our institution were retrospectively analysed. Data on side effects were collected from a local quality registry and supplemented with a review of medical records. Patients receiving a brachytherapy boost first had external beam radiotherapy consisting of 68 Gy in 2 Gy fractions to the gross tumour volume (GTV), and elective radiotherapy to the neck bilaterally. The brachytherapy boost was typically given using pulsed dose rate, 15 fractions and 0.56-0.66 Gy per fraction [total dose in EQD2 = 75.4-76.8 Gy (α/β = 10)]. The typical dose escalated radiotherapy with external beam radiotherapy only, was delivered using SIB with 74,8 Gy in 2.2 Gy fractions [EQD2 = 76.0 Gy (α/β = 10)] to the primary tumour, 68 Gy in 2 Gy fractions to GTV + 10 mm margin and elective radiotherapy to the neck bilaterally.

RESULTS

Dose escalation by SIB was given to 111 patients and brachytherapy boost to 134 patients. The most common type of cancer was base of tongue (55%), followed by tonsillar cancer (42%). The majority of patients had T3- or T4-tumours and 84% were HPV-positive. The 5-year OS was 72,4% (95% CI 66.9-78.3) and the median follow-up was 6.1 years. Comparing the two different dose escalation modalities we found no significant differences in OS or PFS and these results remained after a propensity-score matched analysis was performed. The analysis of grade ≥ 3 side effects showed no significant differences between the two different dose escalation techniques.

CONCLUSIONS

We found no significant differences in survival or grade ≥ 3 side effects comparing simultaneous integrated boost and brachytherapy boost as alternative dose escalation modalities in the treatment of oropharyngeal cancer.

Clinical outcomes associated with evolving treatment modalities and radiation techniques for base-of-tongue carcinoma: thirty years of institutional experience

Curative treatment for base-of-tongue squamous cell carcinoma (BOT SCC) has evolved over time; however, comparative outcomes analysis for various treatment strategies is lacking. The authors reviewed the evolution of treatment modality and radiotherapy (RT) technique for 231 consecutive BOT SCC patients at our institution between 1981 and 2011. Treatment modalities included definitive chemoradiotherapy (chemoRT) (42%), definitive RT (33%), surgery followed by RT (20%), and surgery alone (5%). RT techniques included external beam plus interstitial brachytherapy (EBRT + IB) (37%), conventional EBRT (29%), intensity-modulated radiation therapy ± simultaneous integrated boost (IMRT ± SIB) (34%). Clinical characteristics and outcomes were stratified by modality or RT technique. Treatment modality evolved from definitive RT (1980s–1990s) to definitive chemoRT (1990s–2000s). RT technique evolved from EBRT + IB (1980s–1990s) to conventional EBRT (1990s–2000s) to IMRT + SIB (2000s). With median alive follow-up of 6 years (0.3–28 years), the 5-year LC, LRC, and OS rates were 80%, 73%, and 51%. There was no difference in distribution of gender, age, stage among treatment modalities. Definitive chemoRT had improved LRC (HR 1.6) and OS (HR 1.7) compared to definitive RT. IMRT + SIB had improved LRC (HR 3.2), DFS (HR 3.4), and OS (HR 3.0) compared to conventional EBRT. Over the past 30 years, BOT SCC treatment has undergone major paradigm shifts that incorporate nonsurgical functional preservation, concurrent chemotherapy, and advanced RT techniques. Excellent locoregional control and survival outcomes are associated with accelerated IMRT with chemotherapy.

T but not N stage predicts survival for patients with tonsillar carcinoma treated with external radiotherapy and brachytherapy

BACKGROUND

Our aim was to determine the efficacy of a therapeutic schedule including external radiation and brachytherapy in a consecutive and retrospective series of tonsillar carcinoma patients.

PATIENTS AND METHODS

Ninety-six patients with tonsillar carcinoma were treated between 1988 and 2000 and were followed up for at least for three years. All patients were treated with accelerated hyperfractionated external radiotherapy, 68 patients had additional brachytherapy and 69 patients with advanced stages also received chemotherapy. There was no planned surgery even though 73% had N+ disease. Eleven patients with persistent neck nodes underwent ultimate salvage surgery.

RESULTS

The overall three-year survival (OS) was 70%. OS for the T stage was T1 90%, T2 89%, T3 54% and T4 60%. The corresponding numbers for the N stage were N0 61.5%, N1 73%, N2 78% and N3 66%. Accordingly OS was influenced by the T stage (p>0.001) rather than by N stage. Only four patients with salvage surgery had viable tumour cells in the specimen, their survival was not inferior.

DISCUSSION

The primary tumour stage is an essential determinant for survival in patients with irradiated tonsillar carcinoma. Neck dissection should be confined only as a salvage procedure.