Effect of relevant factors on radiation-induced nasopharyngeal ulcer in patients with primary nasopharyngeal carcinoma treated with intensity-modulated radiation therapy

Post radiation mucosal ulcer risk after a hypofractionated stereotactic boost and conventional fractionated radiotherapy for oropharyngeal carcinoma

BACKGROUND/PURPOSE

Post radiation mucosal ulcers (PRMU) after treatment for oropharyngeal squamous cell carcinoma (OPSCC) can have a huge negative impact on patients' quality of life, but little is known concerning risk factors and the impact of fraction size. Therefore, the goal of this study was to determine the pattern of PRMU development and to identify risk factors after a hypofractionated stereotactic body radiotherapy boost (SBRT) compared to conventionally fractionated radiotherapy for OPSCC.

MATERIAL AND METHODS

We performed a retrospective cohort study (N = 332) of OPSCC patients with ≥ 1-year disease-free survival, treated with 46 Gy Intensity Modulated Radiotherapy (IMRT) (2 Gy fractions) followed by either an SBRT boost of 16.5 Gy (5.5 Gy fractions) (N = 180), or 24 Gy IMRT (2 Gy fractions) (N = 152). PRMU (grade ≥ 2) was scored when observed > three months after the last radiotherapy (RT) fraction (CTCAE v5.0). Potential risk factors were analyzed with Cox regression models using death as competing risk. Dose at the PRMU site was calculated by projecting delineated PRMU on the planning CT.

RESULTS

All cases of PRMU (N = 64) occurred within 24 months; all were grade 2. The cumulative incidence at 2 years in the SBRT boost group was 26% (N = 46) vs. 12% (N = 18) for conventional fractionation (p = 0.003). Most PRMU developed within nine months (N = 48). PRMU occurring > nine months (N = 16) were mainly observed in the SBRT boost group (N = 15). Sex (p = 0.048), acute tube feeding (p = < 0.001), tumor subsite tonsil (p = 0.001), and N stage (p = 0.017) were associated with PRMU risk at multivariable regression in the hypofractionated SBRT boost group. All 25 delineated PRMU were located within the high dose regions.

CONCLUSION

The risk of PRMU should be included in the cost benefit analysis when considering future research using a hypofractionated SBRT boost for OPSCC patients.

Irradiation-induced nasopharyngeal necrosis (INN) in newly diagnosed nasopharyngeal carcinoma treated by intensity-modulated radiation therapy: clinical characteristics and the influence of treatment strategies

Purpose

To define the clinical characteristics of irradiation-induced nasopharyngeal necrosis (INN) after intensity-modulated radiotherapy (IMRT) and identify the influence of treatment strategies on INN in primary nasopharyngeal carcinoma (NPC) patients.

Patients and methods

From 2008 to 2019, NPC patients pathologically diagnosed with INN after primary IMRT were reviewed. Those patients were matched with propensity scores for patients without INN in our center. The impact of treatment strategies on INN occurrence was assessed using univariate and multivariate logistic regression analysis.

Results

The incidence rate of INN was 1.9% among the primary NPC population, and 53 patients with INN were enrolled. Headache and foul odor were the main symptoms, and 71.7% of cases had pseudomembrane during or at the end of radiotherapy. All patients were in early or middle stage INN, and no one presented with skull-based osteoradionecrosis. Then 212 non-INN patients were included based on propensity scores match. Overall survival (p = 0.248) and progression-free survival (p = 0.266) curves were similar between the INN and non-INN groups. Treatment strategies including combining chemotherapy or molecular targeted therapy with radiotherapy were not associated with INN occurrence, while boost dose (OR 7.360; 95% CI 2.301–23.547; p = 0.001) was a predictor factor for it. However, the optimal threshold for an accumulated dose to predict INN's occurrence was failed to determine.

Conclusion

In the IMRT era, the severity of INN in primary NPC patients is lessened. This study showed that treatment strategies contributed little to develop INN, while the accumulated dose of radiation may relate to its occurrence.