Dose-volume factors associated with ear disorders following intensity modulated radiotherapy in nasopharyngeal carcinoma

Evaluation and analysis of risk factors of hearing impairment for nasopharyngeal carcinoma treated using intensity-modulated radiotherapy

BACKGROUND

Treating nasopharyngeal carcinoma (NPC) with radiotherapy frequently causes hearing impairment (HI). HI risk data haven't been evaluated quantitatively. This study aimed to analyze the probability of HI and sever HI (SHI), develop a nomogram to quantify individual prediction, and provide dose limitation suggestions.

METHODS AND MATERIALS

This single-center, retrospective study was conducted based on 588 adolescents and young adults with non-metastatic NPC treated using intensity modulated radiation therapy (IMRT) at Sun Yat-sen University Cancer Center between 2010 and 2016. A least absolute shrinkage and selection operator (LASSO) logistic regression model and univariate analysis were used to screen potential risk factors. The concordance index and a calibration curve evaluated the nomogram models' predictive ability, with bootstrap resampling validation.

RESULTS

We analyzed 588 patients with NPC, with a median follow-up of 103.4 months. HI occurred in 39.5 % of patients, with 29.7 % experiencing SHI. Two factors were classified as precursors for HI (volume 45 Gy of the inner ear (IEV45) and volume 50 Gy of the internal auditory canal (IACV50)), and IACmin and IACV60 for SHI, respectively. Prognostic nomograms were developed to predict HI and SHI probabilities, showing excellent discriminative abilities (c-index values = 0.806 and 0.793, respectively). We also suggested IEV45 < 50 % and/or IACV50 < 40 % as rational dose limitations for HI, and IACmin < 44 Gy and/or the IACV60 < 40 % for SHI.

CONCLUSION

Comprehensive analysis could predict the risk of HI and SHI in NPC after IMRT, proposing rational dose limitations and improving long-term quality of life.

External Auditory Canal Cholesteatoma after Radiation Therapy for Nasopharyngeal Cancer: Case Series and Systematic Review

The authors performed a systematic review, in accordance with the PRISMA guidelines, across multiple databases, including all original studies published until November 2022, focusing on External auditory canal cholesteatoma (EACC) after radiation therapy (RT) for nasopharyngeal cancer (NC). Inclusion criteria were original articles reporting on secondary EACC after RT for NC. Articles were critically appraised to assess level of evidence using the Oxford Center for Evidence-Based Medicine criteria. Overall, 138 papers were identified and after duplicate removal (34 papers) and excluding papers not in English, 93 papers were assessed for eligibility; finally, only five papers were included and summarized with the three cases coming from our institution. These mainly involved the anterior and the inferior part of the EAC. The mean time of diagnosis after RT was the largest series of 6.5 years (with a range from 0.5 to 15.4 years). Patients undergoing RT for NC have 18 times a higher risk of developing EACC compared to the normal population. EACC is probably one of the most underreported side effects, because patients may present variable clinical findings, which could lead to misdiagnosis. Early diagnosis of RT related EACC is advised to enable conservative treatment.

Improved accuracy of auto-segmentation of organs at risk in radiotherapy planning for nasopharyngeal carcinoma based on fully convolutional neural network deep learning

OBJECTIVE

We examined a modified encoder-decoder architecture-based fully convolutional neural network, OrganNet, for simultaneous auto-segmentation of 24 organs at risk (OARs) in the head and neck, followed by validation tests and evaluation of clinical application.

MATERIALS AND METHODS

Computed tomography (CT) images from 310 radiotherapy plans were used as the experimental data set, of which 260 and 50 were used as the training and test sets, respectively. An improved U-Net architecture was established by introducing a batch normalization layer, residual squeeze-and-excitation layer, and unique organ-specific loss function for deep learning training. The performance of the trained network model was evaluated by comparing the manual-delineation and the STAPLE contour of 10 physicians from different centers.

RESULTS

Our model achieved good segmentation in all 24 OARs in nasopharyngeal cancer radiotherapy plan CT images, with an average Dice similarity coefficient of 83.75%. Specifically, the mean Dice coefficients in large-volume organs (brainstem, spinal cord, left/right parotid glands, left/right temporal lobes, and left/right mandibles) were 84.97% - 95.00%, and in small-volume organs (pituitary, lens, optic nerve, and optic chiasma) were 55.46% - 91.56%. respectively. Using the STAPLE contours as standard contour, the OrganNet achieved comparable or better DICE in organ segmentation then that of the manual-delineation as well.

CONCLUSION

The established OrganNet enables simultaneous automatic segmentation of multiple targets on CT images of the head and neck radiotherapy plans, effectively improves the accuracy of U-Net based segmentation for OARs, especially for small-volume organs.

The feasibility of reduced-dose radiotherapy in childhood nasopharyngeal carcinoma with favorable response to neoadjuvant chemotherapy

BACKGROUND

To assess the feasibility of adjusting radiation dose (RD) in childhood NPC with favorable tumor response after neoadjuvant chemotherapy (NAC).

PATIENTS AND METHODS

Using an NPC-specific database, children and adolescents (≤18 years) with locoregionally advanced NPC (CA-LANPC) were retrospectively analyzed. Enrolled patients were those who received favorable tumor response after 2-4 cycles of NAC followed by concurrent chemoradiotherapy. Survival outcomes and treatment-related toxicities were compared for the standard RD on primary tumors (PT-RD_standard, 66-72 Gy) and the reduced RD on primary tumors (PT-RD_reduced, 60-65.9 Gy).

RESULTS

A total of 132 patients were included, and the median follow-up time was 75.2 months (IQR, 53.2-98.7 months) for the entire cohort. The PT-RD_reduced group had a significantly decreased incidence of severe mucositis (51.3 % vs 32.1 %; P = 0.034) when compared to the PT-RD_standard group. The total incidence of severe sequela in the PT-RD_standard group were significantly higher than those in the PT-RD_reduced group (31.8 % vs 13.7 %; P = 0.029). In the propensity-matched analysis, the PT-RD_reduced group resulted in parallel 5-year survival with the PT-RD_standard group from the matched cohort (disease-free survival, 82.7 % vs 80.3 %, P = 0.841; overall survival, 91.7 % vs 91.3 %, P = 0.582; distant metastasis-free survival, 87.5 % vs 82.8 %, P = 0.573; and locoregional relapse-free survival, 95.6 % vs 97.3 %, P = 0.836). In multivariate analysis, the impact of PT-RD_reduced on all survival end points remained insignificant.

CONCLUSIONS

Chemoradiotherapy with RD at levels of 60-65.9 Gy may be a reasonable strategy for CA-LANPC with favorable tumor response after NAC.

Mechanism and Protection of Radiotherapy Induced Sensorineural Hearing Loss for Head and Neck Cancer

Purpose

Radiotherapy-induced sensorineural hearing loss (RISNHL) is a common adverse effect in patients with head and neck cancer. Given that there are few studies on the pathogenesis of RISNHL at present, we summarized the possible pathogenesis of RISNHL and possible protective measures found at present by referring to relevant literatures.

Methods

We performed a comprehensive literature search in the PubMed database, using keywords “sensorineural hearing loss,” “radiotherapy,” and “cancer,” among others. The literature was examined for the possible mechanism and preventive measures of sensorineural hearing loss induced by radiotherapy.

Results

We found that the incidence of RISNHL was closely related to the damage directly caused by ionizing radiation and the radiation-induced bystander effect. It also depends on the dose of radiation and the timing of chemotherapy. Studies confirmed that RISNHL is mainly involved in post-RT inflammatory response and changes in reactive oxygen species, mitogen-activated protein kinase, and p53 signaling pathways, leading to specific manners of cell death. We expect to reduce the incidence of hearing loss through advanced radiotherapy techniques, dose limitation of organs at risk, application of cell signaling inhibitors, use of antioxidants, induction of cochlear hair cell regeneration, and cochlear implantation.

Conclusion

RISNHL is associated with radiation damage to DNA, oxidative stress, and inflammation of cochlear cells, stria vascularis endothelial cells, vascular endothelial cells, spiral ganglion neurons, and other supporting cells. At present, the occurrence mechanism of RISNHL has not been clearly illustrated, and further studies are needed to better understand the underlying mechanism, which is crucial to promote the formulation of better strategies and prevent the occurrence of RISNHL.

Assessment of radiation-induced otitis media in patients with parotid gland malignancy

BACKGROUND

Otitis media with effusion (OME) is a known side effect of radiation therapy in patients with head and neck cancer.

AIMS/OBJECTIVES

To investigate the incidence rate and clinical course of radiation-induced OME, we have reported on the long-term characteristics of OME in patients with parotid gland malignancy.

MATERIAL AND METHODS

This cohort study assessed 200 patients who underwent post-parotidectomy radiation therapy from January 2010 to December 2019 in a tertiary referral center. Postoperative radiation therapy was performed at 6 weeks post-surgery. Serial magnetic resonance images were collected to detect otitis media. Two blinded otologists individually assessed data from radiation therapy initiation to 36 months of post-radiation therapy.

RESULTS

A total of 121 patients were enrolled (male, 61 [50.4%]; mean age, 46.98 ± 15.69 years), of which 14 developed otitis media (11.6%) within 6 months after radiation therapy. Spontaneous remission occurred without intervention within 1 year, excluding one patient who sustained otitis media for 2 years.

CONCLUSIONS AND SIGNIFICANCE

Radiation-induced OME occurred in 11.6% of patients and it remitted within 1 year without intervention. Therefore, cooperation between otolaryngologists and radiation oncologists is required and invasive intervention should be considered with careful risk-benefit evaluation.

Potential benefits of adaptive intensity-modulated proton therapy in nasopharyngeal carcinomas

Purpose

To investigate potential advantages of adaptive intensity‐modulated proton beam therapy (A‐IMPT) by comparing it to adaptive intensity‐modulated X‐ray therapy (A‐IMXT) for nasopharyngeal carcinomas (NPC).

Methods

Ten patients with NPC treated with A‐IMXT (step and shoot approach) and concomitant chemotherapy between 2014 and 2016 were selected. In the actual treatment, 46 Gy in 23 fractions (46Gy/23Fx.) was prescribed using the initial plan and 24Gy/12Fx was prescribed using an adapted plan thereafter. New treatment planning of A‐IMPT was made for the same patients using equivalent dose fractionation schedule and dose constraints. The dose volume statistics based on deformable images and dose accumulation was used in the comparison of A‐IMXT with A‐IMPT.

Results

The means of the D_mean of the right parotid gland (P < 0.001), right TM joint (P < 0.001), left TM joint (P < 0.001), oral cavity (P < 0.001), supraglottic larynx (P = 0.001), glottic larynx (P < 0.001), , middle PCM (P = 0.0371), interior PCM (P < 0.001), cricopharyngeal muscle (P = 0.03643), and thyroid gland (P = 0.00216), in A‐IMPT are lower than those of A‐IMXT, with statistical significance. The means of, D_0.03cc, and D_mean of each sub portion of auditory apparatus and D_30% for Eustachian tube and D_0.5cc for mastoid volume in A‐IMPT are significantly lower than those of A‐IMXT. The mean doses to the oral cavity, supraglottic larynx, and glottic larynx were all reduced by more than 20 Gy (RBE = 1.1).

Conclusions

An adaptive approach is suggested to enhance the potential benefit of IMPT compared to IMXT to reduce adverse effects for patients with NPC.

Dosimetric parameters associated with conductive or sensorineural hearing loss 5 years after intensity-modulated radiation therapy in nasopharyngeal carcinoma

BACKGROUND

Most previous studies are separate dosimetric analyses of conductive or sensorineural hearing loss, and they are not conducive to a comprehensive assessment of auditory radiation damage.

AIMS/OBJECTIVES

Our study aimed to evaluate the long-term incidence of sensorineural hearing loss (SNHL) or conductive hearing loss (CHL) in patients with nasopharyngeal carcinoma (NPC) after intensity-modulated radiation therapy (IMRT), and to investigate the relationship between SNHL or CHL and patient factors, treatment-related factors, and radiation dose parameters.

MATERIAL AND METHODS

Seventy patients (117 ears) with NPC, who were also treated with IMRT in our hospital from 2006 to 2014, were retrospectively analyzed. Radiation doses to the Eustachian tube (ET), middle ear (ME), cochlear (Co), and internal auditory canal (IAC) were assessed. Pure tone audiometry and impedance audiometry were performed before and during the follow-up period. The relationships between low-frequencies (0.5-2 kHz) or high-frequency (4 kHz) SNHL/CHL and radiotherapy dose parameters were analyzed.

RESULTS

Of the 117 ears studied, 7.69% had low-frequency SNHL, 35.9% had high-frequency SNHL, 23.93% had low-frequency CHL, and 18.80% had high-frequency CHL. The incidence of high-frequency CHL was higher in the T4 group than in the T (1-3) group (p < .05). When IAC D_max > 42.13 Gy or IAC D_mean > 32.71 Gy, the risk of high-frequency SNHL increased in NPC patients. When ME D_max > 44.27 Gy, ME D_mean > 29.28 Gy, or ET D_max > 57.23 Gy, the risk of high-frequency CHL in NPC patients increased.

CONCLUSIONS AND SIGNIFICANCE

SNHL and CHL remain common ear complications after IMRT for NPC. IAC D_max, IAC D_mean, ME D_max, ME D_mean, and ET D_max all need to be carefully considered during the IMRT treatment protocol.

Is intensity-modulated radiotherapy superior to conventional techniques to prevent late ear complications of nasopharyngeal cancer?

PURPOSE

This study analyzed the late ear complications of radiotherapy for nasopharyngeal cancer (NPC) and compared the conventional and intensity-modulated radiotherapy (2D-RT and IMRT, respectively).

METHODS

At 2-21 years after the end of NPC treatment, 104 ears of 52 patients were evaluated with the otoscopic examination, pure tone audiometry test, tympanometry, and subjective complaints by being blinded to the radiotherapy technique.

RESULTS

There were no differences in terms of the pathology of the external, middle or inner ear, air and bone-conduction hearing thresholds, and the air-bone (A-B) gap at 500, 1000, 2000, and 4000 Hz, and tympanometry types between 2D-RT and IMRT groups (p > 0.05). There were positive correlations between the values of A500 and A1000 thresholds; gap 500, 4000, and mean cochlear RT dose (p < 0.05). There were positive correlations between the values of A500, A1000, and A4000 thresholds; gap 500, 1000, 2000, 4000, and maximum cochlear RT dose (p < 0.05).

CONCLUSION

IMRT was not found to be superior to 2D-RT to prevent RT-induced ear complications. The solution of the middle ear problems must be the goal of the strategies for complications treatment.

Cochlea sparing with a stratified scheme of dose limitation employed in intensity-modulated radiotherapy for nasopharyngeal carcinoma: A dosimetry study

Hearing loss is 1 of the major complications after radiotherapy in nasopharyngeal carcinoma (NPC) patients, how to minimize dose to cochlea in order to reduce the incidence of sensorineural hearing loss is a critical task. This study is to investigate a stratified scheme of cochlea sparing based on T stage in intensity-modulated radiotherapy. We designed a comparison between 2 plans of cochlea sparing plan (C-Plan) and regular noncochlea sparing plan (R-Plan) from 19 NPC patients with 2, 3, 8, and 6 cases of T1, T2, T3, and T4 stage, respectively. The outcomes showed that target coverage parameters and dose-volume histogram features were of no significant difference, with a significant difference in dose distribution between C-Plan and R-Plan in cochlea and eustachian, e.g., ipsilateral cochlea D_mean 4619.75 ± 1134.09 cGy in C-Plan and 5061.03 ± 1121.09 cGy in R-Plan (p = 0.000), contralateral cochlea D_mean 4386.73 ± 945.14 cGy in C-Plan and 4991.38 ± 961.21 cGy in R-Plan (p = 0.000). Meanwhile, there was no significant difference in dose distribution in spinal cord, brainstem, and other OARs. Our dosimetry study showed cochlea sparing in intensity-modulated radiotherapy for NPC reduced cochlea dose to different extent, so we suggested a stratified scheme of cochlea sparing based on T stage could be a useful and practical tool for both physicists and radiation doctors.

Otitis media with effusion after radiotherapy of the head and neck: a systematic review

BACKGROUND

Otitis media (OM) and associated hearing problems may be side effects to radiotherapy of the head and neck region and affect patient quality of life. The condition is associated with the tumor location.

OBJECTIVE

To perform a systematic review concerning the present knowledge of the risk of OM after radiotherapy of the head and neck.

METHODS

A comprehensive search of PubMed and Embase was carried out between 1 October 2015 and 6 February 2017. The search strategy followed the PRISMA guideline for systematic reviews.

RESULTS

Of 597 articles 11 fulfilled the inclusion criteria. Seven were retrospective and four prospective. There were no randomized controlled trials. Eight studies concerned nasopharyngeal cancer. One study concerned cancer of the parotid gland and two studies concerned other locations of head and neck cancer. Meta-analysis could not be done due to heterogeneity between the studies. The incidence of OM varied considerably (range 8-29%).

CONCLUSIONS

The incidence of OM is high after radiotherapy of cancer of the upper head and neck area and the Eustachian tube (ET) irradiation dosage seems associated with development of OM, but the literature is poor. Research is needed to designate patients at risk of developing OM after radiotherapy. Preferably through analysis of dosage relationships between the ET and middle ear, and development of OM. Reporting of OM should be per ear and follow standardized protocols of middle ear assessment before and after radiotherapy. Furthermore, there is a need to find new ways to prevent and treat radiation-induced OME, preferably through randomized controlled trials.

A prospective study on radiation doses to organs at risk (OARs) during intensity-modulated radiotherapy for nasopharyngeal carcinoma patients

This study is to investigate the dose distribution of organs at risk (OARs) in cases of nasopharyngeal carcinoma (NPC). From July 2013 to October 2014, a prospective cohort study involving 148 patients was carried out at our center. OARs surrounding the nasopharynx were contoured on axial CT planning images in all patients. Dose-volume histograms of OARs and gross tumor volumes (GTV) were calculated. Multivariate analysis showed that radiation dose to OARs was associated with T stage and, especially, GTV. Seven OARs, including the spinal cord, eye and mandible, easily tolerated radiation doses in all patients; six OARs including the brain stem, chiasm and temporal lobe easily tolerated radiation doses in patients with a small GTV, but with difficulty when GTV was large; and other nine OARs including the parotid gland, cochlea and tympanic cavity met tolerance doses with difficulty in all patients. According to the patterns of radiation doses to OARs, it may help us to further reduce subsequent complications by improving the efficiency of plan optimization and evaluation.