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Original article
peer-reviewed

A Dosimetric Comparison of Primary Chemoradiation Versus Postoperative Radiation for Locally Advanced Oropharyngeal Cancer



Abstract

Introduction

Advanced-stage oropharyngeal cancer can be treated with primary chemoradiation (CRT) or primary surgery with adjuvant radiotherapy, both with similar survival outcomes. Though primary CRT prescribes a higher dose, adjuvant radiation requires irradiating the surgical bed, which may increase the high dose planned target volume (PTV). We hypothesize that the integral dose to the neck and dose to critical structures will be lower with primary CRT than adjuvant radiotherapy.

Methods

We selected the last 18 patients who underwent surgery and adjuvant radiotherapy at one institution between July 2015 and August 2016 with American Joint Committee on Cancer (AJCC) stage III or IVA oropharyngeal squamous cell cancer. Primary CRT treatment plans were created on the patients’ preoperative computed tomography (CT) scans and prescribed 70 Gy in 33 fractions, while postoperative plans were prescribed 60 Gy in 30 fractions. The radiation doses received by organs at risk for each primary CRT plan were compared to the corresponding adjuvant radiation plan.

Results

 Primary CRT plans had significantly smaller high dose PTV than adjuvant radiation plans (187.3 cc (95% CI 134.9-239.7) and 466.3 cc (95% CI 356.7-575.9), p<0.0001). The neck integral dose was lower in 14 of 18 plans using primary CRT, although this was not statistically significant (p=0.5375). The primary CRT plans had lower mean doses to ipsilateral (31.8 Gy (95% CI 27.5-36.0) vs 39.3 Gy (95% CI 35.4-43.1), p=0.0009)) and contralateral parotid glands (22.5 Gy (95% CI 22.1-22.8) vs 27.6 Gy (95% CI 23.4-31.8), p=0.0238) and larynx (20.7 Gy (95% CI 19.3-22.2) vs 40.2 Gy (95% CI 30.8-46.6), p<0.0001).

Conclusion

Primary CRT offered a decreased neck integral dose, though it was statistically insignificant. Primary CRT plans reduce mean dose to larynx and parotid glands in comparison to postoperative radiation, which may result in lower toxicities. Clinical trials comparing primary CRT and primary surgery are warranted to compare patient toxicities.

Introduction

Approximately 70% of oropharyngeal cancer patients present at advanced stages [1]. For these patients, two common treatment modalities exist: primary surgery with postoperative radiation (with or without chemotherapy) and primary chemoradiation (with or without salvage surgery). Both modalities achieve comparable survival outcomes for advanced stage oropharyngeal patients [2], but there is still no consensus on a preferred treatment modality.

Modalities are selected based on anatomic location, patient factors/values, and physician influences. Despite similar tumour control rates, surgery causes significantly more complications that require remedial surgery, such as fistulas or permanent gastrostomies [3]. Boscolo-Rizzo et al. [4] found that chemoradiation had significantly higher long-term quality of life scores than surgery with postoperative radiation. A retrospective single centre study found that surgery followed by chemoradiation gave the patient population the best survival rates compared to surgery with postoperative radiotherapy or chemoradiotherapy alone [5]; however, combining more treatment modalities often increases patient morbidity. Therefore, a trade off exists between tumour control and reduced side effects that physicians and patients must consider before selecting a treatment.

Before selecting a preferred modality, patients must consider the radiation dose to organs at risk (OAR) in the head and neck, such as the parotid glands, larynx, and mandible. While primary chemoradiation (CRT) prescribes a higher dose, adjuvant radiation (RT) may deliver more radiation to OAR because the entire post-surgical bed requires irradiation. Irradiating larger tissue volumes can increase the number and severity of side effects.

We hypothesize that the integral dose to the neck and dose to critical structures will be lower with primary CRT than adjuvant radiotherapy. Evaluating the difference in mean dose and maximum dose to OAR and the total integral dose between CRT and adjuvant RT will provide additional insight into the optimal treatment modality for locally advanced oropharyngeal cancer patients.

Materials & Methods

The study was submitted for a Research Ethics Board (REB) review and follows the Tri-Council Policy Statement: Ethical Conduct for Research Involving Human Subjects (TCPS2), as data collection involved retrospective patient information such as computed tomography (CT) scans and radiotherapy treatment plans from the Cross Cancer Institute (Edmonton, Canada). The REB determined that ethics approval was not required as this is a quality improvement based study.

Using a retrospective cohort, we compared the total integral dose and dose to OAR that patients received when they were treated with adjuvant RT to a theoretical CRT plan using their preoperative CT scans. This study included both an experimental and control group as summarized in Figure 1.

 

The last 20 consecutive patients with American Joint Committee on Cancer (AJCC) stage III or IVA oropharyngeal cancer who underwent primary surgery and postoperative radiotherapy for their disease at our centre between July 2015 and August 2016 were included in our study. Apart from the tumour resection surgery, patients had no previous head and neck surgeries for malignancies and no previous head and neck radiotherapy treatments.

We obtained the postoperative radiotherapy plans (60 Gy in 30 fractions delivered daily) and dose-volume-histograms (DVH) from the patients noted above to serve as our control group. Our standard procedure is to treat the post-surgical bed and involved lymph node levels to 60 Gy, and the uninvolved neck to 54 Gy. The radiation treatments were planned and completed at the Cross Cancer Institute. Each patient’s plans and images were anonymized and assigned a random identification number.

For our experimental group, the patients’ preoperative diagnostic CT scans were transferred to the ARIA® oncology information system for radiation oncology, which contains the radiotherapy treatment planning software used clinically at the Cross Cancer Institute. The parotid glands, submandibular glands, mandible, esophagus, larynx, and pharyngeal constrictor muscles were contoured as critical structures using the contouring guidelines from the Radiation Therapy Oncology Group (RTOG) protocol 1016. The RTOG 1016 protocol contains planning guidelines and objectives for target volumes and critical structures for primary chemoradiation of advanced stage oropharyngeal patients. A treatment couch structure was added to each plan to simulate the radiotherapy units. We generated volumetric arc therapy plans, which was the same technique used in postoperative plans, with the Eclipse 3D planning system (version 13.6, Varian Medical Systems, Palo Alto, CA). The dose prescription was different, 70 Gy in 33 fractions delivered daily, but the dose algorithm and plan normalization (95% of PTV received 100% of the dose) were maintained with the adjuvant RT plans to provide intrapatient consistency. Normal tissue optimizations were the same between postoperative and preoperative planning to reduce bias. Clinical target volume (CTV) to PTV margins were 0.5 cm in both groups. To account for the differences in fractionation, integral doses and OAR doses were converted to equivalent doses in 2 Gy fractions (EQD2).

As a form of quality assurance, a head and neck radiation oncologist and dosimetrist from the Cross Cancer Institute reviewed each contour and plan. The constructed primary CRT plan was compared to the patient’s postoperative plan to assess the difference in integral dose and dose to OARs. Integral dose to the overall neck was calculated by multiplying the volume between the cochleas and the cricoid cartilage with the mean dose of that volume.

Data were analyzed using paired T-tests to determine any significant differences between the two regimes for each patient. A p-value of < 0.05 was taken to be statistically significant. To determine our sample size, it was assumed that there would be a difference in integral dose between the two groups of 15% with a standard deviation of 10 for each group. Assuming a type I error of 0.05 and a type II error of 0.20, we required a total of 20 patients for statistical significance.

Results

Data were collected for 20 patients, but two patients were omitted from analysis because of positional and scan size issues. Therefore, 18 patients were analyzed. Table 1 lists the patient characteristics of our sample group.

Demographic Characteristics
Age Median 64 (range 46-76)
Sex 94.7% male
Subsite 50% base of tongue 27.8% tonsil 22.2% base of tongue and tonsil
Clinical AJCC stage 5.3% III 94.7% IVA
p16 status 83.3% positive
16.7% negative
Extracapsular extension (ECE) 66.7% positive 33.3% negative
Lymphovascular invasion (LVI) 38.9% positive
61.1% negative
Perineural invasion (PNI) 33.3% positive 66.7% negative
Positive margins 22.2% positive 77.8% negative
Percutaneous endoscopic gastrostomy tube inserted 44.4% after surgery (before RT) 11.1% during RT

The average high dose PTV volumes for the plans made on the patients’ preoperative CT scans were 40.2% smaller compared to the postoperative plans, as seen in Table 2.

  Primary RT Adjuvant RT P value
High dose PTV volume (cc) 187.3 (95% CI 134.9-239.7) 466.3 (95% CI 356.7-575.9) p < 0.0001
Integral dose to the neck (Gy*L) 152.6 (95% CI 130.3-174.9) 156.6 (95% CI 134.7-178.5) p=0.5375  

The DVH comparison of the control group versus experimental plans revealed significant differences. Table 3 contains the mean and maximum dose averages for the critical structures analyzed between the two treatment groups. The maximum doses for the ipsilateral parotid gland, the mandible, the pharyngeal constrictor muscles, and the spinal cord were significantly lower for the adjuvant RT group. Also, the mean dose to the spinal cord was also significantly lower for the adjuvant RT group. On average, the primary CRT group had lower mean doses for the ipsilateral and contralateral parotid glands, esophagus, larynx, and mandible, but only doses to the ipsilateral and contralateral parotid glands and larynx were significantly lower than the adjuvant RT plans. The primary CRT group also had lower maximum doses for the contralateral parotid and oesophagus, but these differences were not statistically significant. The difference in the mean pharyngeal constrictor dose and max larynx dose was only 0.4 cGy and 1.1 cGy, respectively. Submandibular glands were resected for most patients so their dose comparisons were omitted. For individual patient doses, refer the Appendix.

Structure Primary CRT (Gy) Adjuvant RT (Gy) P value
Maximum dose to ipsilateral parotid 76.8 (95% CI 74.8-78.7) 65.7 (95% CI 64.4 to 67.0) p < 0.0001
Mean dose to ipsilateral parotid 31.8 (95% CI 27.5-36.0) 39.3 (95% CI 35.4-43.1) p = 0.0009
Maximum dose to contralateral parotid 56.2 (95% CI 52.3-59.8) 58.4 (95% CI 52.6-64.1) p = 0.4566
Mean dose to contralateral parotid 22.5 (95% CI 22.1-22.8) 27.6 (95% CI 23.4-31.8) p = 0.0238
Maximum dose to esophagus 46.4 (95% CI 42.3-50.6) 50.8 (95% CI 46.4-55.2) p = 0.1266
Mean dose to esophagus 24.1 (95% CI 21.9 - 26.3) 29.7 (95% CI 23.3-36.1) p = 0.0547
Maximum dose to larynx 59.5 (95% CI 53.2-65.8) 60.6 (95% CI 58.8-62.5) p = 0.7307
Mean dose to larynx 20.7 (95% CI 19.3-22.2) 40.2 (95% CI 30.8-46.6) p < 0.0001
Maximum dose to mandible 75.7 (95% CI 72.9-78.6) 65.3 (95% CI 64.9-65.7) p < 0.0001
Mean dose to mandible 37.8 (95% CI 35.3-40.3) 40.6 (95% CI 38.0-43.2) p = 0.1010
Maximum dose to pharyngeal constrictors 77.4 (95% CI 76.4-78.3) 64.7 (95% CI 64.0 - 65.4) p < 0.0001
Mean dose to pharyngeal constrictors 56.4 (95% CI 52.9-59.8) 56.8 (95% CI 55.0-58.7) p = 0.7745
Maximum dose to spinal cord 43.0 (95% CI 42.3-43.7) 40.9 (95% CI 40.1-41.6) p < 0.0001
Mean dose to spinal cord 31.6 (95% CI 30.4-32.9) 21.1 (95% CI 19.2-22.9) p < 0.0001

Discussion

Radiation therapy is commonly used to treat advanced stage oropharyngeal cancer, whether it be used adjuvant to surgery or as the primary modality along with chemotherapy [2]. Beyond survival rates, there are very few studies that compare these two regimes. There is lack of randomized trials investigating quality of life following treatment with chemoradiation or surgery with postoperative radiation; therefore, a preferential treatment option still does not exist for these patients [2-4]. Though Tillman et al. [6] studied a different tumour site with a different method, their results are consistent with ours in that their postoperative RT cohort had a larger PTV, and OARs such as the heart and lungs received a higher dose. Our study provides a similar dosimetric comparison and analysis that suggests that additional controlled studies are needed to further inform the patient’s decision between these two treatment methods. As predicted, our study showed a significantly smaller mean high dose PTV for the primary CRT cohort, which was hypothesized to result in a lower integral dose. The primary CRT plans on average had lower integral doses. In fact, 14 out of 18 primary CRT plans had lower integral doses than their corresponding postoperative plans, although this was not significantly different, possibly due to the small number of patients in this study. Conversely, the results suggest that adjuvant RT is not advantageous over primary CRT in regards to delivering lower integral doses to a patient’s normal tissues.

The mean ipsilateral and contralateral parotid gland dose was reduced by 19% and 18.5% in the primary CRT cohort, respectively. This reduction in dose to the parotids has major implications for the quality life of these patients, as the risk of xerostomia decreases. For every 1 Gy increase in parotid mean dose, salivary function decreases by 5% [7]. If at least one parotid gland receives a mean dose of less than 25.8 Gy, the risk of grade 4 xerostomia is significantly lower. As the primary CRT contralateral parotid gland received less than 25.8 Gy and both adjuvant RT parotid glands received more than 25.8 Gy, we expect the primary CRT cohort to have a significantly lower risk of severe xerostomia, and, therefore, a better quality of life over the long-term.

While most submandibular RTOG 1016 dose targets were achieved for the primary CRT plans, many postoperative RT patients had their submandibular glands removed so dose statistics between the cohorts could not be compared. Though primary CRT delivers radiation to the submandibular glands, the risk of xerostomia due to submandibular irradiation is better than xerostomia from the absence of submandibular glands.

The primary CRT larynx structure had a 48.5% lower mean dose than adjuvant RT. Caudell et al. [8] found that higher mean doses were significantly associated with severe dysphagia at 12 months post-treatment. Patients began to experience aspiration at a mean dose of 41 Gy to the larynx. At doses higher than the threshold, the risk of severe dysphagia is significantly correlated with increasing dosage. With the average mean dose of 40.2 Gy for adjuvant RT and 20.7 Gy for primary CRT, we would expect primary CRT patients to have a lower risk of aspiration. Also, as Caudell et al. [8] only studied primary CRT, postoperative RT patients may experience more severe comorbidities at a mean dose of 41 Gy as patients irradiated postoperatively suffer lower quality of life and more severe pain with the same dose prescription comparison as our study [4].

Our study’s findings show that opting for surgery would not spare advanced oropharyngeal patients of the integral dose and that primary CRT lowers the mean dose to some OARs. Our results also indicated that treating a smaller volume to a higher dose in the primary CRT setting would not increase the risk of developing radiation-related side effects as there is a predicted lower risk of xerostomia and aspiration. In addition to potentially improving quality of life, lower toxicities can decrease appointment and treatment cancellations, which improves outcomes and decreases healthcare costs.

Due to a higher prescribed dose for the primary CRT cohort, we expected higher maximum doses received by many OARs than in the adjuvant RT cohort. The high dose PTV may overlap with some OARs, so maximum doses in those organs are difficult to avoid. The significantly higher maximum dose observed in the primary CRT cohort for the mandible would result in a higher risk of osteoradionecrosis. According to Emami [9], this risk increases above 5% with a point dose greater than 70 Gy. Thankfully, most of the toxicity in head and neck critical structures are based on mean dose rather than point doses.

There were multiple limitations in our study. The primary CRT cohort was planned on diagnostic CT scans, and therefore the patients were not in a traditional RT position with an immobilizing shell with shoulders depressed and chin extended. This may have resulted in dosimetric differences between the cohorts, with a likely negative effect on the primary CRT group’s OAR optimization abilities because these scans had compressed anatomy due to the lack of neck extension position in diagnostic scans. Secondly, although treating the post-surgical bed and bilateral neck for locally advanced oropharyngeal patients who have undergone surgery is standard at our center, it may not be so at other centers. There is evidence that postoperative radiotherapy to the ipsilateral neck may be all that’s needed for patients with N2a-b disease [10].

Conclusions

In conclusion, primary CRT offered a lower total integral dose to the neck on average, although this was not statistically significant. Given that primary CRT plans prescribed a higher dose, higher maximum organ doses were expected. However, lower mean organ doses suggested that primary CRT plans spare more larynx and parotid gland than postoperative radiation, which may result in lower overall toxicity to the patient. Randomized clinical trials are necessary to further validate these findings and better inform the management decisions of advanced stage oropharyngeal cancer patients.


References

  1. Odell MJ, Walz BJ, Reimers H, et al.: Carcinoma of the oropharynx. Head and Neck Cancer. Thieme Medical Publishers, Inc (ed): New York, NY, 2008; 2008. 24-44.
  2. Chen LA, Anker CJ, Hunt JP, et al.: Clinical outcomes associated with evolving treatment modalities and radiation techniques for base-of-tongue carcinoma: thirty years of institutional experience. Cancer Med. 2015, 4:651–660. 10.1002/cam4.364
  3. Parsons JT, Mendenhall WM, Stringer SP, et al.: Squamous cell carcinoma of the oropharynx: surgery, radiation therapy, or both. Cancer. 2002, 94:2967–2980. 10.1002/cncr.10567
  4. Boscolo-Rizzo P, Stellin M, Fuson R, et al.: Long-term quality of life after treatment for locally advanced oropharyngeal carcinoma: surgery and postoperative radiotherapy versus concurrent chemoradiation. Oral Oncol. 2009, 45:953–957. 10.1016/j.oraloncology.2009.06.005
  5. O’Connell D, Seikaly H, Murphy R, et al.: Primary surgery versus chemoradiotherapy for advanced oropharyngeal cancers: a longitudinal population study. Otolaryngol Head Neck Surg. 2013, 42:31. 10.1186/1916-0216-42-31
  6. Tillman GF, Pawlicki T, Koong AC, et al.: Preoperative versus postoperative radiotherapy for locally advanced gastroesophageal junction and proximal gastric cancers: a comparison of normal tissue radiation doses. Dis Esophagus. 2008, 21:437–444.
  7. Blanco AI, Chao KC, El Naqa I, et al.: Dose-volume modeling of salivary function in patients with head-and-neck cancer receiving radiotherapy. Int J Radiat Oncol Biol Phys. 2005, 62:1055–1069. 10.1016/j.ijrobp.2004.12.076
  8. Caudell JJ, Schaner PE, Meredith RF, et al.: Factors associated with long-term dysphagia after definitive radiotherapy for locally advanced head-and-neck cancer. Int J Radiat Oncol Biol Phys. 2009, 73:410–415. 10.1016/j.ijrobp.2008.04.048
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Appendices

Raw Data and Non-2 Gy Fraction Equivalent Doses for Each Patient and Critical Structure

Patient Max Ipsilateral Parotid  (Gy) Mean Ipsilateral Parotid (Gy) Max Contralateral Parotid (Gy) Mean Contralateral Parotid (Gy)
RT PO RT PO RT PO RT PO
1 75.978 63.095 38.563 54.682 54.718 57.448 25.341 37.933
2 74.210 64.622 36.730 38.668 53.402 65.050 25.344 37.309
3 75.845 67.223 36.689 45.726 53.977 64.805 25.258 39.933
4 73.953 62.092 30.267 37.896 61.910 60.589 24.906 30.711
6 76.897 68.343 25.758 40.633 70.347 64.245 25.124 37.533
7 73.834 59.448 39.063 37.998 56.220 54.438 25.947 19.936
8 75.258 64.982 51.725 50.103 54.314 60.896 25.272 26.159
9 69.377 64.032 25.509 34.649 51.962 60.288 24.414 26.411
10 75.626 66.059 40.951 32.408 54.544 55.916 25.277 24.255
11 79.245 65.102 34.893 36.877 55.340 60.265 24.829 37.243
12 71.596 63.947 29.201 39.117 55.832 58.189 25.430 30.013
13 67.381 64.863 25.424 42.677 53.720 60.184 24.217 29.400
14 75.950 64.450 23.626 41.196 76.040 64.450 23.286 41.196
15 75.710 64.135 43.028 38.344 53.619 62.386 24.418 30.836
17 81.209 65.170 48.659 59.380 56.979 62.166 25.123 19.327
18 74.371 63.987 24.644 39.116 58.963 63.987 24.644 26.565
19 75.496 66.841 35.684 40.245 55.770 16.705 26.419 7.918
20 78.995 68.918 27.872 33.896 54.183 58.292 25.656 35.531
Patient Max Mandible (Gy) Mean Mandible (Gy) Max PC (Gy) Mean PC (Gy)
RT PO RT PO RT PO RT PO
1 68.856 65.511 31.564 44.637 75.970 64.975 55.198 60.188
2 73.175 64.353 37.749 46.025 76.622 65.203 55.609 60.253
3 75.541 64.873 38.780 39.858 74.602 65.756 55.975 60.891
4 74.458 63.852 42.278 37.272 74.226 63.321 64.132 59.135
6 77.206 63.510 46.251 46.686 76.499 64.414 66.692 61.856
7 75.732 63.338 42.309 43.687 74.998 63.101 60.134 59.703
8 75.758 65.564 44.287 35.177 76.066 64.929 60.220 61.241
9 76.277 63.686 47.105 40.354 72.836 63.250 54.780 52.783
10 75.696 65.306 39.936 47.274 75.666 64.125 54.709 53.728
11 77.837 64.064 40.812 49.547 74.624 65.323 56.869 57.235
12 63.747 63.776 33.739 42.059 75.202 64.009 56.302 59.157
13 60.700 64.145 32.319 45.653 76.053 63.792 55.648 60.482
14 76.805 63.892 45.635 47.381 74.715 64.14 60.078 61.575
15 75.589 64.646 40.760 45.521 75.323 63.709 59.134 60.138
17 79.150 65.395 44.039 46.895 76.996 63.544 56.490 55.535
18 76.710 64.474 45.603 41.087 80.179 60.450 57.841 48.406
19 76.005 65.394 37.279 31.915 73.515 64.288 55.708 37.185
20 75.644 65.120 35.364 36.171 75.771 63.771 58.005 52.512
Patient Max Larynx (Gy) Mean Larynx (Gy) Max Esophagus (Gy) Mean Esophagus (Gy)
RT PO RT PO RT PO RT PO
1 55.211 57.797 25.828 46.85 48.947 58.157 29.360 45.744
2 53.781 62.123 25.256 45.202 41.628 52.123 30.268 32.025
3 53.460 60.269 25.091 24.870 58.375 34.771 22.414 16.311
4 63.436 58.689 25.963 52.500 42.979 56.451 30.257 49.662
6 68.064 64.414 25.584 61.856 59.767 62.881 29.832 51.394
7 51.546 61.068 24.969 35.542 48.679 43.772 29.852 24.903
8 77.158 56.392 24.675 30.797 57.147 51.000 17.937 13.933
9 53.470 56.194 24.474 28.057 44.746 52.477 28.725 13.721
10 49.455 60.581 24.688 34.448 47.729 50.196 29.819 25.512
11 67.345 66.255 20.277 45.123 61.083 62.817 24.290 38.646
12 62.682 63.936 20.934 58.526 50.893 59.882 25.541 28.115
13 49.980 63.268 19.560 55.714 52.023 57.241 28.577 55.714
14 55.298 63.130 18.920 58.253 44.076 58.117 26.263 34.192
15 51.699 63.292 19.633 34.621 46.290 47.428 28.781 32.260
17 73.034 60.214 27.990 31.747 49.850 46.782 29.616 29.198
18 87.904 57.702 26.171 42.294 48.628 45.403 29.392 35.469
19 57.484 55.129 18.715 25.358 40.465 37.482 26.139 21.093
20 50.654 58.446 19.079 42.728 28.671 55.548 13.233 24.896
Patient Max Cord (Gy) Mean Cord (Gy) ID (Gy/L) PTV (cc)
RT PO RT PO RT PO RT PO
1 46.862 43.608 37.008 27.592 96.20714 108.7386 61.7 442.3
2 44.382 42.434 31.831 22.836 114.82917 133.9186 166.2 448.9
3 44.891 43.280 34.376 20.895 115.65425 120.4623 174.7 390.5
4 44.243 42.610 29.730 21.671 129.98775 135.6595 117.0 121.2
6 46.612 42.823 37.577 26.060 143.41090 150.5132 315.5 981.7
7 43.399 40.033 34.694 18.327 120.03611 92.2390 146.0 272.7
8 46.314 44.487 29.391 27.487 129.75098 129.1895 267.9 496.2
9 44.649 39.295 36.507 21.422 137.63596 135.1606 157 297.8
10 43.798 43.371 33.189 21.675 97.36787 101.2248 139.4 443.8
11 45.685 43.002 31.444 26.922 77.82079 85.48116 110.3 774.6
12 46.341 42.588 34.935 26.45 117.54916 123.2601 171.2 378.3
13 46.765 44.536 35.079 31.503 111.76074 127.5994 112.9 332
14 43.081 42.441 34.711 21.151 177.38555 157.9239 484.2 836.3
15 43.744 44.211 36.784 22.196 161.03830 174.4947 276.9 667.1
17 47.43 42.632 35.924 22.762 137.34864 166.7237 302.2 462.8
18 45.645 43.011 37.099 20.235 192.49248 170.0389 115.3 400.7
19 47.234 44.071 35.906 15.803 111.88793 77.28451 72.1 212.8
20 45.21 43.58 32.594 26.04 161.80963 140.346 181.6 433.6
Original article
peer-reviewed

A Dosimetric Comparison of Primary Chemoradiation Versus Postoperative Radiation for Locally Advanced Oropharyngeal Cancer


Author Information

Stanley K. Woo

Department of Oncology, University of Alberta

Chad Freeman

Department of Oncology, University of Alberta

Brock J. Debenham Corresponding Author

Department of Oncology, University of Alberta


Ethics Statement and Conflict of Interest Disclosures

Human subjects: Consent was obtained by all participants in this study. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Acknowledgements

We would like to thank Naomi Parker, Brian Chwyl, Kim Rans, Andree Desrochers, and Laura Grose for their help with this project.


Original article
peer-reviewed

A Dosimetric Comparison of Primary Chemoradiation Versus Postoperative Radiation for Locally Advanced Oropharyngeal Cancer


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