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Recovery of Salivary Function: Contralateral Parotid-sparing Intensity-modulated Radiotherapy versus Bilateral Superficial Lobe Parotid-sparing Intensity-modulated Radiotherapy

View Article: PubMed Central - PubMed

ABSTRACT

Aims: To establish whether there is a difference in recovery of salivary function with bilateral superficial lobe parotid-sparing intensity-modulated radiotherapy (BSLPS-IMRT) versus contralateral parotid-sparing IMRT (CLPS-IMRT) in patients with locally advanced head and neck squamous cell cancers.

Materials and methods: A dosimetric analysis was carried out on data from two studies in which patients received BSLPS-IMRT (PARSPORT II) or CLPS-IMRT (PARSPORT). Acute (National Cancer Institute, Common Terminology Criteria for adverse events – NCI CTCAEv3.0) and late (Late Effects of Normal Tissue- subjective, objective, management analytical – LENTSOMA and Radiation Therapy Oncology Group) xerostomia scores were dichotomised: recovery (grade 0–1) versus no recovery (≥grade 2). Incidence of recovery of salivary function was compared between the two techniques and dose-response relationships were determined by fitting dose-response curves to the data using non-linear logistic regression analysis.

Results: Seventy-one patients received BSLPS-IMRT and 35 received CLPS-IMRT. Patients received 65 Gy in 30 fractions to the primary site and involved nodal levels and 54 Gy in 30 fractions to elective nodal levels. There were significant differences in mean doses to contralateral parotid gland (29.4 Gy versus 24.9 Gy, P < 0.005) and superficial lobes (26.8 Gy versus 30.5 Gy, P = 0.02) for BSLPS and CLPS-IMRT, respectively. Lower risk of long-term ≥grade 2 subjective xerostomia (LENTSOMA) was reported with BSLPS-IMRT (odds ratio 0.50; 95% confidence interval 0.29–0.86; P = 0.012). The percentage of patients who reported recovery of parotid saliva flow at 1 year was higher with BSLPS-IMRT compared with CLPS-IMRT techniques (67.1% versus 52.8%), but the difference was not statistically significant (P = 0.12). For the whole parotid gland, the tolerance doses, D50, were 25.6 Gy (95% confidence interval 20.6–30.5), k = 2.7 (0.9–4.5) (CLPS-IMRT) and 28.9 Gy (26.1–31.9), k = 2.4 (1.4–3.4) (BSLPS-IMRT). For the superficial lobe, D50 were similar: BSLPS-IMRT 23.5 Gy (19.3–27.6), k = 1.9 (0.5–3.8); CLPS-IMRT 24.0 Gy (17.7–30.1), k = 2.1 (0.1–4.1).

Conclusion: BSLPS-IMRT reduces the risk of developing high-grade subjective xerostomia compared with CLPS-IMRT. The D50 of the superficial lobe may be a more reliable predictor of recovery of parotid function than the whole gland mean dose.

No MeSH data available.


Related in: MedlinePlus

(a) Axial computed tomography image of contralateral parotid-sparing intensity-modulated radiotherapy (CLPS-IMRT) for a right lateral pharyngeal wall tumour. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The IMRT technique used also produces a dose gradient across the ipsilateral parotid gland on the right, thus allowing modest sparing of the right superficial lobe. (b) Axial computed tomography image of bilateral superficial lobe parotid-sparing intensity-modulated radiotherapy (BSLPS-IMRT) for a midline tumour of the base of tongue. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The deep lobes of both parotid glands are included in the high dose region because of their close proximity to the parapharyngeal spaces.
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fig1: (a) Axial computed tomography image of contralateral parotid-sparing intensity-modulated radiotherapy (CLPS-IMRT) for a right lateral pharyngeal wall tumour. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The IMRT technique used also produces a dose gradient across the ipsilateral parotid gland on the right, thus allowing modest sparing of the right superficial lobe. (b) Axial computed tomography image of bilateral superficial lobe parotid-sparing intensity-modulated radiotherapy (BSLPS-IMRT) for a midline tumour of the base of tongue. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The deep lobes of both parotid glands are included in the high dose region because of their close proximity to the parapharyngeal spaces.

Mentions: The contralateral parapharyngeal space is often spared in cases of LA-HNSCC where the disease at the primary site has not crossed the midline and nodal disease is confined to the ipsilateral side. This allows contralateral parotid gland sparing and elective irradiation of the contralateral lymph nodes below the contralateral parapharyngeal space (Figure 1a). However, many clinicians believe that bilateral parapharyngeal space irradiation is essential in the treatment of midline tumours of the head and neck, where bilateral parapharyngeal space lymphatic drainage occurs (base of tongue, soft palate, nasopharynx) and in patients with bilateral nodal disease. In this situation, IMRT can be used to deliver a bilateral superficial lobe parotid-sparing technique (BSLPS) (Figure 1b) [5].


Recovery of Salivary Function: Contralateral Parotid-sparing Intensity-modulated Radiotherapy versus Bilateral Superficial Lobe Parotid-sparing Intensity-modulated Radiotherapy
(a) Axial computed tomography image of contralateral parotid-sparing intensity-modulated radiotherapy (CLPS-IMRT) for a right lateral pharyngeal wall tumour. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The IMRT technique used also produces a dose gradient across the ipsilateral parotid gland on the right, thus allowing modest sparing of the right superficial lobe. (b) Axial computed tomography image of bilateral superficial lobe parotid-sparing intensity-modulated radiotherapy (BSLPS-IMRT) for a midline tumour of the base of tongue. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The deep lobes of both parotid glands are included in the high dose region because of their close proximity to the parapharyngeal spaces.
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Show All Figures
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fig1: (a) Axial computed tomography image of contralateral parotid-sparing intensity-modulated radiotherapy (CLPS-IMRT) for a right lateral pharyngeal wall tumour. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The IMRT technique used also produces a dose gradient across the ipsilateral parotid gland on the right, thus allowing modest sparing of the right superficial lobe. (b) Axial computed tomography image of bilateral superficial lobe parotid-sparing intensity-modulated radiotherapy (BSLPS-IMRT) for a midline tumour of the base of tongue. Colour wash: red-orange = high dose (95–100% of prescribed dose), blue = low dose (20–30% of prescribed dose). The deep lobes of both parotid glands are included in the high dose region because of their close proximity to the parapharyngeal spaces.
Mentions: The contralateral parapharyngeal space is often spared in cases of LA-HNSCC where the disease at the primary site has not crossed the midline and nodal disease is confined to the ipsilateral side. This allows contralateral parotid gland sparing and elective irradiation of the contralateral lymph nodes below the contralateral parapharyngeal space (Figure 1a). However, many clinicians believe that bilateral parapharyngeal space irradiation is essential in the treatment of midline tumours of the head and neck, where bilateral parapharyngeal space lymphatic drainage occurs (base of tongue, soft palate, nasopharynx) and in patients with bilateral nodal disease. In this situation, IMRT can be used to deliver a bilateral superficial lobe parotid-sparing technique (BSLPS) (Figure 1b) [5].

View Article: PubMed Central - PubMed

ABSTRACT

Aims: To establish whether there is a difference in recovery of salivary function with bilateral superficial lobe parotid-sparing intensity-modulated radiotherapy (BSLPS-IMRT) versus contralateral parotid-sparing IMRT (CLPS-IMRT) in patients with locally advanced head and neck squamous cell cancers.

Materials and methods: A dosimetric analysis was carried out on data from two studies in which patients received BSLPS-IMRT (PARSPORT II) or CLPS-IMRT (PARSPORT). Acute (National Cancer Institute, Common Terminology Criteria for adverse events – NCI CTCAEv3.0) and late (Late Effects of Normal Tissue- subjective, objective, management analytical – LENTSOMA and Radiation Therapy Oncology Group) xerostomia scores were dichotomised: recovery (grade 0–1) versus no recovery (≥grade 2). Incidence of recovery of salivary function was compared between the two techniques and dose-response relationships were determined by fitting dose-response curves to the data using non-linear logistic regression analysis.

Results: Seventy-one patients received BSLPS-IMRT and 35 received CLPS-IMRT. Patients received 65 Gy in 30 fractions to the primary site and involved nodal levels and 54 Gy in 30 fractions to elective nodal levels. There were significant differences in mean doses to contralateral parotid gland (29.4 Gy versus 24.9 Gy, P < 0.005) and superficial lobes (26.8 Gy versus 30.5 Gy, P = 0.02) for BSLPS and CLPS-IMRT, respectively. Lower risk of long-term ≥grade 2 subjective xerostomia (LENTSOMA) was reported with BSLPS-IMRT (odds ratio 0.50; 95% confidence interval 0.29–0.86; P = 0.012). The percentage of patients who reported recovery of parotid saliva flow at 1 year was higher with BSLPS-IMRT compared with CLPS-IMRT techniques (67.1% versus 52.8%), but the difference was not statistically significant (P = 0.12). For the whole parotid gland, the tolerance doses, D50, were 25.6 Gy (95% confidence interval 20.6–30.5), k = 2.7 (0.9–4.5) (CLPS-IMRT) and 28.9 Gy (26.1–31.9), k = 2.4 (1.4–3.4) (BSLPS-IMRT). For the superficial lobe, D50 were similar: BSLPS-IMRT 23.5 Gy (19.3–27.6), k = 1.9 (0.5–3.8); CLPS-IMRT 24.0 Gy (17.7–30.1), k = 2.1 (0.1–4.1).

Conclusion: BSLPS-IMRT reduces the risk of developing high-grade subjective xerostomia compared with CLPS-IMRT. The D50 of the superficial lobe may be a more reliable predictor of recovery of parotid function than the whole gland mean dose.

No MeSH data available.


Related in: MedlinePlus