Sparing the contralateral submandibular gland without compromising PTV coverage by using volumetric modulated arc therapy

Abstract

BackgroundSalivary gland function decreases after radiation doses of 39 Gy or higher. Currently, submandibular glands are not routinely spared. We implemented a technique for sparing contralateral submandibular glands (CLSM) during contralateral elective neck irradiation without compromising PTV coverage.MethodsVolumetric modulated arc therapy (RapidArc™) plans were applied in 31 patients with stage II-IV HNC without contralateral neck metastases, all of whom received elective treatment to contralateral nodal levels II-IV. Group 1 consisted of 21 patients undergoing concurrent chemo-radiotherapy, with elective nodal doses of 57.75 Gy (PTVelect) and 70 Gy to tumor and pathological nodes (PTVboost) in 7 weeks. Group 2 consisted of 10 patients treated with radiotherapy to 54.45 Gy to PTVelect and 70 Gy to PTVboost in 6 weeks. All clinical plans spared the CLSM using individually adapted constraints. For each patient, a second plan was retrospectively generated without CLSM constraints ('non-sparing plan').ResultsPTV coverage was similar for both plans, with 98.7% of PTVelect and 99.2% of PTVboost receiving ≥95% of the prescription dose. The mean CLSM dose in group 1 was 33.2 Gy for clinical plans, versus 50.6 Gy in 'non-sparing plans' (p < 0.001). In group 2, mean CLSM dose was 34.4 Gy for clinical plans, and 46.8 Gy for non-sparing plans (p = 0.002).ConclusionsElective radiotherapy to contralateral nodal levels II-IV using RapidArc consistently limited CLSM doses well below 39 Gy, without compromising PTV-coverage. Future studies will reveal if this extent of dose reduction can reduce patient symptoms.

Evaluation of a Knowledge-Based Planning Solution for Head and Neck Cancer

“…OAR planning goals included maximizing point doses to the spinal cord, brainstem, and their planning atrisk volumes (3-mm expansion), and lowering the mean dose to parotid and submandibular glands (SMGs), individual swallowing muscles, and the oral cavity as much as possible. RapidArc optimization for HNC was performed interactively by continuously adapting the location of the OAR optimization objectives according to our institutional optimization protocol (19)(20)(21). Reduced clinical plan quality could occasionally be obtained if the institutional optimization protocol was not followed thoroughly.…”

Acute effects of Radiotherapy in patients with Head and Neck Cancer: IMRT vs RapidArcTM

“…It is also important to mention that 14 of the 46 patients that started the study underwent RT treatment with a non-conventional fractionation. This was Simultaneous Integrated Boost (SIB) for clinical orientation, which determines the total time of treatment (there is a um comportamento temporário 5,6 . Na irradiação da região de Cabeça e Pescoço os danos nos tecidos normais tornam-se evidentes, principalmente por se tratar de uma área complexa (RTOG), em casos de complicações graves, ou seja, de aparecimento de efeitos agudos severos ao tratamento, este é interrompido por incapacidade do doente em continuar a terapia, o que afeta diretamente a sobrevida e a própria eficácia da terapia na procura pela cura do doente.…”

“…In comparison, the RapidArc TM technique provoked effects in mucosa only in week 6. Patients from both treatment techniques were also undergoing combined treatment with chemotherapy, which could have influenced the toxicity increase in the normal tissues 10,18,5,6 . With regards to the salivary glands results, we have observed that all IMRT patients demonstrated effects in the 4 th week of treatment, with some patients experiencing high-degree effects.…”

“…Fast advances in radiation therapy techniques allow a substantial amount of the normal tissues to be spared; however, most patients treated with curative doses will develop acute side effects to the treatment, which require an intervention of multidisciplinary specialized support. Nevertheless, most of these effects are temporary 5,6 . In the irradiation of the complex area of the head and neck region, the damage to normal tissues becomes evident in cases of serious complications.…”

Comparison of treatment techniques for reduction in the submandibular gland dose: A retrospective study

“…Despite these advancements, xerostomia remains a regular and morbid toxicity experienced by patients following head and neck radiotherapy. This may result in dysphagia, eating and speaking difficulties, increased risk of dental caries and osteoradionecrosis, and can have a significant impact on the quality of life …”