Efficacy of the Dynamic Jaw Mode in Helical Tomotherapy With Static Ports for Breast Cancer

Abstract

The recently developed dynamic jaw technology of tomotherapy can reduce craniocaudal dose spread without much prolonging the treatment time. This study aimed to investigate the efficacy of the dynamic jaw mode for tomotherapy of breast cancer. Static tomotherapy plans of the whole breast and supraclavicular regional lymph nodes, and plans for the whole breast only were generated in 25 patients with left-sided breast cancer. Plans with a field width of 2.5 or 5 cm with the dynamic or fixed jaw modes were made for each patient. The prescribed dose was 50 Gy in 25 fractions. In whole breast and supraclavicular nodal radiotherapy, dose distributions and homogeneity of the planning target volume (PTV) with the dynamic jaw mode were slightly inferior to those with the fixed jaw mode with a 5-cm field width (P < .05). However, lung low-dose volumes and mean doses of the larynx, thyroid, skin, and all the healthy tissues combined were smaller with the dynamic jaw mode than with the fixed jaw mode with a 5-cm field width (P < .001). In whole breast radiotherapy, mean doses of the skin and healthy tissues were lower with the dynamic jaw mode than with the fixed jaw mode with a 5-cm field width (P < .001) without significant differences in PTV dose distributions, homogeneity, and conformity. The dynamic jaw mode provided better sparing of organs at risks with minimal disturbance of dose–volume indices of PTV. Considering the treatment time, the 5-cm-field dynamic jaw mode is more efficient than the 2.5-cm fixed jaw mode.

Efficacy of stereotactic radiotherapy for brain metastases using dynamic jaws technology in the helical tomotherapy system

“…In general, treatment time is influenced by jaw size, pitch and modulation factors in tomotherapy treatment delivery. 5,6 A larger jaw size generally leads to reduction in the monitor unit and treatment time and makes target coverage more uniform. The plan conformity decreases, resulting in structures around the target receiving higher doses.…”

“…Using DJ, radiation doses to the craniocaudal edges of the target can be lowered by narrowing the jaws around the edges (Figure 1). 5,6 Thus, this system can be expected to provide favourable dose distribution compared with the same jaw-size fixed jaws (FJ) mode. Treatment time can also be reduced compared with using smaller jaws modes.…”

Helical tomotherapy for chemo‐refractory multiple liver metastases

“…The primary endpoint was overall survival (OS) and the secondary endpoints were local control (LC), progression-free survival (PFS), safety, and toxicity. The inclusion criteria were as follows: (1) primary lesions diagnosed as malignant solid tumors; (2) age ≥20 years; (3) Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-2; (4) number of liver metastases 3-10; (5) absence of malignant ascites; (6) history of systemic chemotherapy and chemo-refractory status; (7) no indication of SBRT; (8) no previous irradiation to the liver; (9) normal liver volume (NLV) ≥ 700 cm 3 ; (10) Child-Pugh class-A liver function; (11) no organ at risk (OAR) of exceeding dose constraints; (12) tumor volumes outside the liver less than 1/3 of the volume of liver metastases; and (13) written informed consent. The presence of an active primary lesion was allowed.…”

Comparison of Different Combinations of Irradiation Mode and Jaw Width in Helical Tomotherapy for Nasopharyngeal Carcinoma

“…Helical tomotherapy (HT) utilizes the opening and closing of a 64-leaf, pneumatically powered, binary multileaf collimator with 51 equally-spaced beam angles at 360 • and translational motion of the treatment couch at a constant speed to achieve a high degree of freedom and power in dose optimization (1). Since HT can attain superior conformity of the dose distribution and homogeneity of the target dose, it has been widely adopted as a radiotherapy modality for various malignant tumors (2)(3)(4)(5). HT is particularly suitable for the treatment of patients with nasopharyngeal carcinoma (NPC), who have target volumes with complex shapes and numerous organs at risk (OARs) in the surrounding area (6,7).…”