Therapeutic analysis of Intrabeam‐based intraoperative radiation therapy in the treatment of unicentric breast cancer lesions utilizing a spherical target volume model

Abstract

It is postulated that the outcomes in treating breast cancer with intraoperative radiotherapy (IORT) would be affected by the residual cancer cell distribution within the tumor bed. The three‐dimensional (3D) radiation doses of IntrabeamTM (IB) IORT with a 4‐cm spherical applicator at the energy of 50 and 40 kV were calculated. The modified linear quadratic model (MLQ) was used to estimate the radiobiological responses of the cancer cells and interspersed normal tissues with various radiosensitivities. By comparing the average survival fraction of normal tissues in IB‐IORT and uniform dose treatment for the same level of cancer cell killing, the therapeutic ratios (TRs) were derived. The equivalent uniform dose (EUD) was found to increase with the prescription dose and decrease with the cancer cell infiltrating distance. For 50 kV beam at the 20 Gy prescription dose, the EUDs are 18.03, 16.49 and 13.56, 11. 29, and 9.28 Gy respectively, for 1.5, 3.0, 6.0, 9, and 15.0 mm of the cancer cell infiltrating distance into surrounding tissue. The dose rate of 50 kV is at least 1.87× higher than that of 40 kV beam. The EUDs of 50 kV beam are up to 15% higher than that of the 40 kV beam. The TR increases with the prescription dose, but decreases with the distance of cancer cell infiltration distance. Average TRs of 50 kV beam are up to 30% larger than that of 40 kV beam. In conclusion, IB‐IORT can provide a possible therapeutic advantage on sparing more normal tissue compared with the External Beam IORT (EB‐IORT) for shallowly populated unicentric breast lesion. Our data suggest that IB‐IORT dose size should be adjusted based on the individual patient's cancer cell infiltrating distance for delivering an effective dose, one dose‐fits‐all regimen may have undertreated some patients with large cancer infiltrating distance.

Dosimetric effect of nanoparticles in the breast cancer treatment using INTRABEAM® system with spherical applicators in the presence of tissue heterogeneities: A Monte Carlo study

“…After acquiring the measured depth doses by using an ionization chamber type PTW 34013 on water phantom in our previous study [32], the second step was the validation of the simulation procedure used in the present study by comparing the simulation with the measured depth dose profiles. The relative dose shown in figures 5(a) and (b) drops exponentially because the energy used was low kV (50 kV) and this shows a better conformity with the half-Gaussian cancer cell distribution in the tumor bed [58]. Additionally, the results in figures 5(c) and (d) show that, in all of the cases, the gamma indexes were below 1.…”

First Experience of Intra-Operative Radiation Therapy (IORT) during Kyphoplasty in Patients Diagnosed with Spinal Metastasis in Iran

“…However, in recent years, mobile IORT with low voltage (about 20 to 50 kV) such as INTRABEAM (Carl Zeiss AG, Germany) and electronic brachytherapy system Axxent (Fremont, California Xoft Inc.) gained significant popularity in IORT field [30]. These systems harbor gradient radiation slope and do not require special protection equipment and its applicators are sphere shape with different sizes and seldom infiltration depth (0.5 to 1 cm), thus making these devices a proper tool for targets with sphere shapes, or in spherical cavities [31].…”

A simple dosimetric approach to spatially fractionated GRID radiation therapy using the multileaf collimator for treatment of breast cancers in the prone position

“…In 1989, Fowler 22 suggested an α/β ratio of around 4 Gy as an approximation of breast cancer’s radiobiological response. In 2003 Guerrero and Li 21 found some breast cancer cells still have an α/β of 10 Gy with an α of 0.3 Gy −1 , a β of 0.03 Gy −2 , and a half‐life repair time of 1 h. In 2017 Schwid et al 23 found the breast cancer treatment can benefit from a nonuniform dose field radiotherapy regardless of their radiosensitivity. In this study, both of these breast cancer cell lines (α/β = 4 and 10 Gy) were used and respectively named as the acutely responding breast cancer (C1, α/β = 10 Gy) and the slowly responding breast cancer (C2, α/β = 3.846 Gy).…”