Study Reveals How IMRT Spares Heathy Tissues in Breast Cancer Radiation Treatment

Study Reveals How IMRT Spares Heathy Tissues in Breast Cancer Radiation Treatment

radiation therapy for breast cancerIntensity Modulated Radiation Therapy (IMRT) is a precise technique of external beam radiation that uses computer-generated images of the tumor to determine the size, shape, and location of the area that needs treatment. Helical tomotherapy is a type of IMRT where the radiation aimed at the tumor forms a spiral pattern, while the patient lays on a table that is moved through a machine.

During IMRT-HT treatments, thousands of thin radiation beams that can be programmed to different intensities and angles are aimed at the tumor, and because the radiation is so precisely controlled, IMRT-HT can spare nearby healthy tissues, resulting in fewer side effects than normal external beam radiation. However, associated late-toxicity side effects still exist that can have a big impact on the patients’ life quality and ultimately become a determinant of the amount of maximum radiation emitted towards the tumor, affecting its growth.

In line with this concern, a team of researchers designed a clinical study set to evaluate the acute and moderately-late cardiac and lung toxicities of IMRT-HT for locoregional breast radiation treatment, including the internal mammary nodes, in 30 patients with stage III breast cancers receiving adjuvant chemotherapy, during a non-interrupted radiation period of 5 weeks.

The planning target volumes (PTV) included breast/chest wall, axillary level II, III, infra/supraclavicular and internal mammary nodes clinical target volumes (CTV) plus 3 mm margins, with dose to PTV of 50 Gy in 25 fractions. Acute toxicities were analyzed every week and 2 weeks post treatment using the Common Terminology Criteria for Adverse Events (CTCAV) v3.0.scale, with the heart and lungs being defined as critical organs.

The moderately-late toxicities were assessed clinically and by cardiac myoview perfusion tests preformed at baseline, 3 and 12-month follow-up. Additionally, a chest computed tomography (CT) scan was also preformed at 6-month follow-up.

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The researchers observed that in the median follow-up of 58 months, moderately-late side effects were not very frequent. Relatively low skin erythema was observed, mainly grade 1-2 between the 3rd and the 5th week of radiation treatment. Only 4 patients experienced grade 3 skin reactions, mostly seen 2 weeks post radiation, and only 5 patients developed grade 1 or 2 dyspnea, although 3 of them already had symptoms pre-radiation treatment.

Furthermore, cardiac myoview tests done at baseline and 1-year follow-up for 15 out of 18 left sided breast cancers did not show any radiation-related abnormalities.
The 6-month follow-up chest CT-scans preformed in 25 patients revealed minimal anterior lung fibrosis in 7 patients and were completely normal for the other 18. No locoregional recurrence was recorded, and the 5-year survival was an encouraging 78%.

The results of this clinical trial are important for radiation physicians and promising for breast cancer patients that undergo this treatment. Because IMRT-HT for locoregional breast radiation is very well tolerated with no treatment-related cardiac or respiratory symptoms, it can be used to control tumor growth and eventually help tumor regression with only minimal acute or moderately-late side effects.

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