Normal tissue radiosensitivity in breast cancer patients

Area of Science:

• Oncology
• Radiation Biology
• Cell Biology

Background:

• Radiotherapy is a cornerstone of breast cancer treatment.
• Predicting individual patient response and late effects is crucial for personalized medicine.
• In vitro radiosensitivity assays offer a potential method for predicting treatment outcomes.

Purpose of the Study:

• To determine if in vitro lymphocyte radiosensitivity predicts late effects of radiotherapy in breast cancer patients.
• To assess the utility of the MTT assay for measuring lymphoblastoid cell line (LCL) radiosensitivity.
• To compare LCL radiosensitivity with fibroblast radiosensitivity.

Main Methods:

• Collected blood samples from 56 breast cancer patients post-radiotherapy.
• Established lymphoblastoid cell lines (LCLs) and assessed in vitro radiosensitivity using the MTT assay.
• Generated survival curves and compared with controls, including ataxia-telangiectasia (AT) cell lines.
• Assessed late radiotherapy effects using the Radiation Therapy Oncology Group (RTOG) scoring scheme.

Main Results:

• Significant heterogeneity in LCL radiosensitivity was observed among patients.
• A correlation (r = 0.64) was found between LCL and fibroblast radiosensitivity.
• Patients experiencing Grade 2-4 late effects showed significantly higher in vitro sensitivity (p < 0.02) compared to those with Grade 0-1 effects.
• 16% of patients exhibited radiosensitivity comparable to or greater than AT heterozygote cell lines.

Conclusions:

• The MTT assay reveals substantial radiosensitivity variability in breast cancer patients.
• While some correlation exists between in vitro sensitivity and clinical late effects, its predictive value is limited.
• A subset of patients shows in vitro sensitivity but experiences normal clinical responses, indicating limitations for predictive use of this assay.