Immunotherapy as sensitizer for local radiotherapy

Area of Science:

• Oncology
• Radiation Oncology
• Immunotherapy

Background:

• Radiotherapy (RT) is a cornerstone of cancer treatment.
• Traditional radiation sensitizers, like cisplatin, are used to improve RT efficacy.
• The potential of immunotherapy to enhance RT is an area of active research.

Purpose of the Study:

• To systematically review the radiation enhancement factor (REF) of immunotherapy combined with RT for local tumor control.
• To compare the REF of immunotherapy with traditional sensitizers such as cisplatin.
• To evaluate the impact of combined RT and immunotherapy on tumor growth delay and local control.

Main Methods:

• Systematic review of PubMed and Medline databases until February 2019.
• Exclusion of studies reporting abscopal effects.
• Digitization of graphs to calculate tumor growth delay (TGD) and determine REF.
• Analysis of 32 preclinical papers and 9 clinical series with varying RT doses and immunotherapy agents.

Main Results:

• Preclinical studies showed a median REF for immunotherapy ranging from 1.7 to 9.1.
• Clinical studies, primarily using ipilimumab and interleukin-2, reported local control rates from 66% to 100%.
• The REF of immunotherapy was higher than that of cisplatin (1.1), indicating superior enhancement of RT.

Conclusions:

• Combined RT and immunotherapy demonstrates a strong REF, superior to traditional sensitizers.
• This combination improves local tumor control in preclinical models without significant toxicity.
• The findings support the clinical use of combined RT and immunotherapy to enhance local tumor control.