Study on the physical factors related to the exposure dose to organs at risk from radiotherapy for cervical cancer patients

This research was performed to analyze the relationship among the physical factors of cervical cancer patients and the V40-x (volume of the x receiving 40 Gy, x is replaced by bladder or rectum below). In addition, the methods to control the factors affecting these related physical parameters are comprehensively discussed so that the side effects of radiotherapy can be reduced.

Sixty cervical cancer patients treated with volume-modulated-arc therapy (VMAT) were selected. Related physical parameters of the planning target volume (PTV), rectum, and bladder were collected. The Spearman analysis method was used to discuss the relationship between the physical parameters and V40-x.

The parameter of Dmax-rectum (max dose of rectum) and Vbladder (volume of the bladder) were significantly negatively correlated with V40-rectum and V40-bladder, respectively. In addition, we found three dosimetric parameters and four parameters were significantly positively correlated with V40-rectum and V40-bladder. A reduction in V40-x of the organs at risk (OARs) was also displayed in the redesigned planning dose images and the dose-volume histograms (DVH).

It is recommended that patients maintain a filled bladder during localization and radiotherapy. It is also recommended that patients maintain an empty rectum during localization and radiotherapy to ensure the stability of the target. According to the correlation of the physical parameters obtained from the results, medical physics can reduce the V40-x more easily during planning design by specifically controlling some physical parameters, and this can reduce radiation toxicity more effectively.