Dosimetric Comparison between Three-Dimensional Magnetic Resonance Imaging-Guided and Conventional Two-Dimensional Point A-Based Intracavitary Brachytherapy Planning for Cervical Cancer

Evaluation of variation of interfraction doses to organs at risk during brachytherapy of cervical cancer

Background

Two-dimensional treatment planning using radiographs or simulator films was the standard in planning brachytherapy for patients with cervical cancer. Three-dimensional (3D) treatment planning has improved treatment efficacy. This retrospective study compares conventional and 3D treatment planning of brachytherapy in patients with cervical cancer and interfraction dose variation to bladder and rectum (D2cc).

Methods

The mean doses to bladder and rectum (D2cc) were computed by computed tomography (CT)-based planning during 100 sessions of intracavitary brachytherapy for carcinoma cervix with the same source configuration as generated for conventional planning, and these estimates were compared with the doses at International Commission on Radiation Units and measurements (ICRU) rectal, bladder points and point A. Interfraction variation of doses to bladder and rectum during various sessions was also analysed.

Result

The mean ICRU bladder dose and D2cc of the bladder for all patients was 3.7 Gy and 7.4 Gy, respectively (p < 0.001). The mean ICRU rectal dose from conventional plan was 4.3Gy and with CT planning, 4.45 Gy (p = 0.04). Interfraction dose variations for D2cc of the bladder were min -5.3 Gy and max 4.8 Gy and those of the rectum were min -1.8 Gy and max 1.72Gy.

Conclusion

Dosimetric evaluation of conventional and 3D CT-based treatment planning for the same brachytherapy sessions demonstrated underestimation of ICRU bladder dose points (p < 0.001) and the rectal ICRU point dose and D2cc (p=0.04). The doses to organs at risk did not show a statistically significant variation between the fractions. However, large variation was noted between the interfractional maximum and minimum doses to bladder and rectum.

Radiation therapy for elderly patients with uterine cervical cancer: feasibility of curative treatment

As the average lifespan lengthens worldwide, and the older adult population increases, the number of elderly patients with uterine cervical cancer is increasing. Because intensive and invasive treatments, including surgery, are frequently unacceptable in elderly patients, cancer treatments for these patients must be carefully considered. Elderly patients have undergone radiation therapy as less-invasive curative treatment, and it has been shown to be safe and effective for local control of cervical cancer in this population, even among patients aged ≥80 years treated with curative radiation doses. Although concurrent chemoradiotherapy is the standard treatment for locally advanced cervical cancer, it is unclear whether the addition of chemotherapy to radiation therapy prolongs survival in elderly patients. Elderly patients treated with curative radiation therapy for cervical cancer might develop more therapy-related gastrointestinal and hematological toxicities and insufficiency fractures compared with younger patients. However, advanced techniques of radiation therapy (eg, intensity-modulated radiation therapy and volumetric modulated arc therapy with photons, charged-particle radiation therapy with protons and carbon ions in external-beam radiation therapy, and image-guided adaptive brachytherapy) can minimize radiation-induced toxicities and thus make curative treatment safer and more effective for elderly patients with uterine cervical cancer.