Impact of interfractional target motion in locally advanced cervical cancer patients treated with spot scanning proton therapy using an internal target volume strategy

Abstract

Background and purpose The more localized dose deposition of proton therapy (PT) compared to photon therapy might allow a reduction in treatment-related side effects but induces additional challenges to address. The aim of this study was to evaluate the impact of interfractional motion on the target and organs at risk (OARs) in cervical cancer patients treated with spot scanning PT using an internal target volume (ITV) strategy. Methods and materials For ten locally advanced cervical cancer patients, empty and full bladder planning computed tomography (pCT) as well as 25 daily cone beam CTs (CBCTs) were available. The Clinical Target Volume (CTV), the High Risk CTV (CTV HR ) (gross tumor volume and whole cervix), the non-involved uterus as well as the OARs (bowel, bladder and rectum) were contoured on the daily CBCTs and transferred to the pCT through rigid bony match. Using synthetic CTs derived from pCTs, four-beam spot scanning PT plans were generated to target the patient-specific ITV with 45 Gy(RBE) in 25 fractions. This structure was defined based on pre-treatment MRI and CT to anticipate potential target motion throughout the treatment. D98% of the targets and V40Gy(RBE) of the OARs were extracted from the daily anatomies, accumulated and analyzed. In addition, the impact of bladder volume deviations from planning values on target and bowel dose was investigated. Results The ITV strategy ensured a total accumulated dose >42.75 Gy(RBE) to the CTV HR for all ten patients. Two patients with large bladder-related uterus motion had accumulated dose to the non-involved uterus of 35.7 Gy(RBE) and 41.1 Gy(RBE). Variations in bowel V40Gy(RBE) were found to be correlated (Pearson r = −0.55; p-value <0.0001) with changes in bladder volume during treatment. Conclusion The ITV concept ensured adequate dose to the CTV HR , but was insufficient for the non-involved uterus of patients subject to large target interfractional motion. CBCT monitoring and occasional replanning is recommended along the same lines as with photon radiotherapy in cervical cancer.

Comparison of survival, acute toxicities, and dose–volume parameters between intensity‐modulated radiotherapy with or without internal target volume delineation method and three‐dimensional conformal radiotherapy in cervical cancer patients: A retrospective and propensity score‐matched analysis

“…After considering, but not limited to the effects of different radiation techniques, our study showed that the implementation of ITV was an independent favorable prognostic factor for OS and PFS. It is worthy to mention that in one recent study 18 by Niyoteka et al, they found that it was not enough to ensure adequate dose coverage in the high‐risk CTV even though using the ITV concept. There is no doubt that not only the ITV delineation method, but the bladder volume also played an important role in the treatment of cervical cancer.…”

“…There was no statistically significant difference in survival analysis between IMRT and 3DCRT groups in our study, which is the same as several prospective randomized studies 24,26,29 or meta-analysis. 25 Based on the concept of ITV proposed in ICRU62, 30 a large amount of studies 11,12,15,[17][18][19][20][21][22] mainly concentrated on organ motion or contouring margins using the ITV delineation method. However, to our knowledge, there is no study comparing the prognostic difference between the ITV group and the N-ITV group in single radiotherapy techniques such as IMRT and 3DCRT.…”

“…Based on the concept of ITV proposed in ICRU62, 30 a large amount of studies 11 , 12 , 15 , 17 , 18 , 19 , 20 , 21 , 22 mainly concentrated on organ motion or contouring margins using the ITV delineation method. However, to our knowledge, there is no study comparing the prognostic difference between the ITV group and the N‐ITV group in single radiotherapy techniques such as IMRT and 3DCRT.…”

“… 10 Some have proposed creating an ITV to help address the challenge of bladder filling status and vaginal movement, but this has not been supported by all, 9 , 11 , 12 , 13 , 14 and there is a lack of data evaluating the disease outcomes and side effects of using an ITV with IMRT. 15 , 16 Related studies 11 , 12 , 15 , 17 , 18 , 19 , 20 , 21 , 22 mainly assessed the advantages of ITV from organ motion or contouring margins.…”

Significance of Magnetic Resonance Imaging Combining with Detection of Serum HE4, TSGF, and CD105 Levels in Diagnosis and Treatment of Moderate to Advanced Cervical Cancer

“…Patients' Clinical Stages. Before treatment, FIGO staging (2009) [12] and MRI staging [13] were adopted for patients, and the results from the two staging methods were recorded.…”