Non-invasive stereotactic ablative boost in patients with locally advanced cervical cancer

Dose escalation with stereotactic body radiotherapy for cervical cancer treatment

BACKGROUND

Dose escalation with brachytherapy after pelvic irradiation is standard for treating cervical cancer. Its application can be impossible for some patients. Dose escalation with SBRT is widely used with high local control and acceptable toxicity rates in different body parts. The study enrolled patients who underwent SBRT treatment for dose escalation in the cervix.

METHODS

Patients who were pathologically diagnosed and treated with cervical SBRT after definitive CRT were included in the study. A total of 30 Gy in 5 fractions for the high-risk volume was prescribed. The first response evaluation was performed three months after the completion of treatment. Treatment toxicity was documented according to the RTOG-EORTC scale. Oncological outcomes and toxicity were assessed.

RESULTS

Between 02.2019 and 05.2023, 40 patients were treated with an SBRT boost after pelvic irradiation. The median follow-up time was 16 months (7-44 months). The median HR CTV was 47 cc (8,3-168,2 cc). There were 39 patients who achieved a complete response and one who achieved a partial response in the third month after treatment. There were two local or two regional recurrences. The 1-year metastasis-free survival was 88%, and the 1-year progression-free survival was 88%. During the follow-up period, one grade 3 gastrointestinal side effect was observed.

CONCLUSIONS

SBRT which has low toxicity and reasonable locoregional control rates in a short follow-up period, may be an option for dose escalation in brachytherapy-ineligible cervical cancer patients.

Stereotactic body radiotherapy boost as an alternative to brachytherapy for cervical cancer: A scoping review

PURPOSE

This scoping review aims to evaluate the evidence for stereotactic body radiotherapy (SBRT) boost as a potential alternative for brachytherapy (BCT) in treating cervical cancer.

MATERIAL AND METHODS

A comprehensive literature search was conducted across multiple databases. Studies investigating SBRT boost in cervical cancer patients who were either contraindicated for or refused BCT were included. The review examined SBRT efficacy and safety.

RESULTS

Sixteen studies were included, encompassing prospective (n = 4) and retrospective cohort studies (n = 8), as well as phase I and II trials (n = 4). The most common SBRT boost dose was 25 Gray(Gy)/5 fractions (ranging from 18 to 40 Gy/3-5 fractions). Local control rates at 1-year, 3-year, and 5-year ranged from 86 % to 100 %, 78-92 %, and 81-92 %, respectively. Overall survival (OS) rates at 1-year, 3-year, and 5-year rates ranged from 49 % to 95 %, 50-77 %, and 50-69 %, respectively. Two studies reported a pathological complete response rate of 93 % and 94 % three months after the SBRT boost. Most studies reported low rates of late grade 3 or higher genitourinary (0-14 %) and gastrointestinal (0-26 %) toxicities. The overall incidence of rectovaginal fistulas ranged from 0 % to 13 %.

CONCLUSION

This scoping review suggests SBRT boost as a promising alternative to selected cervical cancer patients who cannot receive BCT. The results indicate a high local control with acceptable toxicity profiles. However, further research is needed to define optimal SBRT boost parameters, identify patient selection criteria, and address knowledge gaps regarding long-term outcomes and cost-effectiveness.

Quality Assurance for Stereotactic Body Radiation Therapy for Gynecologic Malignancies

The use of stereotactic body radiation therapy (SBRT) is not well studied or reported in the treatment of gynecologic malignancies, despite its success in the definitive management of other cancer sites. This report describes a rigorous quality assurance process for patients to undergo dose escalation to the pelvis via stereotactic photon beam irradiation. Patients who receive SBRT must be ineligible for conventional brachytherapy boost and undergo comprehensive informed consent. Fiducial placement, bowel prep, Foley catheter placement with standardized bladder filling, computerized tomography (CT) simulation with whole-body immobilization, magnetic resonance imaging (MRI)-assisted target delineation, planning aims based on the established brachytherapy literature, and physics consultation for SBRT plan optimization are necessary. Prior to each fraction, the simulation position is reproduced and verified with on-table cone beam CT, and the position is maintained with whole-body immobilization. Following treatment, the treating physician is active in survivorship and toxicity management. Gynecologic SBRT is an ongoing area of study, and preliminary successes in delivering high-quality stereotactic dose escalation suggest prospective investigation is warranted. By adhering to strict quality control measures and following a pre-defined best standard of practice, patients with gynecologic malignancies who are ineligible for traditional brachytherapy procedures can be safely treated with SBRT.

Boost modalities in cervical cancer: dosimetric comparison between intracavitary BT vs. intracavitary + interstitial BT vs. SBRT

PURPOSE / OBJECTIVE

This study compares the dosimetric plans of three distinct boost modalities in cervical cancer (CC): intracavitary (IC) with tandem/ovoids brachytherapy (BT), IC + interstitial (IS) BT, and Stereotactic-Body-Radiotherapy (SBRT). The aim is to determine the dosimetric impact in terms of target coverage and organ at risk (OAR) doses.

MATERIALS AND METHODS

24 consecutive IC + IS BT boost treatment plans were retrospectively identified. For each plan included, two additional plans were created: IC-BT and SBRT. Importantly, no planning target volume (PTV) or planning (organ at) risk volume (PRV) margins were generated, therefore all structures were identical for any boost modality. Two different normalizations were performed: (1) Normalization to the target: prescription of 7.1 Gy to the D90% (defined as the minimum dose covering 90%) of the high-risk clinical target volume (HR-CTV); (2) Normalization to the OARs. HR-CTV coverage and OARs sparing were compared. The equivalent doses in 2 Gy fractions (EQD2) of EBRT and BT for CTV-HR and OARs were calculated using the linear-quadratic model with α/β of 10 (EQD2₁₀) and 3 (EQD2₃), respectively RESULTS: A total of 72 plans were investigated. In the first normalization, the mean EQD2_3-D2cc (defined as the minimal dose of the 2 cc) of OAR was significantly higher in the IC-BT plans, and the bladder D2cc hard constraint could not be reached. IC + IS BT leads to a 1 Gy mean absolute decrease of bladder EQD2₃-D2cc (relative dose: -19%), allowing to reach the hard constraint. SBRT (without PTV) delivers the lowest EQD2₃-D2cc to the OAR. In the second normalization, IC-BT provides a significantly lower dose to the EQD2₁₀-D90% (6.62 Gy) and cannot achieve the coverage goal. SBRT (without PTV) yields the highest dose to the D90% of HR-CTV and a significantly lower EQD2₁₀-D50% and D30%.

CONCLUSION

The key dosimetric benefit of BT over SBRT without PTV is a significantly higher D50% and D30% in the HR-CTV, which increases the local and conformal dose to the target. IC + IS BT vs. IC-BT provides significantly better target coverage and a lower dose to the OARs, making it the preferred boost modality in CC.

Stereotactic body radiotherapy boost in patients with cervical cancer

Our aim was to evaluate the oncological outcomes of stereotactic body radiotherapy (SBRT) boost in patients with cervical cancer. The data of 21 patients who received SBRT boost after definitive radiotherapy (RT) or chemoradiotherapy (CRT) between March 2012 and April 2019 were retrospectively evaluated. External beam radiotherapy (EBRT) was applied to patients with a total dose of 50.4 Gy in 28 fractions. Kaplan-Meier method was used for survival analysis (IBM SPSS 23 software) and p < .05 value was considered significant. After definitive RT or CRT, there was a complete response in 9 (43%) patients, partial response in 11 (52%) patients and stable disease in 1 (5%) patient. The median follow-up period was 28 months (range, 7.5-88 months). Two-years cancer-specific survival rate was 80%. While 2-year LC rate was 75% in patients with residual tumour size <4 cm, it was 50% when there was ≥4 cm residual tumour after definitive CRT (p = .1). The treatment was well-tolerated and no acute or late toxicity was observed. Although brachytherapy (BRT) is an essential part of the treatment in locally advanced cervical cancer, SBRT may be used in patients with small residual disease who are not candidate for BRT. IMPACT STATEMENTCervical cancer is one of the most common cancers in the world, and external beam radiotherapy (EBRT) and brachytherapy (BRT) are the main treatment options. However, in rare cases where BRT is not feasible, it has been questioned whether stereotactic body radiotherapy (SBRT) as an alternative to BRT.What is already known on this subject? Nowadays, BRT still appears to be the gold standard treatment. However, studies with a small number of patients and short follow-up periods in the literature show that SBRT can be a good alternative in cases where BRT cannot be performed.What do the results of this study add? Our study is one of the series with the largest number of patients in the literature and with the longest follow-up period. In this area where there is no prospective study, we think that retrospective data with high patient numbers are enlightening.What are the implications of these findings for clinical practice and/or further research? Our study shows that SBRT is an alternative option in cases with small residual disease where BRT cannot be applied, and it provides a basis for a prospective randomised study.

Stereotactic ablative body radiotherapy boost for cervical cancer when brachytherapy boost is not feasible

BACKGROUND

The purpose of this study was to analyze the treatment efficacy and safety of stereotactic ablative body radiotherapy (SABR) boost for cervical cancer patients not amenable to brachytherapy.

METHODS

A retrospective review of the medical records from single institution of 25 eligible patients was performed. The patients underwent pelvic radiotherapy (RT) in 25 or 28 fractions with a median dose of 45 Gy (range 44-50.4 Gy). SABR boost was delivered after pelvic RT, with a median dose of 25 Gy (range 20-33 Gy), and a median fraction number of 5 (range 4-6). 21 patients with a follow-up period of more than one year were included in the toxicity analysis, and hematuria and hematochezia that occurred later than 3 months after the RT were graded.

RESULTS

The median follow-up period after radiotherapy was 2.85 years (range 0.33-6.60). The 3-year local control, locoregional control, disease-free survival, and overall survival rates were 80.9%, 75.8%, 40.9%, and 77.1%, respectively. 5 patients experienced grade 3 toxicity (3 genitourinary, 3 gastrointestinal), and no grade 4-5 toxicity was reported. Univariate analysis showed that cumulative D_2cc in equivalent dose in 2 Gy fractions (EQD2) of rectum was marginally predictive for any grade of hematochezia (P = 0.051). Cumulative D_2cc EQD2 of bladder was not predictive for hematuria. In the receiver operating characteristic (ROC) curve analysis, the optimal threshold of cumulative rectal D_2cc EQD2 was 81.2 Gy for any grade of hematochezia.

CONCLUSION

SABR boost for cervical cancer was effective and tolerable. Although it cannot substitute brachytherapy, it can be a treatment option when brachytherapy is not possible.