Recent Advances and Adaptive Strategies in Image Guidance for Cervical Cancer Radiotherapy

Abstract

The standard of care for locally advanced cervical cancer is external beam radiotherapy (EBRT) with simultaneous chemotherapy followed by an internal radiation boost. New imaging methods such as positron-emission tomography and magnetic resonance imaging have been implemented into daily practice for better tumor delineation in radiotherapy planning. The method of delivering radiation has changed with technical advances in qualitative imaging and treatment delivery. Image-guided radiotherapy (IGRT) plays an important role in minimizing treatment toxicity of pelvic radiation and provides a superior conformality for sparing the organs at risk (OARs) such as bone marrow, bowel, rectum, and bladder. Similarly, three-dimensional image-guided adaptive brachytherapy (3D-IGABT) with computed tomography (CT) or magnetic resonance imaging (MRI) has been reported to improve target coverage and reduce the dose to normal tissues. Brachytherapy is a complementary part of radiotherapy treatment for cervical cancer and, over the past 20 years, 3D-image-based brachytherapy has rapidly evolved and established itself as the gold standard. With new techniques and adaptive treatment in cervical cancer, the concept of personalized medicine is introduced with an enhanced comprehension of the therapeutic index not only in terms of volume (three-dimensional) but during treatment too (four-dimensional). Current data show promising results with integrated IGRT and IGABT in clinical practice and, therefore, better local control and overall survival while reducing treatment-related morbidity. This review gives an overview of the substantial impact that occurred in the progress of image-guided adaptive external beam radiotherapy and brachytherapy.

Keywords: ART; IGRT; cervix cancer; external beam radiotherapy; image-guided brachytherapy.

Figure 1

Patient 1 with FIGO stage IIIC2 was treated with EBRT and 3 fractions of HDR CT-based brachytherapy. T2-weighted pretreatment MRI with 6.8 × 6 × 6.2 cm hypointense vaginal wall tumor and superior 1/3 vaginal invasion, bilateral parametrial involvement—sagittal view and axial view.

Figure 2

Patient 2 with FIGO stage IVA was treated with EBRT and 3 fractions of HDR CT-based brachytherapy. T2-weighted pretreatment MRI: 4.5 × 5 × 4.6 cm tumor indicating complete vaginal invasion up to urethral meatus and posterior bladder wall involvement—sagittal view and axial view.

Figure 3

Patient 1 T2-weighted pre-brachytherapy MRI (5th week of CRT): 1.7 × 1.7 × 2.8 cm residual posterior cervix tumor and irregular tumor signal extending to left parametrium (parametrial invasion)—sagittal view and axial view.

Figure 4

Patient 2 T2-weighted pre-brachytherapy MRI (5th week of CRT): residual tumor and irregular tumor signal extending to parametrium, bladder, and vaginal wall—sagittal view and axial view.

Figure 5

An example of pretreatment [¹⁸F] FDG PET–CT showing a locally advanced cervical tumor with complete vaginal invasion and bladder involvement up to urethral meatus—axial view and sagittal view.

Figure 6

Post IGRT/CRT and IGABT treatment modalities in a FIGO IIIC1 case—left (axial view)—¹⁸FDG PET–CT low FDG uptake (SUV max 4) and right (sagittal view)—T2-weighted MR images—no mass in the cervix with low cervical signal intensity. Colposcopy with biopsy was negative for malignancy.

Figure 7

Patient 1 with FIGO stage IIIC2 LACC: left image (week 1)—initial plan of EBRT and right image (week 3) during EBRT—adaptive planning (sagittal view) for tumor shrinkage.

Figure 8

Patient 1 with FIGO stage IIIC2 LACC: left image (week 1)—initial plan of EBRT and right image (week 3) during EBRT—adaptive planning (axial view) for tumor shrinkage.

Figure 9

Combined approach (IC + IS). In this example of FIGO IIIC2, a large cervical tumor at presentation with bilateral parametrial involvement and lower uterine segment infiltration and partial response to treatment pre-brachytherapy with residual tumor to the inner third of parametria bilaterally led to the decision to choose a combined approach (implant representation ring and uterine tandem with 4 needles).

Figure 10

IC approach. The rationale for intracavitary application for the same patient as described in Figure 9: for the last procedure, due to poor blood results (severe thrombocytopenia), the decision was made for an intracavitary approach in order not to prolong overall treatment time (implant representation ring and uterine tandem).

Figure 11

Rationale for interstitial application. In this example, bilateral parametrial involvement at the time of diagnosis and residual tumor to the inner third of parametria bilaterally led to a decision to choose a hybrid approach (implant representation ring and uterine tandem with 8 needles).

Figure 12

Implant representation ring and uterine tandem with 8 needles with isodose curves–tumor coverage and OARs representation.