16. Cervix cancer - The GEC-ESTRO Handbook of Brachytherapy

Cervix cancer

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THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 01/09/2023

resonance imaging (MRI), for improved delineation of tumour and OAR and an understanding of new target concepts of different risk-volumes as proposed by GEC-ESTRO and the International Commission on Radiation Units and Measurements (ICRU). This chapter gives an overview of the concepts and technical developments underpinning the state-of-the-art field of MRI-based image-guided adaptive BT (IGABT) for the treatment of cervix cancer. Strategies to adapt to situations where resources are limited are discussed. Clinical evidence for the improvement in patient outcome resulting from the implementation of IGABT is presented.

The cervix is connected to the bony pelvis laterally by the parametria and is supported by the cardinal ligaments laterally and the uterosacral ligaments posteriorly. Only the posterior part of the cervix is covered by peritoneum (pouch of Douglas). On inspection, the cervix has a central orifice (the external os) with an anterior and a posterior lip. Superiorly, the cervix opens into the endometrial cavity via the internal os at the level of the isthmus. The cervix is divided into the endocervix which is lined with glandular epithelium, and the ectocervix which is lined with squamous epithelium. The size of the cervix varies with parity and age but is approximately 2-3 cm in both diameter and length. The total length of the uterine cavity from the external cervical os to the fundus typically varies from 4-12 cm. The regional lymph nodes (LN) for the cervix are parametrial, obturator, internal iliac, external iliac, common iliac and pre sacral. Para-aortic LN involvement was previously classified as distant metastasis in FIGO 2009 and TNM staging but has been reclassified as Stage IIIC2 disease in FIGO 2018 (Table 1).

3. ANATOMY

The uterus lies between the bladder anteriorly and the rectum posteriorly and is divided into the uterine corpus superiorly and the cervix inferiorly, connected by a narrow portion known as the isthmus. The position of the uterus is typically anteverted and anteflexed, but it may also be straight or retroflexed.

TABLE 1 COMPARISON OF 2009 AND 2018 FIGO STAGING CLASSIFICATION. Stage 2009 FIGO definition

2018 FIGO definition

I

Confined to cervix

Confined to cervix

IA

≤5 mm depth and ≤7 mm width

≤5 mm depth ≤3 mm depth

IA1 IA2

≤3 mm depth

>3 mm and not >5 mm depth

>3 mm and ≤5 mm depth

IB

>5 mm depth

>5 mm depth

IB1 IB2 IB3

≤4 cm greatest dimension >4 cm greatest dimension

≤2 cm greatest dimension

>2 cm and ≤4 cm greatest dimension

>4 cm greatest dimension

Beyond uterus, but not involving lower third vagina or pelvic sidewall

II

Beyond uterus, but not involving lower third vagina or pelvic sidewall

IIA

Upper two-thirds vagina

Upper two-thirds vagina

IIA1 IIA2

Upper two-thirds vagina and ≤4 cm Upper two-thirds vagina and >4 cm

Upper two-thirds vagina and ≤4 cm Upper two-thirds vagina and >4 cm

IIB

Parametrial invasion

Parametrial invasion

III

Lower third vagina, pelvic sidewall and ureters

Lower third vagina, pelvic sidewall, ureters and lymph nodes

IIIA IIIB IIIC

Lower third vagina

Lower third vagina

Pelvic sidewall or ureters

Pelvic sidewall or ureters

Pelvic and para-aortic lymph node involvement

IIIC1 IIIC2

Pelvic node involvement

Para-aortic node involvement

IV

Adjacent and distant organs Rectal or bladder involvement Distant organs outside pelvis

Adjacent and distant organs Rectal or bladder involvement Distant organs outside pelvis

IVA IVB