Localization of Point A in Cervical Cancer

  • participants needed
  • sponsor
    Mackay Memorial Hospital
Updated on 7 November 2020


Point A, the major critical point for dose specification of intracavitary brachytherapy, is defined as the crossing of uterine artery and ureter in treatment of cervical cancer. However, the currently advocated systems use hypothetical point A (HPA) to estimate the dosimetry of brachytherapy. This study is to localize anatomic point A (APA) of cervical cancer patients for reference of radiotherapy. We will use laparoscopic clipping technique to localize APA for cervical cancer patients during pelvic and paraaortic lymph node sampling. When these patients are receiving brachytherapy, orthogonal radiographs will be obtained after insertion of tandem and colpostats by using Henschke afterloading applicators.


Radiation therapy (RT), with a relevant integration of external beam radiotherapy (EBRT) and intracavitary brachytherapy (ICBT), is an important part in the treatment of cervical cancer. Even though concurrent chemoradiation therapy (CCRT) improves the control of locoregional recurrence and distant metastasis for locally advanced disease, the role of RT remains important and essential. ICBT is an essential component of RT and has been used to deliver a high localized dose to the primary cervical lesion and adjacent parametria with an attempt to minimize dose to nearby normal tissues. The conventional point-based dose prescription systems have been applied for decades. Incorporation of modern imaging techniques, namely computerized tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) to ICBT, enable radiation oncologists to individualize treatment volumes but yet, not applicable for routine practice. Point A, since defined by Tod and Meredith in 1938 and revised in 1953, has been widely accepted as a sacrosanct reference point for dose prescription of ICBT. Point A was defined as a point 2 cm above the cervical os and 2 cm apart from os on the line perpendicular to uterine axis. It is a hypothetical point representing the crossover of the ureter and uterine artery, located in the paracervical triangle, and is considered as a critical point for radiation tolerance. This definition of point A provides an easy way to prescribe dose in ICBT and integrate with EBRT. However, its dosimetry according to orthogonal radiographs would depend solely on the applicator geometry but not the individual tumor volume or location. The International Commission on Radiation Units and Measurements (ICRU) report 38 proposed a set of guidelines for uniform reporting. Reporting of the dimensions of reference volumes still depends on the geometry of applied applicator and remains difficult for reporting of ICBT. Thus, point A is still used as a reference point for dose prescription and for correlating the treatment outcome in clinical trials. CCRT has been considered as a standard of care for locally advanced cervical cancer. To further dissect the patient population, which may have a benefit of less morbidity from CCRT, but not radical surgery plus subsequent RT, the sampling of pelvic and paraaortic lymph nodes prior to decision of intended surgery has been utilized by performing laparoscopy or laparotomy for stages IB and IIA. Moreover, this sampling procedure can also provide a pathological proof and delineation of lymph nodes at risk for an important reference of RT field design. During sampling procedures, we observed that the point crossing over the ureter and uterine artery could be visualized and marked by using hemoclips. Therefore, the anatomic position of point A could be visualized on the orthogonal films after closure of abdominal wound. In this study, we attempt to compare the location of and the radiation doses to anatomic point A (APA) and hypothetical point A (HPA) during fractionated ICBT.

Condition Cervical Cancer
Treatment hemoclip
Clinical Study IdentifierNCT00319462
SponsorMackay Memorial Hospital
Last Modified on7 November 2020


How to participate?

Step 1 Connect with a site
What happens next?
  • You can expect the study team to contact you via email or phone in the next few days.
  • Sign up as volunteer to help accelerate the development of new treatments and to get notified about similar trials.

You are contacting

Investigator Avatar

Primary Contact


Preferred Language
Other Language
Please verify that you are not a bot.

Additional screening procedures may be conducted by the study team before you can be confirmed eligible to participate.

Learn more

If you are confirmed eligible after full screening, you will be required to understand and sign the informed consent if you decide to enroll in the study. Once enrolled you may be asked to make scheduled visits over a period of time.

Learn more

Complete your scheduled study participation activities and then you are done. You may receive summary of study results if provided by the sponsor.

Learn more

Similar trials to consider


Browse trials for

Not finding what you're looking for?

Every year hundreds of thousands of volunteers step forward to participate in research. Sign up as a volunteer and receive email notifications when clinical trials are posted in the medical category of interest to you.

Sign up as volunteer

user name

Added by • 



Reply by • Private

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Ipsa vel nobis alias. Quae eveniet velit voluptate quo doloribus maxime et dicta in sequi, corporis quod. Ea, dolor eius? Dolore, vel!

  The passcode will expire in None.

No annotations made yet

Add a private note
  • abc Select a piece of text from the left.
  • Add notes visible only to you.
  • Send it to people through a passcode protected link.
Add a private note