External beam techniques to boost cervical cancer when brachytherapy is not an option-theories and applications

Abstract

The management of locally advanced cervical cancer relies on brachytherapy (BT) as an integral part of the radiotherapy delivery armamentarium. Occasionally, intracavitary BT is neither possible nor available. In these circumstances, post-external beam radiotherapy (EBRT) interstitial brachytherapy and/or hysterectomy may represent viable options that must be adequately executed in a timely manner. However, if these options are not applicable due to patient related or facility related reasons, a formal contingency plan should be in place. Innovative EBRT techniques such as intensity modulated and stereotactic radiotherapy may be considered for patients unable to undergo brachytherapy. Relying on provocative arguments and recent data, this review explores the rationale for and limitations of non-brachytherapy substitutes in that setting aiming to establish a formal process for the optimal execution of this alternative plan.

Keywords: Cervical cancer; brachytherapy alternative; intensity modulated radiation therapy (IMRT); robotic radiosurgery; stereotactic body radiotherapy (SBRT).

Figure 1

BED₁₀ difference between SIF and CF dose fractionation favoring SIF except in high α with long T_k and long T_pot. CF, conventionally fractionated schedule; SIF, short integrated fractionation schedule; T_K, tumor kick off time in days for the start of accelerated repopulation; T_pot, potential tumor doubling time in days.

Figure 2

TCP as a function of tumor volume comparing short integrated versus conventional technique fractionation schedules. CF, conventionally fractionated schedule; SIF, short integrated fractionation schedule; TCP, tumor control probability.

Figure 3

Example of patient set up and SBRT plan to deliver cervical boost in case of brachytherapy non-applicability. (A) Reverse trendelenburg position; (B) the support device attached to the treatment board to permit insertion of vaginal applicator in the vagina reducing cervical tumor motion; (C,D) showing the axial and the sagittal dose distribution of SBRT boost. SBRT, stereotactic body radiotherapy.