In a patient with a 7‑cm cervical cancer invading the bladder and vagina and bilateral pelvic and para‑aortic nodal disease, after delivering 45 Gy to the whole pelvis, what boost dose and target locations are recommended?

Boost Radiotherapy for Locally Advanced Cervical Cancer

After 45 Gy to the whole pelvis, deliver a brachytherapy boost of 30-40 Gy to point A (LDR equivalent) targeting the primary cervical tumor, for a total point A dose of ≥85 Gy, and consider an additional 10-15 Gy highly conformal EBRT boost to grossly involved unresected pelvic and para-aortic lymph nodes. 1

Primary Tumor Boost

For this 7-cm cervical cancer (large-volume tumor), the primary cervical tumor requires aggressive boosting:

• Target location: The primary cervical tumor at the cervix
• Brachytherapy dose: 30-40 Gy to point A (LDR equivalent), achieving a total point A dose of ≥85 Gy when combined with the 45 Gy EBRT 1, 2
• Technique: Intracavitary brachytherapy using tandem and colpostats/ovoids is the standard approach 1

The NCCN guidelines explicitly state that for larger-volume cervical tumors, the total point A dose should be 85 Gy or greater 1. Since your patient received 45 Gy to the pelvis, the brachytherapy boost should deliver 40 Gy to point A (LDR equivalent) to reach the target total of 85 Gy.

HDR Conversion

If using high-dose-rate (HDR) brachytherapy instead of LDR, a common equivalent regimen is 5 insertions of 6 Gy each to point A (30 Gy nominal HDR = 40 Gy LDR equivalent) 1. This would be appropriate for this patient.

Special Consideration for Bladder Invasion

Given the bladder invasion in this case, brachytherapy may be technically challenging. If brachytherapy is not feasible due to unfavorable anatomy or bladder involvement:

• Alternative: Image-guided EBRT boost using IMRT/VMAT with daily image guidance can deliver 25-30 Gy in 5 fractions to the primary tumor 3, 4, 5
• However, brachytherapy remains strongly preferred as the standard of care for intact cervical cancer 1, 2

Nodal Boost

For the bilateral pelvic and para-aortic nodal disease:

• Target location: Grossly involved unresected lymph nodes in both the pelvis and para-aortic region
• Boost dose: Additional 10-15 Gy of highly conformal EBRT 1, 2
• Technique: Use highly conformal and reduced-volume EBRT (such as IMRT) to minimize normal tissue exposure 1

Critical Caveats for Nodal Boost

The guidelines emphasize that "with higher doses, especially of EBRT, care must be taken to exclude, or to severely limit, the volume of normal tissue included in the high-dose region(s)" 1. This is particularly important given the extensive nodal disease and bladder involvement in this patient.

Important note: Recent research suggests that EBRT boost to pelvic lymph nodes may not improve survival outcomes 6, but the NCCN guidelines still recommend considering it for gross unresected adenopathy 1. Given the para-aortic involvement, extended-field coverage to the renal vessels was already included in the initial 45 Gy, and the boost should target only the grossly involved nodes.

Treatment Sequencing

Brachytherapy is typically initiated toward the latter part of EBRT when sufficient tumor regression permits satisfactory applicator geometry 1. The nodal boost can be delivered concurrently or sequentially, using highly conformal techniques to protect bowel, bladder, and other critical structures.

Concurrent Chemotherapy

Throughout both EBRT and brachytherapy, concurrent cisplatin-based chemotherapy (cisplatin alone or cisplatin + 5-FU) should continue 1, 2.