What is the role of brachytherapy in the treatment of cervical cancer?

Brachytherapy in Cervical Cancer

Essential Role in Definitive Treatment

Brachytherapy is an absolutely essential and non-negotiable component of definitive radiation therapy for cervical cancer in patients with an intact cervix, and omitting it significantly compromises survival outcomes. 1, 2

Primary Treatment Indications

Locally Advanced Disease (Stage IB2-IVA)

• Brachytherapy combined with external beam radiation therapy (EBRT) and concurrent cisplatin-based chemotherapy is the standard of care for locally advanced cervical cancer. 1, 3
• This approach achieves local control rates of 88-95% for stage IB, 70-80% for stage IIB, and 30-40% for stage III disease. 1
• Five-year survival rates exceed 80% for stage IB, 65% for stage IIB, and 40% for stage III when brachytherapy is included. 1

Early-Stage Disease

Stage IA2:

• Brachytherapy with or without pelvic radiation (total point A dose 75-80 Gy) is a treatment option for stage IA2 disease, particularly for patients who are medically inoperable or desire fertility preservation. 4

Stage IB1-IIA1:

• For patients who are not surgical candidates or refuse surgery, combined pelvic radiotherapy and brachytherapy with or without concurrent cisplatin-containing chemotherapy is an alternative to radical hysterectomy. 4
• However, there is no published evidence that concurrent chemoradiation is specifically beneficial in early cervical cancer (stages IB1 and IIA <4 cm). 4

Critical Technical Requirements

Dosing Parameters

• Total doses from brachytherapy and EBRT to point A must reach at least 80 Gy for small tumors and ≥85 Gy for larger tumors. 1
• The recommended tumor dose in 2-Gy per fraction radiobiologic equivalence (normalized therapy dose) is 80-90 Gy, depending on tumor size at the time of brachytherapy. 5
• Definitive radiation therapy must be administered at high doses (≥80-90 Gy) within a short timeframe (<55 days). 4, 1

Treatment Timing

• The entire radiation course (including both EBRT and brachytherapy) must be completed within 8 weeks. 1
• Delays beyond 6-8 weeks result in approximately 0.5-1% decrease in pelvic control per extra day. 6
• When used with EBRT, brachytherapy should be initiated toward the latter part of external beam treatment after sufficient tumor regression to permit satisfactory applicator geometry. 6

Applicator Selection

• Intracavitary brachytherapy using an intrauterine tandem combined with vaginal colpostats (ovoids, ring, or cylinder) is the standard technique. 1
• Interstitial brachytherapy should be considered for patients with disease that cannot be optimally encompassed by intracavitary brachytherapy. 7

Critical Pitfall: IMRT/SBRT Cannot Replace Brachytherapy

Conformal external beam therapies such as IMRT or SBRT should NOT be used as routine alternatives to brachytherapy for treatment of central disease in patients with an intact cervix. 1, 2

• A decline in brachytherapy use has been associated with negative impacts on survival in the era of modern EBRT techniques. 2

Postoperative/Adjuvant Indications

After Radical Hysterectomy

• Vaginal brachytherapy is clearly indicated when there is a positive vaginal margin after hysterectomy, as this represents the highest risk for vaginal cuff failure. 6, 1
• Close margins in stage II-III disease warrant consideration of a brachytherapy boost given the low added toxicity and high risk of vaginal recurrence. 6
• For stage IA2 or IB1 tumors with negative margins and negative lymph nodes, vaginal brachytherapy (with or without EBRT) is an option when high-risk pathologic features are present, such as large primary tumor (≥2 cm). 6

Important Contraindication

• Vaginal brachytherapy is NOT appropriate as sole treatment when positive lymph nodes or parametrial invasion are present—these patients require concurrent cisplatin-based chemoradiation with EBRT. 6
• Vaginal brachytherapy may be added as a boost to EBRT in these high-risk scenarios, particularly with margin concerns. 6

Integration with Chemotherapy

• Concurrent cisplatin-based chemotherapy should be administered during EBRT for most patients with cervical cancer. 1
• Meta-analysis of 18 randomized trials demonstrated an absolute 5-year survival benefit of 8% for overall disease-free survival, 9% for locoregional disease-free survival, and 7% for metastases-free survival. 1
• Note that when concurrent chemoradiation is used, chemotherapy is typically given during external-beam pelvic radiation, not during brachytherapy. 4

Modern Image-Guided Approaches

• Current 3D image-guided techniques optimize implant dose coverage of tumor while potentially reducing dose to adjacent bladder, rectum, and bowel structures. 1
• Computed tomography or magnetic resonance image-guided adaptive brachytherapy is evolving as the preferred brachytherapy method. 2
• When implementing 3D image-guided approaches, traditional point A dosing must not be abandoned to avoid underdosing tumors. 1