Sigmoid Point Validation for Dosimetric Evaluation and  Reporting of Accumulated Sigmoid Dose in Multifractionated  Brachytherapy for Carcinoma Cervix

Ayesha Iqbal Maniyar; Revathy P; Janaki M G; Arul Ponni T R; Kirthi Koushik; Mohan Kumar; Lithika Lavanya M; Shanmukhappa B Kaginelli

doi:10.31557/apjcc.2026.11.1.11-16

Authors

Ayesha Iqbal Maniyar M S Ramaiah Institute of Oncology, India.
Revathy P M S Ramaiah Institute of Oncology, India.
Janaki M G M S Ramaiah Institute of Oncology, India.
Arul Ponni T R M S Ramaiah Institute of Oncology, India.
Kirthi Koushik M S Ramaiah Institute of Oncology, India.
Mohan Kumar M S Ramaiah Institute of Oncology, India.
Lithika Lavanya M M S Ramaiah Institute of Oncology, India.
Shanmukhappa B Kaginelli M S Ramaiah Institute of Oncology, India.

DOI:

https://doi.org/10.31557/apjcc.2026.11.1.11-16

Keywords:

Brachytherapy, Cervical Cancer, Sigmoid point, ICRU 38

Abstract

Introduction: Carcinoma of the uterine cervix is the most common cancer in females. The mainstay of treatment is combined external beam radiotherapy (EBRT) and intracavitary brachytherapy (ICBT), especially in the advanced stages. Brachytherapy forms an integral part of radiation therapy and cornerstone for both the local control rates and toxicities. The doses received by organ at risks (OARs) are significantly associated with radiation-related toxicities. An accurate estimation of the cumulative irradiation dose for OARs is crucial. The sigmoid is an important organ at risk for gynecological brachytherapy (BT). However, the reliability of localization of high-dose regions during multi-fractionated treatment is limited. This work reports the methodological development of sigmoid points to summate multi-fractionated doses.

Materials and Methods: Fifty patients who were treated for locally advanced cervical cancer with radical chemoradiation and multifractionated high-dose rate (HDR) brachytherapy from April 2023 to December 2024 were evaluated. Sigmoid points 1 (SP1) and 2 (SP2) were assigned on the treated brachytherapy plans retrospectively. The correlation between SP1 and SP2 with sigmoid D0.1cc and D2cc doses were analyzed.

Results: The study involved 50 patients with a median age of 50 years, ranging from 35 to 70, all diagnosed with squamous cell carcinoma. The FIGO stages were: 6% in IIA, 40% in IIB, 12% in IIIB, 18% in IIICr1, 14% in IIICr2, and 10% in IVA. Treatment doses varied from 6 – 7.5Gy HDR in 2-4 fractions and inter-fraction time was 6-12 hours. The mean values for D0.1cc, D2cc, SP1, and SP2 were 4.12, 3.18, 3.82, and 15.20, respectively. Significant correlations were observed between D0.1cc and D2cc (P = 0.000), SP1 and SP2 (P = 0.002), D0.1cc and SP2 (P = 0.003), D2cc and SP1 (P = 0.004), and D2cc and SP2 (P = 0.001).

Conclusion: SP2 showed significant correlation with D0.1cc and D2cc sigmoid doses, suggesting preliminary utility as a surrogate for volumetric parameters in inter-fraction dose summation. However, further validation with clinical outcome correlation is warranted.