Dosimetric and Radiobiological Comparison of Volumetric Modulated Arc Therapy versus Intensity-Modulated Radiotherapy in Locally Advanced Cervical Cancer: A Retrospective Single-Center Study

Abstract

Author(s): Adil El Badaoui*, Mourad Trihi

Background: Cervical cancer is the second most common cancer among Moroccan women. IMRT and VMAT are both used routinely as intensity-modulated techniques, but when patient enrollment for this study began, a radiobiologically informed comparison of the two had not yet been reported for a North African population. Purpose: To compare VMAT and IMRT dosimetrically and radiobiologically in locally advanced cervical cancer (LACC). Methods: Forty-five patients treated with definitive concurrent chemoradiotherapy (FIGO IB2–IVA) were included retrospectively; twenty-three received VMAT and twenty-two received IMRT. Plans were recalculated with the Acuros XB algorithm (Eclipse v16.1). DVH parameters were extracted for the PTV and pelvic organs at risk. TCP was modeled with the Poisson linear-quadratic formalism, and NTCP with the Lyman–Kutcher–Burman model, using literature-derived parameters. Because the two groups were independent, between-group comparisons used the Mann- Whitney U test. Results: PTV coverage was equivalent between techniques (D95: 97.8% vs 97.5%, p = 0.38). VMAT significantly reduced dose to the rectum, bladder, small bowel, and femoral heads (p ≤ 0.021). Modeled TCP was comparable between groups (78.4% vs 76.9%, p = 0.38), while modeled NTCP for grade ≥ 2 proctitis, cystitis, and enteritis was lower with VMAT (p < 0.01). Monitor units decreased by 30.4% and beam-on time by 63.2% with VMAT. Conclusion: VMAT improved modeled organ-at-risk sparing without compromising tumor coverage. These findings are consistent with the international literature and support a clinical interest in VMAT in this Moroccan setting. Prospective confirmation with clinical toxicity data remains necessary before generalization.

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