Gynecological Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_13_3446 - Number of implanted catheters and dose homogeneity may increase risk for long-term toxicity in cervical cancer patients treated with interstitial brachytherapy: a single-institution analysis.

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Number of implanted catheters and dose homogeneity may increase risk for long-term toxicity in cervical cancer patients treated with interstitial brachytherapy: a single-institution analysis.
J. Byun1, L. Hathout2, I. Vergalasova3, and O. M. E. E. Mahmoud4; 1Rutgers Cancer Institute of New Jersey and Robert Wood Johnson University Hospital, Department of Radiation Oncology, New Brunswick, NJ, 2Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, 3Rutgers Robert Wood Johnson University Hospital & Rutgers Cancer Institue of New Jersey, Department of Radiation Oncology, New Brunswick, NJ, 4Rutgers Newark University Hospital, Newark, NJ

Purpose/Objective(s): Reports of long-term toxicity after interstitial brachytherapy (IBT) are scarce and heterogeneous. We therefore investigated the effect of catheter technique, dosimetry and clinicopathologic variables on patient self-reported and clinician-assessed long-term toxicity.

Materials/Methods: After IRB approval, a retrospective review retrieved 31 patients (pts) who underwent gynecologic interstitial brachytherapy at our institution from 2011-2017. All patients were treated with concurrent weekly cisplatin-based chemoradiotherapy for cervical cancer. Mean follow-up was 16.6 months (median 13.2 months). Urinary, rectal and vaginal toxicity was graded using Common Terminology Criteria for Adverse Events v4.03 criteria. The association between the documented toxicities and covariates, including age, FIGO stage, comorbidity score, overall dosage measured in equivalent dose in 2 Gray fractions (EQD2), fractionation pattern, clinical target size, dosage to 2 cubic centimeters (cc) to rectum and bladder, inpatient length of stay during BT and fistula formation, was measured. Homogeneity indices were also reported, using the ratio of volume receiving 200% of prescription dose (V200) to clinical treatment volume in cc, as well as that of V150. Univariate and multivariate analyses were performed with STATA statistical software (College Station, TX).

Results: The mean age was 56.7 years (range 33-83), and FIGO 2009 Stage IB2, IIA, IIB, IIIA, IIIB and IV disease formed 9.7%, 6.5%, 32.3%, 6.5%, 38.7% and 6.5% of pts, respectively. The median volume of the CTV was 53.8cc. The median overall EQD2 and IBT dose per fraction was 80.2 Gy (range 72.2-89.8) and 5.5 Gy (range 5-7.0), respectively, delivered in 5 fractions (range 3-5). The median number of catheter needles used was 15 (range 6-20). Grade 2 and 3 toxicity was seen in 45.2% and 3.23% respectively. Number of catheters used was independent of the homogeneity indices (p = 0.590). On univariate analysis, number of needles (p = 0.002) and the V200 homogeneity index, at threshold 60% (p = 0.04), were significantly correlated with grade 2 or higher toxicity on non-parametric modeling. The other covariates were not statistically related to grade 2 or 3 toxicity. On multivariate analysis, only number of catheters remained statistically significant (p = 0.04).

Conclusion: Modern IBT allows for advanced treatment planning, facilitating homogeneity optimization. However, this study suggests increasing implanted catheter number may increase risk for long-term toxicity. Future IBT protocols should address the number of placed catheters in addition to standard plan parameters, and importantly, may improve patient toxicity profiles.

Author Disclosure: J. Byun: None. L. Hathout: None. I. Vergalasova: None. O.M. Mahmoud: None.

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TU_13_3446 - Number of implanted catheters and dose homogeneity may increase risk for long-term toxicity in cervical cancer patients treated with interstitial brachytherapy: a single-institution analysis.



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