PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): To compare maximum genitourinary (GU) and gastrointestinal (GI) toxicities within 5 weeks of starting radiation therapy between intensity-modulated radiation therapy (IMRT) and conventional radiation therapy (non-IMRT) in post-hysterectomy patients treated for cervical or endometrial cancer. We also were interested to determine the dose volume histogram (DVH) values that predict grade 2+ toxicities.
Materials/Methods: Post-hysterectomy cervical and endometrial cancer patients treated at our institution were retrospectively analyzed for toxicity. GU and GI toxicities were collected prospectively using CTCAE version 4.0 during weekly on-treatment visits using a centralized database from week 1 to 6 of radiation therapy. DVH parameters were analyzed. Univariate analysis of toxicity, patient characteristics, and DVH parameters was performed using chi-square test and logistic regression.
Results: A total of 105 post-hysterectomy patients with stages I-IIIC2 endometrial (n=83, 79%) or IA-IIA cervical (n=22, 21%) cancer were treated from May 2003-November 2016. Ninety-one patients (87%) had on treatment visit assessments to evaluate (51 with IMRT and 40 with non-IMRT), including 55 patients (30 with IMRT and 25 with non-IMRT) with DVH parameters available. There was no difference between the two groups regarding baseline patient characteristics. Within 5 weeks of treatment, 23.5% patients in IMRT and 40% in non-IMRT had at least one grade 2+ toxicity (p=0.12). Bowel V40 and V45 were lower in the IMRT (median [Q1-Q3] 216cc [145-373]) than non IMRT (570cc [334-668]) cohorts. Among all patients, bowel V25, V30, V40 and V45 were all significantly associated with increased incidences of any grade 2+ toxicity, while bowel V5, V10, V15, V20 and V35 were not (Table 1). The medians (Q1-Q3) of bowel V45 were 199cc (80-457cc) among those had < grade 2 GI toxicity and 527cc (147-829cc) among those had 2+ GI toxicity (p=0.03). Table 1: DVH Parameters and Toxicity
|Bowel DVH: Median cc (Q1-Q3cc)||< Grade 2 Toxicity||Grade 2+ Toxicity||P Value|
|V5||1066 (654-1517)||1200 (826-1615)||0.5|
|V10||907 (588-1392)||1108 (780-1565)||0.36|
|V15||814 (537-1160)||1037 (680-1499)||0.2|
|V20||745 (475-1102)||1004 (508-1393)||0.1|
|V25||605 (408-897)||905 (395-1270)||0.038|
|V30||466 (327-727)||788 (258-1075)||0.027|
|V35||398 (271-615)||681 (214-966)||0.4|
|V40||289 (177-472)||607 (189-887)||0.009|
|V45||184 (78 - 388)||527 (155-800)||0.005|
Conclusion: The rates of experiencing at least one grade 2 or higher toxicity were lower for patients treated with IMRT than non-IMRT. Bowel V45 was associated with Grade 2+ toxicity. IMRT was associated with a lower bowel V40 and V45 in this group of post hysterectomy patients.
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