Abstract
BackgroundThe small bowel (SB) represents the most important dose-limiting structure in pelvic radiotherapy (RT). However, we observed that the majority of rectal cancer patients who received preoperative pelvic intensity modulated RT (IMRT) developed acute tenesmus without watery diarrhea. The objective of this study is to determine if the RT dose to SB affects the acute lower gastrointestinal toxicity (ALGIT) in rectal cancer patients who received neoadjuvant concurrent chemotherapy-IMRT. We will also evaluate if patient and tumor factors affect the ALGIT.MethodsWe retrospectively analyzed 63 rectal cancer patients that consecutively received preoperative IMRT (45 Gy for pelvis and 50 Gy for gross tumor in 25 fractions) with concurrent chemotherapy (oxaliplatin 130 mg/m2 on day 1 and capecitabine 825 mg/m2, twice per day from day 1 to day 14, week 1 and 4) between May 2012 and May 2013. The ALGIT was assessed with Common Terminology Criteria for Adverse Events version 3. The patients were stratified into two groups (with and without grade ≥2 ALGIT). The effect of SB volume receiving 5 to 40 Gy (V5 to V40) at a 5 Gy interval dose level on grade ≥2 ALGIT was evaluated. The volume of small bowel is defined as the volume of the small bowel loop. Other factors evaluated include patient’s age and gender, tumor size and location and preexisting number of daily bowel movements.ResultsOverall, grade ≥2 ALGIT occurred in 57 % (36/63) patients. There was no significant difference between the two groups of patients (with and without grade ≥2 ALGIT) in SB V5 to V40, patient’s age and gender, tumor location and preexisting number of daily bowel movements. There was a significant difference between the two groups of patients in tumor volume (with grade ≥2 ALGIT: 115.5 ± 85.5 cm3 versus without grade ≥2 ALGIT: 58.5 ± 25.2 cm3, p = 0.0001). Multivariate analysis revealed no association between the dose SB received (V5 to V40) and the grade ≥2 ALGIT after adjusting for the tumor volume.ConclusionsWith IMRT technique used in rectal cancer patients undergoing preoperative chemo-radiotherapy, the acute lower GI toxicity is not associated with small bowel V5 to V40; instead it is associated with rectal tumor size.
Highlights
Radiation therapy plays an important role in preoperative and postoperative therapy for locally advanced rectal cancer [1,2,3,4]
Since the German trial reported that preoperative chemo-radiotherapy improved local control and was associated with reduced toxicity as compared with postoperative chemo-radiotherapy, preoperative concurrent chemo-radiotherapy has become a standard of care for locally advanced rectal cancer (T3–4 and/or N positive) [4, 8]
Using intensity modulated RT (IMRT) technique further decreases the small bowel in the radiation field as compared to those using 3D conformal radiotherapy
Summary
Radiation therapy plays an important role in preoperative and postoperative therapy for locally advanced rectal cancer [1,2,3,4]. We noticed that most rectal cancer patients who received preoperative IMRT typically presented with tenesmus and a feeling of incomplete defecation without watery diarrhea and abdominal pain. It seems that such side effects were induced rather by rectal reaction to radiation than by small bowel inflammation. We observed that the majority of rectal cancer patients who received preoperative pelvic intensity modulated RT (IMRT) developed acute tenesmus without watery diarrhea. The objective of this study is to determine if the RT dose to SB affects the acute lower gastrointestinal toxicity (ALGIT) in rectal cancer patients who received neoadjuvant concurrent chemotherapy-IMRT. We will evaluate if patient and tumor factors affect the ALGIT
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