Temporal lung tumor volume changes in small-cell lung cancer patients undergoing chemoradiotherapy.

PURPOSE: Small-cell lung cancer is considered to be relatively chemosensitive and radiosensitive. Small-cell tumor volume changes during concurrent chemoradiotherapy have not been quantified. The purpose of this work is to quantify small-cell lung tumor volume variations in limited-stage patients undergoing chemoradiotherapy.

METHODS AND MATERIALS: Eligible patients had pathologically confirmed limited-stage small-cell lung cancer, underwent concurrent chemoradiotherapy, and signed study-specific consent forms. Patients underwent serial chest computed tomography (CT) scans on a CT simulator with images acquired at the same phase of patients' respiratory cycle. Computed tomography scans were obtained at the time of planning CT scan and 3 times a week during radiotherapy (RT). Gross tumor volumes (GTVs) were contoured on each CT scan. Gross tumor volumes defined on each CT scan were analyzed for volume changes relative to pre-RT scans.

RESULTS: We obtained 104 CT scans (median, 11.5 scans per patient). The median tumor dose was 50 Gy. The median pre-RT GTV was 98.9 cm(3) (range, 57.8-412.4 cm(3)). The median GTV at the final serial CT scan was 10.0 cm(3) (range, 4.2-81.6 cm(3)). The mean GTV relative to pre-RT volume at the end of each RT week was 53.0% for Week 1, 29.8% for Week 2, 22.9% for Week 3, 19.5% for Week 4, and 12.4% for Week 5.

CONCLUSIONS: Dramatic shrinkage of small-cell lung tumors occurred in patients undergoing chemoradiotherapy in this trial. Most of the observed GTV shrinkage occurred during the first week of RT.