Inclusion Criteria:  Minimum 18 years of age Biopsy proven, newly diagnosed, untreated SCLC Completed standard of care staging investigations including: CT chest/abdomen/pelvis, bone scan or PET scan, CT head or MRI brain, or chest X-ray Eligible for platinum doublet chemotherapy Eligible for thoracic radiotherapy, which can also include ipsilateral Capable of providing written, informed consent prior to participation Able and willing to comply with protocol rules and follow-up regimen Performance status of ECOG 0-2 Pulmonary function tests showing FEV-1 >1.0L and DLCO > 50% predicted Radiation-targetable intrathoracic disease supraclavicular lymph node disease  Exclusion Criteria:  No intrathoracic disease seen to target with radiation Thoracic disease is contiguous to extra-thoracic sites, beyond ipsilateral supraclavicular lymph nodes Mixed histology disease Active serious infection requiring therapy Brain metastasis that has not been symptomatically stable on dexamethasone 4 or more sites of extrathoracic disease, even if 2 or more of these are present in the same organ system Previous CNS or thoracic radiotherapy Previous chemotherapy Ineligibility for platinum doublet chemotherapy Life expectancy of less than 3 months Prior thoracic surgery History of carcinoma other than cutaneous basal cell carcinoma Pregnant or breast-feeding In LS-SCLC, patients that are not eligible for concurrent chemoradiotherapy In ES-SCLC, patients that are not eligible for concurrent chemoradiotherapy under the experimental arm CT contrast allergy or kidney disease with irreversibly low creatinine clearance inadequate for IV contrast administration (for the purposes of high quality contrast enhanced CT chest and abdomen for follow-up imaging)