How do you follow patients with Bronchus Associated Lymphoid Tissue Lymphoma treated with 2 Gy x 2 fractions?

For patients with localized MALT lymphoma of the lung, in a distribution amenable to definitive RT, I would typically treat with 24 Gy in 2 Gy fractions. The risk of in-field progression with this dose is expected to be very low. Given the rarity of the presentation, I have only treated a handful of these patients and I have generally obtained an annual/biannual CT scan for ~5 years post-RT for monitoring. There seems to be a propensity for MALT lymphoma in paired organs to progress on the contralateral side, so the primary purpose of follow-up CT imaging in this scenario is to monitor for this. How useful this might be is unknown given the rarity of the disease, but since you can't monitor pulmonary MALT as easily as MALT in other location...