One pill before radiation: a new shield for bones?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Patients must be 18 years or older, but there is no upper limit on age of inclusion. * Patients must have a peripheral lung tumor that is amenable to SBRT as determined by the treating radiation oncologist. To be classified as a peripheral lung tumor, the tumor edge (the edge of the gross tumor volume or GTV in radiation treatment planning software) must be within 2 cm of the chest wall. This is determined by the treating radiation oncologist. The chest wall is defined as the chest wall musculature or ribs/vertebrae immediately adjacent to the lungs. * Patients must have ECOG status of 0-3 * Patients must have a life expectancy of at least 3 months as determined by the treating radiation oncologist. * Patients must have the ability to understand and the willingness to sign an IRB-approved informed consent document. Exclusion Criteria: Prior radiation to any part of the body including the lungs or thorax is not an exclusion criteria * Tumor edge is greater than 2 cm from the chest wall. The edge of tumor is the edge of the gross tumor volume or GTV as defined in radiation treatment planning software. This is determined by the treating radiation oncologist. * Tumors that are expected to require more than 10 fractions of radiation as determined by the treating radiation oncologist. * History of using bone anti-resorptive agents including bisphosphonates or RANK-L inhibitors within the last 1 year. * Inability to stand or sit upright for at least 30 minutes, which is necessary for ingestion of risedronate. * Hypocalcemia defined as serum total calcium lower than 8.5 mg/dL on most recent bloodwork that is within 3 months of administration of study drug/placebo. * Severe renal impairment (EGFR \<30 mL/min) on most recent bloodwork that is within 3 months of administration of study drug/placebo. * Known allergy to risedronate or other bisphosphonates * Surgery affecting the bone or dental operations within the last 6 months. This will be explicitly asked and documented in the EMR by treating radiation oncologist. * Dental operations do not include routine cleaning or cavity fillings * Dental operations that exclude patients refer to any manipulation of mandible. * Positive urine pregnancy test in women of child bearing potential within 1 week of registration. Pregnant women are excluded from this study because radiation has clear teratogenic and potentially abortifacient risks.