It is essential that nurses gain insight about the responses of older adults to standard anticancer therapies because there is ongoing concern about whether the elderly are affected adversely by the prescribed therapy. The purpose of this longitudinal prospective study was to describe selected outcomes and their relationships in a sample of 45 elderly (mean age 69.8 years; range 61–86) patients receiving radiotherapy for either breast (42%) or lung (58%) cancer. The outcome variables were weight and multidimensional functional status; moderator variables were co-morbidity, nutritional intake, estimated adequacy of intake, radiation dose, side effects, and social support. Data were collected at the beginning of radiation (T1), the middle of therapy (T2), the conclusion of therapy (T3), and three months post radiation (T4). Although 81.4% had some concurrent condition, those with a comorbid condition did not respond significantly differently from those without a comorbid condition on any of the major variables at any of the four times. At none of the four times was the caloric intake adequate to meet the estimated energy requirements for usual activity (range 67.9–71.5%).