Skeletal metastases in colorectal carcinomas: a Saskatchewan profile

Colorectal cancer is the third leading cause of cancer-related deaths in the world. Death is usually attributed to progress of the disease with recurrence and metastases. Skeletal metastases in primary colorectal cancer is an uncommon event. When such an event occurs, it is usually a late manifestation of the disease. In our study this phenomenon is analyzed in a population-based database.

This report is a 25-year retrospective review that covers patients with skeletal metastases secondary to colorectal carcinomas registered at The Saskatchewan Cancer Foundation from 1970 to 1995. The latter is the sole registration agency of all cancers in the one million population base of the province of Saskatchewan.

A total of 5,352 cases of primary colorectal carcinomas were seen between 1970 and 1995. Of these, 355 had skeletal metastases. The incidence of osseous metastases in our institution is 6.6 percent. Among the latter, 60 cases (16.9 percent) had skeletal metastases only, whereas 295 cases (83.1 percent) had skeletal metastases in combination with lung, liver or brain metastases. This is in keeping with the fact that solitary skeletal metastases from a primary colonic carcinoma is a rare event, with an incidence of 1.1 percent in our institution. The disease-free interval from the time of diagnosis of the cancer to the onset of skeletal metastases ranged from 10 days to 5,309 days. Thirty-eight percent of the cases with skeletal metastases only were alive at the end of five years in comparison with 16 percent of the cases with skeletal and other metastases. However, there was no significant difference in the ten-year survival curves from the onset of osseous metastases in the two groups. The majority were diagnosed by a bone scan or plain radiography or both. Most cases in our institution received a multimodal treatment consisting of radiotherapy in conjunction with palliative surgery or chemotherapy or both. Radiotherapy was, however, the most effective therapy for painful skeletal metastases.

Skeletal metastasis is a rare event in primary colorectal carcinomas. Among these cases there is an emerging trend of a different clinical-biological behavior pattern between patients who develop solitary skeletal metastases vs. patients with skeletal and other organ metastases.