Discussion
Gastric cancer is still the second leading cause of cancer-related deaths worldwide. (2). It rarely shows dissemination to the bone, as it portends a poor prognosis. In fact, mean survival time is 4-5 months with bone metastasis from gastric cancer. (3)In addition, initial or simultaneous presentation of bone metastasis particularly in asymptomatic gastric cancer is extremely rare. (4) Our patient had initially no specific symptoms in regard to the primitive tumour nor bone metastasis.
The most frequent sites of bone metastasis are the vertebrae (66%), the costa (59%), the pelvic bone (43%), the femur (30%) and the scapula and clavicule (17%) (5). Humeral bone metastases, such as in our case, are exceptional. Bone pain, pathologic fracture and spinal cord compression are the most common symptoms and complications. In bone metastasis, the cancer cells diffusely proliferate in the bone marrow and thus induce bone destruction as well as haematological complications.(6) Therefore, laboratory abnormalities that could suggest the possibility of bone metastasis include elevated alkaline phosphatase (ALP), increased LDH, anaemia or thrombocytopenia. Studies suggest that ALP is the most predictive biological marker for the presence of bone metastasis in gastric cancer. (7) However, serum ALP can be normal, like in our case.
Bone scintigraphy could detect bone metastasis at the time approximately 3 months earlier than that with using plain X-ray. (8). But, the main limitation of scintigraphy is low specificity as it could detect non neoplastic lesions as hot uptake lesions in many conditions (Paget’s disease, degenerative arthritis, infectious bone diseases …). Further investigations may be required to increase accuracy of the diagnosis (positron emission tomography computed tomography, magnetic resonance imaging, bone marrow tapping or bone marrow histological tests). In our case, the presence of an adenocarcinoma of the stomach and a concomitant lytic lesion in the rib supported the diagnosis of bone metastasis. Unfortunately, bone scintigraphy was not done because the patient lost to follow-up.
Gastric cancer patients with bone metastasis have the poorest median survival time compared with those with metastasis in other sites including the thorax, liver or other regions of the abdomen. (9)In addition, survival time following diagnosis of bone metastasis in gastric cancer is slightly longer in the initial bone metastasis patient compared with that in those with late-phase bone metastasis. (4) Systemic chemotherapy could improve survival among patients with initial bone metastasis of gastric cancer. Pain management for patients with bone pain is important and radiation may be quite effective(10). Bisphosphonate has also been used for the treatment of clinical symptoms. As for progressive or recurrent gastric cancer guidelines recommend S1-based chemotherapy (11). On the other hand, since bone metastasis can cause disseminated intravascular coagulation, the poor general condition of the patient or the presence of thrombocytopenia and severe anaemia may make the patient ineligible for chemotherapy (12).