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).