Melanoma metastasis

Dear doctor, My father (age 58, non-smoker, previous health condition excellent) was diagnosed with metastatic malignant melanoma on the lungs and pleura a month ago (main diagnosis: MM - metastaticum pleurae; MM tegmenti thoracis aa XV; PH diagnosis: MM cutis Clark II, Breslow 1 mm). Thoracic CT showed a circular soft tissue infiltrative mass 5 cm in diamater in the left hilus area, encircling and infiltrating the main branch of the pulmonary artery and its branches. Upper abdomen ultrasound showed changes on the liver and spleen (probably tumors), with suspected metastasis on the bones. Slightly over two months have passed since the appearance of the first symptoms (cough, tiredness), and my father's health has deteriorated significantly (cough leading to insomnia, loss of appetite, nausea, weight loss and muscular weakness, immobility, pain in arms, legs and back when changing position). Since his general condition has deteriorated, his oncologist has prescribed as palliative therapy Tamoxifen (20 mg), Megostat - Megestrolum (20 ml) and iron ampules to recover and strengthen his organism in preparation for the main therapy. Two days ago, swelling appeared on his arm and leg joints, along with a large swelling in the stomach area (significant increase in stomach size, as in obesity). I would be grateful if you could answer the following questions: 1) Could this swelling be a result of Tamoxifen (Tamoplex) or Megestrolum? Why has Tamoxifen been prescribed in a case of malignant melanoma, when its original use is in breast cancer treatment? 2) What therapy would you suggest in the treatment of malignant melanoma and is my father even in a condition to receive any kind of therapy in this weakened and nearly immobile state? His last lab results from a week ago showed the following: sedimentation 23, leukocytes 11.1, erythrocytes 5.06, hemoglobin 139, hematocrit 0.431, thrombocytes 644, glucose 7.3, urea 5.3, creatinine 75, AST/ALT 16/36, GGT 94, LDH 262, Fe 3,4, Ca 2,8. Thank you very much for your kind answers!