A Prayer for Cancer Patients

An Orthodox Prayer for Cancer Patients, from the Cell of Elder Gabriel the Athonite, Approved by the Orthodox Church of Greece.

Our Lord Jesus Christ, Who rules over the spirits of affliction and health 

Icon of the Theotokos "Pantanassa" ("Queen of All"), 

also known as "The Healer of Cancer" (source)

for those who call upon You with fervor of heart, and who with faith in You have emptied themselves, hearken to us sinners, along with those afflicted with the dangerous illness of cancer, and who have been seized from among us, and who persist in longstanding and painful illness, our fathers, brethren and children, full of deep sorrows and pains, and who, unable to flee from their death, entreat everyone [to pray for them]. O Lord, through Your illumining and sanctifying Spirit, guide in medical science those who are seeking to discover and use the good medicine and revealing therapy. Grant strength to those who are suffering, and patience and relief from their pains, bestowing on them every healing of soul and body, through the intercessions of our Most-blessed Lady the Theotokos and Ever-Virgin Mary, the Life-giving Spring, whose waters in the queen of cities [Constantinople] healed the passion of cancer, of our Father among the Saints Parthenios, Bishop of Lampsakos, of the holy, glorious and wonderworking Unmercenaries, of the holy, glorious Great Martyr Panteleimon, [of St. Nektarios of Pentapolis, or other Saints desired to be commemorated, etc.] and of all Your Saints. Amen.

(source)

St. Parthenios of Lampsakos, among the Saints 

whose prayers especially help cancer patients (source)

Through the prayers of our Holy Fathers, Lord Jesus Christ our God, have mercy on us and save us! Amen!

Πηγή