The wondrous icon of Panagia Pantanassa from Vatopedi Monastery, Mount Athos. Many cancer patients have been healed through this icon
“Do you know that cancer* is the greatest sickness? Because with the other sicknesses, you don't take the issue seriously, because you hope that you will get better and usually you don't change. With cancer, however, you say 'Here it was, it's over, the lie is finished, now I'm leaving.' Men can't help you, and you find yourself alone before God. Only hope in God remains, and you cling to this hope and are saved.”
St. Porphyrios of Kavsokalyvia
*St. Porphyrios of course is referring to serious forms of cancer (though this also could apply to other serious and incurable diseases). He of course is not saying that miracles don't happen, nor that we should not seek medical treatment and that some people improve and survive. He is saying that our disease is a blessing when it brings us humility and makes us to hope in God.
http://agapienxristou.blogspot.ca/2015/01/saint-porphyrios-on-cancer.html