That doesn't mean Polish and Russian writers weren't influenced by each other. Considering they're next door, and have been neighbors for centuries, it would be impossible for no exchange to take place.
What centuries? Since when? Seriously, don't leave us in our blissful ignorance and tell us all about the early Polish-Russian cultural exchanges.
Well, I'll help you a bit ...
Before the 1480, when Muscovite were still under the Mongol yoke of the Golden Horde? Hardly.
During the rule of Ivan III The Great (or Fierce) (1440-1505), who considered himself an heir to the fallen Byzantine Empire and defender of the Orthodox Church? And his second wife Sophia Paleologina (married in 1472), a niece of the last Emperor of Constantinople? This was the time when Russia was opening to the West and inviting western architects and builders to erect its first stone and brick churches and castles.
[For a comparison it was Polish King, Kazimierz III The Great (1310-1370), who managed similar deeds about 150 years before in Poland. He was considered the great builder of Poland, according to the saying: "Zastał Polskę drewnianą, zostawił murowaną". ]
Well, Iwan III was an ambitious man, and he went into two first wars with the Grand Duchy of Lithuania: 1492-1494, 1500-1503. Then his son Vasil III started the third war (1507-1508), and the fourth war (1512-1522). The fifth Lithuanian-Muscovite war (1534-1537) started after Vasil's death, when his son Ivan IV The Terrible was just a three years old boy.Then there were many years of so-called Livonian wars, when Livonia, Denmark, Sweden, Poland-Lithuania and Muscovite were engaged, alliances formed, broken and reformed. Started by Ivan the Terrible in 1568 (Mark 1569 - Union of Lublin, and establishment of Polish-Lithuanian Commonwealth) and ending in 1583.
Now, considering all of this: where do you see any room whatsoever for the Polish-Muscovite cultural exchange? Should I go on into the 17 century? Time of Troubles (Wielka Smuta, Smutnye vriemia), 1612, Chmielnicki Uprising, Swedish Potop (Deluge), and so on?
Your view of history of Poland is so naive, yet you do not hesitate to share with us your contrived ideas about "centuries old" cultural exchanges between Poland and Russia. Russian literature of XV-XVII, from the reunification period, was mostly devoted to glorification of Muscovite history and to various chronicles. As such, it were completely inconsequential to the Polish culture.
In Poland, chronicles written in Latin (XII c - XV c) were already well known and popular; first poems, and songs written in Polish appeared in the same period; religious texts, such as sermons, translations of Old Testament to Polish or musical codex; first codification of Polish Law (£aski Statuses, 1505) are also from that period. Poland already had its Renaissance poets, writers, publicists, professors: Copernicus, Polish-Latin poet Janicki, Rej, Kochanowski, Skarga, Frycz Modrzewski. So as you see: there is nothing common between Russia and Poland of that era, but the wars.
I do not deny the influence of so-called "golden age" (XIX c.) of Russian literature on Polish culture. Aleksander Puszkin, Fiodor Dostojewski, Michaił Lermontow, Lew Tołstoj, Nikołaj Gogol, Aleksandr Nikołajewicz Ostrowski, Iwan Turgieniew, Nikołaj Niekrasow, Wasilij Żukowski, Fiodor Tiutczew, Michaił Sałtykow-Szczedrin, Wissarion Bieliński i Taras Szewczenko (writing in Ukrainian as well).
But for God's sake, take back your naive "centuries of influence".